Psychology discussion 9

Stuck with a difficult assignment? No time to get your paper done? Feeling confused? If you’re looking for reliable and timely help for assignments, you’ve come to the right place. We promise 100% original, plagiarism-free papers custom-written for you. Yes, we write every assignment from scratch and it’s solely custom-made for you.

Order a Similar Paper Order a Different Paper

See attached

Discuss whether nature (i.e. gentics and biology) or nurture (i.e. environment, learning) play a greater role in influencing human development from birth to adulthood. Support your position with relevant information from the textbook and/or scholarly sources.

Psychology 2e


Rice University
6100 Main Street MS-375
Houston, Texas 77005

To learn more about OpenStax, visit
Individual print copies and bulk orders can be purchased through our website.

©2020 Rice University. Textbook content produced by OpenStax is licensed under a Creative Commons
Attribution 4.0 International License (CC BY 4.0). Under this license, any user of this textbook or the textbook
contents herein must provide proper attribution as follows:

– If you redistribute this textbook in a digital format (including but not limited to PDF and HTML), then you
must retain on every page the following attribution:
“Access for free at”

– If you redistribute this textbook in a print format, then you must include on every physical page the
following attribution:
“Access for free at”

– If you redistribute part of this textbook, then you must retain in every digital format page view (including
but not limited to PDF and HTML) and on every physical printed page the following attribution:
“Access for free at”

– If you use this textbook as a bibliographic reference, please include in your citation.

For questions regarding this licensing, please contact [email protected]

The OpenStax name, OpenStax logo, OpenStax book covers, OpenStax CNX name, OpenStax CNX logo,
OpenStax Tutor name, Openstax Tutor logo, Connexions name, Connexions logo, Rice University name, and
Rice University logo are not subject to the license and may not be reproduced without the prior and express
written consent of Rice University.

HARDCOVER BOOK ISBN-13 978-1-975076-45-0
B&W PAPERBACK BOOK ISBN-13 978-1-975076-44-3


10 9 8 7 6 5 4 3 2 1


OpenStax provides free, peer-reviewed, openly licensed textbooks for introductory college and Advanced
Placement® courses and low-cost, personalized courseware that helps students learn. A nonprofit ed tech
initiative based at Rice University, we’re committed to helping students access the tools they need to complete
their courses and meet their educational goals.


OpenStax, OpenStax CNX, and OpenStax Tutor are initiatives of Rice University. As a leading research university
with a distinctive commitment to undergraduate education, Rice University aspires to path-breaking research,
unsurpassed teaching, and contributions to the betterment of our world. It seeks to fulfill this mission by
cultivating a diverse community of learning and discovery that produces leaders across the spectrum of human


OpenStax is grateful for our generous philanthropic partners, who support our vision to improve educational
opportunities for all learners.

Laura and John Arnold Foundation

Arthur and Carlyse Ciocca Charitable Foundation

Ann and John Doerr

Bill & Melinda Gates Foundation

Girard Foundation

Google Inc.

The William and Flora Hewlett Foundation

Rusty and John Jaggers

The Calvin K. Kazanjian Economics Foundation

Charles Koch Foundation

Leon Lowenstein Foundation, Inc.

The Maxfield Foundation

Burt and Deedee McMurtry

Michelson 20MM Foundation

National Science Foundation

The Open Society Foundations

Jumee Yhu and David E. Park III

Brian D. Patterson USA-International Foundation

The Bill and Stephanie Sick Fund

Robin and Sandy Stuart Foundation

The Stuart Family Foundation

Tammy and Guillermo Treviño

Our textbook’s
new web
version works
with you to
help you study

Access. The future of education.

Whether you’re an expert color-coder or
first-time notetaker, our new web view makes
it easy to highlight and annotate your book
online! And, we’ve created a detailed study
guide to help you prepare for tests and
remember what you’ve read.

Our books are free and flexible, forever.

Get started at

Table of Contents
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Chapter 1: Introduction to Psychology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

1.1 What Is Psychology? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.2 History of Psychology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.3 Contemporary Psychology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
1.4 Careers in Psychology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Chapter 2: Psychological Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
2.1 Why Is Research Important? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
2.2 Approaches to Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
2.3 Analyzing Findings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
2.4 Ethics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

Chapter 3: Biopsychology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
3.1 Human Genetics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
3.2 Cells of the Nervous System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
3.3 Parts of the Nervous System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
3.4 The Brain and Spinal Cord . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
3.5 The Endocrine System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

Chapter 4: States of Consciousness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
4.1 What Is Consciousness? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
4.2 Sleep and Why We Sleep . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
4.3 Stages of Sleep . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
4.4 Sleep Problems and Disorders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
4.5 Substance Use and Abuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
4.6 Other States of Consciousness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143

Chapter 5: Sensation and Perception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
5.1 Sensation versus Perception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
5.2 Waves and Wavelengths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
5.3 Vision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
5.4 Hearing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
5.5 The Other Senses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
5.6 Gestalt Principles of Perception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179

Chapter 6: Learning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
6.1 What Is Learning? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
6.2 Classical Conditioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
6.3 Operant Conditioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
6.4 Observational Learning (Modeling) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214

Chapter 7: Thinking and Intelligence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
7.1 What Is Cognition? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226
7.2 Language . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
7.3 Problem Solving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234
7.4 What Are Intelligence and Creativity? . . . . . . . . . . . . . . . . . . . . . . . . . . 241
7.5 Measures of Intelligence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245
7.6 The Source of Intelligence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252

Chapter 8: Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263
8.1 How Memory Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264
8.2 Parts of the Brain Involved with Memory . . . . . . . . . . . . . . . . . . . . . . . . . 272
8.3 Problems with Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276
8.4 Ways to Enhance Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 286

Chapter 9: Lifespan Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295
9.1 What Is Lifespan Development? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296

9.2 Lifespan Theories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300
9.3 Stages of Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310
9.4 Death and Dying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331

Chapter 10: Emotion and Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341
10.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342
10.2 Hunger and Eating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348
10.3 Sexual Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354
10.4 Emotion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362

Chapter 11: Personality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379
11.1 What Is Personality? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380
11.2 Freud and the Psychodynamic Perspective . . . . . . . . . . . . . . . . . . . . . . . 383
11.3 Neo-Freudians: Adler, Erikson, Jung, and Horney . . . . . . . . . . . . . . . . . . . 389
11.4 Learning Approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395
11.5 Humanistic Approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 399
11.6 Biological Approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 400
11.7 Trait Theorists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 401
11.8 Cultural Understandings of Personality . . . . . . . . . . . . . . . . . . . . . . . . . 406
11.9 Personality Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 408

Chapter 12: Social Psychology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421
12.1 What Is Social Psychology? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422
12.2 Self-presentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428
12.3 Attitudes and Persuasion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 432
12.4 Conformity, Compliance, and Obedience . . . . . . . . . . . . . . . . . . . . . . . . 438
12.5 Prejudice and Discrimination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 446
12.6 Aggression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 452
12.7 Prosocial Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 455

Chapter 13: Industrial-Organizational Psychology . . . . . . . . . . . . . . . . . . . . . . . . . 471
13.1 What Is Industrial and Organizational Psychology? . . . . . . . . . . . . . . . . . . . 472
13.2 Industrial Psychology: Selecting and Evaluating Employees . . . . . . . . . . . . . . 481
13.3 Organizational Psychology: The Social Dimension of Work . . . . . . . . . . . . . . 493
13.4 Human Factors Psychology and Workplace Design . . . . . . . . . . . . . . . . . . 503

Chapter 14: Stress, Lifestyle, and Health . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 511
14.1 What Is Stress? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 512
14.2 Stressors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 522
14.3 Stress and Illness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 528
14.4 Regulation of Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 541
14.5 The Pursuit of Happiness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 548

Chapter 15: Psychological Disorders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 563
15.1 What Are Psychological Disorders? . . . . . . . . . . . . . . . . . . . . . . . . . . . 564
15.2 Diagnosing and Classifying Psychological Disorders . . . . . . . . . . . . . . . . . . 568
15.3 Perspectives on Psychological Disorders . . . . . . . . . . . . . . . . . . . . . . . . 571
15.4 Anxiety Disorders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 575
15.5 Obsessive-Compulsive and Related Disorders . . . . . . . . . . . . . . . . . . . . . 581
15.6 Posttraumatic Stress Disorder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 585
15.7 Mood Disorders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 588
15.8 Schizophrenia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 598
15.9 Dissociative Disorders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 603
15.10 Disorders in Childhood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 604
15.11 Personality Disorders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 611

Chapter 16: Therapy and Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 629
16.1 Mental Health Treatment: Past and Present . . . . . . . . . . . . . . . . . . . . . . 630
16.2 Types of Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 636

This OpenStax book is available for free at

16.3 Treatment Modalities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 648
16.4 Substance-Related and Addictive Disorders: A Special Case . . . . . . . . . . . . . 652
16.5 The Sociocultural Model and Therapy Utilization . . . . . . . . . . . . . . . . . . . . 655

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 759

This OpenStax book is available for free at


Welcome to Psychology 2e, an OpenStax resource. This textbook was written to increase student access to
high-quality learning materials, maintaining highest standards of academic rigor at little to no cost.


OpenStax is a nonprofit based at Rice University, and it’s our mission to improve student access to
education. Our first openly licensed college textbook was published in 2012, and our library has since
scaled to over 35 books for college and AP® courses used by hundreds of thousands of students. OpenStax
Tutor, our low-cost personalized learning tool, is being piloted in college courses throughout the country.
Through our partnerships with philanthropic foundations and our alliance with other educational
resource organizations, OpenStax is breaking down the most common barriers to learning and
empowering students and instructors to succeed.


Psychology 2e is licensed under a Creative Commons Attribution 4.0 International (CC BY) license, which
means that you can distribute, remix, and build upon the content, as long as you provide attribution to
OpenStax and its content contributors.

Because our books are openly licensed, you are free to use the entire book or pick and choose the sections
that are most relevant to the needs of your course. Feel free to remix the content by assigning your students
certain chapters and sections in your syllabus, in the order that you prefer. You can even provide a direct
link in your syllabus to the sections in the web view of your book.

Instructors also have the option of creating a customized version of their OpenStax book. The custom
version can be made available to students in low-cost print or digital form through their campus bookstore.
Visit the Instructor Resources section of your book page on for more information.

Art Attribution in Psychology 2e

In Psychology 2e, most art contains attribution to its title, creator or rights holder, host platform, and license
within the caption. Because the art is openly licensed, anyone may reuse the art as long as they provide the
same attribution to its original source.

To maximize readability and content flow, some art does not include attribution in the text. If you reuse art
from Psychology 2e that does not have attribution provided, use the following attribution: Copyright Rice
University, OpenStax, under CC BY 4.0 license.


All OpenStax textbooks undergo a rigorous review process. However, like any professional-grade
textbook, errors sometimes occur. Since our books are web based, we can make updates periodically when
deemed pedagogically necessary. If you have a correction to suggest, submit it through the link on your
book page on Subject matter experts review all errata suggestions. OpenStax is committed
to remaining transparent about all updates, so you will also find a list of past errata changes on your book
page on


You can access this textbook for free in web view or PDF through, and for a low cost in print.

Preface 1


Psychology 2e is designed to meet scope and sequence requirements for the single-semester introduction to
psychology course. The book offers a comprehensive treatment of core concepts, grounded in both classic
studies and current and emerging research. The text also includes coverage of the DSM-5 in examinations
of psychological disorders. Psychology 2e incorporates discussions that reflect the diversity within the
discipline, as well as the diversity of cultures and communities across the globe.

Coverage and scope

The first edition of Psychology has been used by thousands of faculty and hundreds of thousands of
students since its publication in 2015. OpenStax mined our adopters’ extensive and helpful feedback to
identify the most significant revision needs while maintaining the organization that many instructors had
incorporated into their courses. Specific surveys, pre-revision reviews, and customization analysis, as well
as analytical data from OpenStax partners and online learning environments, all aided in planning the

The result is a book that thoroughly treats psychology’s foundational concepts while adding current and
meaningful coverage in specific areas. Psychology 2e retains its manageable scope and contains ample
features to draw learners into the discipline.

Structurally, the textbook remains similar to the first edition, with no chapter reorganization and very
targeted changes at the section level.

Chapter 1: Introduction to Psychology

Chapter 2: Psychological Research

Chapter 3: Biopsychology

Chapter 4: States of Consciousness

Chapter 5: Sensation and Perception

Chapter 6: Learning

Chapter 7: Thinking and Intelligence

Chapter 8: Memory

Chapter 9: Lifespan Development

Chapter 10: Motivation and Emotion

Chapter 11: Personality

Chapter 12: Social Psychology

Chapter 13: Industrial-Organizational Psychology

Chapter 14: Stress, Lifestyle, and Health

Chapter 15: Psychological Disorders

Chapter 16: Therapy and Treatment


OpenStax only undertakes second editions when significant modifications to the text are necessary. In the
case of Psychology 2e, user feedback indicated that we needed to focus on a few key areas, which we have
done in the following ways.

Content revisions for clarity, accuracy, and currency

The revision plan varied by chapter based on need. Some chapters were significantly updated for
conceptual coverage, research-informed data, and clearer language. In other chapters, the revisions

2 Preface

This OpenStax book is available for free at

focused mostly on currency of examples and updates to statistics.

Over 210 new research references have been added or updated in order to improve the scholarly
underpinnings of the material and broaden the perspective for students. Dozens of examples and feature
boxes have been changed or added to better explain concepts and/or increase relevance for students.

Research replication and validity

To engage students in stronger critical analysis and inform them about research reproducibility,
substantial coverage has been added to the research chapter and strategically throughout the textbook
whenever key studies are discussed. This material is presented in a balanced way and provides instructors
with ample opportunity to discuss the importance of replication in a manner that best suits their course.

Diversity, representation, and inclusion

With the help of researchers and teachers who focus on diversity- and identity-related issues, OpenStax
has engaged in detailed diversity reviews to identify opportunities to improve the textbook. Reviewers
were asked to follow a framework to evaluate the book’s terminology, research citations, key contributors
to the field, photos and illustrations, and related aspects, commenting on the representation and
consideration of diverse groups. Significant additions and revisions were made in this regard, and the
review framework itself is available among the OpenStax Psychology 2e instructor resources.

Art and illustrations

Under the guidance of the authors and expert scientific illustrators, especially those well versed in creating
accessible art, the OpenStax team made changes throughout the art program in Psychology 2e.

Accessibility improvements

As with all OpenStax books, the first edition of Psychology was created with a focus on accessibility.
We have emphasized and improved that approach in the second edition. Our goal is to ensure that all
OpenStax websites and the web view versions of our learning materials follow accessible web design best
practices, so that they will meet the W3C-WAI Web Content Accessibility Guidelines (WCAG) 2.0 at Level
AA and Section 508 of the Rehabilitation Act. The WCAG 2.0 guidelines explain ways to make web content
more accessible for people with disabilities and more user-friendly for everyone.

To accommodate users of specific assistive technologies, all alternative text was reviewed and
revised for comprehensiveness and clarity.

All illustrations were revised to improve the color contrast, which is important for some visually
impaired students.

Overall, the OpenStax platform has been continually upgraded to improve accessibility.

To learn more about our commitment and progress, please view our accessibility statement
( .

A transition guide will be available on to highlight the specific chapter-level changes to the
second edition.

Pedagogical foundation

Psychology 2e engages students through inquiry, self-reflection, and investigation. Features in the second
edition have been carefully updated to remain topical and relevant while deepening students’ relationship
to the material. They include the following:

Everyday Connection features tie psychological topics to everyday issues and behaviors that
students encounter in their lives and the world. Topics include the validity of scores on college

Preface 3

entrance exams, the opioid crisis, the impact of social status on stress and healthcare, and cognitive

What Do You Think? features provide research-based information and ask students their views
on controversial issues. Topics include “Brain Dead and on Life Support,” “Violent Media and
Aggression,” and “Capital Punishment and Criminals with Intellectual Disabilities.”

Dig Deeper features discuss one specific aspect of a topic in greater depth so students can dig more
deeply into the concept. Examples include discussions on the distinction between evolutionary
psychology and behavioral genetics, recent findings on neuroplasticity, the field of forensic
psychology, and a presentation of research on strategies for coping with prejudice and

Connect the Concepts features revisit a concept learned in another chapter, expanding upon it
within a different context. Features include “Emotional Expression and Emotional Regulation,”
“Tweens, Teens, and Social Norms,” and “Conditioning and OCD.”

Art, interactives, and assessments that engage

Our art program is designed to enhance students’ understanding of psychological concepts through
simple, effective graphs, diagrams, and photographs. Psychology 2e also incorporates links to relevant
interactive exercises and animations that help bring topics to life. Selected assessment items touch directly
on students’ lives.

Link to Learning features direct students to online interactive exercises and animations that add a
fuller context to core content and provide an opportunity for application.

Personal Application Questions engage students in topics at a personal level to encourage
reflection and promote discussion.

Student and Instructor Resources

We’ve compiled additional resources for both students and instructors, including Getting Started Guides,
an instructor solution guide, a test bank, and PowerPoint slides. Instructor resources require a verified
instructor account, which you can apply for when you log in or create your account on Take
advantage of these resources to supplement your OpenStax book.

Community Hubs

OpenStax partners with the Institute for the Study of Knowledge Management in Education (ISKME)
to offer Community Hubs on OER Commons—a platform for instructors to share community-created
resources that support OpenStax books, free of charge. Through our Community Hubs, instructors can
upload their own materials or download resources to use in their own courses, including additional
ancillaries, teaching material, multimedia, and relevant course content. We encourage instructors to join
the hubs for the subjects most relevant to your teaching and research as an opportunity both to enrich your
courses and to engage with other faculty.

To reach the Community Hubs, visit

Technology partners

As allies in making high-quality learning materials accessible, our technology partners offer optional low-
cost tools that are integrated with OpenStax books. To access the technology options for your text, visit
your book page on

4 Preface

This OpenStax book is available for free at

Senior contributing authors

Rose M. Spielman (Content Lead)
Dr. Rose Spielman has been teaching psychology and working as a licensed clinical psychologist for
20 years. Her academic career has included positions at Quinnipiac University, Housatonic Community
College, and Goodwin College. As a licensed clinical psychologist, educator, and volunteer director, Rose
is able to connect with people from diverse backgrounds and facilitate treatment, advocacy, and education.
In her years of work as a teacher, therapist, and administrator, she has helped thousands of students
and clients and taught them to advocate for themselves and move their lives forward to become more
productive citizens and family members.

William J. Jenkins, Mercer University
Marilyn D. Lovett, Spelman College

Contributing Authors

Mara Aruguete, Lincoln University
Laura Bryant, Eastern Gateway Community College
Barbara Chappell, Walden University
Kathryn Dumper, Bainbridge State College
Arlene Lacombe, Saint Joseph’s University
Julie Lazzara, Paradise Valley Community College
Tammy McClain, West Liberty University
Barbara B. Oswald, Miami University
Marion Perlmutter, University of Michigan
Mark D. Thomas, Albany State University


Patricia G. Adams, Pitt Community College
Daniel Bellack, Trident Technical College
Christopher M. Bloom, Providence College
Jerimy Blowers, Cayuga Community College
Salena Brody, Collin College
David A. Caicedo, Borough of Manhattan Community College, CUNY
Bettina Casad, University of Missouri–St. Louis
Sharon Chacon, Northeast Wisconsin Technical College
James Corpening
Frank Eyetsemitan, Roger Williams University
Tamara Ferguson, Utah State University
Kathleen Flannery, Saint Anselm College
Johnathan Forbey, Ball State University
Laura Gaudet, Chadron State College
William Goggin, University of Southern Mississippi
Jeffery K. Gray, Charleston Southern University
Heather Griffiths, Fayetteville State University
Mark Holder, University of British Columbia
Rita Houge, Des Moines Area Community College
Colette Jacquot, Strayer University
John Johanson, Winona State University
Andrew Johnson, Park University
Shaila Khan, Tougaloo College

Preface 5

Cynthia Kreutzer, Georgia State University Perimeter College at Clarkston Campus
Carol Laman, Houston Community College
Dana C. Leighton, Texas A&M University—Texarkana
Thomas Malloy, Rhode Island College
Jan Mendoza, Golden West College
Christopher Miller, University of Minnesota
Lisa Moeller, Beckfield College
Amy T. Nusbaum, Heritage University
Jody Resko, Queensborough Community College (CUNY)
Hugh Riley, Baylor University
Juan Salinas, University of Texas at Austin
Brittney Schrick, Southern Arkansas University
Phoebe Scotland, College of the Rockies
Christine Selby, Husson University
Sally B. Seraphin, Centre College
Brian Sexton, Kean University
Nancy Simpson, Trident Technical College
Jason M. Smith, Federal Bureau of Prisons – FCC Hazelton
Robert Stennett, University of Georgia
Jennifer Stevenson, Ursinus College
Eric Weiser, Curry College
Jay L. Wenger, Harrisburg Area Community College
Alan Whitehead, Southern Virginia University
Valjean Whitlow, American Public University
Rachel Wu, University of California, Riverside
Alexandra Zelin, University of Tennessee at Chattanooga

6 Preface

This OpenStax book is available for free at

Chapter 1

Introduction to Psychology

Figure 1.1 Psychology is the scientific study of mind and behavior. (credit “background”: modification of work by
Nattachai Noogure; credit “top left”: modification of work by U.S. Navy; credit “top middle-left”: modification of work by
Peter Shanks; credit “top middle-right”: modification of work by “devinf”/Flickr; credit “top right”: modification of work
by Alejandra Quintero Sinisterra; credit “bottom left”: modification of work by Gabriel Rocha; credit “bottom middle-
left”: modification of work by Caleb Roenigk; credit “bottom middle-right”: modification of work by Staffan Scherz;
credit “bottom right”: modification of work by Czech Provincial Reconstruction Team)

Chapter Outline

1.1 What Is Psychology?

1.2 History of Psychology

1.3 Contemporary Psychology

1.4 Careers in Psychology


Clive Wearing is an accomplished musician who lost his ability to form new memories when he became
sick at the age of 46. While he can remember how to play the piano perfectly, he cannot remember what
he ate for breakfast just an hour ago (Sacks, 2007). James Wannerton experiences a taste sensation that is
associated with the sound of words. His former girlfriend’s name tastes like rhubarb (Mundasad, 2013).
John Nash is a brilliant mathematician and Nobel Prize winner. However, while he was a professor at MIT,
he would tell people that the New York Times contained coded messages from extraterrestrial beings that
were intended for him. He also began to hear voices and became suspicious of the people around him.
Soon thereafter, Nash was diagnosed with schizophrenia and admitted to a state-run mental institution
(O’Connor & Robertson, 2002). Nash was the subject of the 2001 movie A Beautiful Mind. Why did these
people have these experiences? How does the human brain work? And what is the connection between
the brain’s internal processes and people’s external behaviors? This textbook will introduce you to various
ways that the field of psychology has explored these questions.

Chapter 1 | Introduction to Psychology 7

1.1 What Is Psychology?

Learning Objectives

By the end of this section, you will be able to:
• Define psychology
• Understand the merits of an education in psychology

What is creativity? Why do some people become homeless? What are prejudice and discrimination? What
is consciousness? The field of psychology explores questions like these. Psychology refers to the scientific
study of the mind and behavior. Psychologists use the scientific method to acquire knowledge. To apply
the scientific method, a researcher with a question about how or why something happens will propose
a tentative explanation, called a hypothesis, to explain the phenomenon. A hypothesis should fit into the
context of a scientific theory, which is a broad explanation or group of explanations for some aspect of the
natural world that is consistently supported by evidence over time. A theory is the best understanding we
have of that part of the natural world. The researcher then makes observations or carries out an experiment
to test the validity of the hypothesis. Those results are then published or presented at research conferences
so that others can replicate or build on the results.

Scientists test that which is perceivable and measurable. For example, the hypothesis that a bird sings
because it is happy is not a hypothesis that can be tested since we have no way to measure the happiness
of a bird. We must ask a different question, perhaps about the brain state of the bird, since this can be
measured. However, we can ask individuals about whether they sing because they are happy since they
are able to tell us. Thus, psychological science is empirical, based on measurable data.

In general, science deals only with matter and energy, that is, those things that can be measured, and it
cannot arrive at knowledge about values and morality. This is one reason why our scientific understanding
of the mind is so limited, since thoughts, at least as we experience them, are neither matter nor energy. The
scientific method is also a form of empiricism. An empirical method for acquiring knowledge is one based
on observation, including experimentation, rather than a method based only on forms of logical argument
or previous authorities.

It was not until the late 1800s that psychology became accepted as its own academic discipline. Before this
time, the workings of the mind were considered under the auspices of philosophy. Given that any behavior
is, at its roots, biological, some areas of psychology take on aspects of a natural science like biology. No
biological organism exists in isolation, and our behavior is influenced by our interactions with others.
Therefore, psychology is also a social science.


Often, students take their first psychology course because they are interested in helping others and want
to learn more about themselves and why they act the way they do. Sometimes, students take a psychology
course because it either satisfies a general education requirement or is required for a program of study
such as nursing or pre-med. Many of these students develop such an interest in the area that they go
on to declare psychology as their major. As a result, psychology is one of the most popular majors on
college campuses across the United States (Johnson & Lubin, 2011). A number of well-known individuals
were psychology majors. Just a few famous names on this list are Facebook’s creator Mark Zuckerberg,
television personality and political satirist Jon Stewart, actress Natalie Portman, and filmmaker Wes
Craven (Halonen, 2011). About 6 percent of all bachelor degrees granted in the United States are in the
discipline of psychology (U.S. Department of Education, 2016).

An education in psychology is valuable for a number of reasons. Psychology students hone critical
thinking skills and are trained in the use of the scientific method. Critical thinking is the active application
of a set of skills to information for the understanding and evaluation of that information. The evaluation

8 Chapter 1 | Introduction to Psychology

This OpenStax book is available for free at

of information—assessing its reliability and usefulness— is an important skill in a world full of competing
“facts,” many of which are designed to be misleading. For example, critical thinking involves maintaining
an attitude of skepticism, recognizing internal biases, making use of logical thinking, asking appropriate
questions, and making observations. Psychology students also can develop better communication skills
during the course of their undergraduate coursework (American Psychological Association, 2011).
Together, these factors increase students’ scientific literacy and prepare students to critically evaluate the
various sources of information they encounter.

In addition to these broad-based skills, psychology students come to understand the complex factors
that shape one’s behavior. They appreciate the interaction of our biology, our environment, and our
experiences in determining who we are and how we will behave. They learn about basic principles that
guide how we think and behave, and they come to recognize the tremendous diversity that exists across
individuals and across cultural boundaries (American Psychological Association, 2011).

Watch a brief video about some questions to consider before deciding to major in psychology
( to learn more.

1.2 History of Psychology

Learning Objectives

By the end of this section, you will be able to:
• Understand the importance of Wundt and James in the development of psychology
• Appreciate Freud’s influence on psychology
• Understand the basic tenets of Gestalt psychology
• Appreciate the important role that behaviorism played in psychology’s history
• Understand basic tenets of humanism
• Understand how the cognitive revolution shifted psychology’s focus back to the mind

Psychology is a relatively young science with its experimental roots in the 19th century, compared, for
example, to human physiology, which dates much earlier. As mentioned, anyone interested in exploring
issues related to the mind generally did so in a philosophical context prior to the 19th century. Two
19th century scholars, Wilhelm Wundt and William James, are generally credited as being the founders
of psychology as a science and academic discipline that was distinct from philosophy. This section will
provide an overview of the shifts in paradigms that have influenced psychology from Wundt and James
through today.


Wilhelm Wundt (1832–1920) was a German scientist who was the first person to be referred to as a
psychologist. His famous book entitled Principles of Physiological Psychology was published in 1873. Wundt
viewed psychology as a scientific study of conscious experience, and he believed that the goal of
psychology was to identify components of consciousness and how those components combined to result
in our conscious experience. Wundt used introspection (he called it “internal perception”), a process by
which someone examines their own conscious experience as objectively as possible, making the human
mind like any other aspect of nature that a scientist observed. He believed in the notion of


Chapter 1 | Introduction to Psychology 9

voluntarism—that people have free will and should know the intentions of a psychological experiment
if they were participating (Danziger, 1980). Wundt considered his version experimental introspection;
he used instruments such as those that measured reaction time. He also wrote Volkerpsychologie in 1904
in which he suggested that psychology should include the study of culture, as it involves the study of
people. Edward Titchener, one of his students, went on to develop structuralism. Its focus was on the
contents of mental processes rather than their function (Pickren & Rutherford, 2010). Wundt established
his psychology laboratory at the University at Leipzig in 1879 (Figure 1.2). In this laboratory, Wundt
and his students conducted experiments on, for example, reaction times. A subject, sometimes in a room
isolated from the scientist, would receive a stimulus such as a light, image, or sound. The subject’s reaction
to the stimulus would be to push a button, and an apparatus would record the time to reaction. Wundt
could measure reaction time to one-thousandth of a second (Nicolas & Ferrand, 1999).

Figure 1.2 (a) Wilhelm Wundt is credited as one of the founders of psychology. He created the first laboratory for
psychological research. (b) This photo shows him seated and surrounded by fellow researchers and equipment in his
laboratory in Germany.

However, despite his efforts to train individuals in the process of introspection, this process remained
highly subjective, and there was very little agreement between individuals.


William James (1842–1910) was the first American psychologist who espoused a different perspective on
how psychology should operate (Figure 1.3). James was introduced to Darwin’s theory of evolution by
natural selection and accepted it as an explanation of an organism’s characteristics. Key to that theory is
the idea that natural selection leads to organisms that are adapted to their environment, including their
behavior. Adaptation means that a trait of an organism has a function for the survival and reproduction
of the individual, because it has been naturally selected. As James saw it, psychology’s purpose was to
study the function of behavior in the world, and as such, his perspective was known as functionalism.
Functionalism focused on how mental activities helped an organism fit into its environment.
Functionalism has a second, more subtle meaning in that functionalists were more interested in the
operation of the whole mind rather than of its individual parts, which were the focus of structuralism. Like
Wundt, James believed that introspection could serve as one means by which someone might study mental
activities, but James also relied on more objective measures, including the use of various recording devices,
and examinations of concrete products of mental activities and of anatomy and physiology (Gordon, 1995).

10 Chapter 1 | Introduction to Psychology

This OpenStax book is available for free at

Figure 1.3 William James, shown here in a self-portrait, was the first American psychologist.


Perhaps one of the most influential and well-known figures in psychology’s history was Sigmund Freud
(Figure 1.4). Freud (1856–1939) was an Austrian neurologist who was fascinated by patients suffering
from “hysteria” and neurosis. Hysteria was an ancient diagnosis for disorders, primarily of women with
a wide variety of symptoms, including physical symptoms and emotional disturbances, none of which
had an apparent physical cause. Freud theorized that many of his patients’ problems arose from the
unconscious mind. In Freud’s view, the unconscious mind was a repository of feelings and urges of which
we have no awareness. Gaining access to the unconscious, then, was crucial to the successful resolution
of the patient’s problems. According to Freud, the unconscious mind could be accessed through dream
analysis, by examinations of the first words that came to people’s minds, and through seemingly innocent
slips of the tongue. Psychoanalytic theory focuses on the role of a person’s unconscious, as well as early
childhood experiences, and this particular perspective dominated clinical psychology for several decades
(Thorne & Henley, 2005).

Figure 1.4 (a) Sigmund Freud was a highly influential figure in the history of psychology. (b) One of his many books,
A General Introduction to Psychoanalysis, shared his ideas about psychoanalytical therapy; it was published in 1922.

Chapter 1 | Introduction to Psychology 11

Freud’s ideas were influential, and you will learn more about them when you study lifespan development,
personality, and therapy. For instance, many therapists believe strongly in the unconscious and the
impact of early childhood experiences on the rest of a person’s life. The method of psychoanalysis, which
involves the patient talking about their experiences and selves, while not invented by Freud, was certainly
popularized by him and is still used today. Many of Freud’s other ideas, however, are controversial.
Drew Westen (1998) argues that many of the criticisms of Freud’s ideas are misplaced, in that they
attack his older ideas without taking into account later writings. Westen also argues that critics fail to
consider the success of the broad ideas that Freud introduced or developed, such as the importance
of childhood experiences in adult motivations, the role of unconscious versus conscious motivations in
driving our behavior, the fact that motivations can cause conflicts that affect behavior, the effects of mental
representations of ourselves and others in guiding our interactions, and the development of personality
over time. Westen identifies subsequent research support for all of these ideas.

More modern iterations of Freud’s clinical approach have been empirically demonstrated to be effective
(Knekt et al., 2008; Shedler, 2010). Some current practices in psychotherapy involve examining unconscious
aspects of the self and relationships, often through the relationship between the therapist and the client.
Freud’s historical significance and contributions to clinical practice merit his inclusion in a discussion of
the historical movements within psychology.


Max Wertheimer (1880–1943), Kurt Koffka (1886–1941), and Wolfgang Köhler (1887–1967) were three
German psychologists who immigrated to the United States in the early 20th century to escape Nazi
Germany. These scholars are credited with introducing psychologists in the United States to various
Gestalt principles. The word Gestalt roughly translates to “whole;” a major emphasis of Gestalt
psychology deals with the fact that although a sensory experience can be broken down into individual
parts, how those parts relate to each other as a whole is often what the individual responds to in
perception. For example, a song may be made up of individual notes played by different instruments, but
the real nature of the song is perceived in the combinations of these notes as they form the melody, rhythm,
and harmony. In many ways, this particular perspective would have directly contradicted Wundt’s ideas
of structuralism (Thorne & Henley, 2005).

Unfortunately, in moving to the United States, these scientists were forced to abandon much of their
work and were unable to continue to conduct research on a large scale. These factors along with the
rise of behaviorism (described next) in the United States prevented principles of Gestalt psychology from
being as influential in the United States as they had been in their native Germany (Thorne & Henley,
2005). Despite these issues, several Gestalt principles are still very influential today. Considering the
human individual as a whole rather than as a sum of individually measured parts became an important
foundation in humanistic theory late in the century. The ideas of Gestalt have continued to influence
research on sensation and perception.

Structuralism, Freud, and the Gestalt psychologists were all concerned in one way or another with
describing and understanding inner experience. But other researchers had concerns that inner experience
could be a legitimate subject of scientific inquiry and chose instead to exclusively study behavior, the
objectively observable outcome of mental processes.


Early work in the field of behavior was conducted by the Russian physiologist Ivan Pavlov (1849–1936).
Pavlov studied a form of learning behavior called a conditioned reflex, in which an animal or human
produced a reflex (unconscious) response to a stimulus and, over time, was conditioned to produce the
response to a different stimulus that the experimenter associated with the original stimulus. The reflex
Pavlov worked with was salivation in response to the presence of food. The salivation reflex could be
elicited using a second stimulus, such as a specific sound, that was presented in association with the

12 Chapter 1 | Introduction to Psychology

This OpenStax book is available for free at

initial food stimulus several times. Once the response to the second stimulus was “learned,” the food
stimulus could be omitted. Pavlov’s “classical conditioning” is only one form of learning behavior studied
by behaviorists.

John B. Watson (1878–1958) was an influential American psychologist whose most famous work occurred
during the early 20th century at Johns Hopkins University (Figure 1.5). While Wundt and James were
concerned with understanding conscious experience, Watson thought that the study of consciousness
was flawed. Because he believed that objective analysis of the mind was impossible, Watson preferred to
focus directly on observable behavior and try to bring that behavior under control. Watson was a major
proponent of shifting the focus of psychology from the mind to behavior, and this approach of observing
and controlling behavior came to be known as behaviorism. A major object of study by behaviorists was
learned behavior and its interaction with inborn qualities of the organism. Behaviorism commonly used
animals in experiments under the assumption that what was learned using animal models could, to some
degree, be applied to human behavior. Indeed, Tolman (1938) stated, “I believe that everything important
in psychology (except … such matters as involve society and words) can be investigated in essence through
the continued experimental and theoretical analysis of the determiners of rat behavior at a choice-point in
a maze.”

Figure 1.5 John B. Watson is known as the father of behaviorism within psychology.

Behaviorism dominated experimental psychology for several decades, and its influence can still be felt
today (Thorne & Henley, 2005). Behaviorism is largely responsible for establishing psychology as a
scientific discipline through its objective methods and especially experimentation. In addition, it is used
in behavioral and cognitive-behavioral therapy. Behavior modification is commonly used in classroom
settings. Behaviorism has also led to research on environmental influences on human behavior.

B. F. Skinner (1904–1990) was an American psychologist (Figure 1.6). Like Watson, Skinner was a
behaviorist, and he concentrated on how behavior was affected by its consequences. Therefore, Skinner
spoke of reinforcement and punishment as major factors in driving behavior. As a part of his research,
Skinner developed a chamber that allowed the careful study of the principles of modifying behavior
through reinforcement and punishment. This device, known as an operant conditioning chamber (or more
familiarly, a Skinner box), has remained a crucial resource for researchers studying behavior (Thorne &
Henley, 2005).

Chapter 1 | Introduction to Psychology 13

Figure 1.6 (a) B. F. Skinner is famous for his research on operant conditioning. (b) Modified versions of the operant
conditioning chamber, or Skinner box, are still widely used in research settings today. (credit a: modification of work
by “Silly rabbit”/Wikimedia Commons)

The Skinner box is a chamber that isolates the subject from the external environment and has a behavior
indicator such as a lever or a button. When the animal pushes the button or lever, the box is able to
deliver a positive reinforcement of the behavior (such as food) or a punishment (such as a noise) or a token
conditioner (such as a light) that is correlated with either the positive reinforcement or punishment.

Skinner’s focus on positive and negative reinforcement of learned behaviors had a lasting influence in
psychology that has waned somewhat since the growth of research in cognitive psychology. Despite
this, conditioned learning is still used in human behavioral modification. Skinner’s two widely read and
controversial popular science books about the value of operant conditioning for creating happier lives
remain as thought-provoking arguments for his approach (Greengrass, 2004).


During the early 20th century, American psychology was dominated by behaviorism and psychoanalysis.
However, some psychologists were uncomfortable with what they viewed as limited perspectives being
so influential to the field. They objected to the pessimism and determinism (all actions driven by the
unconscious) of Freud. They also disliked the reductionism, or simplifying nature, of behaviorism.
Behaviorism is also deterministic at its core, because it sees human behavior as entirely determined by
a combination of genetics and environment. Some psychologists began to form their own ideas that
emphasized personal control, intentionality, and a true predisposition for “good” as important for our self-
concept and our behavior. Thus, humanism emerged. Humanism is a perspective within psychology that
emphasizes the potential for good that is innate to all humans. Two of the most well-known proponents of
humanistic psychology are Abraham Maslow and Carl Rogers (O’Hara, n.d.).

Abraham Maslow (1908–1970) was an American psychologist who is best known for proposing a hierarchy
of human needs in motivating behavior (Figure 1.7). Although this concept will be discussed in more
detail in a later chapter, a brief overview will be provided here. Maslow asserted that so long as basic needs
necessary for survival were met (e.g., food, water, shelter), higher-level needs (e.g., social needs) would
begin to motivate behavior. According to Maslow, the highest-level needs relate to self-actualization, a
process by which we achieve our full potential. Obviously, the focus on the positive aspects of human
nature that are characteristic of the humanistic perspective is evident (Thorne & Henley, 2005). Humanistic
psychologists rejected, on principle, the research approach based on reductionist experimentation in the
tradition of the physical and biological sciences, because it missed the “whole” human being. Beginning
with Maslow and Rogers, there was an insistence on a humanistic research program. This program
has been largely qualitative (not measurement-based), but there exist a number of quantitative research
strains within humanistic psychology, including research on happiness, self-concept, meditation, and the
outcomes of humanistic psychotherapy (Friedman, 2008).

14 Chapter 1 | Introduction to Psychology

This OpenStax book is available for free at

Figure 1.7 Maslow’s hierarchy of needs is shown.

Carl Rogers (1902–1987) was also an American psychologist who, like Maslow, emphasized the potential
for good that exists within all people (Figure 1.8). Rogers used a therapeutic technique known as client-
centered therapy in helping his clients deal with problematic issues that resulted in their seeking
psychotherapy. Unlike a psychoanalytic approach in which the therapist plays an important role in
interpreting what conscious behavior reveals about the unconscious mind, client-centered therapy
involves the patient taking a lead role in the therapy session. Rogers believed that a therapist needed to
display three features to maximize the effectiveness of this particular approach: unconditional positive
regard, genuineness, and empathy. Unconditional positive regard refers to the fact that the therapist
accepts their client for who they are, no matter what he or she might say. Provided these factors, Rogers
believed that people were more than capable of dealing with and working through their own issues
(Thorne & Henley, 2005).

Figure 1.8 Carl Rogers, shown in this portrait, developed a client-centered therapy method that has been influential
in clinical settings. (credit: “Didius”/Wikimedia Commons)

Humanism has been influential to psychology as a whole. Both Maslow and Rogers are well-known names

Chapter 1 | Introduction to Psychology 15

among students of psychology (you will read more about both later in this text), and their ideas have
influenced many scholars. Furthermore, Rogers’ client-centered approach to therapy is still commonly
used in psychotherapeutic settings today (O’hara, n.d.)

View a brief video of Carl Rogers describing his therapeutic approach (
crogers1) to learn more.


Behaviorism’s emphasis on objectivity and focus on external behavior had pulled psychologists’ attention
away from the mind for a prolonged period of time. The early work of the humanistic psychologists
redirected attention to the individual human as a whole, and as a conscious and self-aware being. By the
1950s, new disciplinary perspectives in linguistics, neuroscience, and computer science were emerging,
and these areas revived interest in the mind as a focus of scientific inquiry. This particular perspective
has come to be known as the cognitive revolution (Miller, 2003). By 1967, Ulric Neisser published the first
textbook entitled Cognitive Psychology, which served as a core text in cognitive psychology courses around
the country (Thorne & Henley, 2005).

Although no one person is entirely responsible for starting the cognitive revolution, Noam Chomsky
was very influential in the early days of this movement (Figure 1.9). Chomsky (1928–), an American
linguist, was dissatisfied with the influence that behaviorism had had on psychology. He believed that
psychology’s focus on behavior was short-sighted and that the field had to re-incorporate mental
functioning into its purview if it were to offer any meaningful contributions to understanding behavior
(Miller, 2003).

Figure 1.9 Noam Chomsky was very influential in beginning the cognitive revolution. In 2010, this mural honoring
him was put up in Philadelphia, Pennsylvania. (credit: Robert Moran)

European psychology had never really been as influenced by behaviorism as had American psychology;
and thus, the cognitive revolution helped reestablish lines of communication between European
psychologists and their American counterparts. Furthermore, psychologists began to cooperate with
scientists in other fields, like anthropology, linguistics, computer science, and neuroscience, among others.
This interdisciplinary approach often was referred to as the cognitive sciences, and the influence and
prominence of this particular perspective resonates in modern-day psychology (Miller, 2003).


16 Chapter 1 | Introduction to Psychology

This OpenStax book is available for free at

Feminist Psychology

The science of psychology has had an impact on human wellbeing, both positive and negative. The dominant
influence of Western, white, and male academics in the early history of psychology meant that psychology
developed with the biases inherent in those individuals, which often had negative consequences for members
of society who were not white or male. Women, members of ethnic minorities in both the United States
and other countries, and individuals with sexual orientations other than straight had difficulties entering the
field of psychology and therefore influencing its development. They also suffered from the attitudes of white
male psychologists who were not immune to the nonscientific attitudes prevalent in the society in which they
developed and worked. Until the 1960s, the science of psychology was largely a “womanless” psychology
(Crawford & Marecek, 1989), meaning that few women were able to practice psychology, so they had little
influence on what was studied. In addition, the experimental subjects of psychology were mostly men, which
resulted from underlying assumptions that gender had no influence on psychology and that women were not
of sufficient interest to study.

An article by Naomi Weisstein, first published in 1968 (Weisstein, 1993), stimulated a feminist revolution
in psychology by presenting a critique of psychology as a science. She also specifically criticized male
psychologists for constructing the psychology of women entirely out of their own cultural biases and without
careful experimental tests to verify any of their characterizations of women. Weisstein used, as examples,
statements by prominent psychologists in the 1960s, such as this quote by Bruno Bettleheim: “We must start
with the realization that, as much as women want to be good scientists or engineers, they want first and
foremost to be womanly companions of men and to be mothers.” Weisstein’s critique formed the foundation
for the subsequent development of a feminist psychology that attempted to be free of the influence of male
cultural biases on our knowledge of the psychology of women.

Crawford & Marecek (1989) identify several feminist approaches to psychology that can be described as
feminist psychology. These include re-evaluating and discovering the contributions of women to the history
of psychology, studying psychological gender differences, and questioning the male bias present across the
practice of the scientific approach to knowledge.


Culture has important impacts on individuals and social psychology, yet the effects of culture on
psychology are under-studied. There is a risk that psychological theories and data derived from white,
American settings could be assumed to apply to individuals and social groups from other cultures and this
is unlikely to be true (Betancourt & López, 1993). One weakness in the field of cross-cultural psychology
is that in looking for differences in psychological attributes across cultures, there remains a need to go
beyond simple descriptive statistics (Betancourt & López, 1993). In this sense, it has remained a descriptive
science, rather than one seeking to determine cause and effect. For example, a study of characteristics
of individuals seeking treatment for a binge eating disorder in Hispanic American, African American,
and Caucasian American individuals found significant differences between groups (Franko et al., 2012).
The study concluded that results from studying any one of the groups could not be extended to the
other groups, and yet potential causes of the differences were not measured. Multicultural psychologists
develop theories and conduct research with diverse populations, typically within one country. Cross-
cultural psychologists compare populations across countries, such as participants from the United States
compared to participants from China.

In 1920, Francis Cecil Sumner was the first African American to receive a PhD in psychology in the United
States. Sumner established a psychology degree program at Howard University, leading to the education
of a new generation of African American psychologists (Black, Spence, and Omari, 2004). Much of the
work of early psychologists from diverse backgrounds was dedicated to challenging intelligence testing
and promoting innovative educational methods for children. George I. Sanchez contested such testing with


Chapter 1 | Introduction to Psychology 17

Mexican American children. As a psychologist of Mexican heritage, he pointed out that the language and
cultural barriers in testing were keeping children from equal opportunities (Guthrie, 1998). By 1940, he was
teaching with his doctoral degree at University of Texas at Austin and challenging segregated educational
practices (Romo, 1986).

Two famous African American researchers and psychologists are Mamie Phipps Clark and her husband,
Kenneth Clark. They are best known for their studies conducted on African American children and doll
preference, research that was instrumental in the Brown v. Board of Education Supreme Court desegregation
case. The Clarks applied their research to social services and opened the first child guidance center in
Harlem (American Psychological Association, 2019).

Listen to the podcast below describing the Clarks’ research and impact on the Supreme Court decision.

Listen to a podcast about the influence of an African American’s psychology research on the
historic Brown v. Board of Education civil rights case ( to learn more.

The American Psychological Association has several ethnically based organizations for professional
psychologists that facilitate interactions among members. Since psychologists belonging to specific ethnic
groups or cultures have the most interest in studying the psychology of their communities, these
organizations provide an opportunity for the growth of research on the interplay between culture and


Although rarely given credit, women have been contributing to psychology since its inception as a field of
study. In 1894, Margaret Floy Washburn was the first woman awarded the doctoral degree in psychology.
She wrote The Animal Mind: A Textbook of Comparative Psychology, and it was the standard in the field for
over 20 years. In the mid 1890s, Mary Whiton Calkins completed all requirements toward the PhD in
psychology, but Harvard University refused to award her that degree because she was a woman. She had
been taught and mentored by William James, who tried and failed to convince Harvard to award her the
doctoral degree. Her memory research studied primacy and recency (Madigan & O’Hara, 1992), and she
also wrote about how structuralism and functionalism both explained self-psychology (Calkins, 1906).

Another influential woman, Mary Cover Jones, conducted a study she considered to be a sequel to
John B. Watson’s study of Little Albert (you’ll learn about this study in the chapter on Learning). Jones
unconditioned fear in Little Peter, who had been afraid of rabbits (Jones, 1924).

Ethnic minority women contributing to the field of psychology include Martha Bernal and Inez Beverly
Prosser; their studies were related to education. Bernal, the first Latina to earn her doctoral degree in
psychology (1962) conducted much of her research with Mexican American children. Prosser was the first
African American woman awarded the PhD in 1933 at the University of Cincinnati (Benjamin, Henry, &
McMahon, 2005).


18 Chapter 1 | Introduction to Psychology

This OpenStax book is available for free at

1.3 Contemporary Psychology

Learning Objectives

By the end of this section, you will be able to:
• Appreciate the diversity of interests and foci within psychology
• Understand basic interests and applications in each of the described areas of psychology
• Demonstrate familiarity with some of the major concepts or important figures in each of the

described areas of psychology

Contemporary psychology is a diverse field that is influenced by all of the historical perspectives described
in the preceding section. Reflective of the discipline’s diversity is the diversity seen within the American
Psychological Association (APA). The APA is a professional organization representing psychologists in
the United States. The APA is the largest organization of psychologists in the world, and its mission is to
advance and disseminate psychological knowledge for the betterment of people. There are 56 divisions
within the APA, representing a wide variety of specialties that range from Societies for the Psychology of
Religion and Spirituality to Exercise and Sport Psychology to Behavioral Neuroscience and Comparative
Psychology. Reflecting the diversity of the field of psychology itself, members, affiliate members, and
associate members span the spectrum from students to doctoral-level psychologists, and come from a
variety of places including educational settings, criminal justice, hospitals, the armed forces, and industry
(American Psychological Association, 2014). G. Stanley Hall was the first president of the APA. Before
he earned his doctoral degree, he was an adjunct instructor at Wilberforce University, a historically
black college/university (HBCU), while serving as faculty at Antioch College. Hall went on to work
under William James, earning his PhD. Eventually, he became the first president of Clark University in
Massachusetts when it was founded (Pickren & Rutherford, 2010).

The Association for Psychological Science (APS) was founded in 1988 and seeks to advance the scientific
orientation of psychology. Its founding resulted from disagreements between members of the scientific
and clinical branches of psychology within the APA. The APS publishes five research journals and
engages in education and advocacy with funding agencies. A significant proportion of its members
are international, although the majority is located in the United States. Other organizations provide
networking and collaboration opportunities for professionals of several ethnic or racial groups working
in psychology, such as the National Latina/o Psychological Association (NLPA), the Asian American
Psychological Association (AAPA), the Association of Black Psychologists (ABPsi), and the Society of
Indian Psychologists (SIP). Most of these groups are also dedicated to studying psychological and social
issues within their specific communities.

This section will provide an overview of the major subdivisions within psychology today in the order
in which they are introduced throughout the remainder of this textbook. This is not meant to be an
exhaustive listing, but it will provide insight into the major areas of research and practice of modern-day

Please visit this website about the divisions within the APA ( to
learn more.

View these student resources ( also provided by the APA.


Chapter 1 | Introduction to Psychology 19


As the name suggests, biopsychology explores how our biology influences our behavior. While biological
psychology is a broad field, many biological psychologists want to understand how the structure and
function of the nervous system is related to behavior (Figure 1.10). As such, they often combine the
research strategies of both psychologists and physiologists to accomplish this goal (as discussed in Carlson,

Figure 1.10 Biological psychologists study how the structure and function of the nervous system generate behavior.

The research interests of biological psychologists span a number of domains, including but not limited
to, sensory and motor systems, sleep, drug use and abuse, ingestive behavior, reproductive behavior,
neurodevelopment, plasticity of the nervous system, and biological correlates of psychological disorders.
Given the broad areas of interest falling under the purview of biological psychology, it will probably
come as no surprise that individuals from all sorts of backgrounds are involved in this research, including
biologists, medical professionals, physiologists, and chemists. This interdisciplinary approach is often
referred to as neuroscience, of which biological psychology is a component (Carlson, 2013).

While biopsychology typically focuses on the immediate causes of behavior based in the physiology of a
human or other animal, evolutionary psychology seeks to study the ultimate biological causes of behavior.
To the extent that a behavior is impacted by genetics, a behavior, like any anatomical characteristic of a
human or animal, will demonstrate adaption to its surroundings. These surroundings include the physical
environment and, since interactions between organisms can be important to survival and reproduction, the
social environment. The study of behavior in the context of evolution has its origins with Charles Darwin,
the co-discoverer of the theory of evolution by natural selection. Darwin was well aware that behaviors
should be adaptive and wrote books titled, The Descent of Man (1871) and The Expression of the Emotions in
Man and Animals (1872), to explore this field.

Evolutionary psychology, and specifically, the evolutionary psychology of humans, has enjoyed a
resurgence in recent decades. To be subject to evolution by natural selection, a behavior must have a
significant genetic cause. In general, we expect all human cultures to express a behavior if it is caused
genetically, since the genetic differences among human groups are small. The approach taken by most
evolutionary psychologists is to predict the outcome of a behavior in a particular situation based on

20 Chapter 1 | Introduction to Psychology

This OpenStax book is available for free at

evolutionary theory and then to make observations, or conduct experiments, to determine whether the
results match the theory. It is important to recognize that these types of studies are not strong evidence
that a behavior is adaptive, since they lack information that the behavior is in some part genetic and not
entirely cultural (Endler, 1986). Demonstrating that a trait, especially in humans, is naturally selected is
extraordinarily difficult; perhaps for this reason, some evolutionary psychologists are content to assume
the behaviors they study have genetic determinants (Confer et al., 2010).

One other drawback of evolutionary psychology is that the traits that we possess now evolved under
environmental and social conditions far back in human history, and we have a poor understanding of what
these conditions were. This makes predictions about what is adaptive for a behavior difficult. Behavioral
traits need not be adaptive under current conditions, only under the conditions of the past when they
evolved, about which we can only hypothesize.

There are many areas of human behavior for which evolution can make predictions. Examples include
memory, mate choice, relationships between kin, friendship and cooperation, parenting, social
organization, and status (Confer et al., 2010).

Evolutionary psychologists have had success in finding experimental correspondence between
observations and expectations. In one example, in a study of mate preference differences between men and
women that spanned 37 cultures, Buss (1989) found that women valued earning potential factors greater
than men, and men valued potential reproductive factors (youth and attractiveness) greater than women in
their prospective mates. In general, the predictions were in line with the predictions of evolution, although
there were deviations in some cultures.


Scientists interested in both physiological aspects of sensory systems as well as in the psychological
experience of sensory information work within the area of sensation and perception (Figure 1.11). As
such, sensation and perception research is also quite interdisciplinary. Imagine walking between buildings
as you move from one class to another. You are inundated with sights, sounds, touch sensations, and
smells. You also experience the temperature of the air around you and maintain your balance as you make
your way. These are all factors of interest to someone working in the domain of sensation and perception.

Figure 1.11 When you look at this image, you may see a duck or a rabbit. The sensory information remains the
same, but your perception can vary dramatically.

As described in a later chapter that focuses on the results of studies in sensation and perception, our
experience of our world is not as simple as the sum total of all of the sensory information (or sensations)
together. Rather, our experience (or perception) is complex and is influenced by where we focus our
attention, our previous experiences, and even our cultural backgrounds.


As mentioned in the previous section, the cognitive revolution created an impetus for psychologists to
focus their attention on better understanding the mind and mental processes that underlie behavior. Thus,
cognitive psychology is the area of psychology that focuses on studying cognitions, or thoughts, and

Chapter 1 | Introduction to Psychology 21

their relationship to our experiences and our actions. Like biological psychology, cognitive psychology is
broad in its scope and often involves collaborations among people from a diverse range of disciplinary
backgrounds. This has led some to coin the term cognitive science to describe the interdisciplinary nature
of this area of research (Miller, 2003).

Cognitive psychologists have research interests that span a spectrum of topics, ranging from attention to
problem solving to language to memory. The approaches used in studying these topics are equally diverse.
Given such diversity, cognitive psychology is not captured in one chapter of this text per se; rather, various
concepts related to cognitive psychology will be covered in relevant portions of the chapters in this text
on sensation and perception, thinking and intelligence, memory, lifespan development, social psychology,
and therapy.


Developmental psychology is the scientific study of development across a lifespan. Developmental
psychologists are interested in processes related to physical maturation. However, their focus is not limited
to the physical changes associated with aging, as they also focus on changes in cognitive skills, moral
reasoning, social behavior, and other psychological attributes.

Early developmental psychologists focused primarily on changes that occurred through reaching
adulthood, providing enormous insight into the differences in physical, cognitive, and social capacities
that exist between very young children and adults. For instance, research by Jean Piaget (Figure 1.12)
demonstrated that very young children do not demonstrate object permanence. Object permanence refers
to the understanding that physical things continue to exist, even if they are hidden from us. If you were to
show an adult a toy, and then hide it behind a curtain, the adult knows that the toy still exists. However,
very young infants act as if a hidden object no longer exists. The age at which object permanence is
achieved is somewhat controversial (Munakata, McClelland, Johnson, and Siegler, 1997).

Figure 1.12 Jean Piaget is famous for his theories regarding changes in cognitive ability that occur as we move from
infancy to adulthood.

While Piaget was focused on cognitive changes during infancy and childhood as we move to adulthood,
there is an increasing interest in extending research into the changes that occur much later in life. This
may be reflective of changing population demographics of developed nations as a whole. As more and
more people live longer lives, the number of people of advanced age will continue to increase. Indeed,
it is estimated that there were just over 40 million people aged 65 or older living in the United States
in 2010. However, by 2020, this number is expected to increase to about 55 million. By the year 2050, it
is estimated that nearly 90 million people in this country will be 65 or older (Department of Health and

22 Chapter 1 | Introduction to Psychology

This OpenStax book is available for free at

Human Services, n.d.).


Personality psychology focuses on patterns of thoughts and behaviors that make each individual unique.
Several individuals (e.g., Freud and Maslow) that we have already discussed in our historical overview of
psychology, and the American psychologist Gordon Allport, contributed to early theories of personality.
These early theorists attempted to explain how an individual’s personality develops from his or her
given perspective. For example, Freud proposed that personality arose as conflicts between the conscious
and unconscious parts of the mind were carried out over the lifespan. Specifically, Freud theorized that
an individual went through various psychosexual stages of development. According to Freud, adult
personality would result from the resolution of various conflicts that centered on the migration of
erogenous (or sexual pleasure-producing) zones from the oral (mouth) to the anus to the phallus to the
genitals. Like many of Freud’s theories, this particular idea was controversial and did not lend itself to
experimental tests (Person, 1980).

More recently, the study of personality has taken on a more quantitative approach. Rather than explaining
how personality arises, research is focused on identifying personality traits, measuring these traits, and
determining how these traits interact in a particular context to determine how a person will behave in
any given situation. Personality traits are relatively consistent patterns of thought and behavior, and
many have proposed that five trait dimensions are sufficient to capture the variations in personality seen
across individuals. These five dimensions are known as the “Big Five” or the Five Factor model, and
include dimensions of conscientiousness, agreeableness, neuroticism, openness, and extraversion (Figure
1.13). Each of these traits has been demonstrated to be relatively stable over the lifespan (e.g., Rantanen,
Metsäpelto, Feldt, Pulkinnen, and Kokko, 2007; Soldz & Vaillant, 1999; McCrae & Costa, 2008) and is
influenced by genetics (e.g., Jang, Livesly, and Vernon, 1996).

Chapter 1 | Introduction to Psychology 23

Figure 1.13 Each of the dimensions of the Five Factor model is shown in this figure. The provided description would
describe someone who scored highly on that given dimension. Someone with a lower score on a given dimension
could be described in opposite terms.


Social psychology focuses on how we interact with and relate to others. Social psychologists conduct
research on a wide variety of topics that include differences in how we explain our own behavior versus
how we explain the behaviors of others, prejudice, and attraction, and how we resolve interpersonal
conflicts. Social psychologists have also sought to determine how being among other people changes our
own behavior and patterns of thinking.

There are many interesting examples of social psychological research, and you will read about many of
these in a later chapter of this textbook. Until then, you will be introduced to one of the most controversial
psychological studies ever conducted. Stanley Milgram was an American social psychologist who is
most famous for research that he conducted on obedience. After the holocaust, in 1961, a Nazi war
criminal, Adolf Eichmann, who was accused of committing mass atrocities, was put on trial. Many people
wondered how German soldiers were capable of torturing prisoners in concentration camps, and they
were unsatisfied with the excuses given by soldiers that they were simply following orders. At the
time, most psychologists agreed that few people would be willing to inflict such extraordinary pain and
suffering, simply because they were obeying orders. Milgram decided to conduct research to determine
whether or not this was true (Figure 1.14). As you will read later in the text, Milgram found that nearly
two-thirds of his participants were willing to deliver what they believed to be lethal shocks to another

24 Chapter 1 | Introduction to Psychology

This OpenStax book is available for free at

person, simply because they were instructed to do so by an authority figure (in this case, a man dressed in
a lab coat). This was in spite of the fact that participants received payment for simply showing up for the
research study and could have chosen not to inflict pain or more serious consequences on another person
by withdrawing from the study. No one was actually hurt or harmed in any way, Milgram’s experiment
was a clever ruse that took advantage of research confederates, those who pretend to be participants in
a research study who are actually working for the researcher and have clear, specific directions on how
to behave during the research study (Hock, 2009). Milgram’s and others’ studies that involved deception
and potential emotional harm to study participants catalyzed the development of ethical guidelines for
conducting psychological research that discourage the use of deception of research subjects, unless it can
be argued not to cause harm and, in general, requiring informed consent of participants.

Figure 1.14 Stanley Milgram’s research demonstrated just how far people will go in obeying orders from an authority
figure. This advertisement was used to recruit subjects for his research.


Industrial-Organizational psychology (I-O psychology) is a subfield of psychology that applies
psychological theories, principles, and research findings in industrial and organizational settings. I-O
psychologists are often involved in issues related to personnel management, organizational structure,
and workplace environment. Businesses often seek the aid of I-O psychologists to make the best hiring
decisions as well as to create an environment that results in high levels of employee productivity and
efficiency. In addition to its applied nature, I-O psychology also involves conducting scientific research on
behavior within I-O settings (Riggio, 2013).

Chapter 1 | Introduction to Psychology 25


Health psychology focuses on how health is affected by the interaction of biological, psychological, and
sociocultural factors. This particular approach is known as the biopsychosocial model (Figure 1.15).
Health psychologists are interested in helping individuals achieve better health through public policy,
education, intervention, and research. Health psychologists might conduct research that explores the
relationship between one’s genetic makeup, patterns of behavior, relationships, psychological stress,
and health. They may research effective ways to motivate people to address patterns of behavior that
contribute to poorer health (MacDonald, 2013).

Figure 1.15 The biopsychosocial model suggests that health/illness is determined by an interaction of these three


Researchers in sport and exercise psychology study the psychological aspects of sport performance,
including motivation and performance anxiety, and the effects of sport on mental and emotional
wellbeing. Research is also conducted on similar topics as they relate to physical exercise in general. The
discipline also includes topics that are broader than sport and exercise but that are related to interactions
between mental and physical performance under demanding conditions, such as fire fighting, military
operations, artistic performance, and surgery.


Clinical psychology is the area of psychology that focuses on the diagnosis and treatment of psychological
disorders and other problematic patterns of behavior. As such, it is generally considered to be a more
applied area within psychology; however, some clinicians are also actively engaged in scientific research.
Counseling psychology is a similar discipline that focuses on emotional, social, vocational, and health-
related outcomes in individuals who are considered psychologically healthy.

As mentioned earlier, both Freud and Rogers provided perspectives that have been influential in shaping
how clinicians interact with people seeking psychotherapy. While aspects of the psychoanalytic theory are
still found among some of today’s therapists who are trained from a psychodynamic perspective, Roger’s
ideas about client-centered therapy have been especially influential in shaping how many clinicians
operate. Furthermore, both behaviorism and the cognitive revolution have shaped clinical practice in the
forms of behavioral therapy, cognitive therapy, and cognitive-behavioral therapy (Figure 1.16). Issues

26 Chapter 1 | Introduction to Psychology

This OpenStax book is available for free at

related to the diagnosis and treatment of psychological disorders and problematic patterns of behavior will
be discussed in detail in later chapters of this textbook.

Figure 1.16 Cognitive-behavioral therapists take cognitive processes and behaviors into account when providing
psychotherapy. This is one of several strategies that may be used by practicing clinical psychologists.

By far, this is the area of psychology that receives the most attention in popular media, and many people
mistakenly assume that all psychology is clinical psychology.


Forensic psychology is a branch of psychology that deals questions of psychology as they arise in the
context of the justice system. For example, forensic psychologists (and forensic psychiatrists) will assess
a person’s competency to stand trial, assess the state of mind of a defendant, act as consultants on
child custody cases, consult on sentencing and treatment recommendations, and advise on issues such as
eyewitness testimony and children’s testimony (American Board of Forensic Psychology, 2014). In these
capacities, they will typically act as expert witnesses, called by either side in a court case to provide their
research- or experience-based opinions. As expert witnesses, forensic psychologists must have a good
understanding of the law and provide information in the context of the legal system rather than just within
the realm of psychology. Forensic psychologists are also used in the jury selection process and witness
preparation. They may also be involved in providing psychological treatment within the criminal justice
system. Criminal profilers are a relatively small proportion of psychologists that act as consultants to law

1.4 Careers in Psychology

Learning Objectives

By the end of this section, you will be able to:
• Understand educational requirements for careers in academic settings
• Understand the demands of a career in an academic setting
• Understand career options outside of academic settings

Psychologists can work in many different places doing many different things. In general, anyone wishing
to continue a career in psychology at a 4-year institution of higher education will have to earn a doctoral
degree in psychology for some specialties and at least a master’s degree for others. In most areas of
psychology, this means earning a PhD in a relevant area of psychology. Literally, PhD refers to a doctor
of philosophy degree, but here, philosophy does not refer to the field of philosophy per se. Rather,

Chapter 1 | Introduction to Psychology 27

philosophy in this context refers to many different disciplinary perspectives that would be housed in a
traditional college of liberal arts and sciences.

The requirements to earn a PhD vary from country to country and even from school to school, but usually,
individuals earning this degree must complete a dissertation. A dissertation is essentially a long research
paper or bundled published articles describing research that was conducted as a part of the candidate’s
doctoral training. In the United States, a dissertation generally has to be defended before a committee of
expert reviewers before the degree is conferred (Figure 1.17).

Figure 1.17 Doctoral degrees are generally conferred in formal ceremonies involving special attire and rites. (credit:
Public Affairs Office Fort Wainwright)

Once someone earns a PhD, they may seek a faculty appointment at a college or university. Being on the
faculty of a college or university often involves dividing time between teaching, research, and service to
the institution and profession. The amount of time spent on each of these primary responsibilities varies
dramatically from school to school, and it is not uncommon for faculty to move from place to place in
search of the best personal fit among various academic environments. The previous section detailed some
of the major areas that are commonly represented in psychology departments around the country; thus,
depending on the training received, an individual could be anything from a biological psychologist to a
clinical psychologist in an academic setting (Figure 1.18).

Figure 1.18 Individuals earning a PhD in psychology have a range of employment options.

28 Chapter 1 | Introduction to Psychology

This OpenStax book is available for free at

Use this interactive tool and explore different careers in psychology based on degree levels
( to learn more.


Often times, schools offer more courses in psychology than their full-time faculty can teach. In these cases,
it is not uncommon to bring in an adjunct faculty member or instructor. Adjunct faculty members and
instructors usually have an advanced degree in psychology, but they often have primary careers outside
of academia and serve in this role as a secondary job. Alternatively, they may not hold the doctoral
degree required by most 4-year institutions and use these opportunities to gain experience in teaching.
Furthermore, many 2-year colleges and schools need faculty to teach their courses in psychology. In
general, many of the people who pursue careers at these institutions have master’s degrees in psychology,
although some PhDs make careers at these institutions as well.

Some people earning PhDs may enjoy research in an academic setting. However, they may not be
interested in teaching. These individuals might take on faculty positions that are exclusively devoted
to conducting research. This type of position would be more likely an option at large, research-focused

In some areas in psychology, it is common for individuals who have recently earned their PhD to seek out
positions in postdoctoral training programs that are available before going on to serve as faculty. In most
cases, young scientists will complete one or two postdoctoral programs before applying for a full-time
faculty position. Postdoctoral training programs allow young scientists to further develop their research
programs and broaden their research skills under the supervision of other professionals in the field.


Individuals who wish to become practicing clinical psychologists have another option for earning a
doctoral degree, which is known as a PsyD. A PsyD is a doctor of psychology degree that is increasingly
popular among individuals interested in pursuing careers in clinical psychology. PsyD programs generally
place less emphasis on research-oriented skills and focus more on application of psychological principles
in the clinical context (Norcorss & Castle, 2002).

Regardless of whether earning a PhD or PsyD, in most states, an individual wishing to practice as
a licensed clinical or counseling psychologist may complete postdoctoral work under the supervision
of a licensed psychologist. Within the last few years, however, several states have begun to remove
this requirement, which would allow people to get an earlier start in their careers (Munsey, 2009).
After an individual has met the state requirements, their credentials are evaluated to determine whether
they can sit for the licensure exam. Only individuals that pass this exam can call themselves licensed
clinical or counseling psychologists (Norcross, n.d.). Licensed clinical or counseling psychologists can
then work in a number of settings, ranging from private clinical practice to hospital settings. It should
be noted that clinical psychologists and psychiatrists do different things and receive different types of
education. While both can conduct therapy and counseling, clinical psychologists have a PhD or a PsyD,
whereas psychiatrists have a doctor of medicine degree (MD). As such, licensed clinical psychologists can
administer and interpret psychological tests, while psychiatrists can prescribe medications.

Individuals earning a PhD can work in a variety of settings, depending on their areas of specialization.
For example, someone trained as a biopsychologist might work in a pharmaceutical company to help test
the efficacy of a new drug. Someone with a clinical background might become a forensic psychologist and
work within the legal system to make recommendations during criminal trials and parole hearings, or


Chapter 1 | Introduction to Psychology 29

serve as an expert in a court case.

While earning a doctoral degree in psychology is a lengthy process, usually taking between 5–6 years of
graduate study (DeAngelis, 2010), there are a number of careers that can be attained with a master’s degree
in psychology. People who wish to provide psychotherapy can become licensed to serve as various types
of professional counselors (Hoffman, 2012). Relevant master’s degrees are also sufficient for individuals
seeking careers as school psychologists (National Association of School Psychologists, n.d.), in some
capacities related to sport psychology (American Psychological Association, 2014), or as consultants in
various industrial settings (Landers, 2011, June 14). Undergraduate coursework in psychology may be
applicable to other careers such as psychiatric social work or psychiatric nursing, where assessments and
therapy may be a part of the job.

As mentioned in the opening section of this chapter, an undergraduate education in psychology is
associated with a knowledge base and skill set that many employers find quite attractive. It should come as
no surprise, then, that individuals earning bachelor’s degrees in psychology find themselves in a number
of different careers, as shown in Table 1.1. Examples of a few such careers can involve serving as case
managers, working in sales, working in human resource departments, and teaching in high schools. The
rapidly growing realm of healthcare professions is another field in which an education in psychology is
helpful and sometimes required. For example, the Medical College Admission Test (MCAT) exam that
people must take to be admitted to medical school now includes a section on the psychological foundations
of behavior.

Top Occupations Employing Graduates with a BA in Psychology (Fogg, Harrington, Harrington,
& Shatkin, 2012)

Ranking Occupation

1 Mid- and top-level management (executive, administrator)

2 Sales

3 Social work

4 Other management positions

5 Human resources (personnel, training)

6 Other administrative positions

7 Insurance, real estate, business

8 Marketing and sales

9 Healthcare (nurse, pharmacist, therapist)

10 Finance (accountant, auditor)

Table 1.1

30 Chapter 1 | Introduction to Psychology

This OpenStax book is available for free at

The APA provides career information ( about various areas of


Chapter 1 | Introduction to Psychology 31

American Psychological Association (APA)



biopsychosocial model

clinical psychology

cognitive psychology

counseling psychology

developmental psychology


empirical method

forensic psychology





personality psychology

personality trait


postdoctoral training program

psychoanalytic theory



Key Terms

professional organization representing psychologists in the
United States

focus on observing and controlling behavior

study of how biology influences behavior

perspective that asserts that biology, psychology, and social factors interact to
determine an individual’s health

area of psychology that focuses on the diagnosis and treatment of psychological
disorders and other problematic patterns of behavior

study of cognitions, or thoughts, and their relationship to experiences and actions

area of psychology that focuses on improving emotional, social, vocational, and
other aspects of the lives of psychologically healthy individuals

scientific study of development across a lifespan

long research paper about research that was conducted as a part of the candidate’s doctoral

method for acquiring knowledge based on observation, including experimentation,
rather than a method based only on forms of logical argument or previous authorities

area of psychology that applies the science and practice of psychology to issues
within and related to the justice system

focused on how mental activities helped an organism adapt to its environment

perspective within psychology that emphasizes the potential for good that is innate to all

process by which someone examines their own conscious experience in an attempt to
break it into its component parts

suffix that denotes “scientific study of”

study of patterns of thoughts and behaviors that make each individual unique

consistent pattern of thought and behavior

(doctor of philosophy) doctoral degree conferred in many disciplinary perspectives housed in a
traditional college of liberal arts and sciences

allows programs and broaden their research skills under the supervision
of other professionals in the field

focus on the role of the unconscious in affecting conscious behavior

scientific study of the mind and behavior

(doctor of psychology) doctoral degree that places less emphasis on research-oriented skills and
focuses more on application of psychological principles in the clinical context

32 Chapter 1 | Introduction to Psychology

This OpenStax book is available for free at

sport and exercise psychology


area of psychology that focuses on the interactions between mental and
emotional factors and physical performance in sports, exercise, and other activities

understanding the conscious experience through introspection


1.1 What Is Psychology?
Psychology is defined as the scientific study of mind and behavior. Students of psychology develop critical
thinking skills, become familiar with the scientific method, and recognize the complexity of behavior.

1.2 History of Psychology
Before the time of Wundt and James, questions about the mind were considered by philosophers.
However, both Wundt and James helped create psychology as a distinct scientific discipline. Wundt was a
structuralist, which meant he believed that our cognitive experience was best understood by breaking that
experience into its component parts. He thought this was best accomplished by introspection.

William James was the first American psychologist, and he was a proponent of functionalism. This
particular perspective focused on how mental activities served as adaptive responses to an organism’s
environment. Like Wundt, James also relied on introspection; however, his research approach also
incorporated more objective measures as well.

Sigmund Freud believed that understanding the unconscious mind was absolutely critical to understand
conscious behavior. This was especially true for individuals that he saw who suffered from various
hysterias and neuroses. Freud relied on dream analysis, slips of the tongue, and free association as means
to access the unconscious. Psychoanalytic theory remained a dominant force in clinical psychology for
several decades.

Gestalt psychology was very influential in Europe. Gestalt psychology takes a holistic view of an
individual and his experiences. As the Nazis came to power in Germany, Wertheimer, Koffka, and Köhler
immigrated to the United States. Although they left their laboratories and their research behind, they did
introduce America to Gestalt ideas. Some of the principles of Gestalt psychology are still very influential
in the study of sensation and perception.

One of the most influential schools of thought within psychology’s history was behaviorism. Behaviorism
focused on making psychology an objective science by studying overt behavior and deemphasizing the
importance of unobservable mental processes. John Watson is often considered the father of behaviorism,
and B. F. Skinner’s contributions to our understanding of principles of operant conditioning cannot be

As behaviorism and psychoanalytic theory took hold of so many aspects of psychology, some began to
become dissatisfied with psychology’s picture of human nature. Thus, a humanistic movement within
psychology began to take hold. Humanism focuses on the potential of all people for good. Both Maslow
and Rogers were influential in shaping humanistic psychology.

During the 1950s, the landscape of psychology began to change. A science of behavior began to shift back
to its roots of focus on mental processes. The emergence of neuroscience and computer science aided this
transition. Ultimately, the cognitive revolution took hold, and people came to realize that cognition was
crucial to a true appreciation and understanding of behavior.

1.3 Contemporary Psychology
Psychology is a diverse discipline that is made up of several major subdivisions with unique perspectives.
Biological psychology involves the study of the biological bases of behavior. Sensation and perception
refer to the area of psychology that is focused on how information from our sensory modalities is
received, and how this information is transformed into our perceptual experiences of the world around
us. Cognitive psychology is concerned with the relationship that exists between thought and behavior,

Chapter 1 | Introduction to Psychology 33

and developmental psychologists study the physical and cognitive changes that occur throughout one’s
lifespan. Personality psychology focuses on individuals’ unique patterns of behavior, thought, and
emotion. Industrial and organizational psychology, health psychology, sport and exercise psychology,
forensic psychology, and clinical psychology are all considered applied areas of psychology. Industrial
and organizational psychologists apply psychological concepts to I-O settings. Health psychologists look
for ways to help people live healthier lives, and clinical psychology involves the diagnosis and treatment
of psychological disorders and other problematic behavioral patterns. Sport and exercise psychologists
study the interactions between thoughts, emotions, and physical performance in sports, exercise, and other
activities. Forensic psychologists carry out activities related to psychology in association with the justice

1.4 Careers in Psychology
Generally, academic careers in psychology require doctoral degrees. However, there are a number of
nonacademic career options for people who have master’s degrees in psychology. While people with
bachelor’s degrees in psychology have more limited psychology-related career options, the skills acquired
as a function of an undergraduate education in psychology are useful in a variety of work contexts.

Review Questions

1. Which of the following was mentioned as a
skill to which psychology students would be

a. critical thinking
b. use of the scientific method
c. critical evaluation of sources of information
d. all of the above

2. Before psychology became a recognized
academic discipline, matters of the mind were
undertaken by those in ________.

a. biology
b. chemistry
c. philosophy
d. physics

3. In the scientific method, a hypothesis is a(n)

a. observation
b. measurement
c. test
d. proposed explanation

4. Based on your reading, which theorist would
have been most likely to agree with this statement:
Perceptual phenomena are best understood as a
combination of their components.

a. William James
b. Max Wertheimer
c. Carl Rogers
d. Noam Chomsky

5. ________ is most well-known for proposing his
hierarchy of needs.

a. Noam Chomsky
b. Carl Rogers
c. Abraham Maslow
d. Sigmund Freud

6. Rogers believed that providing genuineness,
empathy, and ________ in the therapeutic
environment for his clients was critical to their
being able to deal with their problems.

a. structuralism
b. functionalism
c. Gestalt
d. unconditional positive regard

7. The operant conditioning chamber (aka
________ box) is a device used to study the
principles of operant conditioning.

a. Skinner
b. Watson
c. James
d. Koffka

34 Chapter 1 | Introduction to Psychology

This OpenStax book is available for free at

8. A researcher interested in how changes in the
cells of the hippocampus (a structure in the brain
related to learning and memory) are related to
memory formation would be most likely to
identify as a(n) ________ psychologist.

a. biological
b. health
c. clinical
d. social

9. An individual’s consistent pattern of thought
and behavior is known as a(n) ________.

a. psychosexual stage
b. object permanence
c. personality
d. perception

10. In Milgram’s controversial study on
obedience, nearly ________ of the participants
were willing to administer what appeared to be
lethal electrical shocks to another person because
they were told to do so by an authority figure.

a. 1/3
b. 2/3
c. 3/4
d. 4/5

11. A researcher interested in what factors make
an employee best suited for a given job would
most likely identify as a(n) ________ psychologist.

a. personality
b. clinical
c. social
d. I-O

12. If someone wanted to become a psychology
professor at a 4-year college, they would probably
need a ________ degree in psychology.

a. bachelor of science
b. bachelor of art
c. master’s
d. PhD

13. The ________ places less emphasis on
research and more emphasis on application of
therapeutic skills.

a. PhD
b. PsyD
c. postdoctoral training program
d. dissertation

14. Which of the following degrees would be the
minimum required to teach psychology courses in
high school?

a. PhD
b. PsyD
c. master’s degree
d. bachelor’s degree

15. One would need at least a(n) ________ degree
to serve as a school psychologist.

a. associate’s
b. bachelor’s
c. master’s
d. doctoral

Critical Thinking Questions

16. Why do you think psychology courses like this one are often requirements of so many different
programs of study?

17. Why do you think many people might be skeptical about psychology being a science?

18. How did the object of study in psychology change over the history of the field since the 19th century?

19. In part, what aspect of psychology was the behaviorist approach to psychology a reaction to?

20. Given the incredible diversity among the various areas of psychology that were described in this
section, how do they all fit together?

21. What are the potential ethical concerns associated with Milgram’s research on obedience?

Chapter 1 | Introduction to Psychology 35

22. Why is an undergraduate education in psychology so helpful in a number of different lines of work?

23. Other than a potentially greater salary, what would be the reasons an individual would continue on
to get a graduate degree in psychology?

Personal Application Questions

24. Why are you taking this course? What do you hope to learn about during this course?

25. Freud is probably one of the most well-known historical figures in psychology. Where have you
encountered references to Freud or his ideas about the role that the unconscious mind plays in determining
conscious behavior?

26. Now that you’ve been briefly introduced to some of the major areas within psychology, which are you
most interested in learning more about? Why?

27. Which of the career options in the field of psychology is most appealing to you?

36 Chapter 1 | Introduction to Psychology

This OpenStax book is available for free at

Chapter 2

Psychological Research

Figure 2.1 How does television content impact children’s behavior? (credit: modification of work by

Chapter Outline

2.1 Why Is Research Important?

2.2 Approaches to Research

2.3 Analyzing Findings

2.4 Ethics


Have you ever wondered whether the violence you see on television affects your behavior? Are you more
likely to behave aggressively in real life after watching people behave violently in dramatic situations on
the screen? Or, could seeing fictional violence actually get aggression out of your system, causing you to be
more peaceful? How are children influenced by the media they are exposed to? A psychologist interested
in the relationship between behavior and exposure to violent images might ask these very questions.

Since ancient times, humans have been concerned about the effects of new technologies on our behaviors
and thinking processes. The Greek philosopher Socrates, for example, worried that writing—a new
technology at that time—would diminish people’s ability to remember because they could rely on written
records rather than committing information to memory. In our world of rapidly changing technologies,
questions about their effects on our daily lives and their resulting long-term impacts continue to emerge.
In addition to the impact of screen time (on smartphones, tablets, computers, and gaming), technology is
emerging in our vehicles (such as GPS and smart cars) and residences (with devices like Alexa or Google
Home and doorbell cameras). As these technologies become integrated into our lives, we are faced with
questions about their positive and negative impacts. Many of us find ourselves with a strong opinion on
these issues, only to find the person next to us bristling with the opposite view.

Chapter 2 | Psychological Research 37

How can we go about finding answers that are supported not by mere opinion, but by evidence that we
can all agree on? The findings of psychological research can help us navigate issues like this.

2.1 Why Is Research Important?

Learning Objectives

By the end of this section, you will be able to:
• Explain how scientific research addresses questions about behavior
• Discuss how scientific research guides public policy
• Appreciate how scientific research can be important in making personal decisions

Scientific research is a critical tool for successfully navigating our complex world. Without it, we would be
forced to rely solely on intuition, other people’s authority, and blind luck. While many of us feel confident
in our abilities to decipher and interact with the world around us, history is filled with examples of how
very wrong we can be when we fail to recognize the need for evidence in supporting claims. At various
times in history, we would have been certain that the sun revolved around a flat earth, that the earth’s
continents did not move, and that mental illness was caused by possession (Figure 2.2). It is through
systematic scientific research that we divest ourselves of our preconceived notions and superstitions and
gain an objective understanding of ourselves and our world.

Figure 2.2 Some of our ancestors, across the world and over the centuries, believed that trephination—the practice
of making a hole in the skull, as shown here—allowed evil spirits to leave the body, thus curing mental illness and
other disorders. (credit: “taiproject”/Flickr)

The goal of all scientists is to better understand the world around them. Psychologists focus their attention
on understanding behavior, as well as the cognitive (mental) and physiological (body) processes that
underlie behavior. In contrast to other methods that people use to understand the behavior of others,
such as intuition and personal experience, the hallmark of scientific research is that there is evidence to
support a claim. Scientific knowledge is empirical: It is grounded in objective, tangible evidence that can
be observed time and time again, regardless of who is observing.

While behavior is observable, the mind is not. If someone is crying, we can see behavior. However, the
reason for the behavior is more difficult to determine. Is the person crying due to being sad, in pain,
or happy? Sometimes we can learn the reason for someone’s behavior by simply asking a question, like
“Why are you crying?” However, there are situations in which an individual is either uncomfortable or
unwilling to answer the question honestly, or is incapable of answering. For example, infants would not
be able to explain why they are crying. In such circumstances, the psychologist must be creative in finding
ways to better understand behavior. This chapter explores how scientific knowledge is generated, and how

38 Chapter 2 | Psychological Research

This OpenStax book is available for free at

important that knowledge is in forming decisions in our personal lives and in the public domain.


Trying to determine which theories are and are not accepted by the scientific community can be difficult,
especially in an area of research as broad as psychology. More than ever before, we have an incredible
amount of information at our fingertips, and a simple internet search on any given research topic might
result in a number of contradictory studies. In these cases, we are witnessing the scientific community
going through the process of reaching a consensus, and it could be quite some time before a consensus
emerges. For example, the explosion in our use of technology has led researchers to question whether
this ultimately helps or hinders us. The use and implementation of technology in educational settings has
become widespread over the last few decades. Researchers are coming to different conclusions regarding
the use of technology. To illustrate this point, a study investigating a smartphone app targeting surgery
residents (graduate students in surgery training) found that the use of this app can increase student
engagement and raise test scores (Shaw & Tan, 2015). Conversely, another study found that the use of
technology in undergraduate student populations had negative impacts on sleep, communication, and
time management skills (Massimini & Peterson, 2009). Until sufficient amounts of research have been
conducted, there will be no clear consensus on the effects that technology has on a student’s acquisition of
knowledge, study skills, and mental health.

In the meantime, we should strive to think critically about the information we encounter by exercising a
degree of healthy skepticism. When someone makes a claim, we should examine the claim from a number
of different perspectives: what is the expertise of the person making the claim, what might they gain if the
claim is valid, does the claim seem justified given the evidence, and what do other researchers think of
the claim? This is especially important when we consider how much information in advertising campaigns
and on the internet claims to be based on “scientific evidence” when in actuality it is a belief or perspective
of just a few individuals trying to sell a product or draw attention to their perspectives.

We should be informed consumers of the information made available to us because decisions based on
this information have significant consequences. One such consequence can be seen in politics and public
policy. Imagine that you have been elected as the governor of your state. One of your responsibilities is
to manage the state budget and determine how to best spend your constituents’ tax dollars. As the new
governor, you need to decide whether to continue funding early intervention programs. These programs
are designed to help children who come from low-income backgrounds, have special needs, or face
other disadvantages. These programs may involve providing a wide variety of services to maximize the
children’s development and position them for optimal levels of success in school and later in life (Blann,
2005). While such programs sound appealing, you would want to be sure that they also proved effective
before investing additional money in these programs. Fortunately, psychologists and other scientists have
conducted vast amounts of research on such programs and, in general, the programs are found to be
effective (Neil & Christensen, 2009; Peters-Scheffer, Didden, Korzilius, & Sturmey, 2011). While not all
programs are equally effective, and the short-term effects of many such programs are more pronounced,
there is reason to believe that many of these programs produce long-term benefits for participants (Barnett,
2011). If you are committed to being a good steward of taxpayer money, you would want to look at
research. Which programs are most effective? What characteristics of these programs make them effective?
Which programs promote the best outcomes? After examining the research, you would be best equipped
to make decisions about which programs to fund.

Chapter 2 | Psychological Research 39

Watch this video about early childhood program effectiveness (
to learn how scientists evaluate effectiveness and how best to invest money into programs that are most

Ultimately, it is not just politicians who can benefit from using research in guiding their decisions. We all
might look to research from time to time when making decisions in our lives. Imagine you just found out
that a close friend has breast cancer or that one of your young relatives has recently been diagnosed with
autism. In either case, you want to know which treatment options are most successful with the fewest side
effects. How would you find that out? You would probably talk with your doctor and personally review
the research that has been done on various treatment options—always with a critical eye to ensure that
you are as informed as possible.

In the end, research is what makes the difference between facts and opinions. Facts are observable realities,
and opinions are personal judgments, conclusions, or attitudes that may or may not be accurate. In the
scientific community, facts can be established only using evidence collected through empirical research.


Psychological research has a long history involving important figures from diverse backgrounds. While
the introductory chapter discussed several researchers who made significant contributions to the
discipline, there are many more individuals who deserve attention in considering how psychology has
advanced as a science through their work (Figure 2.3). For instance, Margaret Floy Washburn (1871–1939)
was the first woman to earn a PhD in psychology. Her research focused on animal behavior and cognition
(Margaret Floy Washburn, PhD, n.d.). Mary Whiton Calkins (1863–1930) was a preeminent first-generation
American psychologist who opposed the behaviorist movement, conducted significant research into
memory, and established one of the earliest experimental psychology labs in the United States (Mary
Whiton Calkins, n.d.).

Francis Sumner (1895–1954) was the first African American to receive a PhD in psychology in 1920. His
dissertation focused on issues related to psychoanalysis. Sumner also had research interests in racial
bias and educational justice. Sumner was one of the founders of Howard University’s department of
psychology, and because of his accomplishments, he is sometimes referred to as the “Father of Black
Psychology.” Thirteen years later, Inez Beverly Prosser (1895–1934) became the first African American
woman to receive a PhD in psychology. Prosser’s research highlighted issues related to education in
segregated versus integrated schools, and ultimately, her work was very influential in the hallmark
Brown v. Board of Education Supreme Court ruling that segregation of public schools was unconstitutional
(Ethnicity and Health in America Series: Featured Psychologists, n.d.).


40 Chapter 2 | Psychological Research

This OpenStax book is available for free at

Figure 2.3 (a) Margaret Floy Washburn was the first woman to earn a doctorate degree in psychology. (b) The
outcome of Brown v. Board of Education was influenced by the research of psychologist Inez Beverly Prosser, who
was the first African American woman to earn a PhD in psychology.

Although the establishment of psychology’s scientific roots occurred first in Europe and the United States,
it did not take much time until researchers from around the world began to establish their own laboratories
and research programs. For example, some of the first experimental psychology laboratories in South
America were founded by Horatio Piñero (1869–1919) at two institutions in Buenos Aires, Argentina
(Godoy & Brussino, 2010). In India, Gunamudian David Boaz (1908–1965) and Narendra Nath Sen Gupta
(1889–1944) established the first independent departments of psychology at the University of Madras
and the University of Calcutta, respectively. These developments provided an opportunity for Indian
researchers to make important contributions to the field (Gunamudian David Boaz, n.d.; Narendra Nath
Sen Gupta, n.d.).

When the American Psychological Association (APA) was first founded in 1892, all of the members were
white males (Women and Minorities in Psychology, n.d.). However, by 1905, Mary Whiton Calkins was
elected as the first female president of the APA, and by 1946, nearly one-quarter of American psychologists
were female. Psychology became a popular degree option for students enrolled in the nation’s historically
black higher education institutions, increasing the number of black Americans who went on to become
psychologists. Given demographic shifts occurring in the United States and increased access to higher
educational opportunities among historically underrepresented populations, there is reason to hope that
the diversity of the field will increasingly match the larger population, and that the research contributions
made by the psychologists of the future will better serve people of all backgrounds (Women and Minorities
in Psychology, n.d.).


Scientific knowledge is advanced through a process known as the scientific method. Basically, ideas (in the
form of theories and hypotheses) are tested against the real world (in the form of empirical observations),
and those empirical observations lead to more ideas that are tested against the real world, and so on. In this
sense, the scientific process is circular. The types of reasoning within the circle are called deductive and
inductive. In deductive reasoning, ideas are tested in the real world; in inductive reasoning, real-world
observations lead to new ideas (Figure 2.4). These processes are inseparable, like inhaling and exhaling,
but different research approaches place different emphasis on the deductive and inductive aspects.

Chapter 2 | Psychological Research 41

Figure 2.4 Psychological research relies on both inductive and deductive reasoning.

In the scientific context, deductive reasoning begins with a generalization—one hypothesis—that is then
used to reach logical conclusions about the real world. If the hypothesis is correct, then the logical
conclusions reached through deductive reasoning should also be correct. A deductive reasoning argument
might go something like this: All living things require energy to survive (this would be your hypothesis).
Ducks are living things. Therefore, ducks require energy to survive (logical conclusion). In this example,
the hypothesis is correct; therefore, the conclusion is correct as well. Sometimes, however, an incorrect
hypothesis may lead to a logical but incorrect conclusion. Consider this argument: all ducks are born with
the ability to see. Quackers is a duck. Therefore, Quackers was born with the ability to see. Scientists
use deductive reasoning to empirically test their hypotheses. Returning to the example of the ducks,
researchers might design a study to test the hypothesis that if all living things require energy to survive,
then ducks will be found to require energy to survive.

Deductive reasoning starts with a generalization that is tested against real-world observations; however,
inductive reasoning moves in the opposite direction. Inductive reasoning uses empirical observations to
construct broad generalizations. Unlike deductive reasoning, conclusions drawn from inductive reasoning
may or may not be correct, regardless of the observations on which they are based. For instance, you may
notice that your favorite fruits—apples, bananas, and oranges—all grow on trees; therefore, you assume
that all fruit must grow on trees. This would be an example of inductive reasoning, and, clearly, the
existence of strawberries, blueberries, and kiwi demonstrate that this generalization is not correct despite
it being based on a number of direct observations. Scientists use inductive reasoning to formulate theories,
which in turn generate hypotheses that are tested with deductive reasoning. In the end, science involves
both deductive and inductive processes.

For example, case studies, which you will read about in the next section, are heavily weighted on the
side of empirical observations. Thus, case studies are closely associated with inductive processes as
researchers gather massive amounts of observations and seek interesting patterns (new ideas) in the data.
Experimental research, on the other hand, puts great emphasis on deductive reasoning.

We’ve stated that theories and hypotheses are ideas, but what sort of ideas are they, exactly? A theory is a
well-developed set of ideas that propose an explanation for observed phenomena. Theories are repeatedly
checked against the world, but they tend to be too complex to be tested all at once; instead, researchers
create hypotheses to test specific aspects of a theory.

A hypothesis is a testable prediction about how the world will behave if our idea is correct, and it is
often worded as an if-then statement (e.g., if I study all night, I will get a passing grade on the test). The
hypothesis is extremely important because it bridges the gap between the realm of ideas and the real
world. As specific hypotheses are tested, theories are modified and refined to reflect and incorporate the
result of these tests Figure 2.5.

42 Chapter 2 | Psychological Research

This OpenStax book is available for free at

Figure 2.5 The scientific method involves deriving hypotheses from theories and then testing those hypotheses. If
the results are consistent with the theory, then the theory is supported. If the results are not consistent, then the
theory should be modified and new hypotheses will be generated.

To see how this process works, let’s consider a specific theory and a hypothesis that might be generated
from that theory. As you’ll learn in a later chapter, the James-Lange theory of emotion asserts that
emotional experience relies on the physiological arousal associated with the emotional state. If you walked
out of your home and discovered a very aggressive snake waiting on your doorstep, your heart would
begin to race and your stomach churn. According to the James-Lange theory, these physiological changes
would result in your feeling of fear. A hypothesis that could be derived from this theory might be that a
person who is unaware of the physiological arousal that the sight of the snake elicits will not feel fear.

A scientific hypothesis is also falsifiable, or capable of being shown to be incorrect. Recall from the
introductory chapter that Sigmund Freud had lots of interesting ideas to explain various human behaviors
(Figure 2.6). However, a major criticism of Freud’s theories is that many of his ideas are not falsifiable;
for example, it is impossible to imagine empirical observations that would disprove the existence of the id,
the ego, and the superego—the three elements of personality described in Freud’s theories. Despite this,
Freud’s theories are widely taught in introductory psychology texts because of their historical significance
for personality psychology and psychotherapy, and these remain the root of all modern forms of therapy.

Chapter 2 | Psychological Research 43

Figure 2.6 Many of the specifics of (a) Freud’s theories, such as (b) his division of the mind into id, ego, and
superego, have fallen out of favor in recent decades because they are not falsifiable. In broader strokes, his views set
the stage for much of psychological thinking today, such as the unconscious nature of the majority of psychological

In contrast, the James-Lange theory does generate falsifiable hypotheses, such as the one described
above. Some individuals who suffer significant injuries to their spinal columns are unable to feel the
bodily changes that often accompany emotional experiences. Therefore, we could test the hypothesis by
determining how emotional experiences differ between individuals who have the ability to detect these
changes in their physiological arousal and those who do not. In fact, this research has been conducted and
while the emotional experiences of people deprived of an awareness of their physiological arousal may be
less intense, they still experience emotion (Chwalisz, Diener, & Gallagher, 1988).

Scientific research’s dependence on falsifiability allows for great confidence in the information that it
produces. Typically, by the time information is accepted by the scientific community, it has been tested

2.2 Approaches to Research

Learning Objectives

By the end of this section, you will be able to:
• Describe the different research methods used by psychologists
• Discuss the strengths and weaknesses of case studies, naturalistic observation, surveys, and

archival research
• Compare longitudinal and cross-sectional approaches to research
• Compare and contrast correlation and causation

There are many research methods available to psychologists in their efforts to understand, describe,
and explain behavior and the cognitive and biological processes that underlie it. Some methods rely
on observational techniques. Other approaches involve interactions between the researcher and the
individuals who are being studied—ranging from a series of simple questions to extensive, in-depth
interviews—to well-controlled experiments.

Each of these research methods has unique strengths and weaknesses, and each method may only be

44 Chapter 2 | Psychological Research

This OpenStax book is available for free at

appropriate for certain types of research questions. For example, studies that rely primarily on observation
produce incredible amounts of information, but the ability to apply this information to the larger
population is somewhat limited because of small sample sizes. Survey research, on the other hand,
allows researchers to easily collect data from relatively large samples. While this allows for results to
be generalized to the larger population more easily, the information that can be collected on any given
survey is somewhat limited and subject to problems associated with any type of self-reported data. Some
researchers conduct archival research by using existing records. While this can be a fairly inexpensive
way to collect data that can provide insight into a number of research questions, researchers using this
approach have no control on how or what kind of data was collected. All of the methods described thus
far are correlational in nature. This means that researchers can speak to important relationships that might
exist between two or more variables of interest. However, correlational data cannot be used to make claims
about cause-and-effect relationships.

Correlational research can find a relationship between two variables, but the only way a researcher can
claim that the relationship between the variables is cause and effect is to perform an experiment. In
experimental research, which will be discussed later in this chapter, there is a tremendous amount of
control over variables of interest. While this is a powerful approach, experiments are often conducted in
very artificial settings. This calls into question the validity of experimental findings with regard to how
they would apply in real-world settings. In addition, many of the questions that psychologists would like
to answer cannot be pursued through experimental research because of ethical concerns.


In 2011, the New York Times published a feature story on Krista and Tatiana Hogan, Canadian twin girls.
These particular twins are unique because Krista and Tatiana are conjoined twins, connected at the head.
There is evidence that the two girls are connected in a part of the brain called the thalamus, which is
a major sensory relay center. Most incoming sensory information is sent through the thalamus before
reaching higher regions of the cerebral cortex for processing.

Watch this CBC video about Krista’s and Tatiana’s lives ( to learn more.

The implications of this potential connection mean that it might be possible for one twin to experience the
sensations of the other twin. For instance, if Krista is watching a particularly funny television program,
Tatiana might smile or laugh even if she is not watching the program. This particular possibility has
piqued the interest of many neuroscientists who seek to understand how the brain uses sensory

These twins represent an enormous resource in the study of the brain, and since their condition is very
rare, it is likely that as long as their family agrees, scientists will follow these girls very closely throughout
their lives to gain as much information as possible (Dominus, 2011).

Over time, it has become clear that while Krista and Tatiana share some sensory experiences and motor
control, they remain two distinct individuals, which provides tremendous insight into researchers
interested in the mind and the brain (Egnor, 2017).

In observational research, scientists are conducting a clinical or case study when they focus on one person
or just a few individuals. Indeed, some scientists spend their entire careers studying just 10–20 individuals.
Why would they do this? Obviously, when they focus their attention on a very small number of people,
they can gain a tremendous amount of insight into those cases. The richness of information that is collected


Chapter 2 | Psychological Research 45

in clinical or case studies is unmatched by any other single research method. This allows the researcher to
have a very deep understanding of the individuals and the particular phenomenon being studied.

If clinical or case studies provide so much information, why are they not more frequent among
researchers? As it turns out, the major benefit of this particular approach is also a weakness. As mentioned
earlier, this approach is often used when studying individuals who are interesting to researchers because
they have a rare characteristic. Therefore, the individuals who serve as the focus of case studies are not like
most other people. If scientists ultimately want to explain all behavior, focusing attention on such a special
group of people can make it difficult to generalize any observations to the larger population as a whole.
Generalizing refers to the ability to apply the findings of a particular research project to larger segments of
society. Again, case studies provide enormous amounts of information, but since the cases are so specific,
the potential to apply what’s learned to the average person may be very limited.


If you want to understand how behavior occurs, one of the best ways to gain information is to simply
observe the behavior in its natural context. However, people might change their behavior in unexpected
ways if they know they are being observed. How do researchers obtain accurate information when people
tend to hide their natural behavior? As an example, imagine that your professor asks everyone in your
class to raise their hand if they always wash their hands after using the restroom. Chances are that almost
everyone in the classroom will raise their hand, but do you think hand washing after every trip to the
restroom is really that universal?

This is very similar to the phenomenon mentioned earlier in this chapter: many individuals do not feel
comfortable answering a question honestly. But if we are committed to finding out the facts about hand
washing, we have other options available to us.

Suppose we send a classmate into the restroom to actually watch whether everyone washes their hands
after using the restroom. Will our observer blend into the restroom environment by wearing a white
lab coat, sitting with a clipboard, and staring at the sinks? We want our researcher to be
inconspicuous—perhaps standing at one of the sinks pretending to put in contact lenses while secretly
recording the relevant information. This type of observational study is called naturalistic observation:
observing behavior in its natural setting. To better understand peer exclusion, Suzanne Fanger
collaborated with colleagues at the University of Texas to observe the behavior of preschool children
on a playground. How did the observers remain inconspicuous over the duration of the study? They
equipped a few of the children with wireless microphones (which the children quickly forgot about) and
observed while taking notes from a distance. Also, the children in that particular preschool (a “laboratory
preschool”) were accustomed to having observers on the playground (Fanger, Frankel, & Hazen, 2012).

It is critical that the observer be as unobtrusive and as inconspicuous as possible: when people know they
are being watched, they are less likely to behave naturally. If you have any doubt about this, ask yourself
how your driving behavior might differ in two situations: In the first situation, you are driving down a
deserted highway during the middle of the day; in the second situation, you are being followed by a police
car down the same deserted highway (Figure 2.7).

46 Chapter 2 | Psychological Research

This OpenStax book is available for free at

Figure 2.7 Seeing a police car behind you would probably affect your driving behavior. (credit: Michael Gil)

It should be pointed out that naturalistic observation is not limited to research involving humans. Indeed,
some of the best-known examples of naturalistic observation involve researchers going into the field to
observe various kinds of animals in their own environments. As with human studies, the researchers
maintain their distance and avoid interfering with the animal subjects so as not to influence their natural
behaviors. Scientists have used this technique to study social hierarchies and interactions among animals
ranging from ground squirrels to gorillas. The information provided by these studies is invaluable in
understanding how those animals organize socially and communicate with one another. The
anthropologist Jane Goodall, for example, spent nearly five decades observing the behavior of
chimpanzees in Africa (Figure 2.8). As an illustration of the types of concerns that a researcher might
encounter in naturalistic observation, some scientists criticized Goodall for giving the chimps names
instead of referring to them by numbers—using names was thought to undermine the emotional
detachment required for the objectivity of the study (McKie, 2010).

Figure 2.8 (a) Jane Goodall made a career of conducting naturalistic observations of (b) chimpanzee behavior.
(credit “Jane Goodall”: modification of work by Erik Hersman; “chimpanzee”: modification of work by “Afrika

The greatest benefit of naturalistic observation is the validity, or accuracy, of information collected
unobtrusively in a natural setting. Having individuals behave as they normally would in a given situation
means that we have a higher degree of ecological validity, or realism, than we might achieve with
other research approaches. Therefore, our ability to generalize the findings of the research to real-world
situations is enhanced. If done correctly, we need not worry about people or animals modifying their
behavior simply because they are being observed. Sometimes, people may assume that reality programs
give us a glimpse into authentic human behavior. However, the principle of inconspicuous observation
is violated as reality stars are followed by camera crews and are interviewed on camera for personal
confessionals. Given that environment, we must doubt how natural and realistic their behaviors are.

The major downside of naturalistic observation is that they are often difficult to set up and control. In
our restroom study, what if you stood in the restroom all day prepared to record people’s hand washing
behavior and no one came in? Or, what if you have been closely observing a troop of gorillas for weeks
only to find that they migrated to a new place while you were sleeping in your tent? The benefit of realistic
data comes at a cost. As a researcher you have no control of when (or if) you have behavior to observe. In

Chapter 2 | Psychological Research 47

addition, this type of observational research often requires significant investments of time, money, and a
good dose of luck.

Sometimes studies involve structured observation. In these cases, people are observed while engaging in
set, specific tasks. An excellent example of structured observation comes from Strange Situation by Mary
Ainsworth (you will read more about this in the chapter on lifespan development). The Strange Situation is
a procedure used to evaluate attachment styles that exist between an infant and caregiver. In this scenario,
caregivers bring their infants into a room filled with toys. The Strange Situation involves a number of
phases, including a stranger coming into the room, the caregiver leaving the room, and the caregiver’s
return to the room. The infant’s behavior is closely monitored at each phase, but it is the behavior of the
infant upon being reunited with the caregiver that is most telling in terms of characterizing the infant’s
attachment style with the caregiver.

Another potential problem in observational research is observer bias. Generally, people who act as
observers are closely involved in the research project and may unconsciously skew their observations to
fit their research goals or expectations. To protect against this type of bias, researchers should have clear
criteria established for the types of behaviors recorded and how those behaviors should be classified. In
addition, researchers often compare observations of the same event by multiple observers, in order to test
inter-rater reliability: a measure of reliability that assesses the consistency of observations by different


Often, psychologists develop surveys as a means of gathering data. Surveys are lists of questions to be
answered by research participants, and can be delivered as paper-and-pencil questionnaires, administered
electronically, or conducted verbally (Figure 2.9). Generally, the survey itself can be completed in a short
time, and the ease of administering a survey makes it easy to collect data from a large number of people.

Surveys allow researchers to gather data from larger samples than may be afforded by other research
methods. A sample is a subset of individuals selected from a population, which is the overall group of
individuals that the researchers are interested in. Researchers study the sample and seek to generalize their
findings to the population. Generally, researchers will begin this process by calculating various measures
of central tendency from the data they have collected. These measures provide an overall summary of what
a typical response looks like. There are three measures of central tendency: mode, median, and mean. The
mode is the most frequently occurring response, the median lies at the middle of a given data set, and the
mean is the arithmetic average of all data points. Means tend to be most useful in conducting additional
analyses like those described below; however, means are very sensitive to the effects of outliers, and so
one must be aware of those effects when making assessments of what measures of central tendency tell us
about a data set in question.

48 Chapter 2 | Psychological Research

This OpenStax book is available for free at

Figure 2.9 Surveys can be administered in a number of ways, including electronically administered research, like
the survey shown here. (credit: Robert Nyman)

There is both strength and weakness of the survey in comparison to case studies. By using surveys, we
can collect information from a larger sample of people. A larger sample is better able to reflect the actual
diversity of the population, thus allowing better generalizability. Therefore, if our sample is sufficiently
large and diverse, we can assume that the data we collect from the survey can be generalized to the larger
population with more certainty than the information collected through a case study. However, given the
greater number of people involved, we are not able to collect the same depth of information on each person
that would be collected in a case study.

Another potential weakness of surveys is something we touched on earlier in this chapter: People don’t
always give accurate responses. They may lie, misremember, or answer questions in a way that they think
makes them look good. For example, people may report drinking less alcohol than is actually the case.

Any number of research questions can be answered through the use of surveys. One real-world example
is the research conducted by Jenkins, Ruppel, Kizer, Yehl, and Griffin (2012) about the backlash against
the US Arab-American community following the terrorist attacks of September 11, 2001. Jenkins and
colleagues wanted to determine to what extent these negative attitudes toward Arab-Americans still
existed nearly a decade after the attacks occurred. In one study, 140 research participants filled out a
survey with 10 questions, including questions asking directly about the participant’s overt prejudicial
attitudes toward people of various ethnicities. The survey also asked indirect questions about how likely
the participant would be to interact with a person of a given ethnicity in a variety of settings (such as,
“How likely do you think it is that you would introduce yourself to a person of Arab-American descent?”).
The results of the research suggested that participants were unwilling to report prejudicial attitudes
toward any ethnic group. However, there were significant differences between their pattern of responses
to questions about social interaction with Arab-Americans compared to other ethnic groups: they indicated
less willingness for social interaction with Arab-Americans compared to the other ethnic groups. This
suggested that the participants harbored subtle forms of prejudice against Arab-Americans, despite their
assertions that this was not the case (Jenkins et al., 2012).


Some researchers gain access to large amounts of data without interacting with a single research
participant. Instead, they use existing records to answer various research questions. This type of research
approach is known as archival research. Archival research relies on looking at past records or data sets to
look for interesting patterns or relationships.

For example, a researcher might access the academic records of all individuals who enrolled in college
within the past ten years and calculate how long it took them to complete their degrees, as well as course
loads, grades, and extracurricular involvement. Archival research could provide important information

Chapter 2 | Psychological Research 49

about who is most likely to complete their education, and it could help identify important risk factors for
struggling students (Figure 2.10).

Figure 2.10 A researcher doing archival research examines records, whether archived as a (a) hardcopy or (b)
electronically. (credit “paper files”: modification of work by “Newtown graffiti”/Flickr; “computer”: modification of work
by INPIVIC Family/Flickr)

In comparing archival research to other research methods, there are several important distinctions. For
one, the researcher employing archival research never directly interacts with research participants.
Therefore, the investment of time and money to collect data is considerably less with archival research.
Additionally, researchers have no control over what information was originally collected. Therefore,
research questions have to be tailored so they can be answered within the structure of the existing data sets.
There is also no guarantee of consistency between the records from one source to another, which might
make comparing and contrasting different data sets problematic.


Sometimes we want to see how people change over time, as in studies of human development and
lifespan. When we test the same group of individuals repeatedly over an extended period of time, we
are conducting longitudinal research. Longitudinal research is a research design in which data-gathering
is administered repeatedly over an extended period of time. For example, we may survey a group of
individuals about their dietary habits at age 20, retest them a decade later at age 30, and then again at age

Another approach is cross-sectional research. In cross-sectional research, a researcher compares multiple
segments of the population at the same time. Using the dietary habits example above, the researcher might
directly compare different groups of people by age. Instead of studying a group of people for 20 years
to see how their dietary habits changed from decade to decade, the researcher would study a group of
20-year-old individuals and compare them to a group of 30-year-old individuals and a group of 40-year-
old individuals. While cross-sectional research requires a shorter-term investment, it is also limited by
differences that exist between the different generations (or cohorts) that have nothing to do with age per
se, but rather reflect the social and cultural experiences of different generations of individuals make them
different from one another.

To illustrate this concept, consider the following survey findings. In recent years there has been significant
growth in the popular support of same-sex marriage. Many studies on this topic break down survey
participants into different age groups. In general, younger people are more supportive of same-sex
marriage than are those who are older (Jones, 2013). Does this mean that as we age we become less open to
the idea of same-sex marriage, or does this mean that older individuals have different perspectives because
of the social climates in which they grew up? Longitudinal research is a powerful approach because the
same individuals are involved in the research project over time, which means that the researchers need to
be less concerned with differences among cohorts affecting the results of their study.

Often longitudinal studies are employed when researching various diseases in an effort to understand

50 Chapter 2 | Psychological Research

This OpenStax book is available for free at

particular risk factors. Such studies often involve tens of thousands of individuals who are followed
for several decades. Given the enormous number of people involved in these studies, researchers can
feel confident that their findings can be generalized to the larger population. The Cancer Prevention
Study-3 (CPS-3) is one of a series of longitudinal studies sponsored by the American Cancer Society aimed
at determining predictive risk factors associated with cancer. When participants enter the study, they
complete a survey about their lives and family histories, providing information on factors that might cause
or prevent the development of cancer. Then every few years the participants receive additional surveys
to complete. In the end, hundreds of thousands of participants will be tracked over 20 years to determine
which of them develop cancer and which do not.

Clearly, this type of research is important and potentially very informative. For instance, earlier
longitudinal studies sponsored by the American Cancer Society provided some of the first scientific
demonstrations of the now well-established links between increased rates of cancer and smoking
(American Cancer Society, n.d.) (Figure 2.11).

Figure 2.11 Longitudinal research like the CPS-3 help us to better understand how smoking is associated with
cancer and other diseases. (credit: CDC/Debora Cartagena)

As with any research strategy, longitudinal research is not without limitations. For one, these studies
require an incredible time investment by the researcher and research participants. Given that some
longitudinal studies take years, if not decades, to complete, the results will not be known for a considerable
period of time. In addition to the time demands, these studies also require a substantial financial
investment. Many researchers are unable to commit the resources necessary to see a longitudinal project
through to the end.

Research participants must also be willing to continue their participation for an extended period of time,
and this can be problematic. People move, get married and take new names, get ill, and eventually die.
Even without significant life changes, some people may simply choose to discontinue their participation
in the project. As a result, the attrition rates, or reduction in the number of research participants due to
dropouts, in longitudinal studies are quite high and increases over the course of a project. For this reason,
researchers using this approach typically recruit many participants fully expecting that a substantial
number will drop out before the end. As the study progresses, they continually check whether the sample
still represents the larger population, and make adjustments as necessary.

Chapter 2 | Psychological Research 51

2.3 Analyzing Findings

Learning Objectives

By the end of this section, you will be able to:
• Explain what a correlation coefficient tells us about the relationship between variables
• Recognize that correlation does not indicate a cause-and-effect relationship between

• Discuss our tendency to look for relationships between variables that do not really exist
• Explain random sampling and assignment of participants into experimental and control

• Discuss how experimenter or participant bias could affect the results of an experiment
• Identify independent and dependent variables

Did you know that as sales in ice cream increase, so does the overall rate of crime? Is it possible that
indulging in your favorite flavor of ice cream could send you on a crime spree? Or, after committing crime
do you think you might decide to treat yourself to a cone? There is no question that a relationship exists
between ice cream and crime (e.g., Harper, 2013), but it would be pretty foolish to decide that one thing
actually caused the other to occur.

It is much more likely that both ice cream sales and crime rates are related to the temperature outside.
When the temperature is warm, there are lots of people out of their houses, interacting with each other,
getting annoyed with one another, and sometimes committing crimes. Also, when it is warm outside, we
are more likely to seek a cool treat like ice cream. How do we determine if there is indeed a relationship
between two things? And when there is a relationship, how can we discern whether it is attributable to
coincidence or causation?


Correlation means that there is a relationship between two or more variables (such as ice cream
consumption and crime), but this relationship does not necessarily imply cause and effect. When two
variables are correlated, it simply means that as one variable changes, so does the other. We can measure
correlation by calculating a statistic known as a correlation coefficient. A correlation coefficient is a
number from -1 to +1 that indicates the strength and direction of the relationship between variables. The
correlation coefficient is usually represented by the letter r.

The number portion of the correlation coefficient indicates the strength of the relationship. The closer
the number is to 1 (be it negative or positive), the more strongly related the variables are, and the more
predictable changes in one variable will be as the other variable changes. The closer the number is to zero,
the weaker the relationship, and the less predictable the relationships between the variables becomes. For
instance, a correlation coefficient of 0.9 indicates a far stronger relationship than a correlation coefficient of
0.3. If the variables are not related to one another at all, the correlation coefficient is 0. The example above
about ice cream and crime is an example of two variables that we might expect to have no relationship to
each other.

The sign—positive or negative—of the correlation coefficient indicates the direction of the relationship
(Figure 2.12). A positive correlation means that the variables move in the same direction. Put another
way, it means that as one variable increases so does the other, and conversely, when one variable decreases
so does the other. A negative correlation means that the variables move in opposite directions. If two
variables are negatively correlated, a decrease in one variable is associated with an increase in the other
and vice versa.

The example of ice cream and crime rates is a positive correlation because both variables increase when

52 Chapter 2 | Psychological Research

This OpenStax book is available for free at

temperatures are warmer. Other examples of positive correlations are the relationship between an
individual’s height and weight or the relationship between a person’s age and number of wrinkles. One
might expect a negative correlation to exist between someone’s tiredness during the day and the number
of hours they slept the previous night: the amount of sleep decreases as the feelings of tiredness increase.
In a real-world example of negative correlation, student researchers at the University of Minnesota found
a weak negative correlation (r = -0.29) between the average number of days per week that students got
fewer than 5 hours of sleep and their GPA (Lowry, Dean, & Manders, 2010). Keep in mind that a negative
correlation is not the same as no correlation. For example, we would probably find no correlation between
hours of sleep and shoe size.

As mentioned earlier, correlations have predictive value. Imagine that you are on the admissions
committee of a major university. You are faced with a huge number of applications, but you are able
to accommodate only a small percentage of the applicant pool. How might you decide who should be
admitted? You might try to correlate your current students’ college GPA with their scores on standardized
tests like the SAT or ACT. By observing which correlations were strongest for your current students, you
could use this information to predict relative success of those students who have applied for admission
into the university.

Figure 2.12 Scatterplots are a graphical view of the strength and direction of correlations. The stronger the
correlation, the closer the data points are to a straight line. In these examples, we see that there is (a) a positive
correlation between weight and height, (b) a negative correlation between tiredness and hours of sleep, and (c) no
correlation between shoe size and hours of sleep.

Manipulate this interactive scatterplot ( to practice your understanding
of positive and negative correlation.

Correlation Does Not Indicate Causation

Correlational research is useful because it allows us to discover the strength and direction of relationships
that exist between two variables. However, correlation is limited because establishing the existence of a
relationship tells us little about cause and effect. While variables are sometimes correlated because one
does cause the other, it could also be that some other factor, a confounding variable, is actually causing the
systematic movement in our variables of interest. In the ice cream/crime rate example mentioned earlier,
temperature is a confounding variable that could account for the relationship between the two variables.

Even when we cannot point to clear confounding variables, we should not assume that a correlation
between two variables implies that one variable causes changes in another. This can be frustrating when a


Chapter 2 | Psychological Research 53

cause-and-effect relationship seems clear and intuitive. Think back to our discussion of the research done
by the American Cancer Society and how their research projects were some of the first demonstrations of
the link between smoking and cancer. It seems reasonable to assume that smoking causes cancer, but if we
were limited to correlational research, we would be overstepping our bounds by making this assumption.

Unfortunately, people mistakenly make claims of causation as a function of correlations all the time. Such
claims are especially common in advertisements and news stories. For example, recent research found
that people who eat cereal on a regular basis achieve healthier weights than those who rarely eat cereal
(Frantzen, Treviño, Echon, Garcia-Dominic, & DiMarco, 2013; Barton et al., 2005). Guess how the cereal
companies report this finding. Does eating cereal really cause an individual to maintain a healthy weight,
or are there other possible explanations, such as, someone at a healthy weight is more likely to regularly
eat a healthy breakfast than someone who is obese or someone who avoids meals in an attempt to diet
(Figure 2.13)? While correlational research is invaluable in identifying relationships among variables, a
major limitation is the inability to establish causality. Psychologists want to make statements about cause
and effect, but the only way to do that is to conduct an experiment to answer a research question. The next
section describes how scientific experiments incorporate methods that eliminate, or control for, alternative
explanations, which allow researchers to explore how changes in one variable cause changes in another

Figure 2.13 Does eating cereal really cause someone to be a healthy weight? (credit: Tim Skillern)

Illusory Correlations

The temptation to make erroneous cause-and-effect statements based on correlational research is not
the only way we tend to misinterpret data. We also tend to make the mistake of illusory correlations,
especially with unsystematic observations. Illusory correlations, or false correlations, occur when people
believe that relationships exist between two things when no such relationship exists. One well-known
illusory correlation is the supposed effect that the moon’s phases have on human behavior. Many people
passionately assert that human behavior is affected by the phase of the moon, and specifically, that people
act strangely when the moon is full (Figure 2.14).

Figure 2.14 Many people believe that a full moon makes people behave oddly. (credit: Cory Zanker)

There is no denying that the moon exerts a powerful influence on our planet. The ebb and flow of the
ocean’s tides are tightly tied to the gravitational forces of the moon. Many people believe, therefore, that

54 Chapter 2 | Psychological Research

This OpenStax book is available for free at

it is logical that we are affected by the moon as well. After all, our bodies are largely made up of water.
A meta-analysis of nearly 40 studies consistently demonstrated, however, that the relationship between
the moon and our behavior does not exist (Rotton & Kelly, 1985). While we may pay more attention to
odd behavior during the full phase of the moon, the rates of odd behavior remain constant throughout the
lunar cycle.

Why are we so apt to believe in illusory correlations like this? Often we read or hear about them and
simply accept the information as valid. Or, we have a hunch about how something works and then look
for evidence to support that hunch, ignoring evidence that would tell us our hunch is false; this is known
as confirmation bias. Other times, we find illusory correlations based on the information that comes most
easily to mind, even if that information is severely limited. And while we may feel confident that we can
use these relationships to better understand and predict the world around us, illusory correlations can
have significant drawbacks. For example, research suggests that illusory correlations—in which certain
behaviors are inaccurately attributed to certain groups—are involved in the formation of prejudicial
attitudes that can ultimately lead to discriminatory behavior (Fiedler, 2004).


As you’ve learned, the only way to establish that there is a cause-and-effect relationship between two
variables is to conduct a scientific experiment. Experiment has a different meaning in the scientific context
than in everyday life. In everyday conversation, we often use it to describe trying something for the first
time, such as experimenting with a new hair style or a new food. However, in the scientific context, an
experiment has precise requirements for design and implementation.

The Experimental Hypothesis

In order to conduct an experiment, a researcher must have a specific hypothesis to be tested. As you’ve
learned, hypotheses can be formulated either through direct observation of the real world or after careful
review of previous research. For example, if you think that the use of technology in the classroom has
negative impacts on learning, then you have basically formulated a hypothesis—namely, that the use of
technology in the classroom should be limited because it decreases learning. How might you have arrived
at this particular hypothesis? You may have noticed that your classmates who take notes on their laptops
perform at lower levels on class exams than those who take notes by hand, or those who receive a lesson
via a computer program versus via an in-person teacher have different levels of performance when tested
(Figure 2.15).

Chapter 2 | Psychological Research 55

Figure 2.15 How might the use of technology in the classroom impact learning? (credit: modification of work by
Nikolay Georgiev/Pixabay)

These sorts of personal observations are what often lead us to formulate a specific hypothesis, but
we cannot use limited personal observations and anecdotal evidence to rigorously test our hypothesis.
Instead, to find out if real-world data supports our hypothesis, we have to conduct an experiment.

Designing an Experiment

The most basic experimental design involves two groups: the experimental group and the control group.
The two groups are designed to be the same except for one difference— experimental manipulation. The
experimental group gets the experimental manipulation—that is, the treatment or variable being tested (in
this case, the use of technology)—and the control group does not. Since experimental manipulation is the
only difference between the experimental and control groups, we can be sure that any differences between
the two are due to experimental manipulation rather than chance.

In our example of how the use of technology should be limited in the classroom, we have the experimental
group learn algebra using a computer program and then test their learning. We measure the learning in
our control group after they are taught algebra by a teacher in a traditional classroom. It is important for
the control group to be treated similarly to the experimental group, with the exception that the control
group does not receive the experimental manipulation.

We also need to precisely define, or operationalize, how we measure learning of algebra. An operational
definition is a precise description of our variables, and it is important in allowing others to understand
exactly how and what a researcher measures in a particular experiment. In operationalizing learning, we
might choose to look at performance on a test covering the material on which the individuals were taught
by the teacher or the computer program. We might also ask our participants to summarize the information
that was just presented in some way. Whatever we determine, it is important that we operationalize
learning in such a way that anyone who hears about our study for the first time knows exactly what we
mean by learning. This aids peoples’ ability to interpret our data as well as their capacity to repeat our
experiment should they choose to do so.

Once we have operationalized what is considered use of technology and what is considered learning in
our experiment participants, we need to establish how we will run our experiment. In this case, we might
have participants spend 45 minutes learning algebra (either through a computer program or with an in-
person math teacher) and then give them a test on the material covered during the 45 minutes.

56 Chapter 2 | Psychological Research

This OpenStax book is available for free at

Ideally, the people who score the tests are unaware of who was assigned to the experimental or control
group, in order to control for experimenter bias. Experimenter bias refers to the possibility that a
researcher’s expectations might skew the results of the study. Remember, conducting an experiment
requires a lot of planning, and the people involved in the research project have a vested interest in
supporting their hypotheses. If the observers knew which child was in which group, it might influence
how they interpret ambiguous responses, such as sloppy handwriting or minor computational mistakes.
By being blind to which child is in which group, we protect against those biases. This situation is a
single-blind study, meaning that one of the groups (participants) are unaware as to which group they
are in (experiment or control group) while the researcher who developed the experiment knows which
participants are in each group.

In a double-blind study, both the researchers and the participants are blind to group assignments. Why
would a researcher want to run a study where no one knows who is in which group? Because by doing
so, we can control for both experimenter and participant expectations. If you are familiar with the phrase
placebo effect, you already have some idea as to why this is an important consideration. The placebo effect
occurs when people’s expectations or beliefs influence or determine their experience in a given situation.
In other words, simply expecting something to happen can actually make it happen.

The placebo effect is commonly described in terms of testing the effectiveness of a new medication.
Imagine that you work in a pharmaceutical company, and you think you have a new drug that is effective
in treating depression. To demonstrate that your medication is effective, you run an experiment with two
groups: The experimental group receives the medication, and the control group does not. But you don’t
want participants to know whether they received the drug or not.

Why is that? Imagine that you are a participant in this study, and you have just taken a pill that you
think will improve your mood. Because you expect the pill to have an effect, you might feel better simply
because you took the pill and not because of any drug actually contained in the pill—this is the placebo

To make sure that any effects on mood are due to the drug and not due to expectations, the control group
receives a placebo (in this case a sugar pill). Now everyone gets a pill, and once again neither the researcher
nor the experimental participants know who got the drug and who got the sugar pill. Any differences in
mood between the experimental and control groups can now be attributed to the drug itself rather than to
experimenter bias or participant expectations (Figure 2.16).

Figure 2.16 Providing the control group with a placebo treatment protects against bias caused by expectancy.
(credit: Elaine and Arthur Shapiro)

Chapter 2 | Psychological Research 57

Independent and Dependent Variables

In a research experiment, we strive to study whether changes in one thing cause changes in another. To
achieve this, we must pay attention to two important variables, or things that can be changed, in any
experimental study: the independent variable and the dependent variable. An independent variable is
manipulated or controlled by the experimenter. In a well-designed experimental study, the independent
variable is the only important difference between the experimental and control groups. In our example of
how technology use in the classroom affects learning, the independent variable is the type of learning by
participants in the study (Figure 2.17). A dependent variable is what the researcher measures to see how
much effect the independent variable had. In our example, the dependent variable is the learning exhibited
by our participants.

Figure 2.17 In an experiment, manipulations of the independent variable are expected to result in changes in the
dependent variable. (credit: “classroom” modification of work by Nikolay Georgiev/Pixabay; credit “note taking”:
modification of work by KF/Wikimedia)

We expect that the dependent variable will change as a function of the independent variable. In other
words, the dependent variable depends on the independent variable. A good way to think about the
relationship between the independent and dependent variables is with this question: What effect does the
independent variable have on the dependent variable? Returning to our example, what is the effect of
being taught a lesson through a computer program versus through an in-person instructor?

Selecting and Assigning Experimental Participants

Now that our study is designed, we need to obtain a sample of individuals to include in our experiment.
Our study involves human participants so we need to determine who to include. Participants are the
subjects of psychological research, and as the name implies, individuals who are involved in psychological
research actively participate in the process. Often, psychological research projects rely on college students
to serve as participants. In fact, the vast majority of research in psychology subfields has historically
involved students as research participants (Sears, 1986; Arnett, 2008). But are college students truly
representative of the general population? College students tend to be younger, more educated, more
liberal, and less diverse than the general population. Although using students as test subjects is an
accepted practice, relying on such a limited pool of research participants can be problematic because it is
difficult to generalize findings to the larger population.

58 Chapter 2 | Psychological Research

This OpenStax book is available for free at

Our hypothetical experiment involves high school students, and we must first generate a sample of
students. Samples are used because populations are usually too large to reasonably involve every member
in our particular experiment (Figure 2.18). If possible, we should use a random sample (there are other
types of samples, but for the purposes of this chapter, we will focus on random samples). A random
sample is a subset of a larger population in which every member of the population has an equal chance
of being selected. Random samples are preferred because if the sample is large enough we can be
reasonably sure that the participating individuals are representative of the larger population. This means
that the percentages of characteristics in the sample—sex, ethnicity, socioeconomic level, and any other
characteristics that might affect the results—are close to those percentages in the larger population.

In our example, let’s say we decide our population of interest is algebra students. But all algebra students
is a very large population, so we need to be more specific; instead we might say our population of interest
is all algebra students in a particular city. We should include students from various income brackets,
family situations, races, ethnicities, religions, and geographic areas of town. With this more manageable
population, we can work with the local schools in selecting a random sample of around 200 algebra
students who we want to participate in our experiment.

In summary, because we cannot test all of the algebra students in a city, we want to find a group of about
200 that reflects the composition of that city. With a representative group, we can generalize our findings
to the larger population without fear of our sample being biased in some way.

Figure 2.18 Researchers may work with (a) a large population or (b) a sample group that is a subset of the larger
population. (credit “crowd”: modification of work by James Cridland; credit “students”: modification of work by Laurie

Now that we have a sample, the next step of the experimental process is to split the participants into
experimental and control groups through random assignment. With random assignment, all participants
have an equal chance of being assigned to either group. There is statistical software that will randomly
assign each of the algebra students in the sample to either the experimental or the control group.

Random assignment is critical for sound experimental design. With sufficiently large samples, random
assignment makes it unlikely that there are systematic differences between the groups. So, for instance, it
would be very unlikely that we would get one group composed entirely of males, a given ethnic identity,
or a given religious ideology. This is important because if the groups were systematically different before
the experiment began, we would not know the origin of any differences we find between the groups: Were
the differences preexisting, or were they caused by manipulation of the independent variable? Random
assignment allows us to assume that any differences observed between experimental and control groups
result from the manipulation of the independent variable.

Chapter 2 | Psychological Research 59

Use this online random number generator ( to learn more about
random sampling and assignments.

Issues to Consider

While experiments allow scientists to make cause-and-effect claims, they are not without problems. True
experiments require the experimenter to manipulate an independent variable, and that can complicate
many questions that psychologists might want to address. For instance, imagine that you want to know
what effect sex (the independent variable) has on spatial memory (the dependent variable). Although you
can certainly look for differences between males and females on a task that taps into spatial memory, you
cannot directly control a person’s sex. We categorize this type of research approach as quasi-experimental
and recognize that we cannot make cause-and-effect claims in these circumstances.

Experimenters are also limited by ethical constraints. For instance, you would not be able to conduct an
experiment designed to determine if experiencing abuse as a child leads to lower levels of self-esteem
among adults. To conduct such an experiment, you would need to randomly assign some experimental
participants to a group that receives abuse, and that experiment would be unethical.

Interpreting Experimental Findings

Once data is collected from both the experimental and the control groups, a statistical analysis is
conducted to find out if there are meaningful differences between the two groups. A statistical analysis
determines how likely any difference found is due to chance (and thus not meaningful). For example, if
an experiment is done on the effectiveness of a nutritional supplement, and those taking a placebo pill
(and not the supplement) have the same result as those taking the supplement, then the experiment has
shown that the nutritional supplement is not effective. Generally, psychologists consider differences to be
statistically significant if there is less than a five percent chance of observing them if the groups did not
actually differ from one another. Stated another way, psychologists want to limit the chances of making
“false positive” claims to five percent or less.

The greatest strength of experiments is the ability to assert that any significant differences in the findings
are caused by the independent variable. This occurs because random selection, random assignment, and
a design that limits the effects of both experimenter bias and participant expectancy should create groups
that are similar in composition and treatment. Therefore, any difference between the groups is attributable
to the independent variable, and now we can finally make a causal statement. If we find that watching a
violent television program results in more violent behavior than watching a nonviolent program, we can
safely say that watching violent television programs causes an increase in the display of violent behavior.

Reporting Research

When psychologists complete a research project, they generally want to share their findings with other
scientists. The American Psychological Association (APA) publishes a manual detailing how to write
a paper for submission to scientific journals. Unlike an article that might be published in a magazine
like Psychology Today, which targets a general audience with an interest in psychology, scientific journals
generally publish peer-reviewed journal articles aimed at an audience of professionals and scholars who
are actively involved in research themselves.


60 Chapter 2 | Psychological Research

This OpenStax book is available for free at

The Online Writing Lab (OWL) ( at Purdue University can walk you through
the APA writing guidelines.

A peer-reviewed journal article is read by several other scientists (generally anonymously) with expertise
in the subject matter. These peer reviewers provide feedback—to both the author and the journal
editor—regarding the quality of the draft. Peer reviewers look for a strong rationale for the research being
described, a clear description of how the research was conducted, and evidence that the research was
conducted in an ethical manner. They also look for flaws in the study’s design, methods, and statistical
analyses. They check that the conclusions drawn by the authors seem reasonable given the observations
made during the research. Peer reviewers also comment on how valuable the research is in advancing the
discipline’s knowledge. This helps prevent unnecessary duplication of research findings in the scientific
literature and, to some extent, ensures that each research article provides new information. Ultimately, the
journal editor will compile all of the peer reviewer feedback and determine whether the article will be
published in its current state (a rare occurrence), published with revisions, or not accepted for publication.

Peer review provides some degree of quality control for psychological research. Poorly conceived or
executed studies can be weeded out, and even well-designed research can be improved by the revisions
suggested. Peer review also ensures that the research is described clearly enough to allow other scientists
to replicate it, meaning they can repeat the experiment using different samples to determine reliability.
Sometimes replications involve additional measures that expand on the original finding. In any case,
each replication serves to provide more evidence to support the original research findings. Successful
replications of published research make scientists more apt to adopt those findings, while repeated failures
tend to cast doubt on the legitimacy of the original article and lead scientists to look elsewhere. For
example, it would be a major advancement in the medical field if a published study indicated that taking
a new drug helped individuals achieve a healthy weight without changing their diet. But if other scientists
could not replicate the results, the original study’s claims would be questioned.

In recent years, there has been increasing concern about a “replication crisis” that has affected a number of
scientific fields, including psychology. Some of the most well-known studies and scientists have produced
research that has failed to be replicated by others (as discussed in Shrout & Rodgers, 2018). In fact, even a
famous Nobel Prize-winning scientist has recently retracted a published paper because she had difficulty
replicating her results (Nobel Prize-winning scientist Frances Arnold retracts paper, 2020 January 3). These
kinds of outcomes have prompted some scientists to begin to work together and more openly, and some
would argue that the current “crisis” is actually improving the ways in which science is conducted and in
how its results are shared with others (Aschwanden, 2018).

The Vaccine-Autism Myth and Retraction of Published Studies

Some scientists have claimed that routine childhood vaccines cause some children to develop autism, and,
in fact, several peer-reviewed publications published research making these claims. Since the initial reports,
large-scale epidemiological research has suggested that vaccinations are not responsible for causing autism
and that it is much safer to have your child vaccinated than not. Furthermore, several of the original studies
making this claim have since been retracted.

A published piece of work can be rescinded when data is called into question because of falsification,



Chapter 2 | Psychological Research 61

fabrication, or serious research design problems. Once rescinded, the scientific community is informed that
there are serious problems with the original publication. Retractions can be initiated by the researcher who
led the study, by research collaborators, by the institution that employed the researcher, or by the editorial
board of the journal in which the article was originally published. In the vaccine-autism case, the retraction
was made because of a significant conflict of interest in which the leading researcher had a financial interest
in establishing a link between childhood vaccines and autism (Offit, 2008). Unfortunately, the initial studies
received so much media attention that many parents around the world became hesitant to have their children
vaccinated (Figure 2.19). Continued reliance on such debunked studies has significant consequences. For
instance, between January and October of 2019, there were 22 measles outbreaks across the United States
and more than a thousand cases of individuals contracting measles (Patel et al., 2019). This is likely due to
the anti-vaccination movements that have risen from the debunked research. For more information about how
the vaccine/autism story unfolded, as well as the repercussions of this story, take a look at Paul Offit’s book,
Autism’s False Prophets: Bad Science, Risky Medicine, and the Search for a Cure.

Figure 2.19 Some people still think vaccinations cause autism. (credit: modification of work by UNICEF


Reliability and validity are two important considerations that must be made with any type of data
collection. Reliability refers to the ability to consistently produce a given result. In the context of
psychological research, this would mean that any instruments or tools used to collect data do so in
consistent, reproducible ways. There are a number of different types of reliability. Some of these include
inter-rater reliability (the degree to which two or more different observers agree on what has been
observed), internal consistency (the degree to which different items on a survey that measure the same
thing correlate with one another), and test-retest reliability (the degree to which the outcomes of a
particular measure remain consistent over multiple administrations).

Unfortunately, being consistent in measurement does not necessarily mean that you have measured
something correctly. To illustrate this concept, consider a kitchen scale that would be used to measure the
weight of cereal that you eat in the morning. If the scale is not properly calibrated, it may consistently
under- or overestimate the amount of cereal that’s being measured. While the scale is highly reliable in

62 Chapter 2 | Psychological Research

This OpenStax book is available for free at

producing consistent results (e.g., the same amount of cereal poured onto the scale produces the same
reading each time), those results are incorrect. This is where validity comes into play. Validity refers to
the extent to which a given instrument or tool accurately measures what it’s supposed to measure, and
once again, there are a number of ways in which validity can be expressed. Ecological validity (the degree
to which research results generalize to real-world applications), construct validity (the degree to which a
given variable actually captures or measures what it is intended to measure), and face validity (the degree
to which a given variable seems valid on the surface) are just a few types that researchers consider. While
any valid measure is by necessity reliable, the reverse is not necessarily true. Researchers strive to use
instruments that are both highly reliable and valid.

How Valid Are the SAT and ACT?

Standardized tests like the SAT and ACT are supposed to measure an individual’s aptitude for a college
education, but how reliable and valid are such tests? Research conducted by the College Board suggests that
scores on the SAT have high predictive validity for first-year college students’ GPA (Kobrin, Patterson, Shaw,
Mattern, & Barbuti, 2008). In this context, predictive validity refers to the test’s ability to effectively predict
the GPA of college freshmen. Given that many institutions of higher education require the SAT or ACT for
admission, this high degree of predictive validity might be comforting.

However, the emphasis placed on SAT or ACT scores in college admissions has generated some controversy
on a number of fronts. For one, some researchers assert that these tests are biased and place minority
students at a disadvantage and unfairly reduces the likelihood of being admitted into a college (Santelices &
Wilson, 2010). Additionally, some research has suggested that the predictive validity of these tests is grossly
exaggerated in how well they are able to predict the GPA of first-year college students. In fact, it has been
suggested that the SAT’s predictive validity may be overestimated by as much as 150% (Rothstein, 2004).
Many institutions of higher education are beginning to consider de-emphasizing the significance of SAT scores
in making admission decisions (Rimer, 2008).

Recent examples of high profile cheating scandals both domestically and abroad have only increased the
scrutiny being placed on these types of tests, and as of March 2019, more than 1000 institutions of higher
education have either relaxed or eliminated the requirements for SAT or ACT testing for admissions (Strauss,
2019, March 19).

2.4 Ethics

Learning Objectives

By the end of this section, you will be able to:
• Discuss how research involving human subjects is regulated
• Summarize the processes of informed consent and debriefing
• Explain how research involving animal subjects is regulated

Today, scientists agree that good research is ethical in nature and is guided by a basic respect for human
dignity and safety. However, as you will read in the feature box, this has not always been the case. Modern
researchers must demonstrate that the research they perform is ethically sound. This section presents how
ethical considerations affect the design and implementation of research conducted today.


Any experiment involving the participation of human subjects is governed by extensive, strict guidelines


Chapter 2 | Psychological Research 63

designed to ensure that the experiment does not result in harm. Any research institution that receives
federal support for research involving human participants must have access to an institutional review
board (IRB). The IRB is a committee of individuals often made up of members of the institution’s
administration, scientists, and community members (Figure 2.20). The purpose of the IRB is to review
proposals for research that involves human participants. The IRB reviews these proposals with the
principles mentioned above in mind, and generally, approval from the IRB is required in order for the
experiment to proceed.

Figure 2.20 An institution’s IRB meets regularly to review experimental proposals that involve human participants.
(credit: International Hydropower Association/Flickr)

An institution’s IRB requires several components in any experiment it approves. For one, each participant
must sign an informed consent form before they can participate in the experiment. An informed consent
form provides a written description of what participants can expect during the experiment, including
potential risks and implications of the research. It also lets participants know that their involvement is
completely voluntary and can be discontinued without penalty at any time. Furthermore, the informed
consent guarantees that any data collected in the experiment will remain completely confidential. In cases
where research participants are under the age of 18, the parents or legal guardians are required to sign the
informed consent form.

View this example of a consent form ( to learn more.

While the informed consent form should be as honest as possible in describing exactly what participants
will be doing, sometimes deception is necessary to prevent participants’ knowledge of the exact research
question from affecting the results of the study. Deception involves purposely misleading experiment
participants in order to maintain the integrity of the experiment, but not to the point where the deception
could be considered harmful. For example, if we are interested in how our opinion of someone is affected
by their attire, we might use deception in describing the experiment to prevent that knowledge from
affecting participants’ responses. In cases where deception is involved, participants must receive a full
debriefing upon conclusion of the study—complete, honest information about the purpose of the
experiment, how the data collected will be used, the reasons why deception was necessary, and
information about how to obtain additional information about the study.


64 Chapter 2 | Psychological Research

This OpenStax book is available for free at

Ethics and the Tuskegee Syphilis Study

Unfortunately, the ethical guidelines that exist for research today were not always applied in the past. In 1932,
poor, rural, black, male sharecroppers from Tuskegee, Alabama, were recruited to participate in an experiment
conducted by the U.S. Public Health Service, with the aim of studying syphilis in black men (Figure 2.21). In
exchange for free medical care, meals, and burial insurance, 600 men agreed to participate in the study. A little
more than half of the men tested positive for syphilis, and they served as the experimental group (given that
the researchers could not randomly assign participants to groups, this represents a quasi-experiment). The
remaining syphilis-free individuals served as the control group. However, those individuals that tested positive
for syphilis were never informed that they had the disease.

While there was no treatment for syphilis when the study began, by 1947 penicillin was recognized as an
effective treatment for the disease. Despite this, no penicillin was administered to the participants in this
study, and the participants were not allowed to seek treatment at any other facilities if they continued in the
study. Over the course of 40 years, many of the participants unknowingly spread syphilis to their wives (and
subsequently their children born from their wives) and eventually died because they never received treatment
for the disease. This study was discontinued in 1972 when the experiment was discovered by the national
press (Tuskegee University, n.d.). The resulting outrage over the experiment led directly to the National
Research Act of 1974 and the strict ethical guidelines for research on humans described in this chapter. Why
is this study unethical? How were the men who participated and their families harmed as a function of this

Figure 2.21 A participant in the Tuskegee Syphilis Study receives an injection.

Visit this website about the Tuskegee Syphilis Study ( to learn more.


Many psychologists conduct research involving animal subjects. Often, these researchers use rodents
(Figure 2.22) or birds as the subjects of their experiments—the APA estimates that 90% of all animal
research in psychology uses these species (American Psychological Association, n.d.). Because many basic
processes in animals are sufficiently similar to those in humans, these animals are acceptable substitutes



Chapter 2 | Psychological Research 65

for research that would be considered unethical in human participants.

Figure 2.22 Rats, like the one shown here, often serve as the subjects of animal research.

This does not mean that animal researchers are immune to ethical concerns. Indeed, the humane and
ethical treatment of animal research subjects is a critical aspect of this type of research. Researchers must
design their experiments to minimize any pain or distress experienced by animals serving as research

Whereas IRBs review research proposals that involve human participants, animal experimental proposals
are reviewed by an Institutional Animal Care and Use Committee (IACUC). An IACUC consists of
institutional administrators, scientists, veterinarians, and community members. This committee is charged
with ensuring that all experimental proposals require the humane treatment of animal research subjects. It
also conducts semi-annual inspections of all animal facilities to ensure that the research protocols are being
followed. No animal research project can proceed without the committee’s approval.

66 Chapter 2 | Psychological Research

This OpenStax book is available for free at

archival research


cause-and-effect relationship

clinical or case study

confirmation bias

confounding variable

control group


correlation coefficient

cross-sectional research



deductive reasoning

dependent variable

double-blind study


experimental group

experimenter bias



Key Terms

method of research using past records or data sets to answer various research
questions, or to search for interesting patterns or relationships

reduction in number of research participants as some drop out of the study over time

changes in one variable cause the changes in the other variable; can be
determined only through an experimental research design

observational research study focusing on one or a few people

tendency to ignore evidence that disproves ideas or beliefs

unanticipated outside factor that affects both variables of interest, often giving the
false impression that changes in one variable causes changes in the other variable, when, in actuality, the
outside factor causes changes in both variables

serves as a basis for comparison and controls for chance factors that might influence the
results of the study—by holding such factors constant across groups so that the experimental
manipulation is the only difference between groups

relationship between two or more variables; when two variables are correlated, one variable
changes as the other does

number from -1 to +1, indicating the strength and direction of the relationship
between variables, and usually represented by r

compares multiple segments of a population at a single time

when an experiment involved deception, participants are told complete and truthful
information about the experiment at its conclusion

purposely misleading experiment participants in order to maintain the integrity of the

results are predicted based on a general premise

variable that the researcher measures to see how much effect the independent
variable had

experiment in which both the researchers and the participants are blind to group

grounded in objective, tangible evidence that can be observed time and time again, regardless
of who is observing

group designed to answer the research question; experimental manipulation is the
only difference between the experimental and control groups, so any differences between the two are due
to experimental manipulation rather than chance

researcher expectations skew the results of the study

objective and verifiable observation, established using evidence collected through empirical research

able to be disproven by experimental results

Chapter 2 | Psychological Research 67



illusory correlation

independent variable

inductive reasoning

informed consent

Institutional Animal Care and Use Committee (IACUC)

Institutional Review Board (IRB)

inter-rater reliability

longitudinal research

naturalistic observation

negative correlation

observer bias

operational definition



peer-reviewed journal article

placebo effect


positive correlation

random assignment

inferring that the results for a sample apply to the larger population

(plural: hypotheses) tentative and testable statement about the relationship between two or
more variables

seeing relationships between two things when in reality no such relationship exists

variable that is influenced or controlled by the experimenter; in a sound
experimental study, the independent variable is the only important difference between the experimental
and control group

conclusions are drawn from observations

process of informing a research participant about what to expect during an
experiment, any risks involved, and the implications of the research, and then obtaining the person’s
consent to participate

committee of administrators, scientists,
veterinarians, and community members that reviews proposals for research involving non-human

committee of administrators, scientists, and community members that
reviews proposals for research involving human participants

measure of agreement among observers on how they record and classify a
particular event

studies in which the same group of individuals is surveyed or measured
repeatedly over an extended period of time

observation of behavior in its natural setting

two variables change in different directions, with one becoming larger as the other
becomes smaller; a negative correlation is not the same thing as no correlation

when observations may be skewed to align with observer expectations

description of what actions and operations will be used to measure the dependent
variables and manipulate the independent variables

personal judgments, conclusions, or attitudes that may or may not be accurate

subjects of psychological research

article read by several other scientists (usually anonymously) with
expertise in the subject matter, who provide feedback regarding the quality of the manuscript before it is
accepted for publication

people’s expectations or beliefs influencing or determining their experience in a given

overall group of individuals that the researchers are interested in

two variables change in the same direction, both becoming either larger or smaller

method of experimental group assignment in which all participants have an equal
chance of being assigned to either group

68 Chapter 2 | Psychological Research

This OpenStax book is available for free at

random sample




single-blind study

statistical analysis




subset of a larger population in which every member of the population has an equal
chance of being selected

consistency and reproducibility of a given result

repeating an experiment using different samples to determine the research’s reliability

subset of individuals selected from the larger population

experiment in which the researcher knows which participants are in the experimental
group and which are in the control group

determines how likely any difference between experimental groups is due to chance

list of questions to be answered by research participants—given as paper-and-pencil
questionnaires, administered electronically, or conducted verbally—allowing researchers to collect data
from a large number of people

well-developed set of ideas that propose an explanation for observed phenomena

accuracy of a given result in measuring what it is designed to measure


2.1 Why Is Research Important?
Scientists are engaged in explaining and understanding how the world around them works, and they are
able to do so by coming up with theories that generate hypotheses that are testable and falsifiable. Theories
that stand up to their tests are retained and refined, while those that do not are discarded or modified.
In this way, research enables scientists to separate fact from simple opinion. Having good information
generated from research aids in making wise decisions both in public policy and in our personal lives.

2.2 Approaches to Research
The clinical or case study involves studying just a few individuals for an extended period of time. While
this approach provides an incredible depth of information, the ability to generalize these observations to
the larger population is problematic. Naturalistic observation involves observing behavior in a natural
setting and allows for the collection of valid, true-to-life information from realistic situations. However,
naturalistic observation does not allow for much control and often requires quite a bit of time and money
to perform. Researchers strive to ensure that their tools for collecting data are both reliable (consistent and
replicable) and valid (accurate).

Surveys can be administered in a number of ways and make it possible to collect large amounts of data
quickly. However, the depth of information that can be collected through surveys is somewhat limited
compared to a clinical or case study.

Archival research involves studying existing data sets to answer research questions.

Longitudinal research has been incredibly helpful to researchers who need to collect data on how people
change over time. Cross-sectional research compares multiple segments of a population at a single time.

2.3 Analyzing Findings
A correlation is described with a correlation coefficient, r, which ranges from -1 to 1. The correlation
coefficient tells us about the nature (positive or negative) and the strength of the relationship between
two or more variables. Correlations do not tell us anything about causation—regardless of how strong
the relationship is between variables. In fact, the only way to demonstrate causation is by conducting an
experiment. People often make the mistake of claiming that correlations exist when they really do not.

Chapter 2 | Psychological Research 69

Researchers can test cause-and-effect hypotheses by conducting experiments. Ideally, experimental
participants are randomly selected from the population of interest. Then, the participants are randomly
assigned to their respective groups. Sometimes, the researcher and the participants are blind to group
membership to prevent their expectations from influencing the results.

In ideal experimental design, the only difference between the experimental and control groups is whether
participants are exposed to the experimental manipulation. Each group goes through all phases of the
experiment, but each group will experience a different level of the independent variable: the experimental
group is exposed to the experimental manipulation, and the control group is not exposed to the
experimental manipulation. The researcher then measures the changes that are produced in the dependent
variable in each group. Once data is collected from both groups, it is analyzed statistically to determine if
there are meaningful differences between the groups.

Psychologists report their research findings in peer-reviewed journal articles. Research published in this
format is checked by several other psychologists who serve as a filter separating ideas that are supported
by evidence from ideas that are not. Replication has an important role in ensuring the legitimacy of
published research. In the long run, only those findings that are capable of being replicated consistently
will achieve consensus in the scientific community.

2.4 Ethics
Ethics in research is an evolving field, and some practices that were accepted or tolerated in the past
would be considered unethical today. Researchers are expected to adhere to basic ethical guidelines when
conducting experiments that involve human participants. Any experiment involving human participants
must be approved by an IRB. Participation in experiments is voluntary and requires informed consent of
the participants. If any deception is involved in the experiment, each participant must be fully debriefed
upon the conclusion of the study.

Animal research is also held to a high ethical standard. Researchers who use animals as experimental
subjects must design their projects so that pain and distress are minimized. Animal research requires the
approval of an IACUC, and all animal facilities are subject to regular inspections to ensure that animals are
being treated humanely.

Review Questions

1. Scientific hypotheses are ________ and

a. observable
b. original
c. provable
d. testable

2. ________ are defined as observable realities.
a. behaviors
b. facts
c. opinions
d. theories

3. Scientific knowledge is ________.
a. intuitive
b. empirical
c. permanent
d. subjective

4. A major criticism of Freud’s early theories
involves the fact that his theories ________.

a. were too limited in scope
b. were too outrageous
c. were too broad
d. were not testable

5. Sigmund Freud developed his theory of
human personality by conducting in-depth
interviews over an extended period of time with a
few clients. This type of research approach is
known as a(n): ________.

a. archival research
b. case study
c. naturalistic observation
d. survey

70 Chapter 2 | Psychological Research

This OpenStax book is available for free at

6. ________ involves observing behavior in
individuals in their natural environments.

a. archival research
b. case study
c. naturalistic observation
d. survey

7. The major limitation of case studies is

a. the superficial nature of the information
collected in this approach

b. the lack of control that the researcher has in
this approach

c. the inability to generalize the findings from
this approach to the larger population

d. the absence of inter-rater reliability

8. The benefit of naturalistic observation studies
is ________.

a. the honesty of the data that is collected in a
realistic setting

b. how quick and easy these studies are to

c. the researcher’s capacity to make sure that
data is collected as efficiently as possible

d. the ability to determine cause and effect in
this particular approach

9. Using existing records to try to answer a
research question is known as ________.

a. naturalistic observation
b. survey research
c. longitudinal research
d. archival research

10. ________ involves following a group of
research participants for an extended period of

a. archival research
b. longitudinal research
c. naturalistic observation
d. cross-sectional research

11. A(n) ________ is a list of questions developed
by a researcher that can be administered in paper

a. archive
b. case Study
c. naturalistic observation
d. survey

12. Longitudinal research is complicated by high
rates of ________.

a. deception
b. observation
c. attrition
d. generalization

13. Height and weight are positively correlated.
This means that:

a. There is no relationship between height and

b. Usually, the taller someone is, the thinner
they are.

c. Usually, the shorter someone is, the heavier
they are.

d. As height increases, typically weight

14. Which of the following correlation coefficients
indicates the strongest relationship between two

a. –.90
b. –.50
c. +.80
d. +.25

15. Which statement best illustrates a negative
correlation between the number of hours spent
watching TV the week before an exam and the
grade on that exam?

a. Watching too much television leads to poor
exam performance.

b. Smart students watch less television.
c. Viewing television interferes with a

student’s ability to prepare for the
upcoming exam.

d. Students who watch more television
perform more poorly on their exams.

16. The correlation coefficient indicates the
weakest relationship when ________.

a. it is closest to 0
b. it is closest to -1
c. it is positive
d. it is negative

Chapter 2 | Psychological Research 71

17. ________ means that everyone in the
population has the same likelihood of being asked
to participate in the study.

a. operationalizing
b. placebo effect
c. random assignment
d. random sampling

18. The ________ is controlled by the
experimenter, while the ________ represents the
information collected and statistically analyzed by
the experimenter.

a. dependent variable; independent variable
b. independent variable; dependent variable
c. placebo effect; experimenter bias
d. experiment bias; placebo effect

19. Researchers must ________ important
concepts in their studies so others would have a
clear understanding of exactly how those concepts
were defined.

a. randomly assign
b. randomly select
c. operationalize
d. generalize

20. Sometimes, researchers will administer a(n)
________ to participants in the control group to
control for the effects that participant expectation
might have on the experiment.

a. dependent variable
b. independent variable
c. statistical analysis
d. placebo

21. ________ is to animal research as ________ is
to human research.

a. informed consent; deception
d. deception; debriefing

22. Researchers might use ________ when
providing participants with the full details of the
experiment could skew their responses.

a. informed consent
b. deception
c. ethics
d. debriefing

23. A person’s participation in a research project
must be ________.

a. random
b. rewarded
c. voluntary
d. public

24. Before participating in an experiment,
individuals should read and sign the ________

a. informed consent
b. debriefing
c. IRB
d. ethics

Critical Thinking Questions

25. In this section, the D.A.R.E. program was described as an incredibly popular program in schools
across the United States despite the fact that research consistently suggests that this program is largely
ineffective. How might one explain this discrepancy?

26. The scientific method is often described as self-correcting and cyclical. Briefly describe your
understanding of the scientific method with regard to these concepts.

27. In this section, conjoined twins, Krista and Tatiana, were described as being potential participants in a
case study. In what other circumstances would you think that this particular research approach would be
especially helpful and why?

72 Chapter 2 | Psychological Research

This OpenStax book is available for free at

28. Presumably, reality television programs aim to provide a realistic portrayal of the behavior displayed
by the characters featured in such programs. This section pointed out why this is not really the case. What
changes could be made in the way that these programs are produced that would result in more honest
portrayals of realistic behavior?

29. Which of the research methods discussed in this section would be best suited to research the
effectiveness of the D.A.R.E. program in preventing the use of alcohol and other drugs? Why?

30. Aside from biomedical research, what other areas of research could greatly benefit by both
longitudinal and archival research?

31. Earlier in this section, we read about research suggesting that there is a correlation between eating
cereal and weight. Cereal companies that present this information in their advertisements could lead
someone to believe that eating more cereal causes healthy weight. Why would they make such a claim and
what arguments could you make to counter this cause-and-effect claim?

32. Recently a study was published in the journal, Nutrition and Cancer, which established a negative
correlation between coffee consumption and breast cancer. Specifically, it was found that women
consuming more than 5 cups of coffee a day were less likely to develop breast cancer than women who
never consumed coffee (Lowcock, Cotterchio, Anderson, Boucher, & El-Sohemy, 2013). Imagine you see
a newspaper story about this research that says, “Coffee Protects Against Cancer.” Why is this headline
misleading and why would a more accurate headline draw less interest?

33. Sometimes, true random sampling can be very difficult to obtain. Many researchers make use of
convenience samples as an alternative. For example, one popular convenience sample would involve
students enrolled in Introduction to Psychology courses. What are the implications of using this sampling

34. Peer review is an important part of publishing research findings in many scientific disciplines. This
process is normally conducted anonymously; in other words, the author of the article being reviewed does
not know who is reviewing the article, and the reviewers are unaware of the author’s identity. Why would
this be an important part of this process?

35. Some argue that animal research is inherently flawed in terms of being ethical because unlike human
participants, animals do not consent to be involved in research. Do you agree with this perspective? Given
that animals do not consent to be involved in research projects, what sorts of extra precautions should be
taken to ensure that they receive the most humane treatment possible?

36. At the end of the last section, you were asked to design a basic experiment to answer some question
of interest. What ethical considerations should be made with the study you proposed to ensure that your
experiment would conform to the scientific community’s expectations of ethical research?

Personal Application Questions

37. Healthcare professionals cite an enormous number of health problems related to obesity, and many
people have an understandable desire to attain a healthy weight. There are many diet programs, services,
and products on the market to aid those who wish to lose weight. If a close friend was considering
purchasing or participating in one of these products, programs, or services, how would you make sure
your friend was fully aware of the potential consequences of this decision? What sort of information would
you want to review before making such an investment or lifestyle change yourself?

Chapter 2 | Psychological Research 73

38. A friend of yours is working part-time in a local pet store. Your friend has become increasingly
interested in how dogs normally communicate and interact with each other, and is thinking of visiting a
local veterinary clinic to see how dogs interact in the waiting room. After reading this section, do you think
this is the best way to better understand such interactions? Do you have any suggestions that might result
in more valid data?

39. As a college student, you are no doubt concerned about the grades that you earn while completing
your coursework. If you wanted to know how overall GPA is related to success in life after college, how
would you choose to approach this question and what kind of resources would you need to conduct this

40. We all have a tendency to make illusory correlations from time to time. Try to think of an illusory
correlation that is held by you, a family member, or a close friend. How do you think this illusory
correlation came about and what can be done in the future to combat them?

41. Are there any questions about human or animal behavior that you would really like to answer?
Generate a hypothesis and briefly describe how you would conduct an experiment to answer your

42. Take a few minutes to think about all of the advancements that our society has achieved as a function
of research involving animal subjects. How have you, a friend, or a family member benefited directly from
this kind of research?

74 Chapter 2 | Psychological Research

This OpenStax book is available for free at

Chapter 3


Figure 3.1 Different brain imaging techniques provide scientists with insight into different aspects of how the human
brain functions. Left to right, PET scan (positron emission tomography), CT scan (computerized tomography), and
fMRI (functional magnetic resonance imaging) are three types of scans. (credit “left”: modification of work by Health
and Human Services Department, National Institutes of Health; credit “center”: modification of work by
“Aceofhearts1968″/Wikimedia Commons; credit “right”: modification of work by Kim J, Matthews NL, Park S.)

Chapter Outline

3.1 Human Genetics

3.2 Cells of the Nervous System

3.3 Parts of the Nervous System

3.4 The Brain and Spinal Cord

3.5 The Endocrine System


Have you ever taken a device apart to find out how it works? Many of us have done so, whether to attempt
a repair or simply to satisfy our curiosity. A device’s internal workings are often distinct from its user
interface on the outside. For example, we don’t think about microchips and circuits when we turn up
the volume on a mobile phone; instead, we think about getting the volume just right. Similarly, the inner
workings of the human body are often distinct from the external expression of those workings. It is the
job of psychologists to find the connection between these—for example, to figure out how the firings of
millions of neurons become a thought.

This chapter strives to explain the biological mechanisms that underlie behavior. These physiological and
anatomical foundations are the basis for many areas of psychology. In this chapter, you will learn how
genetics influence both physiological and psychological traits. You will become familiar with the structure
and function of the nervous system. And, finally, you will learn how the nervous system interacts with the
endocrine system.

Chapter 3 | Biopsychology 75

3.1 Human Genetics

Learning Objectives

By the end of this section, you will be able to:
• Explain the basic principles of the theory of evolution by natural selection
• Describe the differences between genotype and phenotype
• Discuss how gene-environment interactions are critical for expression of physical and

psychological characteristics

Psychological researchers study genetics in order to better understand the biological factors that contribute
to certain behaviors. While all humans share certain biological mechanisms, we are each unique. And
while our bodies have many of the same parts—brains and hormones and cells with genetic codes—these
are expressed in a wide variety of behaviors, thoughts, and reactions.

Why do two people infected by the same disease have different outcomes: one surviving and one
succumbing to the ailment? How are genetic diseases passed through family lines? Are there genetic
components to psychological disorders, such as depression or schizophrenia? To what extent might there
be a psychological basis to health conditions such as childhood obesity?

To explore these questions, let’s start by focusing on a specific genetic disorder, sickle cell anemia, and
how it might manifest in two affected sisters. Sickle-cell anemia is a genetic condition in which red blood
cells, which are normally round, take on a crescent-like shape (Figure 3.2). The changed shape of these
cells affects how they function: sickle-shaped cells can clog blood vessels and block blood flow, leading to
high fever, severe pain, swelling, and tissue damage.

Figure 3.2 Normal blood cells travel freely through the blood vessels, while sickle-shaped cells form blockages
preventing blood flow.

Many people with sickle-cell anemia—and the particular genetic mutation that causes it—die at an early
age. While the notion of “survival of the fittest” may suggest that people suffering from this disorder have
a low survival rate and therefore the disorder will become less common, this is not the case. Despite the
negative evolutionary effects associated with this genetic mutation, the sickle-cell gene remains relatively
common among people of African descent. Why is this? The explanation is illustrated with the following

Imagine two young women—Luwi and Sena—sisters in rural Zambia, Africa. Luwi carries the gene for
sickle-cell anemia; Sena does not carry the gene. Sickle-cell carriers have one copy of the sickle-cell gene but
do not have full-blown sickle-cell anemia. They experience symptoms only if they are severely dehydrated
or are deprived of oxygen (as in mountain climbing). Carriers are thought to be immune from malaria
(an often deadly disease that is widespread in tropical climates) because changes in their blood chemistry

76 Chapter 3 | Biopsychology

This OpenStax book is available for free at

and immune functioning prevent the malaria parasite from having its effects (Gong, Parikh, Rosenthal, &
Greenhouse, 2013). However, full-blown sickle-cell anemia, with two copies of the sickle-cell gene, does
not provide immunity to malaria.

While walking home from school, both sisters are bitten by mosquitos carrying the malaria parasite. Luwi
is protected against malaria because she carries the sickle-cell mutation. Sena, on the other hand, develops
malaria and dies just two weeks later. Luwi survives and eventually has children, to whom she may pass
on the sickle-cell mutation.

Visit this website about how a mutation in DNA leads to sickle cell anemia (
sickle1) to learn more.

Malaria is rare in the United States, so the sickle-cell gene benefits nobody: the gene manifests primarily
in minor health problems for carriers with one copy, or a severe full-blown disease with no health benefits
for carriers with two copies. However, the situation is quite different in other parts of the world. In parts of
Africa where malaria is prevalent, having the sickle-cell mutation does provide health benefits for carriers
(protection from malaria).

The story of malaria fits with Charles Darwin’s theory of evolution by natural selection (Figure 3.3). In
simple terms, the theory states that organisms that are better suited for their environment will survive and
reproduce, while those that are poorly suited for their environment will die off. In our example, we can see
that, as a carrier, Luwi’s mutation is highly adaptive in her African homeland; however, if she resided in
the United States (where malaria is rare), her mutation could prove costly—with a high probability of the
disease in her descendants and minor health problems of her own.

Figure 3.3 (a) In 1859, Charles Darwin proposed his theory of evolution by natural selection in his book, On the
Origin of Species. (b) The book contains just one illustration: this diagram that shows how species evolve over time
through natural selection.


Chapter 3 | Biopsychology 77

Two Perspectives on Genetics and Behavior

It’s easy to get confused about two fields that study the interaction of genes and the environment, such as the
fields of evolutionary psychology and behavioral genetics. How can we tell them apart?

In both fields, it is understood that genes not only code for particular traits, but also contribute to certain
patterns of cognition and behavior. Evolutionary psychology focuses on how universal patterns of behavior
and cognitive processes have evolved over time. Therefore, variations in cognition and behavior would make
individuals more or less successful in reproducing and passing those genes on to their offspring. Evolutionary
psychologists study a variety of psychological phenomena that may have evolved as adaptations, including
fear response, food preferences, mate selection, and cooperative behaviors (Confer et al., 2010).

Whereas evolutionary psychologists focus on universal patterns that evolved over millions of years, behavioral
geneticists study how individual differences arise, in the present, through the interaction of genes and the
environment. When studying human behavior, behavioral geneticists often employ twin and adoption studies
to research questions of interest. Twin studies compare the likelihood that a given behavioral trait is shared
among identical and fraternal twins; adoption studies compare those rates among biologically related relatives
and adopted relatives. Both approaches provide some insight into the relative importance of genes and
environment for the expression of a given trait.

Watch this interview with renowned evolutionary psychologist David Buss (
buss) to learn more about how a psychologist approaches evolution and how this approach fits within the
social sciences.


Genetic variation, the genetic difference between individuals, is what contributes to a species’ adaptation
to its environment. In humans, genetic variation begins with an egg, about 100 million sperm, and
fertilization. Fertile women ovulate roughly once per month, releasing an egg from follicles in the ovary.
During the egg’s journey from the ovary through the fallopian tubes, to the uterus, a sperm may fertilize
the egg.

The egg and the sperm each contain 23 chromosomes. Chromosomes are long strings of genetic material
known as deoxyribonucleic acid (DNA). DNA is a helix-shaped molecule made up of nucleotide base
pairs. In each chromosome, sequences of DNA make up genes that control or partially control a number
of visible characteristics, known as traits, such as eye color, hair color, and so on. A single gene may have
multiple possible variations, or alleles. An allele is a specific version of a gene. So, a given gene may code
for the trait of hair color, and the different alleles of that gene affect which hair color an individual has.

When a sperm and egg fuse, their 23 chromosomes combine to create a zygote with 46 chromosomes
(23 pairs). Therefore, each parent contributes half the genetic information carried by the offspring; the
resulting physical characteristics of the offspring (called the phenotype) are determined by the interaction
of genetic material supplied by the parents (called the genotype). A person’s genotype is the genetic
makeup of that individual. Phenotype, on the other hand, refers to the individual’s inherited physical
characteristics, which are a combination of genetic and environmental influences (Figure 3.4).



78 Chapter 3 | Biopsychology

This OpenStax book is available for free at

Figure 3.4 (a) Genotype refers to the genetic makeup of an individual based on the genetic material (DNA) inherited
from one’s parents. (b) Phenotype describes an individual’s observable characteristics, such as hair color, skin color,
height, and build. (credit a: modification of work by Caroline Davis; credit b: modification of work by Cory Zanker)

Most traits are controlled by multiple genes, but some traits are controlled by one gene. A characteristic
like cleft chin, for example, is influenced by a single gene from each parent. In this example, we will call
the gene for cleft chin “B,” and the gene for smooth chin “b.” Cleft chin is a dominant trait, which means
that having the dominant allele either from one parent (Bb) or both parents (BB) will always result in the
phenotype associated with the dominant allele. When someone has two copies of the same allele, they are
said to be homozygous for that allele. When someone has a combination of alleles for a given gene, they
are said to be heterozygous. For example, smooth chin is a recessive trait, which means that an individual
will only display the smooth chin phenotype if they are homozygous for that recessive allele (bb).

Imagine that a woman with a cleft chin mates with a man with a smooth chin. What type of chin will their
child have? The answer to that depends on which alleles each parent carries. If the woman is homozygous
for cleft chin (BB), her offspring will always have cleft chin. It gets a little more complicated, however, if
the mother is heterozygous for this gene (Bb). Since the father has a smooth chin—therefore homozygous
for the recessive allele (bb)—we can expect the offspring to have a 50% chance of having a cleft chin and a
50% chance of having a smooth chin (Figure 3.5).

Figure 3.5 (a) A Punnett square is a tool used to predict how genes will interact in the production of offspring. The
capital B represents the dominant allele, and the lowercase b represents the recessive allele. In the example of the
cleft chin, where B is cleft chin (dominant allele), wherever a pair contains the dominant allele, B, you can expect a
cleft chin phenotype. You can expect a smooth chin phenotype only when there are two copies of the recessive allele,
bb. (b) A cleft chin, shown here, is an inherited trait.

In sickle cell anemia, heterozygous carriers (like Luwi from the example) can develop blood resistance to
malaria infection while those who are homozygous (like Sena) have a potentially lethal blood disorder.
Sickle-cell anemia is just one of many genetic disorders caused by the pairing of two recessive genes.
For example, phenylketonuria (PKU) is a condition in which individuals lack an enzyme that normally

Chapter 3 | Biopsychology 79

converts harmful amino acids into harmless byproducts. If someone with this condition goes untreated, he
or she will experience significant deficits in cognitive function, seizures, and an increased risk of various
psychiatric disorders. Because PKU is a recessive trait, each parent must have at least one copy of the
recessive allele in order to produce a child with the condition (Figure 3.6).

So far, we have discussed traits that involve just one gene, but few human characteristics are controlled
by a single gene. Most traits are polygenic: controlled by more than one gene. Height is one example of a
polygenic trait, as are skin color and weight.

Figure 3.6 In this Punnett square, N represents the normal allele, and p represents the recessive allele that is
associated with PKU. If two individuals mate who are both heterozygous for the allele associated with PKU, their
offspring have a 25% chance of expressing the PKU phenotype.

Where do harmful genes that contribute to diseases like PKU come from? Gene mutations provide one
source of harmful genes. A mutation is a sudden, permanent change in a gene. While many mutations can
be harmful or lethal, once in a while, a mutation benefits an individual by giving that person an advantage
over those who do not have the mutation. Recall that the theory of evolution asserts that individuals best
adapted to their particular environments are more likely to reproduce and pass on their genes to future
generations. In order for this process to occur, there must be competition—more technically, there must
be variability in genes (and resultant traits) that allow for variation in adaptability to the environment.
If a population consisted of identical individuals, then any dramatic changes in the environment would
affect everyone in the same way, and there would be no variation in selection. In contrast, diversity in
genes and associated traits allows some individuals to perform slightly better than others when faced with
environmental change. This creates a distinct advantage for individuals best suited for their environments
in terms of successful reproduction and genetic transmission.

Human Diversity

This chapter focuses on biology. Later in this course you will learn about social psychology and issues of race,
prejudice, and discrimination. When we focus strictly on biology, race becomes a weak construct. After the


80 Chapter 3 | Biopsychology

This OpenStax book is available for free at

sequencing of the human genome at the turn of the millennium, many scientists began to argue that race was
not a useful variable in genetic research and that its continued use represents a potential source of confusion
and harm. The racial categories that some believed to be helpful in studying genetic diversity in humans are
largely irrelevant. A person’s skin tone, eye color, and hair texture are functions of their genetic makeups, but
there is actually more genetic variation within a given racial category than there is between racial categories.
In some cases, focus on race has led to difficulties with misdiagnoses and/or under-diagnoses of diseases
ranging from sickle cell anemia to cystic fibrosis. Some argue that we need to distinguish between ancestry
and race and then focus on ancestry. This approach would facilitate greater understanding of human genetic
diversity (Yudell, Roberts, DeSalle, & Tishkoff, 2016).


Genes do not exist in a vacuum. Although we are all biological organisms, we also exist in an environment
that is incredibly important in determining not only when and how our genes express themselves, but
also in what combination. Each of us represents a unique interaction between our genetic makeup and our
environment; range of reaction is one way to describe this interaction. Range of reaction asserts that our
genes set the boundaries within which we can operate, and our environment interacts with the genes to
determine where in that range we will fall. For example, if an individual’s genetic makeup predisposes
her to high levels of intellectual potential and she is reared in a rich, stimulating environment, then she
will be more likely to achieve her full potential than if she were raised under conditions of significant
deprivation. According to the concept of range of reaction, genes set definite limits on potential, and
environment determines how much of that potential is achieved. Some disagree with this theory and
argue that genes do not set a limit on a person’s potential with reaction norms being determined by
the environment. For example, when individuals experience neglect or abuse early in life, they are more
likely to exhibit adverse psychological and/or physical conditions that can last throughout their lives.
These conditions may develop as a function of the negative environmental experiences in individuals from
dissimilar genetic backgrounds (Miguel, Pereira, Silveira, & Meaney, 2019; Short & Baram, 2019).

Another perspective on the interaction between genes and the environment is the concept of genetic
environmental correlation. Stated simply, our genes influence our environment, and our environment
influences the expression of our genes (Figure 3.7). Not only do our genes and environment interact,
as in range of reaction, but they also influence one another bidirectionally. For example, the child of an
NBA player would probably be exposed to basketball from an early age. Such exposure might allow the
child to realize his or her full genetic, athletic potential. Thus, the parents’ genes, which the child shares,
influence the child’s environment, and that environment, in turn, is well suited to support the child’s
genetic potential.

Chapter 3 | Biopsychology 81

Figure 3.7 Nature and nurture work together like complex pieces of a human puzzle. The interaction of our
environment and genes makes us the individuals we are. (credit “puzzle”: modification of work by Cory Zanker; credit
“houses”: modification of work by Ben Salter; credit “DNA”: modification of work by NHGRI)

In another approach to gene-environment interactions, the field of epigenetics looks beyond the genotype
itself and studies how the same genotype can be expressed in different ways. In other words, researchers
study how the same genotype can lead to very different phenotypes. As mentioned earlier, gene
expression is often influenced by environmental context in ways that are not entirely obvious. For instance,
identical twins share the same genetic information (identical twins develop from a single fertilized egg
that split, so the genetic material is exactly the same in each; in contrast, fraternal twins usually result from
two different eggs fertilized by different sperm, so the genetic material varies as with non-twin siblings).
But even with identical genes, there remains an incredible amount of variability in how gene expression
can unfold over the course of each twin’s life. Sometimes, one twin will develop a disease and the other
will not. In one example, Aliya, an identical twin, died from cancer at age 7, but her twin, now 19 years
old, has never had cancer. Although these individuals share an identical genotype, their phenotypes differ
as a result of how that genetic information is expressed over time and through their unique environmental
interactions. The epigenetic perspective is very different from range of reaction, because here the genotype
is not fixed and limited.

Watch this video about the epigenetics of twin studies ( to learn

Genes affect more than our physical characteristics. Indeed, scientists have found genetic linkages to
a number of behavioral characteristics, ranging from basic personality traits to sexual orientation to
spirituality (for examples, see Mustanski et al., 2005; Comings, Gonzales, Saucier, Johnson, & MacMurray,
2000). Genes are also associated with temperament and a number of psychological disorders, such as
depression and schizophrenia. So while it is true that genes provide the biological blueprints for our cells,
tissues, organs, and body, they also have a significant impact on our experiences and our behaviors.

Let’s look at the following findings regarding schizophrenia in light of our three views of gene-
environment interactions. Which view do you think best explains this evidence?

In a 2004 study by Tienari and colleagues, of people who were given up for adoption, adoptees whose
biological mothers had schizophrenia and who had been raised in a disturbed family environment were
much more likely to develop schizophrenia or another psychotic disorder than were any of the other


82 Chapter 3 | Biopsychology

This OpenStax book is available for free at

groups in the study:

• Of adoptees whose biological mothers had schizophrenia (high genetic risk) and who were raised
in disturbed family environments, 36.8% were likely to develop schizophrenia.

• Of adoptees whose biological mothers had schizophrenia (high genetic risk) and who were raised
in healthy family environments, 5.8% were likely to develop schizophrenia.

• Of adoptees with a low genetic risk (whose mothers did not have schizophrenia) and who were
raised in disturbed family environments, 5.3% were likely to develop schizophrenia.

• Of adoptees with a low genetic risk (whose mothers did not have schizophrenia) and who were
raised in healthy family environments, 4.8% were likely to develop schizophrenia.

The study shows that adoptees with high genetic risk were most likely to develop schizophrenia if they
were raised in disturbed home environments. This research lends credibility to the notion that both genetic
vulnerability and environmental stress are necessary for schizophrenia to develop, and that genes alone
do not tell the full tale.

3.2 Cells of the Nervous System

Learning Objectives

By the end of this section, you will be able to:
• Identify the basic parts of a neuron
• Describe how neurons communicate with each other
• Explain how drugs act as agonists or antagonists for a given neurotransmitter system

Psychologists striving to understand the human mind may study the nervous system. Learning how the
body’s cells and organs function can help us understand the biological basis of human psychology. The
nervous system is composed of two basic cell types: glial cells (also known as glia) and neurons. Glial
cells are traditionally thought to play a supportive role to neurons, both physically and metabolically.
Glial cells provide scaffolding on which the nervous system is built, help neurons line up closely with
each other to allow neuronal communication, provide insulation to neurons, transport nutrients and waste
products, and mediate immune responses. For years, researchers believed that there were many more glial
cells than neurons; however, more recent work from Suzanna Herculano-Houzel’s laboratory has called
this long-standing assumption into question and has provided important evidence that there may be a
nearly 1:1 ratio of glia cells to neurons. This is important because it suggests that human brains are more
similar to other primate brains than previously thought (Azevedo et al, 2009; Hercaulano-Houzel, 2012;
Herculano-Houzel, 2009). Neurons, on the other hand, serve as interconnected information processors that
are essential for all of the tasks of the nervous system. This section briefly describes the structure and
function of neurons.


Neurons are the central building blocks of the nervous system, 100 billion strong at birth. Like all cells,
neurons consist of several different parts, each serving a specialized function (Figure 3.8). A neuron’s
outer surface is made up of a semipermeable membrane. This membrane allows smaller molecules
and molecules without an electrical charge to pass through it, while stopping larger or highly charged

Chapter 3 | Biopsychology 83

Figure 3.8 This illustration shows a prototypical neuron, which is being myelinated by a glial cell.

The nucleus of the neuron is located in the soma, or cell body. The soma has branching extensions known
as dendrites. The neuron is a small information processor, and dendrites serve as input sites where signals
are received from other neurons. These signals are transmitted electrically across the soma and down a
major extension from the soma known as the axon, which ends at multiple terminal buttons. The terminal
buttons contain synaptic vesicles that house neurotransmitters, the chemical messengers of the nervous

Axons range in length from a fraction of an inch to several feet. In some axons, glial cells form a fatty
substance known as the myelin sheath, which coats the axon and acts as an insulator, increasing the
speed at which the signal travels. The myelin sheath is not continuous and there are small gaps that
occur down the length of the axon. These gaps in the myelin sheath are known as the Nodes of Ranvier.
The myelin sheath is crucial for the normal operation of the neurons within the nervous system: the
loss of the insulation it provides can be detrimental to normal function. To understand how this works,
let’s consider an example. PKU, a genetic disorder discussed earlier, causes a reduction in myelin and
abnormalities in white matter cortical and subcortical structures. The disorder is associated with a variety
of issues including severe cognitive deficits, exaggerated reflexes, and seizures (Anderson & Leuzzi, 2010;
Huttenlocher, 2000). Another disorder, multiple sclerosis (MS), an autoimmune disorder, involves a large-
scale loss of the myelin sheath on axons throughout the nervous system. The resulting interference in
the electrical signal prevents the quick transmittal of information by neurons and can lead to a number
of symptoms, such as dizziness, fatigue, loss of motor control, and sexual dysfunction. While some
treatments may help to modify the course of the disease and manage certain symptoms, there is currently
no known cure for multiple sclerosis.

In healthy individuals, the neuronal signal moves rapidly down the axon to the terminal buttons, where
synaptic vesicles release neurotransmitters into the synaptic cleft (Figure 3.9). The synaptic cleft is a
very small space between two neurons and is an important site where communication between neurons
occurs. Once neurotransmitters are released into the synaptic cleft, they travel across it and bind with
corresponding receptors on the dendrite of an adjacent neuron. Receptors, proteins on the cell surface
where neurotransmitters attach, vary in shape, with different shapes “matching” different

How does a neurotransmitter “know” which receptor to bind to? The neurotransmitter and the receptor
have what is referred to as a lock-and-key relationship—specific neurotransmitters fit specific receptors
similar to how a key fits a lock. The neurotransmitter binds to any receptor that it fits.

84 Chapter 3 | Biopsychology

This OpenStax book is available for free at

Figure 3.9 (a) The synaptic cleft is the space between the terminal button of one neuron and the dendrite of another
neuron. (b) In this pseudo-colored image from a scanning electron microscope, a terminal button (green) has been
opened to reveal the synaptic vesicles (orange and blue) inside. Each vesicle contains about 10,000 neurotransmitter
molecules. (credit b: modification of work by Tina Carvalho, NIH-NIGMS; scale-bar data from Matt Russell)


Now that we have learned about the basic structures of the neuron and the role that these structures play
in neuronal communication, let’s take a closer look at the signal itself—how it moves through the neuron
and then jumps to the next neuron, where the process is repeated.

We begin at the neuronal membrane. The neuron exists in a fluid environment—it is surrounded by
extracellular fluid and contains intracellular fluid (i.e., cytoplasm). The neuronal membrane keeps these
two fluids separate—a critical role because the electrical signal that passes through the neuron depends
on the intra- and extracellular fluids being electrically different. This difference in charge across the
membrane, called the membrane potential, provides energy for the signal.

The electrical charge of the fluids is caused by charged molecules (ions) dissolved in the fluid. The
semipermeable nature of the neuronal membrane somewhat restricts the movement of these charged
molecules, and, as a result, some of the charged particles tend to become more concentrated either inside
or outside the cell.

Between signals, the neuron membrane’s potential is held in a state of readiness, called the resting
potential. Like a rubber band stretched out and waiting to spring into action, ions line up on either side
of the cell membrane, ready to rush across the membrane when the neuron goes active and the membrane
opens its gates (i.e., a sodium-potassium pump that allows movement of ions across the membrane). Ions
in high-concentration areas are ready to move to low-concentration areas, and positive ions are ready to
move to areas with a negative charge.

In the resting state, sodium (Na+) is at higher concentrations outside the cell, so it will tend to move into
the cell. Potassium (K+), on the other hand, is more concentrated inside the cell, and will tend to move out
of the cell (Figure 3.10). In addition, the inside of the cell is slightly negatively charged compared to the
outside. This provides an additional force on sodium, causing it to move into the cell.

Chapter 3 | Biopsychology 85

Figure 3.10 At resting potential, Na+ (blue pentagons) is more highly concentrated outside the cell in the
extracellular fluid (shown in blue), whereas K+ (purple squares) is more highly concentrated near the membrane in
the cytoplasm or intracellular fluid. Other molecules, such as chloride ions (yellow circles) and negatively charged
proteins (brown squares), help contribute to a positive net charge in the extracellular fluid and a negative net charge
in the intracellular fluid.

From this resting potential state, the neuron receives a signal and its state changes abruptly (Figure
3.11). When a neuron receives signals at the dendrites—due to neurotransmitters from an adjacent neuron
binding to its receptors—small pores, or gates, open on the neuronal membrane, allowing Na+ ions,
propelled by both charge and concentration differences, to move into the cell. With this influx of positive
ions, the internal charge of the cell becomes more positive. If that charge reaches a certain level, called the
threshold of excitation, the neuron becomes active and the action potential begins.

Many additional pores open, causing a massive influx of Na+ ions and a huge positive spike in the
membrane potential, the peak action potential. At the peak of the spike, the sodium gates close and the
potassium gates open. As positively charged potassium ions leave, the cell quickly begins repolarization.
At first, it hyperpolarizes, becoming slightly more negative than the resting potential, and then it levels
off, returning to the resting potential.

Figure 3.11 During the action potential, the electrical charge across the membrane changes dramatically.

This positive spike constitutes the action potential: the electrical signal that typically moves from the cell
body down the axon to the axon terminals. The electrical signal moves down the axon with the impulses
jumping in a leapfrog fashion between the Nodes of Ranvier. The Nodes of Ranvier are natural gaps in the
myelin sheath. At each point, some of the sodium ions that enter the cell diffuse to the next section of the

86 Chapter 3 | Biopsychology

This OpenStax book is available for free at

axon, raising the charge past the threshold of excitation and triggering a new influx of sodium ions. The
action potential moves all the way down the axon in this fashion until reaching the terminal buttons.

The action potential is an all-or-none phenomenon. In simple terms, this means that an incoming signal
from another neuron is either sufficient or insufficient to reach the threshold of excitation. There is no in-
between, and there is no turning off an action potential once it starts. Think of it like sending an email or
a text message. You can think about sending it all you want, but the message is not sent until you hit the
send button. Furthermore, once you send the message, there is no stopping it.

Because it is all or none, the action potential is recreated, or propagated, at its full strength at every point
along the axon. Much like the lit fuse of a firecracker, it does not fade away as it travels down the axon. It
is this all-or-none property that explains the fact that your brain perceives an injury to a distant body part
like your toe as equally painful as one to your nose.

As noted earlier, when the action potential arrives at the terminal button, the synaptic vesicles release
their neurotransmitters into the synaptic cleft. The neurotransmitters travel across the synapse and bind
to receptors on the dendrites of the adjacent neuron, and the process repeats itself in the new neuron
(assuming the signal is sufficiently strong to trigger an action potential). Once the signal is delivered,
excess neurotransmitters in the synaptic cleft drift away, are broken down into inactive fragments, or
are reabsorbed in a process known as reuptake. Reuptake involves the neurotransmitter being pumped
back into the neuron that released it, in order to clear the synapse (Figure 3.12). Clearing the synapse
serves both to provide a clear “on” and “off” state between signals and to regulate the production of
neurotransmitter (full synaptic vesicles provide signals that no additional neurotransmitters need to be

Figure 3.12 Reuptake involves moving a neurotransmitter from the synapse back into the axon terminal from which
it was released.

Neuronal communication is often referred to as an electrochemical event. The movement of the action
potential down the length of the axon is an electrical event, and movement of the neurotransmitter across
the synaptic space represents the chemical portion of the process. However, there are some specialized
connections between neurons that are entirely electrical. In such cases, the neurons are said to
communicate via an electrical synapse. In these cases, two neurons physically connect to one another via
gap junctions, which allows the current from one cell to pass into the next. There are far fewer electrical
synapses in the brain, but those that do exist are much faster than the chemical synapses that have been
described above (Connors & Long, 2004).

Chapter 3 | Biopsychology 87

Watch this video about neuronal communication ( to learn more.


There are several different types of neurotransmitters released by different neurons, and we can speak in
broad terms about the kinds of functions associated with different neurotransmitters (Table 3.1). Much
of what psychologists know about the functions of neurotransmitters comes from research on the effects
of drugs in psychological disorders. Psychologists who take a biological perspective and focus on the
physiological causes of behavior assert that psychological disorders like depression and schizophrenia are
associated with imbalances in one or more neurotransmitter systems. In this perspective, psychotropic
medications can help improve the symptoms associated with these disorders. Psychotropic medications
are drugs that treat psychiatric symptoms by restoring neurotransmitter balance.

Major Neurotransmitters and How They Affect Behavior

Neurotransmitter Involved in Potential Effect on Behavior

Acetylcholine Muscle action, memory Increased arousal, enhanced

Beta-endorphin Pain, pleasure Decreased anxiety, decreased

Dopamine Mood, sleep, learning Increased pleasure, suppressed

Gamma-aminobutyric acid

Brain function, sleep Decreased anxiety, decreased

Glutamate Memory, learning Increased learning, enhanced

Norepinephrine Heart, intestines,

Increased arousal, suppressed

Serotonin Mood, sleep Modulated mood, suppressed

Table 3.1

Psychoactive drugs can act as agonists or antagonists for a given neurotransmitter system. Agonists
are chemicals that mimic a neurotransmitter at the receptor site. An antagonist, on the other hand,
blocks or impedes the normal activity of a neurotransmitter at the receptor. Agonists and antagonists
represent drugs that are prescribed to correct the specific neurotransmitter imbalances underlying a
person’s condition. For example, Parkinson’s disease, a progressive nervous system disorder, is associated
with low levels of dopamine. Therefore, a common treatment strategy for Parkinson’s disease involves
using dopamine agonists, which mimic the effects of dopamine by binding to dopamine receptors.

Certain symptoms of schizophrenia are associated with overactive dopamine neurotransmission. The


88 Chapter 3 | Biopsychology

This OpenStax book is available for free at

antipsychotics used to treat these symptoms are antagonists for dopamine—they block dopamine’s effects
by binding its receptors without activating them. Thus, they prevent dopamine released by one neuron
from signaling information to adjacent neurons.

In contrast to agonists and antagonists, which both operate by binding to receptor sites, reuptake inhibitors
prevent unused neurotransmitters from being transported back to the neuron. This allows
neurotransmitters to remain active in the synaptic cleft for longer durations, increasing their effectiveness.
Depression, which has been consistently linked with reduced serotonin levels, is commonly treated with
selective serotonin reuptake inhibitors (SSRIs). By preventing reuptake, SSRIs strengthen the effect of
serotonin, giving it more time to interact with serotonin receptors on dendrites. Common SSRIs on the
market today include Prozac, Paxil, and Zoloft. The drug LSD is structurally very similar to serotonin,
and it affects the same neurons and receptors as serotonin. Psychotropic drugs are not instant solutions
for people suffering from psychological disorders. Often, an individual must take a drug for several
weeks before seeing improvement, and many psychoactive drugs have significant negative side effects.
Furthermore, individuals vary dramatically in how they respond to the drugs. To improve chances for
success, it is not uncommon for people receiving pharmacotherapy to undergo psychological and/or
behavioral therapies as well. Some research suggests that combining drug therapy with other forms of
therapy tends to be more effective than any one treatment alone (for one such example, see March et al.,

3.3 Parts of the Nervous System

Learning Objectives

By the end of this section, you will be able to:
• Describe the difference between the central and peripheral nervous systems
• Explain the difference between the somatic and autonomic nervous systems
• Differentiate between the sympathetic and parasympathetic divisions of the autonomic

nervous system

The nervous system can be divided into two major subdivisions: the central nervous system (CNS) and
the peripheral nervous system (PNS), shown in Figure 3.13. The CNS is comprised of the brain and spinal
cord; the PNS connects the CNS to the rest of the body. In this section, we focus on the peripheral nervous
system; later, we look at the brain and spinal cord.

Chapter 3 | Biopsychology 89

Figure 3.13 The nervous system is divided into two major parts: (a) the Central Nervous System and (b) the
Peripheral Nervous System.


The peripheral nervous system is made up of thick bundles of axons, called nerves, carrying messages
back and forth between the CNS and the muscles, organs, and senses in the periphery of the body (i.e.,
everything outside the CNS). The PNS has two major subdivisions: the somatic nervous system and the
autonomic nervous system.

The somatic nervous system is associated with activities traditionally thought of as conscious or
voluntary. It is involved in the relay of sensory and motor information to and from the CNS; therefore,
it consists of motor neurons and sensory neurons. Motor neurons, carrying instructions from the CNS to
the muscles, are efferent fibers (efferent means “moving away from”). Sensory neurons, carrying sensory
information to the CNS, are afferent fibers (afferent means “moving toward”). A helpful way to remember
this is that efferent = exit and afferent = arrive. Each nerve is basically a bundle of neurons forming a two-
way superhighway, containing thousands of axons, both efferent and afferent.

The autonomic nervous system controls our internal organs and glands and is generally considered
to be outside the realm of voluntary control. It can be further subdivided into the sympathetic and
parasympathetic divisions (Figure 3.14). The sympathetic nervous system is involved in preparing the
body for stress-related activities; the parasympathetic nervous system is associated with returning the
body to routine, day-to-day operations. The two systems have complementary functions, operating in
tandem to maintain the body’s homeostasis. Homeostasis is a state of equilibrium, or balance, in which
biological conditions (such as body temperature) are maintained at optimal levels.

90 Chapter 3 | Biopsychology

This OpenStax book is available for free at

Figure 3.14 The sympathetic and parasympathetic divisions of the autonomic nervous system have the opposite
effects on various systems.

The sympathetic nervous system is activated when we are faced with stressful or high-arousal situations.
The activity of this system was adaptive for our ancestors, increasing their chances of survival. Imagine,
for example, that one of our early ancestors, out hunting small game, suddenly disturbs a large bear
with her cubs. At that moment, his body undergoes a series of changes—a direct function of sympathetic
activation—preparing him to face the threat. His pupils dilate, his heart rate and blood pressure increase,
his bladder relaxes, his liver releases glucose, and adrenaline surges into his bloodstream. This
constellation of physiological changes, known as the fight or flight response, allows the body access to
energy reserves and heightened sensory capacity so that it might fight off a threat or run away to safety.

Watch this video about the Fight Flight Freeze response ( to learn

While it is clear that such a response would be critical for survival for our ancestors, who lived in a world
full of real physical threats, many of the high-arousal situations we face in the modern world are more
psychological in nature. For example, think about how you feel when you have to stand up and give a
presentation in front of a roomful of people, or right before taking a big test. You are in no real physical
danger in those situations, and yet you have evolved to respond to a perceived threat with the fight or
flight response. This kind of response is not nearly as adaptive in the modern world; in fact, we suffer


Chapter 3 | Biopsychology 91

negative health consequences when faced constantly with psychological threats that we can neither fight
nor flee. Recent research suggests that an increase in susceptibility to heart disease (Chandola, Brunner,
& Marmot, 2006) and impaired function of the immune system (Glaser & Kiecolt-Glaser, 2005) are among
the many negative consequences of persistent and repeated exposure to stressful situations. Some of this
tendency for stress reactivity can be wired by early experiences of trauma.

Once the threat has been resolved, the parasympathetic nervous system takes over and returns bodily
functions to a relaxed state. Our hunter’s heart rate and blood pressure return to normal, his pupils
constrict, he regains control of his bladder, and the liver begins to store glucose in the form of glycogen
for future use. These restorative processes are associated with activation of the parasympathetic nervous

3.4 The Brain and Spinal Cord

Learning Objectives

By the end of this section, you will be able to:
• Explain the functions of the spinal cord
• Identify the hemispheres and lobes of the brain
• Describe the types of techniques available to clinicians and researchers to image or scan the


The brain is a remarkably complex organ comprised of billions of interconnected neurons and glia. It is
a bilateral, or two-sided, structure that can be separated into distinct lobes. Each lobe is associated with
certain types of functions, but, ultimately, all of the areas of the brain interact with one another to provide
the foundation for our thoughts and behaviors. In this section, we discuss the overall organization of
the brain and the functions associated with different brain areas, beginning with what can be seen as an
extension of the brain, the spinal cord.


It can be said that the spinal cord is what connects the brain to the outside world. Because of it, the brain
can act. The spinal cord is like a relay station, but a very smart one. It not only routes messages to and from
the brain, but it also has its own system of automatic processes, called reflexes.

The top of the spinal cord is a bundle of nerves that merges with the brain stem, where the basic processes
of life are controlled, such as breathing and digestion. In the opposite direction, the spinal cord ends just
below the ribs—contrary to what we might expect, it does not extend all the way to the base of the spine.

The spinal cord is functionally organized in 30 segments, corresponding with the vertebrae. Each segment
is connected to a specific part of the body through the peripheral nervous system. Nerves branch out
from the spine at each vertebra. Sensory nerves bring messages in; motor nerves send messages out to the
muscles and organs. Messages travel to and from the brain through every segment.

Some sensory messages are immediately acted on by the spinal cord, without any input from the brain.
Withdrawal from a hot object and the knee jerk are two examples. When a sensory message meets certain
parameters, the spinal cord initiates an automatic reflex. The signal passes from the sensory nerve to a
simple processing center, which initiates a motor command. Seconds are saved, because messages don’t
have to go the brain, be processed, and get sent back. In matters of survival, the spinal reflexes allow the
body to react extraordinarily fast.

The spinal cord is protected by bony vertebrae and cushioned in cerebrospinal fluid, but injuries still
occur. When the spinal cord is damaged in a particular segment, all lower segments are cut off from the
brain, causing paralysis. Therefore, the lower on the spine damage occurs, the fewer functions an injured

92 Chapter 3 | Biopsychology

This OpenStax book is available for free at

individual will lose.


Bob Woodruff, a reporter for ABC, suffered a traumatic brain injury after a bomb exploded next to the
vehicle he was in while covering a news story in Iraq. As a consequence of these injuries, Woodruff
experienced many cognitive deficits including difficulties with memory and language. However, over time
and with the aid of intensive amounts of cognitive and speech therapy, Woodruff has shown an incredible
recovery of function (Fernandez, 2008, October 16).

One of the factors that made this recovery possible was neuroplasticity. Neuroplasticity refers to how the
nervous system can change and adapt. Neuroplasticity can occur in a variety of ways including personal
experiences, developmental processes, or, as in Woodruff’s case, in response to some sort of damage or
injury that has occurred. Neuroplasticity can involve creation of new synapses, pruning of synapses that
are no longer used, changes in glial cells, and even the birth of new neurons. Because of neuroplasticity,
our brains are constantly changing and adapting, and while our nervous system is most plastic when we
are very young, as Woodruff’s case suggests, it is still capable of remarkable changes later in life.


The surface of the brain, known as the cerebral cortex, is very uneven, characterized by a distinctive
pattern of folds or bumps, known as gyri (singular: gyrus), and grooves, known as sulci (singular: sulcus),
shown in Figure 3.15. These gyri and sulci form important landmarks that allow us to separate the brain
into functional centers. The most prominent sulcus, known as the longitudinal fissure, is the deep groove
that separates the brain into two halves or hemispheres: the left hemisphere and the right hemisphere.

Figure 3.15 The surface of the brain is covered with gyri and sulci. A deep sulcus is called a fissure, such as the
longitudinal fissure that divides the brain into left and right hemispheres. (credit: modification of work by Bruce Blaus)

There is evidence of specialization of function—referred to as lateralization—in each hemisphere, mainly
regarding differences in language functions. The left hemisphere controls the right half of the body,
and the right hemisphere controls the left half of the body. Decades of research on lateralization of
function by Michael Gazzaniga and his colleagues suggest that a variety of functions ranging from cause-
and-effect reasoning to self-recognition may follow patterns that suggest some degree of hemispheric
dominance (Gazzaniga, 2005). For example, the left hemisphere has been shown to be superior for forming
associations in memory, selective attention, and positive emotions. The right hemisphere, on the other
hand, has been shown to be superior in pitch perception, arousal, and negative emotions (Ehret, 2006).
However, it should be pointed out that research on which hemisphere is dominant in a variety of different
behaviors has produced inconsistent results, and therefore, it is probably better to think of how the
two hemispheres interact to produce a given behavior rather than attributing certain behaviors to one

Chapter 3 | Biopsychology 93

hemisphere versus the other (Banich & Heller, 1998).

The two hemispheres are connected by a thick band of neural fibers known as the corpus callosum,
consisting of about 200 million axons. The corpus callosum allows the two hemispheres to communicate
with each other and allows for information being processed on one side of the brain to be shared with the
other side.

Normally, we are not aware of the different roles that our two hemispheres play in day-to-day functions,
but there are people who come to know the capabilities and functions of their two hemispheres quite well.
In some cases of severe epilepsy, doctors elect to sever the corpus callosum as a means of controlling the
spread of seizures (Figure 3.16). While this is an effective treatment option, it results in individuals who
have “split brains.” After surgery, these split-brain patients show a variety of interesting behaviors. For
instance, a split-brain patient is unable to name a picture that is shown in the patient’s left visual field
because the information is only available in the largely nonverbal right hemisphere. However, they are
able to recreate the picture with their left hand, which is also controlled by the right hemisphere. When the
more verbal left hemisphere sees the picture that the hand drew, the patient is able to name it (assuming
the left hemisphere can interpret what was drawn by the left hand).

Figure 3.16 (a, b) The corpus callosum connects the left and right hemispheres of the brain. (c) A scientist spreads
this dissected sheep brain apart to show the corpus callosum between the hemispheres. (credit c: modification of
work by Aaron Bornstein)

Much of what we know about the functions of different areas of the brain comes from studying changes in
the behavior and ability of individuals who have suffered damage to the brain. For example, researchers
study the behavioral changes caused by strokes to learn about the functions of specific brain areas. A
stroke, caused by an interruption of blood flow to a region in the brain, causes a loss of brain function in
the affected region. The damage can be in a small area, and, if it is, this gives researchers the opportunity
to link any resulting behavioral changes to a specific area. The types of deficits displayed after a stroke will
be largely dependent on where in the brain the damage occurred.

Consider Theona, an intelligent, self-sufficient woman, who is 62 years old. Recently, she suffered a stroke
in the front portion of her right hemisphere. As a result, she has great difficulty moving her left leg. (As you
learned earlier, the right hemisphere controls the left side of the body; also, the brain’s main motor centers
are located at the front of the head, in the frontal lobe.) Theona has also experienced behavioral changes.
For example, while in the produce section of the grocery store, she sometimes eats grapes, strawberries,
and apples directly from their bins before paying for them. This behavior—which would have been very
embarrassing to her before the stroke—is consistent with damage in another region in the frontal lobe—the
prefrontal cortex, which is associated with judgment, reasoning, and impulse control.


The two hemispheres of the cerebral cortex are part of the forebrain (Figure 3.17), which is the largest part
of the brain. The forebrain contains the cerebral cortex and a number of other structures that lie beneath
the cortex (called subcortical structures): thalamus, hypothalamus, pituitary gland, and the limbic system

94 Chapter 3 | Biopsychology

This OpenStax book is available for free at

(a collection of structures). The cerebral cortex, which is the outer surface of the brain, is associated with
higher level processes such as consciousness, thought, emotion, reasoning, language, and memory. Each
cerebral hemisphere can be subdivided into four lobes, each associated with different functions.

Figure 3.17 The brain and its parts can be divided into three main categories: the forebrain, midbrain, and hindbrain.

Lobes of the Brain

The four lobes of the brain are the frontal, parietal, temporal, and occipital lobes (Figure 3.18). The frontal
lobe is located in the forward part of the brain, extending back to a fissure known as the central sulcus. The
frontal lobe is involved in reasoning, motor control, emotion, and language. It contains the motor cortex,
which is involved in planning and coordinating movement; the prefrontal cortex, which is responsible for
higher-level cognitive functioning; and Broca’s area, which is essential for language production.

Figure 3.18 The lobes of the brain are shown.

People who suffer damage to Broca’s area have great difficulty producing language of any form (Figure
3.18). For example, Padma was an electrical engineer who was socially active and a caring, involved
parent. About twenty years ago, she was in a car accident and suffered damage to her Broca’s area. She
completely lost the ability to speak and form any kind of meaningful language. There is nothing wrong
with her mouth or her vocal cords, but she is unable to produce words. She can follow directions but can’t
respond verbally, and she can read but no longer write. She can do routine tasks like running to the market
to buy milk, but she could not communicate verbally if a situation called for it.

Probably the most famous case of frontal lobe damage is that of a man by the name of Phineas Gage. On
September 13, 1848, Gage (age 25) was working as a railroad foreman in Vermont. He and his crew were

Chapter 3 | Biopsychology 95

using an iron rod to tamp explosives down into a blasting hole to remove rock along the railway’s path.
Unfortunately, the iron rod created a spark and caused the rod to explode out of the blasting hole, into
Gage’s face, and through his skull (Figure 3.19). Although lying in a pool of his own blood with brain
matter emerging from his head, Gage was conscious and able to get up, walk, and speak. But in the months
following his accident, people noticed that his personality had changed. Many of his friends described him
as no longer being himself. Before the accident, it was said that Gage was a well-mannered, soft-spoken
man, but he began to behave in odd and inappropriate ways after the accident. Such changes in personality
would be consistent with loss of impulse control—a frontal lobe function.

Beyond the damage to the frontal lobe itself, subsequent investigations into the rod’s path also identified
probable damage to pathways between the frontal lobe and other brain structures, including the limbic
system. With connections between the planning functions of the frontal lobe and the emotional processes
of the limbic system severed, Gage had difficulty controlling his emotional impulses.

However, there is some evidence suggesting that the dramatic changes in Gage’s personality were
exaggerated and embellished. Gage’s case occurred in the midst of a 19th century debate over
localization—regarding whether certain areas of the brain are associated with particular functions. On the
basis of extremely limited information about Gage, the extent of his injury, and his life before and after the
accident, scientists tended to find support for their own views, on whichever side of the debate they fell
(Macmillan, 1999).

Figure 3.19 (a) Phineas Gage holds the iron rod that penetrated his skull in an 1848 railroad construction accident.
(b) Gage’s prefrontal cortex was severely damaged in the left hemisphere. The rod entered Gage’s face on the left
side, passed behind his eye, and exited through the top of his skull, before landing about 80 feet away. (credit a:
modification of work by Jack and Beverly Wilgus)

The brain’s parietal lobe is located immediately behind the frontal lobe, and is involved in processing
information from the body’s senses. It contains the somatosensory cortex, which is essential for processing
sensory information from across the body, such as touch, temperature, and pain. The somatosensory cortex
is organized topographically, which means that spatial relationships that exist in the body are generally
maintained on the surface of the somatosensory cortex (Figure 3.20). For example, the portion of the cortex
that processes sensory information from the hand is adjacent to the portion that processes information
from the wrist.

96 Chapter 3 | Biopsychology

This OpenStax book is available for free at

One fascinating example of neuroplasticity involves reorganization of the somatosensory cortex following
limb amputation. Check out this NPR segment about amputees’ experiences of “phantom limbs”
following amputation ( to learn more.

Figure 3.20 Spatial relationships in the body are mirrored in the organization of the somatosensory cortex.

The temporal lobe is located on the side of the head (temporal means “near the temples”), and is associated
with hearing, memory, emotion, and some aspects of language. The auditory cortex, the main area
responsible for processing auditory information, is located within the temporal lobe. Wernicke’s area,
important for speech comprehension, is also located here. Whereas individuals with damage to Broca’s
area have difficulty producing language, those with damage to Wernicke’s area can produce sensible
language, but they are unable to understand it (Figure 3.21).

Figure 3.21 Damage to either Broca’s area or Wernicke’s area can result in language deficits. The types of deficits
are very different, however, depending on which area is affected.

The occipital lobe is located at the very back of the brain, and contains the primary visual cortex, which is


Chapter 3 | Biopsychology 97

responsible for interpreting incoming visual information. The occipital cortex is organized retinotopically,
which means there is a close relationship between the position of an object in a person’s visual field and
the position of that object’s representation on the cortex. You will learn much more about how visual
information is processed in the occipital lobe when you study sensation and perception.

Other Areas of the Forebrain

Other areas of the forebrain, located beneath the cerebral cortex, include the thalamus and the limbic
system. The thalamus is a sensory relay for the brain. All of our senses, with the exception of smell, are
routed through the thalamus before being directed to other areas of the brain for processing (Figure 3.22).

Figure 3.22 The thalamus serves as the relay center of the brain where most senses are routed for processing.

The limbic system is involved in processing both emotion and memory. Interestingly, the sense of smell
projects directly to the limbic system; therefore, not surprisingly, smell can evoke emotional responses
in ways that other sensory modalities cannot. The limbic system is made up of a number of different
structures, but three of the most important are the hippocampus, the amygdala, and the hypothalamus
(Figure 3.23). The hippocampus is an essential structure for learning and memory. The amygdala is
involved in our experience of emotion and in tying emotional meaning to our memories. The
hypothalamus regulates a number of homeostatic processes, including the regulation of body
temperature, appetite, and blood pressure. The hypothalamus also serves as an interface between the
nervous system and the endocrine system and in the regulation of sexual motivation and behavior.

98 Chapter 3 | Biopsychology

This OpenStax book is available for free at

Figure 3.23 The limbic system is involved in mediating emotional response and memory.

The Case of Henry Molaison (H.M.)

In 1953, Henry Gustav Molaison (H. M.) was a 27-year-old man who experienced severe seizures. In
an attempt to control his seizures, H. M. underwent brain surgery to remove his hippocampus and
amygdala. Following the surgery, H.M’s seizures became much less severe, but he also suffered some
unexpected—and devastating—consequences of the surgery: he lost his ability to form many types of new
memories. For example, he was unable to learn new facts, such as who was president of the United States.
He was able to learn new skills, but afterward he had no recollection of learning them. For example, while
he might learn to use a computer, he would have no conscious memory of ever having used one. He could
not remember new faces, and he was unable to remember events, even immediately after they occurred.
Researchers were fascinated by his experience, and he is considered one of the most studied cases in
medical and psychological history (Hardt, Einarsson, & Nader, 2010; Squire, 2009). Indeed, his case has
provided tremendous insight into the role that the hippocampus plays in the consolidation of new learning
into explicit memory.

Clive Wearing, an accomplished musician, lost the ability to form new memories when his hippocampus
was damaged through illness. Check out the first few minutes of this documentary video about this
man and his condition ( to learn more.


The midbrain is comprised of structures located deep within the brain, between the forebrain and the
hindbrain. The reticular formation is centered in the midbrain, but it actually extends up into the forebrain
and down into the hindbrain. The reticular formation is important in regulating the sleep/wake cycle,
arousal, alertness, and motor activity.

The substantia nigra (Latin for “black substance”) and the ventral tegmental area (VTA) are also located
in the midbrain (Figure 3.24). Both regions contain cell bodies that produce the neurotransmitter
dopamine, and both are critical for movement. Degeneration of the substantia nigra and VTA is involved
in Parkinson’s disease. In addition, these structures are involved in mood, reward, and addiction (Berridge


Chapter 3 | Biopsychology 99

& Robinson, 1998; Gardner, 2011; George, Le Moal, & Koob, 2012).

Figure 3.24 The substantia nigra and ventral tegmental area (VTA) are located in the midbrain.

The hindbrain is located at the back of the head and looks like an extension of the spinal cord. It contains
the medulla, pons, and cerebellum (Figure 3.25). The medulla controls the automatic processes of the
autonomic nervous system, such as breathing, blood pressure, and heart rate. The word pons literally
means “bridge,” and as the name suggests, the pons serves to connect the hindbrain to the rest of the brain.
It also is involved in regulating brain activity during sleep. The medulla, pons, and various structures are
known as the brainstem, and aspects of the brainstem span both the midbrain and the hindbrain.

Figure 3.25 The pons, medulla, and cerebellum make up the hindbrain.

The cerebellum (Latin for “little brain”) receives messages from muscles, tendons, joints, and structures
in our ear to control balance, coordination, movement, and motor skills. The cerebellum is also thought
to be an important area for processing some types of memories. In particular, procedural memory, or
memory involved in learning and remembering how to perform tasks, is thought to be associated with the
cerebellum. Recall that H. M. was unable to form new explicit memories, but he could learn new tasks.
This is likely due to the fact that H. M.’s cerebellum remained intact.

100 Chapter 3 | Biopsychology

This OpenStax book is available for free at

Brain Dead and on Life Support

What would you do if your spouse or loved one was declared brain dead but his or her body was being kept
alive by medical equipment? Whose decision should it be to remove a feeding tube? Should medical care
costs be a factor?

On February 25, 1990, a Florida woman named Terri Schiavo went into cardiac arrest, apparently triggered by
a bulimic episode. She was eventually revived, but her brain had been deprived of oxygen for a long time. Brain
scans indicated that there was no activity in her cerebral cortex, and she suffered from severe and permanent
cerebral atrophy. Basically, Schiavo was in a vegetative state. Medical professionals determined that she would
never again be able to move, talk, or respond in any way. To remain alive, she required a feeding tube, and
there was no chance that her situation would ever improve.

On occasion, Schiavo’s eyes would move, and sometimes she would groan. Despite the doctors’ insistence to
the contrary, her parents believed that these were signs that she was trying to communicate with them.

After 12 years, Schiavo’s husband argued that his wife would not have wanted to be kept alive with no
feelings, sensations, or brain activity. Her parents, however, were very much against removing her feeding
tube. Eventually, the case made its way to the courts, both in the state of Florida and at the federal level. By
2005, the courts found in favor of Schiavo’s husband, and the feeding tube was removed on March 18, 2005.
Schiavo died 13 days later.

Why did Schiavo’s eyes sometimes move, and why did she groan? Although the parts of her brain that
control thought, voluntary movement, and feeling were completely damaged, her brainstem was still intact. Her
medulla and pons maintained her breathing and caused involuntary movements of her eyes and the occasional
groans. Over the 15-year period that she was on a feeding tube, Schiavo’s medical costs may have topped $7
million (Arnst, 2003).

These questions were brought to popular conscience decades ago in the case of Terri Schiavo, and they
have persisted. In 2013, a 13-year-old girl who suffered complications after tonsil surgery was declared brain
dead. There was a battle between her family, who wanted her to remain on life support, and the hospital’s
policies regarding persons declared brain dead. In another complicated 2013–14 case in Texas, a pregnant
EMT professional declared brain dead was kept alive for weeks, despite her spouse’s directives, which were
based on her wishes should this situation arise. In this case, state laws designed to protect an unborn fetus
came into consideration until doctors determined the fetus unviable.

Decisions surrounding the medical response to patients declared brain dead are complex. What do you think
about these issues?


You have learned how brain injury can provide information about the functions of different parts of the
brain. Increasingly, however, we are able to obtain that information using brain imaging techniques on
individuals who have not suffered brain injury. In this section, we take a more in-depth look at some of the
techniques that are available for imaging the brain, including techniques that rely on radiation, magnetic
fields, or electrical activity within the brain.

Techniques Involving Radiation

A computerized tomography (CT) scan involves taking a number of x-rays of a particular section of a
person’s body or brain (Figure 3.26). The x-rays pass through tissues of different densities at different
rates, allowing a computer to construct an overall image of the area of the body being scanned. A CT scan
is often used to determine whether someone has a tumor or significant brain atrophy.


Chapter 3 | Biopsychology 101

Figure 3.26 A CT scan can be used to show brain tumors. (a) The image on the left shows a healthy brain, whereas
(b) the image on the right indicates a brain tumor in the left frontal lobe. (credit a: modification of work by
“Aceofhearts1968″/Wikimedia Commons; credit b: modification of work by Roland Schmitt et al)

Positron emission tomography (PET) scans create pictures of the living, active brain (Figure 3.27). An
individual receiving a PET scan drinks or is injected with a mildly radioactive substance, called a tracer.
Once in the bloodstream, the amount of tracer in any given region of the brain can be monitored. As
a brain area becomes more active, more blood flows to that area. A computer monitors the movement
of the tracer and creates a rough map of active and inactive areas of the brain during a given behavior.
PET scans show little detail, are unable to pinpoint events precisely in time, and require that the brain be
exposed to radiation; therefore, this technique has been replaced by the fMRI as an alternative diagnostic
tool. However, combined with CT, PET technology is still being used in certain contexts. For example,
CT/PET scans allow better imaging of the activity of neurotransmitter receptors and open new avenues in
schizophrenia research. In this hybrid CT/PET technology, CT contributes clear images of brain structures,
while PET shows the brain’s activity.

Figure 3.27 A PET scan is helpful for showing activity in different parts of the brain. (credit: Health and Human
Services Department, National Institutes of Health)

Techniques Involving Magnetic Fields

In magnetic resonance imaging (MRI), a person is placed inside a machine that generates a strong
magnetic field. The magnetic field causes the hydrogen atoms in the body’s cells to move. When the
magnetic field is turned off, the hydrogen atoms emit electromagnetic signals as they return to their
original positions. Tissues of different densities give off different signals, which a computer interprets and
displays on a monitor. Functional magnetic resonance imaging (fMRI) operates on the same principles,
but it shows changes in brain activity over time by tracking blood flow and oxygen levels. The fMRI
provides more detailed images of the brain’s structure, as well as better accuracy in time, than is possible
in PET scans (Figure 3.28). With their high level of detail, MRI and fMRI are often used to compare the

102 Chapter 3 | Biopsychology

This OpenStax book is available for free at

brains of healthy individuals to the brains of individuals diagnosed with psychological disorders. This
comparison helps determine what structural and functional differences exist between these populations.

Figure 3.28 An fMRI shows activity in the brain over time. This image represents a single frame from an fMRI.
(credit: modification of work by Kim J, Matthews NL, Park S.)

Visit this virtual lab about MRI and fMRI ( to learn more.

Techniques Involving Electrical Activity

In some situations, it is helpful to gain an understanding of the overall activity of a person’s brain, without
needing information on the actual location of the activity. Electroencephalography (EEG) serves this
purpose by providing a measure of a brain’s electrical activity. An array of electrodes is placed around
a person’s head (Figure 3.29). The signals received by the electrodes result in a printout of the electrical
activity of his or her brain, or brainwaves, showing both the frequency (number of waves per second) and
amplitude (height) of the recorded brainwaves, with an accuracy within milliseconds. Such information is
especially helpful to researchers studying sleep patterns among individuals with sleep disorders.

Figure 3.29 Using caps with electrodes, modern EEG research can study the precise timing of overall brain
activities. (credit: SMI Eye Tracking)


Chapter 3 | Biopsychology 103

3.5 The Endocrine System

Learning Objectives

By the end of this section, you will be able to:
• Identify the major glands of the endocrine system
• Identify the hormones secreted by each gland
• Describe each hormone’s role in regulating bodily functions

The endocrine system consists of a series of glands that produce chemical substances known as hormones
(Figure 3.30). Like neurotransmitters, hormones are chemical messengers that must bind to a receptor in
order to send their signal. However, unlike neurotransmitters, which are released in close proximity to
cells with their receptors, hormones are secreted into the bloodstream and travel throughout the body,
affecting any cells that contain receptors for them. Thus, whereas neurotransmitters’ effects are localized,
the effects of hormones are widespread. Also, hormones are slower to take effect, and tend to be longer

Figure 3.30 The major glands of the endocrine system are shown.

Hormones are involved in regulating all sorts of bodily functions, and they are ultimately controlled
through interactions between the hypothalamus (in the central nervous system) and the pituitary gland (in
the endocrine system). Imbalances in hormones are related to a number of disorders. This section explores
some of the major glands that make up the endocrine system and the hormones secreted by these glands
(Table 3.2).


The pituitary gland descends from the hypothalamus at the base of the brain, and acts in close association
with it. The pituitary is often referred to as the “master gland” because its messenger hormones control

104 Chapter 3 | Biopsychology

This OpenStax book is available for free at

all the other glands in the endocrine system, although it mostly carries out instructions from the
hypothalamus. In addition to messenger hormones, the pituitary also secretes growth hormone,
endorphins for pain relief, and a number of key hormones that regulate fluid levels in the body.

Located in the neck, the thyroid gland releases hormones that regulate growth, metabolism, and appetite.
In hyperthyroidism, or Grave’s disease, the thyroid secretes too much of the hormone thyroxine, causing
agitation, bulging eyes, and weight loss. In hypothyroidism, reduced hormone levels cause sufferers to
experience tiredness, and they often complain of feeling cold. Fortunately, thyroid disorders are often
treatable with medications that help reestablish a balance in the hormones secreted by the thyroid.

The adrenal glands sit atop our kidneys and secrete hormones involved in the stress response, such
as epinephrine (adrenaline) and norepinephrine (noradrenaline). The pancreas is an internal organ that
secretes hormones that regulate blood sugar levels: insulin and glucagon. These pancreatic hormones are
essential for maintaining stable levels of blood sugar throughout the day by lowering blood glucose levels
(insulin) or raising them (glucagon). People who suffer from diabetes do not produce enough insulin;
therefore, they must take medications that stimulate or replace insulin production, and they must closely
control the amount of sugars and carbohydrates they consume.

The gonads secrete sexual hormones, which are important in reproduction, and mediate both sexual
motivation and behavior. The female gonads are the ovaries; the male gonads are the testes. Ovaries
secrete estrogens and progesterone, and the testes secrete androgens, such as testosterone.

Major Endocrine Glands and Associated Hormone Functions


Associated Hormones Function

Hypothalamus Releasing and inhibiting hormones, such as

Regulate hormone release
from pituitary gland

Pituitary Growth hormone, releasing and inhibiting
hormones (such as thyroid stimulating hormone)

Regulate growth, regulate
hormone release

Thyroid Thyroxine, triiodothyronine Regulate metabolism and

Pineal Melatonin Regulate some biological
rhythms such as sleep cycles

Adrenal Epinephrine, norepinephrine Stress response, increase
metabolic activities

Pancreas Insulin, glucagon Regulate blood sugar levels

Ovaries Estrogen, progesterone Mediate sexual motivation
and behavior, reproduction

Testes Androgens, such as testosterone Mediate sexual motivation
and behavior, reproduction

Table 3.2

Chapter 3 | Biopsychology 105

Athletes and Anabolic Steroids

Although it is against Federal laws and many professional athletic associations (The National Football League,
for example) have banned their use, anabolic steroid drugs continue to be used by amateur and professional
athletes. The drugs are believed to enhance athletic performance. Anabolic steroid drugs mimic the effects
of the body’s own steroid hormones, like testosterone and its derivatives. These drugs have the potential to
provide a competitive edge by increasing muscle mass, strength, and endurance, although not all users may
experience these results. Moreover, use of performance-enhancing drugs (PEDs) does not come without risks.
Anabolic steroid use has been linked with a wide variety of potentially negative outcomes, ranging in severity
from largely cosmetic (acne) to life threatening (heart attack). Furthermore, use of these substances can result
in profound changes in mood and can increase aggressive behavior (National Institute on Drug Abuse, 2001).

Baseball player Alex Rodriguez (A-Rod) has been at the center of a media storm regarding his use of illegal
PEDs. Rodriguez’s performance on the field was unparalleled while using the drugs; his success played a
large role in negotiating a contract that made him the highest paid player in professional baseball. Although
Rodriguez maintains that he has not used PEDs for the several years, he received a substantial suspension
in 2013 that, if upheld, will cost him more than 20 million dollars in earnings (Gaines, 2013). What are your
thoughts on athletes and doping? Why or why not should the use of PEDs be banned? What advice would you
give an athlete who was considering using PEDs?


106 Chapter 3 | Biopsychology

This OpenStax book is available for free at

action potential

adrenal gland






auditory cortex

autonomic nervous system


biological perspective

Broca’s area

central nervous system (CNS)


cerebral cortex


computerized tomography (CT) scan

corpus callosum


deoxyribonucleic acid (DNA)


dominant allele

electroencephalography (EEG)

endocrine system


Key Terms

electrical signal that moves down the neuron’s axon

sits atop our kidneys and secretes hormones involved in the stress response

drug that mimics or strengthens the effects of a neurotransmitter

phenomenon that incoming signal from another neuron is either sufficient or insufficient to
reach the threshold of excitation

specific version of a gene

structure in the limbic system involved in our experience of emotion and tying emotional
meaning to our memories

drug that blocks or impedes the normal activity of a given neurotransmitter

strip of cortex in the temporal lobe that is responsible for processing auditory

controls our internal organs and glands

major extension of the soma

view that psychological disorders like depression and schizophrenia are
associated with imbalances in one or more neurotransmitter systems

region in the left hemisphere that is essential for language production

brain and spinal cord

hindbrain structure that controls our balance, coordination, movement, and motor skills, and
it is thought to be important in processing some types of memory

surface of the brain that is associated with our highest mental capabilities

long strand of genetic information

imaging technique in which a computer coordinates and integrates
multiple x-rays of a given area

thick band of neural fibers connecting the brain’s two hemispheres

branch-like extension of the soma that receives incoming signals from other neurons

helix-shaped molecule made of nucleotide base pairs

disease related to insufficient insulin production

allele whose phenotype will be expressed in an individual that possesses that allele

recording the electrical activity of the brain via electrodes on the scalp

series of glands that produce chemical substances known as hormones

study of gene-environment interactions, such as how the same genotype leads to different

Chapter 3 | Biopsychology 107

fight or flight response


fraternal twins

frontal lobe

functional magnetic resonance imaging (fMRI)


genetic environmental correlation


glial cell











identical twins


limbic system

longitudinal fissure

magnetic resonance imaging (MRI)

activation of the sympathetic division of the autonomic nervous system,
allowing access to energy reserves and heightened sensory capacity so that we might fight off a given
threat or run away to safety

largest part of the brain, containing the cerebral cortex, the thalamus, and the limbic system,
among other structures

twins who develop from two different eggs fertilized by different sperm, so their genetic
material varies the same as in non-twin siblings

part of the cerebral cortex involved in reasoning, motor control, emotion, and language;
contains motor cortex

MRI that shows changes in metabolic activity over time

sequence of DNA that controls or partially controls physical characteristics

view of gene-environment interaction that asserts our genes affect
our environment, and our environment influences the expression of our genes

genetic makeup of an individual

nervous system cell that provides physical and metabolic support to neurons, including
neuronal insulation and communication, and nutrient and waste transport

secretes sexual hormones, which are important for successful reproduction, and mediate both
sexual motivation and behavior

(plural: gyri) bump or ridge on the cerebral cortex

left or right half of the brain

consisting of two different alleles

division of the brain containing the medulla, pons, and cerebellum

structure in the temporal lobe associated with learning and memory

state of equilibrium—biological conditions, such as body temperature, are maintained at
optimal levels

consisting of two identical alleles

chemical messenger released by endocrine glands

forebrain structure that regulates sexual motivation and behavior and a number of
homeostatic processes; serves as an interface between the nervous system and the endocrine system

twins that develop from the same sperm and egg

concept that each hemisphere of the brain is associated with specialized functions

collection of structures involved in processing emotion and memory

deep groove in the brain’s cortex

magnetic fields used to produce a picture of the tissue being imaged

108 Chapter 3 | Biopsychology

This OpenStax book is available for free at


membrane potential


motor cortex


myelin sheath




Nodes of Ranvier

occipital lobe


parasympathetic nervous system

parietal lobe

peripheral nervous system (PNS)


pituitary gland



positron emission tomography (PET) scan

prefrontal cortex

psychotropic medication

range of reaction


hindbrain structure that controls automated processes like breathing, blood pressure, and heart

difference in charge across the neuronal membrane

division of the brain located between the forebrain and the hindbrain; contains the reticular

strip of cortex involved in planning and coordinating movement

sudden, permanent change in a gene

fatty substance that insulates axons

cells in the nervous system that act as interconnected information processors, which are essential
for all of the tasks of the nervous system

nervous system’s ability to change

chemical messenger of the nervous system

open spaces that are found in the myelin sheath that encases the axon

part of the cerebral cortex associated with visual processing; contains the primary visual

secretes hormones that regulate blood sugar

associated with routine, day-to-day operations of the body

part of the cerebral cortex involved in processing various sensory and perceptual
information; contains the primary somatosensory cortex

connects the brain and spinal cord to the muscles, organs and senses
in the periphery of the body

individual’s inheritable physical characteristics

secretes a number of key hormones, which regulate fluid levels in the body, and a
number of messenger hormones, which direct the activity of other glands in the endocrine system

multiple genes affecting a given trait

hindbrain structure that connects the brain and spinal cord; involved in regulating brain activity
during sleep

involves injecting individuals with a mildly radioactive
substance and monitoring changes in blood flow to different regions of the brain

area in the frontal lobe responsible for higher-level cognitive functioning

drugs that treat psychiatric symptoms by restoring neurotransmitter balance

asserts our genes set the boundaries within which we can operate, and our
environment interacts with the genes to determine where in that range we will fall

protein on the cell surface where neurotransmitters attach

Chapter 3 | Biopsychology 109

recessive allele

resting potential

reticular formation


semipermeable membrane


somatic nervous system

somatosensory cortex

substantia nigra


sympathetic nervous system

synaptic cleft

synaptic vesicle

temporal lobe

terminal button


theory of evolution by natural selection

threshold of excitation


ventral tegmental area (VTA)

Wernicke’s area

allele whose phenotype will be expressed only if an individual is homozygous for that

the state of readiness of a neuron membrane’s potential between signals

midbrain structure important in regulating the sleep/wake cycle, arousal, alertness,
and motor activity

neurotransmitter is pumped back into the neuron that released it

cell membrane that allows smaller molecules or molecules without an
electrical charge to pass through it, while stopping larger or highly charged molecules

cell body

relays sensory and motor information to and from the CNS

essential for processing sensory information from across the body, such as touch,
temperature, and pain

midbrain structure where dopamine is produced; involved in control of movement

(plural: sulci) depressions or grooves in the cerebral cortex

involved in stress-related activities and functions

small gap between two neurons where communication occurs

storage site for neurotransmitters

part of cerebral cortex associated with hearing, memory, emotion, and some aspects of
language; contains primary auditory cortex

axon terminal containing synaptic vesicles

sensory relay for the brain

states that organisms that are better suited for their
environments will survive and reproduce compared to those that are poorly suited for their

level of charge in the membrane that causes the neuron to become active

secretes hormones that regulate growth, metabolism, and appetite

midbrain structure where dopamine is produced: associated with mood,
reward, and addiction

important for speech comprehension


3.1 Human Genetics
Genes are sequences of DNA that code for a particular trait. Different versions of a gene are called
alleles—sometimes alleles can be classified as dominant or recessive. A dominant allele always results in
the dominant phenotype. In order to exhibit a recessive phenotype, an individual must be homozygous

110 Chapter 3 | Biopsychology

This OpenStax book is available for free at

for the recessive allele. Genes affect both physical and psychological characteristics. Ultimately, how and
when a gene is expressed, and what the outcome will be—in terms of both physical and psychological
characteristics—is a function of the interaction between our genes and our environments.

3.2 Cells of the Nervous System
Glia and neurons are the two cell types that make up the nervous system. While glia generally play
supporting roles, the communication between neurons is fundamental to all of the functions associated
with the nervous system. Neuronal communication is made possible by the neuron’s specialized
structures. The soma contains the cell nucleus, and the dendrites extend from the soma in tree-like
branches. The axon is another major extension of the cell body; axons are often covered by a myelin sheath,
which increases the speed of transmission of neural impulses. At the end of the axon are terminal buttons
that contain synaptic vesicles filled with neurotransmitters.

Neuronal communication is an electrochemical event. The dendrites contain receptors for
neurotransmitters released by nearby neurons. If the signals received from other neurons are sufficiently
strong, an action potential will travel down the length of the axon to the terminal buttons, resulting in the
release of neurotransmitters into the synaptic cleft. Action potentials operate on the all-or-none principle
and involve the movement of Na+ and K+ across the neuronal membrane.

Different neurotransmitters are associated with different functions. Often, psychological disorders involve
imbalances in a given neurotransmitter system. Therefore, psychotropic drugs are prescribed in an attempt
to bring the neurotransmitters back into balance. Drugs can act either as agonists or as antagonists for a
given neurotransmitter system.

3.3 Parts of the Nervous System
The brain and spinal cord make up the central nervous system. The peripheral nervous system is
comprised of the somatic and autonomic nervous systems. The somatic nervous system transmits sensory
and motor signals to and from the central nervous system. The autonomic nervous system controls the
function of our organs and glands, and can be divided into the sympathetic and parasympathetic divisions.
Sympathetic activation prepares us for fight or flight, while parasympathetic activation is associated with
normal functioning under relaxed conditions.

3.4 The Brain and Spinal Cord
The brain consists of two hemispheres, each controlling the opposite side of the body. Each hemisphere
can be subdivided into different lobes: frontal, parietal, temporal, and occipital. In addition to the lobes
of the cerebral cortex, the forebrain includes the thalamus (sensory relay) and limbic system (emotion and
memory circuit). The midbrain contains the reticular formation, which is important for sleep and arousal,
as well as the substantia nigra and ventral tegmental area. These structures are important for movement,
reward, and addictive processes. The hindbrain contains the structures of the brainstem (medulla, pons,
and midbrain), which control automatic functions like breathing and blood pressure. The hindbrain also
contains the cerebellum, which helps coordinate movement and certain types of memories.

Individuals with brain damage have been studied extensively to provide information about the role of
different areas of the brain, and recent advances in technology allow us to glean similar information by
imaging brain structure and function. These techniques include CT, PET, MRI, fMRI, and EEG.

3.5 The Endocrine System
The glands of the endocrine system secrete hormones to regulate normal body functions. The
hypothalamus serves as the interface between the nervous system and the endocrine system, and it
controls the secretions of the pituitary. The pituitary serves as the master gland, controlling the secretions
of all other glands. The thyroid secretes thyroxine, which is important for basic metabolic processes
and growth; the adrenal glands secrete hormones involved in the stress response; the pancreas secretes
hormones that regulate blood sugar levels; and the ovaries and testes produce sex hormones that regulate
sexual motivation and behavior.

Chapter 3 | Biopsychology 111

Review Questions

1. A(n) ________ is a sudden, permanent change
in a sequence of DNA.

a. allele
b. chromosome
c. epigenetic
d. mutation

2. ________ refers to a person’s genetic makeup,
while ________ refers to a person’s physical

a. Phenotype; genotype
b. Genotype; phenotype
c. DNA; gene
d. Gene; DNA

3. ________ is the field of study that focuses on
genes and their expression.

a. Social psychology
b. Evolutionary psychology
c. Epigenetics
d. Behavioral neuroscience

4. Humans have ________ pairs of chromosomes.
a. 15
b. 23
c. 46
d. 78

5. The ________ receive(s) incoming signals from
other neurons.

a. soma
b. terminal buttons
c. myelin sheath
d. dendrites

6. A(n) ________ facilitates or mimics the activity
of a given neurotransmitter system.

a. axon
c. agonist
d. antagonist

7. Multiple sclerosis involves a breakdown of the

a. soma
b. myelin sheath
c. synaptic vesicles
d. dendrites

8. An action potential involves Na+ moving
________ the cell and K+ moving ________ the cell.

a. inside; outside
b. outside; inside
c. inside; inside
d. outside; outside

9. Our ability to make our legs move as we walk
across the room is controlled by the ________
nervous system.

a. autonomic
b. somatic
c. sympathetic
d. parasympathetic

10. If your ________ is activated, you will feel
relatively at ease.

a. somatic nervous system
b. sympathetic nervous system
c. parasympathetic nervous system
d. spinal cord

11. The central nervous system is comprised of

a. sympathetic and parasympathetic nervous

b. organs and glands
c. somatic and autonomic nervous systems
d. brain and spinal cord

12. Sympathetic activation is associated with

a. pupil dilation
b. storage of glucose in the liver
c. increased heart rate
d. both A and C

13. The ________ is a sensory relay station where
all sensory information, except for smell, goes
before being sent to other areas of the brain for
further processing.

a. amygdala
b. hippocampus
c. hypothalamus
d. thalamus

112 Chapter 3 | Biopsychology

This OpenStax book is available for free at

14. Damage to the ________ disrupts one’s ability
to comprehend language, but it leaves one’s ability
to produce words intact.

a. amygdala
b. Broca’s Area
c. Wernicke’s Area
d. occipital lobe

15. A(n) ________ uses magnetic fields to create
pictures of a given tissue.

a. EEG
b. MRI
c. PET scan
d. CT scan

16. Which of the following is not a structure of
the forebrain?

a. thalamus
b. hippocampus
c. amygdala
d. substantia nigra

17. The two major hormones secreted from the
pancreas are:

a. estrogen and progesterone
b. norepinephrine and epinephrine
c. thyroxine and oxytocin
d. glucagon and insulin

18. The ________ secretes messenger hormones
that direct the function of the rest of the endocrine

a. ovary
b. thyroid
c. pituitary
d. pancreas

19. The ________ gland secretes epinephrine.
a. adrenal
b. thyroid
c. pituitary
d. master

20. The ________ secretes hormones that regulate
the body’s fluid levels.

a. adrenal
b. pituitary
c. testes
d. thyroid

Critical Thinking Questions

21. The theory of evolution by natural selection requires variability of a given trait. Why is variability
necessary and where does it come from?

22. Cocaine has two effects on synaptic transmission: it impairs reuptake of dopamine and it causes more
dopamine to be released into the synaptic cleft. Would cocaine be classified as an agonist or antagonist?

23. Drugs such as lidocaine and novocaine act as Na+ channel blockers. In other words, they prevent
sodium from moving across the neuronal membrane. Why would this particular effect make these drugs
such effective local anesthetics?

24. What are the implications of compromised immune function as a result of exposure to chronic stress?

25. Examine Figure 3.14, illustrating the effects of sympathetic nervous system activation. How would
all of these things play into the fight or flight response?

26. Before the advent of modern imaging techniques, scientists and clinicians relied on autopsies of
people who suffered brain injury with resultant change in behavior to determine how different areas of
the brain were affected. What are some of the limitations associated with this kind of approach?

Chapter 3 | Biopsychology 113

27. Which of the techniques discussed would be viable options for you to determine how activity in the
reticular formation is related to sleep and wakefulness? Why?

28. Hormone secretion is often regulated through a negative feedback mechanism, which means that once
a hormone is secreted it will cause the hypothalamus and pituitary to shut down the production of signals
necessary to secrete the hormone in the first place. Most oral contraceptives are made of small doses of
estrogen and/or progesterone. Why would this be an effective means of contraception?

29. Chemical messengers are used in both the nervous system and the endocrine system. What properties
do these two systems share? What properties are different? Which one would be faster? Which one would
result in long-lasting changes?

Personal Application Questions

30. You share half of your genetic makeup with each of your parents, but you are no doubt very different
from both of them. Spend a few minutes jotting down the similarities and differences between you and
your parents. How do you think your unique environment and experiences have contributed to some of
the differences you see?

31. Have you or someone you know ever been prescribed a psychotropic medication? If so, what side
effects were associated with the treatment?

32. Hopefully, you do not face real physical threats from potential predators on a daily basis. However,
you probably have your fair share of stress. What situations are your most common sources of stress? What
can you do to try to minimize the negative consequences of these particular stressors in your life?

33. You read about H. M.’s memory deficits following the bilateral removal of his hippocampus and
amygdala. Have you encountered a character in a book, television program, or movie that suffered
memory deficits? How was that character similar to and different from H. M.?

34. Given the negative health consequences associated with the use of anabolic steroids, what kinds of
considerations might be involved in a person’s decision to use them?

114 Chapter 3 | Biopsychology

This OpenStax book is available for free at

Chapter 4

States of Consciousness

Figure 4.1 Sleep, which we all experience, is a quiet and mysterious pause in our daily lives. Two sleeping children
are depicted in this 1895 oil painting titled Zwei schlafende Mädchen auf der Ofenbank, which translates as “two
sleeping girls on the stove,” by Swiss painter Albert Anker.

Chapter Outline

4.1 What Is Consciousness?

4.2 Sleep and Why We Sleep

4.3 Stages of Sleep

4.4 Sleep Problems and Disorders

4.5 Substance Use and Abuse

4.6 Other States of Consciousness


Our lives involve regular, dramatic changes in the degree to which we are aware of our surroundings and
our internal states. While awake, we feel alert and aware of the many important things going on around us.
Our experiences change dramatically while we are in deep sleep and once again when we are dreaming.
Some people also experience altered states of consciousness through meditation, hypnosis, or alcohol and
other drugs.

This chapter will discuss states of consciousness with a particular emphasis on sleep. The different stages
of sleep will be identified, and sleep disorders will be described. The chapter will close with discussions of
altered states of consciousness produced by psychoactive drugs, hypnosis, and meditation.

Chapter 4 | States of Consciousness 115

4.1 What Is Consciousness?

Learning Objectives

By the end of this section, you will be able to:
• Understand what is meant by consciousness
• Explain how circadian rhythms are involved in regulating the sleep-wake cycle, and how

circadian cycles can be disrupted
• Discuss the concept of sleep debt

Consciousness describes our awareness of internal and external stimuli. Awareness of internal stimuli
includes feeling pain, hunger, thirst, sleepiness, and being aware of our thoughts and emotions. Awareness
of external stimuli includes experiences such as seeing the light from the sun, feeling the warmth of a room,
and hearing the voice of a friend.

We experience different states of consciousness and different levels of awareness on a regular basis. We
might even describe consciousness as a continuum that ranges from full awareness to a deep sleep. Sleep
is a state marked by relatively low levels of physical activity and reduced sensory awareness that is
distinct from periods of rest that occur during wakefulness. Wakefulness is characterized by high levels
of sensory awareness, thought, and behavior. Beyond being awake or asleep, there are many other states
of consciousness people experience. These include daydreaming, intoxication, and unconsciousness due to
anesthesia. We might also experience unconscious states of being via drug-induced anesthesia for medical
purposes. Often, we are not completely aware of our surroundings, even when we are fully awake. For
instance, have you ever daydreamed while driving home from work or school without really thinking
about the drive itself? You were capable of engaging in the all of the complex tasks involved with operating
a motor vehicle even though you were not aware of doing so. Many of these processes, like much of
psychological behavior, are rooted in our biology.


Biological rhythms are internal rhythms of biological activity. A woman’s menstrual cycle is an example
of a biological rhythm—a recurring, cyclical pattern of bodily changes. One complete menstrual cycle
takes about 28 days—a lunar month—but many biological cycles are much shorter. For example, body
temperature fluctuates cyclically over a 24-hour period (Figure 4.2). Alertness is associated with higher
body temperatures, and sleepiness with lower body temperatures.

116 Chapter 4 | States of Consciousness

This OpenStax book is available for free at

Figure 4.2 This chart illustrates the circadian change in body temperature over 28 hours in a group of eight young
men. Body temperature rises throughout the waking day, peaking in the afternoon, and falls during sleep with the
lowest point occurring during the very early morning hours.

This pattern of temperature fluctuation, which repeats every day, is one example of a circadian rhythm. A
circadian rhythm is a biological rhythm that takes place over a period of about 24 hours. Our sleep-wake
cycle, which is linked to our environment’s natural light-dark cycle, is perhaps the most obvious example
of a circadian rhythm, but we also have daily fluctuations in heart rate, blood pressure, blood sugar, and
body temperature. Some circadian rhythms play a role in changes in our state of consciousness.

If we have biological rhythms, then is there some sort of biological clock? In the brain, the hypothalamus,
which lies above the pituitary gland, is a main center of homeostasis. Homeostasis is the tendency to
maintain a balance, or optimal level, within a biological system.

The brain’s clock mechanism is located in an area of the hypothalamus known as the suprachiasmatic
nucleus (SCN). The axons of light-sensitive neurons in the retina provide information to the SCN based on
the amount of light present, allowing this internal clock to be synchronized with the outside world (Klein,
Moore, & Reppert, 1991; Welsh, Takahashi, & Kay, 2010) (Figure 4.3).

Chapter 4 | States of Consciousness 117

Figure 4.3 The suprachiasmatic nucleus (SCN) serves as the brain’s clock mechanism. The clock sets itself with
light information received through projections from the retina.


Generally, and for most people, our circadian cycles are aligned with the outside world. For example, most
people sleep during the night and are awake during the day. One important regulator of sleep-wake cycles
is the hormone melatonin. The pineal gland, an endocrine structure located inside the brain that releases
melatonin, is thought to be involved in the regulation of various biological rhythms and of the immune
system during sleep (Hardeland, Pandi-Perumal, & Cardinali, 2006). Melatonin release is stimulated by
darkness and inhibited by light.

There are individual differences in regard to our sleep-wake cycle. For instance, some people would say
they are morning people, while others would consider themselves to be night owls. These individual
differences in circadian patterns of activity are known as a person’s chronotype, and research
demonstrates that morning larks and night owls differ with regard to sleep regulation (Taillard, Philip,
Coste, Sagaspe, & Bioulac, 2003). Sleep regulation refers to the brain’s control of switching between sleep
and wakefulness as well as coordinating this cycle with the outside world.

Watch this brief video about circadian rhythms and how they affect sleep (
circadian) to learn more.

Disruptions of Normal Sleep

Whether lark, owl, or somewhere in between, there are situations in which a person’s circadian clock gets
out of synchrony with the external environment. One way that this happens involves traveling across
multiple time zones. When we do this, we often experience jet lag. Jet lag is a collection of symptoms that
results from the mismatch between our internal circadian cycles and our environment. These symptoms
include fatigue, sluggishness, irritability, and insomnia (i.e., a consistent difficulty in falling or staying
asleep for at least three nights a week over a month’s time) (Roth, 2007).

Individuals who do rotating shift work are also likely to experience disruptions in circadian cycles.


118 Chapter 4 | States of Consciousness

This OpenStax book is available for free at

Rotating shift work refers to a work schedule that changes from early to late on a daily or weekly
basis. For example, a person may work from 7:00 a.m. to 3:00 p.m. on Monday, 3:00 a.m. to 11:00 a.m.
on Tuesday, and 11:00 a.m. to 7:00 p.m. on Wednesday. In such instances, the individual’s schedule
changes so frequently that it becomes difficult for a normal circadian rhythm to be maintained. This
often results in sleeping problems, and it can lead to signs of depression and anxiety. These kinds of
schedules are common for individuals working in health care professions and service industries, and they
are associated with persistent feelings of exhaustion and agitation that can make someone more prone to
making mistakes on the job (Gold et al., 1992; Presser, 1995).

Rotating shift work has pervasive effects on the lives and experiences of individuals engaged in that
kind of work, which is clearly illustrated in stories reported in a qualitative study that researched the
experiences of middle-aged nurses who worked rotating shifts (West, Boughton & Byrnes, 2009). Several of
the nurses interviewed commented that their work schedules affected their relationships with their family.
One of the nurses said,

If you’ve had a partner who does work regular job 9 to 5 office hours . . . the ability to spend
time, good time with them when you’re not feeling absolutely exhausted . . . that would be one
of the problems that I’ve encountered. (West et al., 2009, p. 114)

While disruptions in circadian rhythms can have negative consequences, there are things we can do to help
us realign our biological clocks with the external environment. Some of these approaches, such as using
a bright light as shown in Figure 4.4, have been shown to alleviate some of the problems experienced by
individuals suffering from jet lag or from the consequences of rotating shift work. Because the biological
clock is driven by light, exposure to bright light during working shifts and dark exposure when not
working can help combat insomnia and symptoms of anxiety and depression (Huang, Tsai, Chen, & Hsu,

Figure 4.4 Devices like this are designed to provide exposure to bright light to help people maintain a regular
circadian cycle. They can be helpful for people working night shifts or for people affected by seasonal variations in

Watch this video about overcoming jet lag ( to learn some tips.

Insufficient Sleep

When people have difficulty getting sleep due to their work or the demands of day-to-day life, they
accumulate a sleep debt. A person with a sleep debt does not get sufficient sleep on a chronic basis. The
consequences of sleep debt include decreased levels of alertness and mental efficiency. Interestingly, since
the advent of electric light, the amount of sleep that people get has declined. While we certainly welcome


Chapter 4 | States of Consciousness 119

the convenience of having the darkness lit up, we also suffer the consequences of reduced amounts of sleep
because we are more active during the nighttime hours than our ancestors were. As a result, many of us
sleep less than 7–8 hours a night and accrue a sleep debt. While there is tremendous variation in any given
individual’s sleep needs, the National Sleep Foundation (n.d.) cites research to estimate that newborns
require the most sleep (between 12 and 18 hours a night) and that this amount declines to just 7–9 hours
by the time we are adults.

If you lie down to take a nap and fall asleep very easily, chances are you may have sleep debt. Given that
college students are notorious for suffering from significant sleep debt (Hicks, Fernandez, & Pelligrini,
2001; Hicks, Johnson, & Pelligrini, 1992; Miller, Shattuck, & Matsangas, 2010), chances are you and your
classmates deal with sleep debt-related issues on a regular basis. In 2015, the National Sleep Foundation
updated their sleep duration hours, to better accommodate individual differences. Table 4.1 shows the
new recommendations, which describe sleep durations that are “recommended”, “may be appropriate”,
and “not recommended”.

Sleep Needs at Different Ages

Age Recommended May be appropriate Not recommended

0–3 months 14–17 hours 11–13 hours
18–19 hours

Fewer than 11 hours
More than 19 hours

4–11 months 12–15 hours 10–11 hours
16–18 hours

Fewer than 10 hours
More than 18 hours

1–2 years 11–14 hours 9–10 hours
15–16 hours

Fewer than 9 hours
More than 16 hours

3–5 years 10–13 hours 8–9 hours
14 hours

Fewer than 8 hours
More than 14 hours

6–13 years 9–11 hours 7–8 hours
12 hours

Fewer than 7 hours
More than 12 hours

14–17 years 8–10 hours 7 hours
11 hours

Fewer than 7 hours
More than 11 hours

18–25 years 7–9 hours 6 hours
10–11 hours

Fewer than 6 hours
More than 11 hours

26–64 years 7–9 hours 6 hours
10 hours

Fewer than 6 hours
More than 10 hours

≥65 years 7–8 hours 5–6 hours
9 hours

Fewer than 5 hours
More than 9 hours

Table 4.1

Sleep debt and sleep deprivation have significant negative psychological and physiological consequences
Figure 4.5. As mentioned earlier, lack of sleep can result in decreased mental alertness and cognitive
function. In addition, sleep deprivation often results in depression-like symptoms. These effects can occur
as a function of accumulated sleep debt or in response to more acute periods of sleep deprivation. It may
surprise you to know that sleep deprivation is associated with obesity, increased blood pressure, increased
levels of stress hormones, and reduced immune functioning (Banks & Dinges, 2007). A sleep deprived

120 Chapter 4 | States of Consciousness

This OpenStax book is available for free at

individual generally will fall asleep more quickly than if she were not sleep deprived. Some sleep-deprived
individuals have difficulty staying awake when they stop moving (example sitting and watching television
or driving a car). That is why individuals suffering from sleep deprivation can also put themselves and
others at risk when they put themselves behind the wheel of a car or work with dangerous machinery.
Some research suggests that sleep deprivation affects cognitive and motor function as much as, if not more
than, alcohol intoxication (Williamson & Feyer, 2000). Research shows that the most severe effects of sleep
deprivation occur when a person stays awake for more than 24 hours (Killgore & Weber, 2014; Killgore
et al., 2007), or following repeated nights with fewer than four hours in bed (Wickens, Hutchins, Lauk,
Seebook, 2015). For example, irritability, distractibility, and impairments in cognitive and moral judgment
can occur with fewer than four hours of sleep. If someone stays awake for 48 consecutive hours, they could
start to hallucinate.

Figure 4.5 This figure illustrates some of the negative consequences of sleep deprivation. While cognitive deficits
may be the most obvious, many body systems are negatively impacted by lack of sleep. (credit: modification of work
by Mikael Häggström)

Read this article about sleep needs ( to assess your own sleeping

The amount of sleep we get varies across the lifespan. When we are very young, we spend up to 16 hours
a day sleeping. As we grow older, we sleep less. In fact, a meta-analysis, which is a study that combines
the results of many related studies, conducted within the last decade indicates that by the time we are 65
years old, we average fewer than 7 hours of sleep per day (Ohayon, Carskadon, Guilleminault, & Vitiello,


Chapter 4 | States of Consciousness 121

4.2 Sleep and Why We Sleep

Learning Objectives

By the end of this section, you will be able to:
• Describe areas of the brain involved in sleep
• Understand hormone secretions associated with sleep
• Describe several theories aimed at explaining the function of sleep

We spend approximately one-third of our lives sleeping. Given the average life expectancy for U.S. citizens
falls between 73 and 79 years old (Singh & Siahpush, 2006), we can expect to spend approximately 25 years
of our lives sleeping. Some animals never sleep (e.g., some fish and amphibian species); other animals sleep
very little without apparent negative consequences (e.g., giraffes); yet some animals (e.g., rats) die after
two weeks of sleep deprivation (Siegel, 2008). Why do we devote so much time to sleeping? Is it absolutely
essential that we sleep? This section will consider these questions and explore various explanations for
why we sleep.


You have read that sleep is distinguished by low levels of physical activity and reduced sensory
awareness. As discussed by Siegel (2008), a definition of sleep must also include mention of the interplay
of the circadian and homeostatic mechanisms that regulate sleep. Homeostatic regulation of sleep is
evidenced by sleep rebound following sleep deprivation. Sleep rebound refers to the fact that a sleep-
deprived individual will fall asleep more quickly during subsequent opportunities for sleep. Sleep is
characterized by certain patterns of activity of the brain that can be visualized using
electroencephalography (EEG), and different phases of sleep can be differentiated using EEG as well.

Sleep-wake cycles seem to be controlled by multiple brain areas acting in conjunction with one another.
Some of these areas include the thalamus, the hypothalamus, and the pons. As already mentioned, the
hypothalamus contains the SCN—the biological clock of the body—in addition to other nuclei that, in
conjunction with the thalamus, regulate slow-wave sleep. The pons is important for regulating rapid eye
movement (REM) sleep (National Institutes of Health, n.d.).

Sleep is also associated with the secretion and regulation of a number of hormones from several endocrine
glands including: melatonin, follicle stimulating hormone (FSH), luteinizing hormone (LH), and growth
hormone (National Institutes of Health, n.d.). You have read that the pineal gland releases melatonin
during sleep (Figure 4.6). Melatonin is thought to be involved in the regulation of various biological
rhythms and the immune system (Hardeland et al., 2006). During sleep, the pituitary gland secretes both
FSH and LH which are important in regulating the reproductive system (Christensen et al., 2012; Sofikitis
et al., 2008). The pituitary gland also secretes growth hormone, during sleep, which plays a role in physical
growth and maturation as well as other metabolic processes (Bartke, Sun, & Longo, 2013).

122 Chapter 4 | States of Consciousness

This OpenStax book is available for free at

Figure 4.6 The pineal and pituitary glands secrete a number of hormones during sleep.


Given the central role that sleep plays in our lives and the number of adverse consequences that have been
associated with sleep deprivation, one would think that we would have a clear understanding of why it
is that we sleep. Unfortunately, this is not the case; however, several hypotheses have been proposed to
explain the function of sleep.

Adaptive Function of Sleep

One popular hypothesis of sleep incorporates the perspective of evolutionary psychology. Evolutionary
psychology is a discipline that studies how universal patterns of behavior and cognitive processes have
evolved over time as a result of natural selection. Variations and adaptations in cognition and behavior
make individuals more or less successful in reproducing and passing their genes to their offspring. One
hypothesis from this perspective might argue that sleep is essential to restore resources that are expended
during the day. Just as bears hibernate in the winter when resources are scarce, perhaps people sleep at
night to reduce their energy expenditures. While this is an intuitive explanation of sleep, there is little
research that supports this explanation. In fact, it has been suggested that there is no reason to think that
energetic demands could not be addressed with periods of rest and inactivity (Frank, 2006; Rial et al., 2007),
and some research has actually found a negative correlation between energetic demands and the amount
of time spent sleeping (Capellini, Barton, McNamara, Preston, & Nunn, 2008).

Another evolutionary hypothesis of sleep holds that our sleep patterns evolved as an adaptive response
to predatory risks, which increase in darkness. Thus we sleep in safe areas to reduce the chance of harm.
Again, this is an intuitive and appealing explanation for why we sleep. Perhaps our ancestors spent
extended periods of time asleep to reduce attention to themselves from potential predators. Comparative
research indicates, however, that the relationship that exists between predatory risk and sleep is very
complex and equivocal. Some research suggests that species that face higher predatory risks sleep fewer
hours than other species (Capellini et al., 2008), while other researchers suggest there is no relationship
between the amount of time a given species spends in deep sleep and its predation risk (Lesku, Roth,
Amlaner, & Lima, 2006).

It is quite possible that sleep serves no single universally adaptive function, and different species have
evolved different patterns of sleep in response to their unique evolutionary pressures. While we have
discussed the negative outcomes associated with sleep deprivation, it should be pointed out that there
are many benefits that are associated with adequate amounts of sleep. A few such benefits listed by the

Chapter 4 | States of Consciousness 123

National Sleep Foundation (n.d.) include maintaining healthy weight, lowering stress levels, improving
mood, and increasing motor coordination, as well as a number of benefits related to cognition and memory

Cognitive Function of Sleep

Another theory regarding why we sleep involves sleep’s importance for cognitive function and memory
formation (Rattenborg, Lesku, Martinez-Gonzalez, & Lima, 2007). Indeed, we know sleep deprivation
results in disruptions in cognition and memory deficits (Brown, 2012), leading to impairments in our
abilities to maintain attention, make decisions, and recall long-term memories. Moreover, these
impairments become more severe as the amount of sleep deprivation increases (Alhola & Polo-Kantola,
2007). Furthermore, slow-wave sleep after learning a new task can improve resultant performance on that
task (Huber, Ghilardi, Massimini, & Tononi, 2004) and seems essential for effective memory formation
(Stickgold, 2005). Understanding the impact of sleep on cognitive function should help you understand
that cramming all night for a test may be not effective and can even prove counterproductive.

Watch this brief video that gives sleep tips for college students ( to
learn more.

Getting the optimal amount of sleep has also been associated with other cognitive benefits. Research
indicates that included among these possible benefits are increased capacities for creative thinking (Cai,
Mednick, Harrison, Kanady, & Mednick, 2009; Wagner, Gais, Haider, Verleger, & Born, 2004), language
learning (Fenn, Nusbaum, & Margoliash, 2003; Gómez, Bootzin, & Nadel, 2006), and inferential judgments
(Ellenbogen, Hu, Payne, Titone, & Walker, 2007). It is possible that even the processing of emotional
information is influenced by certain aspects of sleep (Walker, 2009).

Watch this brief video about the relationship between sleep and memory (
sleepmemory) to learn more.

4.3 Stages of Sleep

Learning Objectives

By the end of this section, you will be able to:
• Differentiate between REM and non-REM sleep
• Describe the differences between the three stages of non-REM sleep
• Understand the role that REM and non-REM sleep play in learning and memory

Sleep is not a uniform state of being. Instead, sleep is composed of several different stages that can
be differentiated from one another by the patterns of brain wave activity that occur during each stage.
These changes in brain wave activity can be visualized using EEG and are distinguished from one



124 Chapter 4 | States of Consciousness

This OpenStax book is available for free at

another by both the frequency and amplitude of brain waves (Figure 4.7). Sleep can be divided into
two different general phases: REM sleep and non-REM (NREM) sleep. Rapid eye movement (REM)
sleep is characterized by darting movements of the eyes under closed eyelids. Brain waves during REM
sleep appear very similar to brain waves during wakefulness. In contrast, non-REM (NREM) sleep is
subdivided into four stages distinguished from each other and from wakefulness by characteristic patterns
of brain waves. The first three stages of sleep are NREM sleep, while the fourth and final stage of sleep
is REM sleep. In this section, we will discuss each of these stages of sleep and their associated patterns of
brain wave activity.

Figure 4.7 Brainwave activity changes dramatically across the different stages of sleep. (credit “sleeping”:
modification of work by Ryan Vaarsi)


The first stage of NREM sleep is known as stage 1 sleep. Stage 1 sleep is a transitional phase that occurs
between wakefulness and sleep, the period during which we drift off to sleep. During this time, there is
a slowdown in both the rates of respiration and heartbeat. In addition, stage 1 sleep involves a marked
decrease in both overall muscle tension and core body temperature.

In terms of brain wave activity, stage 1 sleep is associated with both alpha and theta waves. The early
portion of stage 1 sleep produces alpha waves, which are relatively low frequency (8–13Hz), high
amplitude patterns of electrical activity (waves) that become synchronized (Figure 4.8). This pattern of
brain wave activity resembles that of someone who is very relaxed, yet awake. As an individual continues
through stage 1 sleep, there is an increase in theta wave activity. Theta waves are even lower frequency
(4–7 Hz), higher amplitude brain waves than alpha waves. It is relatively easy to wake someone from stage
1 sleep; in fact, people often report that they have not been asleep if they are awoken during stage 1 sleep.

Chapter 4 | States of Consciousness 125

Figure 4.8 Brainwave activity changes dramatically across the different stages of sleep.

As we move into stage 2 sleep, the body goes into a state of deep relaxation. Theta waves still dominate
the activity of the brain, but they are interrupted by brief bursts of activity known as sleep spindles
(Figure 4.9). A sleep spindle is a rapid burst of higher frequency brain waves that may be important for
learning and memory (Fogel & Smith, 2011; Poe, Walsh, & Bjorness, 2010). In addition, the appearance of
K-complexes is often associated with stage 2 sleep. A K-complex is a very high amplitude pattern of brain
activity that may in some cases occur in response to environmental stimuli. Thus, K-complexes might serve
as a bridge to higher levels of arousal in response to what is going on in our environments (Halász, 1993;
Steriade & Amzica, 1998).

Figure 4.9 Stage 2 sleep is characterized by the appearance of both sleep spindles and K-complexes.

Stage 3 is often referred to as deep sleep or slow-wave sleep because this stage is characterized by low
frequency (less than 3 Hz), high amplitude delta waves (Figure 4.10). During this time, an individual’s
heart rate and respiration slow dramatically. It is much more difficult to awaken someone from sleep
during stage 3 than during earlier stages. Interestingly, individuals who have increased levels of alpha
brain wave activity (more often associated with wakefulness and transition into stage 1 sleep) during stage
3 often report that they do not feel refreshed upon waking, regardless of how long they slept (Stone,
Taylor, McCrae, Kalsekar, & Lichstein, 2008).

126 Chapter 4 | States of Consciousness

This OpenStax book is available for free at

Figure 4.10 (a) Delta waves, which are low frequency and high amplitude, characterize (b) slow-wave stage 3 and
stage 4 sleep.


As mentioned earlier, REM sleep is marked by rapid movements of the eyes. The brain waves associated
with this stage of sleep are very similar to those observed when a person is awake, as shown in Figure
4.11, and this is the period of sleep in which dreaming occurs. It is also associated with paralysis of muscle
systems in the body with the exception of those that make circulation and respiration possible. Therefore,
no movement of voluntary muscles occurs during REM sleep in a normal individual; REM sleep is often
referred to as paradoxical sleep because of this combination of high brain activity and lack of muscle tone.
Like NREM sleep, REM has been implicated in various aspects of learning and memory (Wagner, Gais, &
Born, 2001; Siegel, 2001).

Figure 4.11 (a) A period of rapid eye movement is marked by the short red line segment. The brain waves
associated with REM sleep, outlined in the red box in (a), look very similar to those seen (b) during wakefulness.

If people are deprived of REM sleep and then allowed to sleep without disturbance, they will spend more
time in REM sleep in what would appear to be an effort to recoup the lost time in REM. This is known as
the REM rebound, and it suggests that REM sleep is also homeostatically regulated. Aside from the role
that REM sleep may play in processes related to learning and memory, REM sleep may also be involved in
emotional processing and regulation. In such instances, REM rebound may actually represent an adaptive
response to stress in nondepressed individuals by suppressing the emotional salience of aversive events
that occurred in wakefulness (Suchecki, Tiba, & Machado, 2012). Sleep deprivation in general is associated

Chapter 4 | States of Consciousness 127

with a number of negative consequences (Brown, 2012).

The hypnogram below (Figure 4.12) shows a person’s passage through the stages of sleep.

Figure 4.12 A hypnogram is a diagram of the stages of sleep as they occur during a period of sleep. This
hypnogram illustrates how an individual moves through the various stages of sleep.

View this video about the various stages of sleep ( to learn more.


Dreams and their associated meanings vary across different cultures and periods of time. By the late
19th century, German psychiatrist Sigmund Freud had become convinced that dreams represented an
opportunity to gain access to the unconscious. By analyzing dreams, Freud thought people could increase
self-awareness and gain valuable insight to help them deal with the problems they faced in their lives.
Freud made distinctions between the manifest content and the latent content of dreams. Manifest content
is the actual content, or storyline, of a dream. Latent content, on the other hand, refers to the hidden
meaning of a dream. For instance, if a woman dreams about being chased by a snake, Freud might have
argued that this represents the woman’s fear of sexual intimacy, with the snake serving as a symbol of a
man’s penis.

Freud was not the only theorist to focus on the content of dreams. The 20th century Swiss psychiatrist Carl
Jung believed that dreams allowed us to tap into the collective unconscious. The collective unconscious,
as described by Jung, is a theoretical repository of information he believed to be shared by everyone.
According to Jung, certain symbols in dreams reflected universal archetypes with meanings that are
similar for all people regardless of culture or location.

The sleep and dreaming researcher Rosalind Cartwright, however, believes that dreams simply reflect life
events that are important to the dreamer. Unlike Freud and Jung, Cartwright’s ideas about dreaming have
found empirical support. For example, she and her colleagues published a study in which women going
through divorce were asked several times over a five month period to report the degree to which their
former spouses were on their minds. These same women were awakened during REM sleep in order to
provide a detailed account of their dream content. There was a significant positive correlation between the
degree to which women thought about their former spouses during waking hours and the number of times


128 Chapter 4 | States of Consciousness

This OpenStax book is available for free at

their former spouses appeared as characters in their dreams (Cartwright, Agargun, Kirkby, & Friedman,
2006). Recent research (Horikawa, Tamaki, Miyawaki, & Kamitani, 2013) has uncovered new techniques
by which researchers may effectively detect and classify the visual images that occur during dreaming by
using fMRI for neural measurement of brain activity patterns, opening the way for additional research in
this area.

Alan Hobson, a neuroscientist, is credited for developing activation-synthesis theory of dreaming. Early
versions of this theory proposed that dreams were not the meaning-filled representations of angst
proposed by Freud and others, but were rather the result of our brain attempting to make sense of
(“synthesize”) the neural activity (“activation”) that was happening during REM sleep. Recent adaptations
(e.g., Hobson, 2002) continue to update the theory based on accumulating evidence. For example, Hobson
(2009) suggests that dreaming may represent a state of protoconsciousness. In other words, dreaming
involves constructing a virtual reality in our heads that we might use to help us during wakefulness.
Among a variety of neurobiological evidence, John Hobson cites research on lucid dreams as an
opportunity to better understand dreaming in general. Lucid dreams are dreams in which certain aspects
of wakefulness are maintained during a dream state. In a lucid dream, a person becomes aware of the fact
that they are dreaming, and as such, they can control the dream’s content (LaBerge, 1990).

4.4 Sleep Problems and Disorders

Learning Objectives

By the end of this section, you will be able to:
• Describe the symptoms and treatments of insomnia
• Recognize the symptoms of several parasomnias
• Describe the symptoms and treatments for sleep apnea
• Recognize risk factors associated with sudden infant death syndrome (SIDS) and steps to

prevent it
• Describe the symptoms and treatments for narcolepsy

Many people experience disturbances in their sleep at some point in their lives. Depending on the
population and sleep disorder being studied, between 30% and 50% of the population suffers from a sleep
disorder at some point in their lives (Bixler, Kales, Soldatos, Kaels, & Healey, 1979; Hossain & Shapiro,
2002; Ohayon, 1997, 2002; Ohayon & Roth, 2002). This section will describe several sleep disorders as well
as some of their treatment options.


Insomnia, a consistent difficulty in falling or staying asleep, is the most common of the sleep disorders.
Individuals with insomnia often experience long delays between the times that they go to bed and actually
fall asleep. In addition, these individuals may wake up several times during the night only to find that
they have difficulty getting back to sleep. As mentioned earlier, one of the criteria for insomnia involves
experiencing these symptoms for at least three nights a week for at least one month’s time (Roth, 2007).

It is not uncommon for people suffering from insomnia to experience increased levels of anxiety about
their inability to fall asleep. This becomes a self-perpetuating cycle because increased anxiety leads to
increased arousal, and higher levels of arousal make the prospect of falling asleep even more unlikely.
Chronic insomnia is almost always associated with feeling overtired and may be associated with
symptoms of depression.

There may be many factors that contribute to insomnia, including age, drug use, exercise, mental status,
and bedtime routines. Not surprisingly, insomnia treatment may take one of several different approaches.

Chapter 4 | States of Consciousness 129

People who suffer from insomnia might limit their use of stimulant drugs (such as caffeine) or increase
their amount of physical exercise during the day. Some people might turn to over-the-counter (OTC) or
prescribed sleep medications to help them sleep, but this should be done sparingly because many sleep
medications result in dependence and alter the nature of the sleep cycle, and they can increase insomnia
over time. Those who continue to have insomnia, particularly if it affects their quality of life, should seek
professional treatment.

Some forms of psychotherapy, such as cognitive-behavioral therapy, can help sufferers of insomnia.
Cognitive-behavioral therapy is a type of psychotherapy that focuses on cognitive processes and problem
behaviors. The treatment of insomnia likely would include stress management techniques and changes
in problematic behaviors that could contribute to insomnia (e.g., spending more waking time in bed).
Cognitive-behavioral therapy has been demonstrated to be quite effective in treating insomnia (Savard,
Simard, Ivers, & Morin, 2005; Williams, Roth, Vatthauer, & McCrae, 2013).

Solutions to Support Healthy Sleep

Has something like this ever happened to you? My sophomore college housemate got so stressed out during
finals sophomore year he drank almost a whole bottle of Nyquil to try to fall asleep. When he told me, I made
him go see the college therapist.

Many college students struggle getting the recommended 7–9 hours of sleep each night. However, for some,
it’s not because of all-night partying or late-night study sessions. It’s simply that they feel so overwhelmed and
stressed that they cannot fall asleep or stay asleep. One or two nights of sleep difficulty is not unusual, but if
you experience anything more than that, you should seek a doctor’s advice.

Here are some tips to maintain healthy sleep:

• Stick to a sleep schedule, even on the weekends. Try going to bed and waking up at the same time
every day to keep your biological clock in sync so your body gets in the habit of sleeping every night.

• Avoid anything stimulating for an hour before bed. That includes exercise and bright light from devices.

• Exercise daily.

• Avoid naps.

• Keep your bedroom temperature between 60 and 67 degrees. People sleep better in cooler

• Avoid alcohol, cigarettes, caffeine, and heavy meals before bed. It may feel like alcohol helps you
sleep, but it actually disrupts REM sleep and leads to frequent awakenings. Heavy meals may make
you sleepy, but they can also lead to frequent awakenings due to gastric distress.

• If you cannot fall asleep, leave your bed and do something else until you feel tired again. Train your
body to associate the bed with sleeping rather than other activities like studying, eating, or watching
television shows.


A parasomnia is one of a group of sleep disorders in which unwanted, disruptive motor activity and/
or experiences during sleep play a role. Parasomnias can occur in either REM or NREM phases of sleep.
Sleepwalking, restless leg syndrome, and night terrors are all examples of parasomnias (Mahowald &
Schenck, 2000).


130 Chapter 4 | States of Consciousness

This OpenStax book is available for free at


In sleepwalking, or somnambulism, the sleeper engages in relatively complex behaviors ranging from
wandering about to driving an automobile. During periods of sleepwalking, sleepers often have their eyes
open, but they are not responsive to attempts to communicate with them. Sleepwalking most often occurs
during slow-wave sleep, but it can occur at any time during a sleep period in some affected individuals
(Mahowald & Schenck, 2000).

Historically, somnambulism has been treated with a variety of pharmacotherapies ranging from
benzodiazepines to antidepressants. However, the success rate of such treatments is questionable.
Guilleminault et al. (2005) found that sleepwalking was not alleviated with the use of benzodiazepines.
However, all of their somnambulistic patients who also suffered from sleep-related breathing problems
showed a marked decrease in sleepwalking when their breathing problems were effectively treated.

A Sleepwalking Defense?

On January 16, 1997, Scott Falater sat down to dinner with his wife and children and told them about difficulties
he was experiencing on a project at work. After dinner, he prepared some materials to use in leading a church
youth group the following morning, and then he attempted to repair the family’s swimming pool pump before
retiring to bed. The following morning, he awoke to barking dogs and unfamiliar voices from downstairs. As
he went to investigate what was going on, he was met by a group of police officers who arrested him for the
murder of his wife (Cartwright, 2004; CNN, 1999).

Yarmila Falater’s body was found in the family’s pool with 44 stab wounds. A neighbor called the police after
witnessing Falater standing over his wife’s body before dragging her into the pool. Upon a search of the
premises, police found blood-stained clothes and a bloody knife in the trunk of Falater’s car, and he had blood
stains on his neck.

Remarkably, Falater insisted that he had no recollection of hurting his wife in any way. His children and his
wife’s parents all agreed that Falater had an excellent relationship with his wife and they couldn’t think of a
reason that would provide any sort of motive to murder her (Cartwright, 2004).

Scott Falater had a history of regular episodes of sleepwalking as a child, and he had even behaved violently
toward his sister once when she tried to prevent him from leaving their home in his pajamas during a
sleepwalking episode. He suffered from no apparent anatomical brain anomalies or psychological disorders. It
appeared that Scott Falater had killed his wife in his sleep, or at least, that is the defense he used when he
was tried for his wife’s murder (Cartwright, 2004; CNN, 1999). In Falater’s case, a jury found him guilty of first
degree murder in June of 1999 (CNN, 1999); however, there are other murder cases where the sleepwalking
defense has been used successfully. As scary as it sounds, many sleep researchers believe that homicidal
sleepwalking is possible in individuals suffering from the types of sleep disorders described below (Broughton
et al., 1994; Cartwright, 2004; Mahowald, Schenck, & Cramer Bornemann, 2005; Pressman, 2007).

REM Sleep Behavior Disorder (RBD)

REM sleep behavior disorder (RBD) occurs when the muscle paralysis associated with the REM sleep
phase does not occur. Individuals who suffer from RBD have high levels of physical activity during REM
sleep, especially during disturbing dreams. These behaviors vary widely, but they can include kicking,
punching, scratching, yelling, and behaving like an animal that has been frightened or attacked. People
who suffer from this disorder can injure themselves or their sleeping partners when engaging in these
behaviors. Furthermore, these types of behaviors ultimately disrupt sleep, although affected individuals
have no memories that these behaviors have occurred (Arnulf, 2012).

This disorder is associated with a number of neurodegenerative diseases such as Parkinson’s disease. In
fact, this relationship is so robust that some view the presence of RBD as a potential aid in the diagnosis


Chapter 4 | States of Consciousness 131

and treatment of a number of neurodegenerative diseases (Ferini-Strambi, 2011). Clonazepam, an anti-
anxiety medication with sedative properties, is most often used to treat RBD. It is administered alone or
in conjunction with doses of melatonin (the hormone secreted by the pineal gland). As part of treatment,
the sleeping environment is often modified to make it a safer place for those suffering from RBD (Zangini,
Calandra-Buonaura, Grimaldi, & Cortelli, 2011).

Other Parasomnias

A person with restless leg syndrome has uncomfortable sensations in the legs during periods of inactivity
or when trying to fall asleep. This discomfort is relieved by deliberately moving the legs, which, not
surprisingly, contributes to difficulty in falling or staying asleep. Restless leg syndrome is quite common
and has been associated with a number of other medical diagnoses, such as chronic kidney disease and
diabetes (Mahowald & Schenck, 2000). There are a variety of drugs that treat restless leg syndrome:
benzodiazepines, opiates, and anticonvulsants (Restless Legs Syndrome Foundation, n.d.).

Night terrors result in a sense of panic in the sufferer and are often accompanied by screams and attempts
to escape from the immediate environment (Mahowald & Schenck, 2000). Although individuals suffering
from night terrors appear to be awake, they generally have no memories of the events that occurred, and
attempts to console them are ineffective. Typically, individuals suffering from night terrors will fall back
asleep again within a short time. Night terrors apparently occur during the NREM phase of sleep (Provini,
Tinuper, Bisulli, & Lagaresi, 2011). Generally, treatment for night terrors is unnecessary unless there is
some underlying medical or psychological condition that is contributing to the night terrors (Mayo Clinic,


Sleep apnea is defined by episodes during which a sleeper’s breathing stops. These episodes can last 10–20
seconds or longer and often are associated with brief periods of arousal. While individuals suffering from
sleep apnea may not be aware of these repeated disruptions in sleep, they do experience increased levels of
fatigue. Many individuals diagnosed with sleep apnea first seek treatment because their sleeping partners
indicate that they snore loudly and/or stop breathing for extended periods of time while sleeping (Henry
& Rosenthal, 2013). Sleep apnea is much more common in overweight people and is often associated
with loud snoring. Surprisingly, sleep apnea may exacerbate cardiovascular disease (Sánchez-de-la-Torre,
Campos-Rodriguez, & Barbé, 2012). While sleep apnea is less common in thin people, anyone, regardless
of their weight, who snores loudly or gasps for air while sleeping, should be checked for sleep apnea.

While people are often unaware of their sleep apnea, they are keenly aware of some of the adverse
consequences of insufficient sleep. Consider a patient who believed that as a result of his sleep apnea he
“had three car accidents in six weeks. They were ALL my fault. Two of them I didn’t even know I was
involved in until afterwards” (Henry & Rosenthal, 2013, p. 52). It is not uncommon for people suffering
from undiagnosed or untreated sleep apnea to fear that their careers will be affected by the lack of sleep,
illustrated by this statement from another patient, “I’m in a job where there’s a premium on being mentally
alert. I was really sleepy… and having trouble concentrating…. It was getting to the point where it was
kind of scary” (Henry & Rosenthal, 2013, p. 52).

There are two types of sleep apnea: obstructive sleep apnea and central sleep apnea. Obstructive sleep
apnea occurs when an individual’s airway becomes blocked during sleep, and air is prevented from
entering the lungs. In central sleep apnea, disruption in signals sent from the brain that regulate breathing
cause periods of interrupted breathing (White, 2005).

One of the most common treatments for sleep apnea involves the use of a special device during sleep.
A continuous positive airway pressure (CPAP) device includes a mask that fits over the sleeper’s nose
and mouth, which is connected to a pump that pumps air into the person’s airways, forcing them to
remain open, as shown in Figure 4.13. Some newer CPAP masks are smaller and cover only the nose.
This treatment option has proven to be effective for people suffering from mild to severe cases of sleep

132 Chapter 4 | States of Consciousness

This OpenStax book is available for free at

apnea (McDaid et al., 2009). However, alternative treatment options are being explored because consistent
compliance by users of CPAP devices is a problem. Recently, a new EPAP (expiratory positive air pressure)
device has shown promise in double-blind trials as one such alternative (Berry, Kryger, & Massie, 2011).

Figure 4.13 (a) A typical CPAP device used in the treatment of sleep apnea is (b) affixed to the head with straps,
and a mask that covers the nose and mouth.


In sudden infant death syndrome (SIDS) an infant stops breathing during sleep and dies. Infants younger
than 12 months appear to be at the highest risk for SIDS, and boys have a greater risk than girls. A number
of risk factors have been associated with SIDS including premature birth, smoking within the home, and
hyperthermia. There may also be differences in both brain structure and function in infants that die from
SIDS (Berkowitz, 2012; Mage & Donner, 2006; Thach, 2005).

The substantial amount of research on SIDS has led to a number of recommendations to parents to protect
their children (Figure 4.14). For one, research suggests that infants should be placed on their backs when
put down to sleep, and their cribs should not contain any items which pose suffocation threats, such as
blankets, pillows or padded crib bumpers (cushions that cover the bars of a crib). Infants should not have
caps placed on their heads when put down to sleep in order to prevent overheating, and people in the
child’s household should abstain from smoking in the home. Recommendations like these have helped
to decrease the number of infant deaths from SIDS in recent years (Mitchell, 2009; Task Force on Sudden
Infant Death Syndrome, 2011).

Figure 4.14 The Safe to Sleep campaign educates the public about how to minimize risk factors associated with
SIDS. This campaign is sponsored in part by the National Institute of Child Health and Human Development.


Unlike the other sleep disorders described in this section, a person with narcolepsy cannot resist falling
asleep at inopportune times. These sleep episodes are often associated with cataplexy, which is a lack of
muscle tone or muscle weakness, and in some cases involves complete paralysis of the voluntary muscles.
This is similar to the kind of paralysis experienced by healthy individuals during REM sleep (Burgess
& Scammell, 2012; Hishikawa & Shimizu, 1995; Luppi et al., 2011). Narcoleptic episodes take on other
features of REM sleep. For example, around one third of individuals diagnosed with narcolepsy experience
vivid, dream-like hallucinations during narcoleptic attacks (Chokroverty, 2010).

Surprisingly, narcoleptic episodes are often triggered by states of heightened arousal or stress. The typical

Chapter 4 | States of Consciousness 133

episode can last from a minute or two to half an hour. Once awakened from a narcoleptic attack, people
report that they feel refreshed (Chokroverty, 2010). Obviously, regular narcoleptic episodes could interfere
with the ability to perform one’s job or complete schoolwork, and in some situations, narcolepsy can result
in significant harm and injury (e.g., driving a car or operating machinery or other potentially dangerous

Generally, narcolepsy is treated using psychomotor stimulant drugs, such as amphetamines (Mignot,
2012). These drugs promote increased levels of neural activity. Narcolepsy is associated with reduced
levels of the signaling molecule hypocretin in some areas of the brain (De la Herrán-Arita & Drucker-Colín,
2012; Han, 2012), and the traditional stimulant drugs do not have direct effects on this system. Therefore,
it is quite likely that new medications that are developed to treat narcolepsy will be designed to target the
hypocretin system.

There is a tremendous amount of variability among sufferers, both in terms of how symptoms of
narcolepsy manifest and the effectiveness of currently available treatment options. This is illustrated by
McCarty’s (2010) case study of a 50-year-old woman who sought help for the excessive sleepiness during
normal waking hours that she had experienced for several years. She indicated that she had fallen asleep
at inappropriate or dangerous times, including while eating, while socializing with friends, and while
driving her car. During periods of emotional arousal, the woman complained that she felt some weakness
in the right side of her body. Although she did not experience any dream-like hallucinations, she was
diagnosed with narcolepsy as a result of sleep testing. In her case, the fact that her cataplexy was confined
to the right side of her body was quite unusual. Early attempts to treat her condition with a stimulant
drug alone were unsuccessful. However, when a stimulant drug was used in conjunction with a popular
antidepressant, her condition improved dramatically.

4.5 Substance Use and Abuse

Learning Objectives

By the end of this section, you will be able to:
• Describe the diagnostic criteria for substance use disorders
• Identify the neurotransmitter systems impacted by various categories of drugs
• Describe how different categories of drugs affect behavior and experience

While we all experience altered states of consciousness in the form of sleep on a regular basis, some
people use drugs and other substances that result in altered states of consciousness as well. This section
will present information relating to the use of various psychoactive drugs and problems associated with
such use. This will be followed by brief descriptions of the effects of some of the more well-known drugs
commonly used today.


The fifth edition of the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) is used by
clinicians to diagnose individuals suffering from various psychological disorders. Drug use disorders are
addictive disorders, and the criteria for specific substance (drug) use disorders are described in DSM-5. A
person who has a substance use disorder often uses more of the substance than they originally intended to
and continues to use that substance despite experiencing significant adverse consequences. In individuals
diagnosed with a substance use disorder, there is a compulsive pattern of drug use that is often associated
with both physical and psychological dependence.

Physical dependence involves changes in normal bodily functions—the user will experience withdrawal
from the drug upon cessation of use. In contrast, a person who has psychological dependence has an

134 Chapter 4 | States of Consciousness

This OpenStax book is available for free at

emotional, rather than physical, need for the drug and may use the drug to relieve psychological distress.
Tolerance is linked to physiological dependence, and it occurs when a person requires more and more
drug to achieve effects previously experienced at lower doses. Tolerance can cause the user to increase the
amount of drug used to a dangerous level—even to the point of overdose and death.

Drug withdrawal includes a variety of negative symptoms experienced when drug use is discontinued.
These symptoms usually are opposite of the effects of the drug. For example, withdrawal from sedative
drugs often produces unpleasant arousal and agitation. In addition to withdrawal, many individuals who
are diagnosed with substance use disorders will also develop tolerance to these substances. Psychological
dependence, or drug craving, is a recent addition to the diagnostic criteria for substance use disorder in
DSM-5. This is an important factor because we can develop tolerance and experience withdrawal from any
number of drugs that we do not abuse. In other words, physical dependence in and of itself is of limited
utility in determining whether or not someone has a substance use disorder.


The effects of all psychoactive drugs occur through their interactions with our endogenous
neurotransmitter systems. Many of these drugs, and their relationships, are shown in Table 4.2. As you
have learned, drugs can act as agonists or antagonists of a given neurotransmitter system. An agonist
facilitates the activity of a neurotransmitter system, and antagonists impede neurotransmitter activity.

Drugs and Their Effects

Class of Drug Examples
Effects on
the Body

Effects When Used

Stimulants Cocaine,
(including some
ADHD medications
such as Adderall),
MDMA (“Ecstasy”
or “Molly”)

heart rate,

Increased alertness,
mild euphoria,
decreased appetite in
low doses. High
doses increase
agitation, paranoia,
can cause
hallucinations. Some
can cause heightened
sensitivity to physical
stimuli. High doses
of MDMA can cause
brain toxicity and



barbiturates (e.g.,
(e.g., Xanax)

heart rate,

Low doses increase
relaxation, decrease
inhibitions. High
doses can induce
sleep, cause motor
disturbance, memory
loss, decreased
respiratory function,
and death.


Chapter 4 | States of Consciousness 135

Drugs and Their Effects

Class of Drug Examples
Effects on
the Body

Effects When Used

Opiates Opium, Heroin,
Fentanyl, Morphine,
methadone, and
other prescription
pain relievers

pain, pupil

Pain relief, euphoria,
sleepiness. High
doses can cause
death due to


Hallucinogens Marijuana, LSD,
Peyote, mescaline,
DMT, dissociative
including ketamine
and PCP

heart rate
and blood
that may
over time

Mild to intense
perceptual changes
with high variability
in effects based on
strain, method of
ingestion, and


Table 4.2

Alcohol and Other Depressants

Ethanol, which we commonly refer to as alcohol, is in a class of psychoactive drugs known as depressants
(Figure 4.15). A depressant is a drug that tends to suppress central nervous system activity. Other
depressants include barbiturates and benzodiazepines. These drugs share in common their ability to serve
as agonists of the gamma-Aminobutyric acid (GABA) neurotransmitter system. Because GABA has a
quieting effect on the brain, GABA agonists also have a quieting effect; these types of drugs are often
prescribed to treat both anxiety and insomnia.

136 Chapter 4 | States of Consciousness

This OpenStax book is available for free at

Figure 4.15 The GABA-gated chloride (Cl–) channel is embedded in the cell membrane of certain neurons. The
channel has multiple receptor sites where alcohol, barbiturates, and benzodiazepines bind to exert their effects. The
binding of these molecules opens the chloride channel, allowing negatively-charged chloride ions (Cl–) into the
neuron’s cell body. Changing its charge in a negative direction pushes the neuron away from firing; thus, activating a
GABA neuron has a quieting effect on the brain.

Acute alcohol administration results in a variety of changes to consciousness. At rather low doses, alcohol
use is associated with feelings of euphoria. As the dose increases, people report feeling sedated. Generally,
alcohol is associated with decreases in reaction time and visual acuity, lowered levels of alertness, and
reduction in behavioral control. With excessive alcohol use, a person might experience a complete loss of
consciousness and/or difficulty remembering events that occurred during a period of intoxication (McKim
& Hancock, 2013). In addition, if a pregnant woman consumes alcohol, her infant may be born with a
cluster of birth defects and symptoms collectively called fetal alcohol spectrum disorder (FASD) or fetal
alcohol syndrome (FAS).

With repeated use of many central nervous system depressants, such as alcohol, a person becomes
physically dependent upon the substance and will exhibit signs of both tolerance and withdrawal.
Psychological dependence on these drugs is also possible. Therefore, the abuse potential of central nervous
system depressants is relatively high.

Drug withdrawal is usually an aversive experience, and it can be a life-threatening process in individuals
who have a long history of very high doses of alcohol and/or barbiturates. This is of such concern
that people who are trying to overcome addiction to these substances should only do so under medical


Stimulants are drugs that tend to increase overall levels of neural activity. Many of these drugs act as
agonists of the dopamine neurotransmitter system. Dopamine activity is often associated with reward
and craving; therefore, drugs that affect dopamine neurotransmission often have abuse liability. Drugs in

Chapter 4 | States of Consciousness 137

this category include cocaine, amphetamines (including methamphetamine), cathinones (i.e., bath salts),
MDMA (ecstasy), nicotine, and caffeine.

Cocaine can be taken in multiple ways. While many users snort cocaine, intravenous injection and
inhalation (smoking) are also common. The freebase version of cocaine, known as crack, is a potent,
smokable version of the drug. Like many other stimulants, cocaine agonizes the dopamine
neurotransmitter system by blocking the reuptake of dopamine in the neuronal synapse.


Methamphetamine in its smokable form, often called “crystal meth” due to its resemblance to rock crystal
formations, is highly addictive. The smokable form reaches the brain very quickly to produce an intense
euphoria that dissipates almost as fast as it arrives, prompting users to continuing taking the drug. Users often
consume the drug every few hours across days-long binges called “runs,” in which the user forgoes food and
sleep. In the wake of the opiate epidemic, many drug cartels in Mexico are shifting from producing heroin
to producing highly potent but inexpensive forms of methamphetamine. The low cost coupled with lower risk
of overdose than with opiate drugs is making crystal meth a popular choice among drug users today (NIDA,
2019). Using crystal meth poses a number of serious long-term health issues, including dental problems (often
called “meth mouth”), skin abrasions caused by excessive scratching, memory loss, sleep problems, violent
behavior, paranoia, and hallucinations. Methamphetamine addiction produces an intense craving that is difficult
to treat.

Amphetamines have a mechanism of action quite similar to cocaine in that they block the reuptake of
dopamine in addition to stimulating its release (Figure 4.16). While amphetamines are often abused, they
are also commonly prescribed to children diagnosed with attention deficit hyperactivity disorder (ADHD).
It may seem counterintuitive that stimulant medications are prescribed to treat a disorder that involves
hyperactivity, but the therapeutic effect comes from increases in neurotransmitter activity within certain
areas of the brain associated with impulse control. These brain areas include the prefrontal cortex and basal


138 Chapter 4 | States of Consciousness

This OpenStax book is available for free at

Figure 4.16 As one of their mechanisms of action, cocaine and amphetamines block the reuptake of dopamine from
the synapse into the presynaptic cell.

In recent years, methamphetamine (meth) use has become increasingly widespread. Methamphetamine
is a type of amphetamine that can be made from ingredients that are readily available (e.g., medications
containing pseudoephedrine, a compound found in many over-the-counter cold and flu remedies).
Despite recent changes in laws designed to make obtaining pseudoephedrine more difficult,
methamphetamine continues to be an easily accessible and relatively inexpensive drug option (Shukla,
Crump, & Chrisco, 2012).

Stimulant users seek a euphoric high, feelings of intense elation and pleasure, especially in those users
who take the drug via intravenous injection or smoking. MDMA (3.4-methelynedioxy-methamphetamine,
commonly known as “ecstasy” or “Molly”) is a mild stimulant with perception-altering effects. It is typically
consumed in pill form. Users experience increased energy, feelings of pleasure, and emotional warmth.
Repeated use of these stimulants can have significant adverse consequences. Users can experience physical
symptoms that include nausea, elevated blood pressure, and increased heart rate. In addition, these
drugs can cause feelings of anxiety, hallucinations, and paranoia (Fiorentini et al., 2011). Normal brain
functioning is altered after repeated use of these drugs. For example, repeated use can lead to overall
depletion among the monoamine neurotransmitters (dopamine, norepinephrine, and serotonin).
Depletion of certain neurotransmitters can lead to mood dysphoria, cognitive problems, and other factors.
This can lead to people compulsively using stimulants such as cocaine and amphetamines, in part to try
to reestablish the person’s physical and psychological pre-use baseline. (Jayanthi & Ramamoorthy, 2005;
Rothman, Blough, & Baumann, 2007).

Caffeine is another stimulant drug. While it is probably the most commonly used drug in the world, the
potency of this particular drug pales in comparison to the other stimulant drugs described in this section.
Generally, people use caffeine to maintain increased levels of alertness and arousal. Caffeine is found in
many common medicines (such as weight loss drugs), beverages, foods, and even cosmetics (Herman &
Herman, 2013). While caffeine may have some indirect effects on dopamine neurotransmission, its primary
mechanism of action involves antagonizing adenosine activity (Porkka-Heiskanen, 2011). Adenosine is

Chapter 4 | States of Consciousness 139

a neurotransmitter that promotes sleep. Caffeine is an adenosine antagonist, so caffeine inhibits the
adenosine receptors, thus decreasing sleepiness and promoting wakefulness.

While caffeine is generally considered a relatively safe drug, high blood levels of caffeine can result
in insomnia, agitation, muscle twitching, nausea, irregular heartbeat, and even death (Reissig, Strain, &
Griffiths, 2009; Wolt, Ganetsky, & Babu, 2012). In 2012, Kromann and Nielson reported on a case study of
a 40-year-old woman who suffered significant ill effects from her use of caffeine. The woman used caffeine
in the past to boost her mood and to provide energy, but over the course of several years, she increased
her caffeine consumption to the point that she was consuming three liters of soda each day. Although she
had been taking a prescription antidepressant, her symptoms of depression continued to worsen and she
began to suffer physically, displaying significant warning signs of cardiovascular disease and diabetes.
Upon admission to an outpatient clinic for treatment of mood disorders, she met all of the diagnostic
criteria for substance dependence and was advised to dramatically limit her caffeine intake. Once she was
able to limit her use to less than 12 ounces of soda a day, both her mental and physical health gradually
improved. Despite the prevalence of caffeine use and the large number of people who confess to suffering
from caffeine addiction, this was the first published description of soda dependence appearing in scientific

Nicotine is highly addictive, and the use of tobacco products is associated with increased risks of heart
disease, stroke, and a variety of cancers. Nicotine exerts its effects through its interaction with acetylcholine
receptors. Acetylcholine functions as a neurotransmitter in motor neurons. In the central nervous system,
it plays a role in arousal and reward mechanisms. Nicotine is most commonly used in the form of
tobacco products like cigarettes or chewing tobacco; therefore, there is a tremendous interest in developing
effective smoking cessation techniques. To date, people have used a variety of nicotine replacement
therapies in addition to various psychotherapeutic options in an attempt to discontinue their use of
tobacco products. In general, smoking cessation programs may be effective in the short term, but it is
unclear whether these effects persist (Cropley, Theadom, Pravettoni, & Webb, 2008; Levitt, Shaw, Wong, &
Kaczorowski, 2007; Smedslund, Fisher, Boles, & Lichtenstein, 2004). Vaping as a means to deliver nicotine
is becoming increasingly popular, especially among teens and young adults. Vaping uses battery-powered
devices, sometimes called e-cigarettes, that deliver liquid nicotine and flavorings as a vapor. Originally
reported as a safe alternative to the known cancer-causing agents found in cigarettes, vaping is now known
to be very dangerous and has led to serious lung disease and death in users.


An opioid is one of a category of drugs that includes heroin, morphine, methadone, and codeine. Opioids
have analgesic properties; that is, they decrease pain. Humans have an endogenous opioid
neurotransmitter system—the body makes small quantities of opioid compounds that bind to opioid
receptors reducing pain and producing euphoria. Thus, opioid drugs, which mimic this endogenous
painkilling mechanism, have an extremely high potential for abuse. Natural opioids, called opiates, are
derivatives of opium, which is a naturally occurring compound found in the poppy plant. There are
now several synthetic versions of opiate drugs (correctly called opioids) that have very potent painkilling
effects, and they are often abused. For example, the National Institutes of Drug Abuse has sponsored
research that suggests the misuse and abuse of the prescription pain killers hydrocodone and oxycodone
are significant public health concerns (Maxwell, 2006). In 2013, the U.S. Food and Drug Administration
recommended tighter controls on their medical use.

Historically, heroin has been a major opioid drug of abuse (Figure 4.17). Heroin can be snorted, smoked,
or injected intravenously. Heroin produces intense feelings of euphoria and pleasure, which are amplified
when the heroin is injected intravenously. Following the initial “rush,” users experience 4–6 hours of “going
on the nod,” alternating between conscious and semiconscious states. Heroin users often shoot the drug
directly into their veins. Some people who have injected many times into their arms will show “track
marks,” while other users will inject into areas between their fingers or between their toes, so as not to
show obvious track marks and, like all abusers of intravenous drugs, have an increased risk for contraction

140 Chapter 4 | States of Consciousness

This OpenStax book is available for free at

of both tuberculosis and HIV.

Figure 4.17 (a) Common paraphernalia for heroin preparation and use are shown here in a needle exchange kit. (b)
Heroin is cooked on a spoon over a candle. (credit a: modification of work by Todd Huffman)

Aside from their utility as analgesic drugs, opioid-like compounds are often found in cough suppressants,
anti-nausea, and anti-diarrhea medications. Given that withdrawal from a drug often involves an
experience opposite to the effect of the drug, it should be no surprise that opioid withdrawal resembles
a severe case of the flu. While opioid withdrawal can be extremely unpleasant, it is not life-threatening
(Julien, 2005). Still, people experiencing opioid withdrawal may be given methadone to make withdrawal
from the drug less difficult. Methadone is a synthetic opioid that is less euphorigenic than heroin and
similar drugs. Methadone clinics help people who previously struggled with opioid addiction manage
withdrawal symptoms through the use of methadone. Other drugs, including the opioid buprenorphine,
have also been used to alleviate symptoms of opiate withdrawal.

Codeine is an opioid with relatively low potency. It is often prescribed for minor pain, and it is available
over-the-counter in some other countries. Like all opioids, codeine does have abuse potential. In fact, abuse
of prescription opioid medications is becoming a major concern worldwide (Aquina, Marques-Baptista,
Bridgeman, & Merlin, 2009; Casati, Sedefov, & Pfeiffer-Gerschel, 2012).

The Opioid Crisis

Few people in the United States remain untouched by the recent opioid epidemic. It seems like everyone
knows a friend, family member, or neighbor who has died of an overdose. Opioid addiction reached crisis levels
in the United States such that by 2019, an average of 130 people died each day of an opioid overdose (NIDA,

The crisis actually began in the 1990s, when pharmaceutical companies began mass-marketing pain-relieving
opioid drugs like OxyContin with the promise (now known to be false) that they were non-addictive. Increased
prescriptions led to greater rates of misuse, along with greater incidence of addiction, even among patients
who used these drugs as prescribed. Physiologically, the body can become addicted to opiate drugs in less
than a week, including when taken as prescribed. Withdrawal from opioids includes pain, which patients often
misinterpret as pain caused by the problem that led to the original prescription, and which motivates patients
to continue using the drugs.

The FDA’s 2013 recommendation for tighter controls on opiate prescriptions left many patients addicted to
prescription drugs like OxyContin unable to obtain legitimate prescriptions. This created a black market for
the drug, where prices soared to $80 or more for a single pill. To prevent withdrawal, many people turned to
cheaper heroin, which could be bought for $5 a dose or less. To keep heroin affordable, many dealers began
adding more potent synthetic opioids including fentanyl and carfentanyl to increase the effects of heroin. These
synthetic drugs are so potent that even small doses can cause overdose and death.


Chapter 4 | States of Consciousness 141

Large-scale public health campaigns by the National Institutes of Health and the National Institute of Drug
Abuse have led to recent declines in the opioid crisis. These initiatives include increasing access to treatment
and recovery services, increasing access to overdose-reversal drugs like Naloxone, and implementing better
public health monitoring systems (NIDA, 2019).


A hallucinogen is one of a class of drugs that results in profound alterations in sensory and perceptual
experiences (Figure 4.18). In some cases, users experience vivid visual hallucinations. It is also common
for these types of drugs to cause hallucinations of body sensations (e.g., feeling as if you are a giant) and a
skewed perception of the passage of time.

Figure 4.18 Psychedelic images like this are often associated with hallucinogenic compounds. (credit: modification
of work by “new 1lluminati”/Flickr)

As a group, hallucinogens are incredibly varied in terms of the neurotransmitter systems they affect.
Mescaline and LSD are serotonin agonists, and PCP (angel dust) and ketamine (an animal anesthetic) act
as antagonists of the NMDA glutamate receptor. In general, these drugs are not thought to possess the
same sort of abuse potential as other classes of drugs discussed in this section.

To learn more about some of the most commonly abused prescription and street drugs, check out the
Commonly Abused Drugs Chart ( and the Commonly Abused
Prescription Drugs Chart ( from the National Institute on Drug Abuse.

Medical Marijuana

The decade from 2010–2019 brought many changes in laws regarding marijuana. While the possession and
use of marijuana remains illegal in many states, it is now legal to possess limited quantities of marijuana
for recreational use in eleven states: Alaska, California, Colorado, Illinois, Maine, Massachusetts, Michigan,
Nevada, Oregon, Vermont, and Washington. Medical marijuana is legal in over half of the United States and
in the District of Columbia (Figure 4.19). Medical marijuana is marijuana that is prescribed by a doctor for
the treatment of a health condition. For example, people who undergo chemotherapy will often be prescribed



142 Chapter 4 | States of Consciousness

This OpenStax book is available for free at

marijuana to stimulate their appetites and prevent excessive weight loss resulting from the side effects of
chemotherapy treatment. Marijuana may also have some promise in the treatment of a variety of medical
conditions (Mather, Rauwendaal, Moxham-Hall, & Wodak, 2013; Robson, 2014; Schicho & Storr, 2014).

Figure 4.19 Medical marijuana shops are becoming more and more common in the United States. (credit:
Laurie Avocado)

While medical marijuana laws have been passed on a state-by-state basis, federal laws still classify this as
an illicit substance, making conducting research on the potentially beneficial medicinal uses of marijuana
problematic. There is quite a bit of controversy within the scientific community as to the extent to which
marijuana might have medicinal benefits due to a lack of large-scale, controlled research (Bostwick, 2012). As
a result, many scientists have urged the federal government to allow for relaxation of current marijuana laws
and classifications in order to facilitate a more widespread study of the drug’s effects (Aggarwal et al., 2009;
Bostwick, 2012; Kogan & Mechoulam, 2007).

Until recently, the United States Department of Justice routinely arrested people involved and seized marijuana
used in medicinal settings. In the latter part of 2013, however, the United States Department of Justice issued
statements indicating that they would not continue to challenge state medical marijuana laws. This shift in
policy may be in response to the scientific community’s recommendations and/or reflect changing public
opinion regarding marijuana.

4.6 Other States of Consciousness

Learning Objectives

By the end of this section, you will be able to:
• Define hypnosis and meditation
• Understand the similarities and differences of hypnosis and meditation

Our states of consciousness change as we move from wakefulness to sleep. We also alter our consciousness
through the use of various psychoactive drugs. This final section will consider hypnotic and meditative
states as additional examples of altered states of consciousness experienced by some individuals.


Hypnosis is a state of extreme self-focus and attention in which minimal attention is given to external
stimuli. In the therapeutic setting, a clinician may use relaxation and suggestion in an attempt to alter the
thoughts and perceptions of a patient. Hypnosis has also been used to draw out information believed to be
buried deeply in someone’s memory. For individuals who are especially open to the power of suggestion,
hypnosis can prove to be a very effective technique, and brain imaging studies have demonstrated
that hypnotic states are associated with global changes in brain functioning (Del Casale et al., 2012;
Guldenmund, Vanhaudenhuyse, Boly, Laureys, & Soddu, 2012).

Historically, hypnosis has been viewed with some suspicion because of its portrayal in popular media

Chapter 4 | States of Consciousness 143

and entertainment (Figure 4.20). Therefore, it is important to make a distinction between hypnosis as
an empirically based therapeutic approach versus as a form of entertainment. Contrary to popular belief,
individuals undergoing hypnosis usually have clear memories of the hypnotic experience and are in
control of their own behaviors. While hypnosis may be useful in enhancing memory or a skill, such
enhancements are very modest in nature (Raz, 2011).

Figure 4.20 Popular portrayals of hypnosis have led to some widely-held misconceptions.

How exactly does a hypnotist bring a participant to a state of hypnosis? While there are variations, there
are four parts that appear consistent in bringing people into the state of suggestibility associated with
hypnosis (National Research Council, 1994). These components include:

• The participant is guided to focus on one thing, such as the hypnotist’s words or a ticking watch.

• The participant is made comfortable and is directed to be relaxed and sleepy.

• The participant is told to be open to the process of hypnosis, trust the hypnotist and let go.

• The participant is encouraged to use his or her imagination.

These steps are conducive to being open to the heightened suggestibility of hypnosis.

People vary in terms of their ability to be hypnotized, but a review of available research suggests that
most people are at least moderately hypnotizable (Kihlstrom, 2013). Hypnosis in conjunction with other
techniques is used for a variety of therapeutic purposes and has shown to be at least somewhat effective
for pain management, treatment of depression and anxiety, smoking cessation, and weight loss (Alladin,
2012; Elkins, Johnson, & Fisher, 2012; Golden, 2012; Montgomery, Schnur, & Kravits, 2012).

How does hypnosis work? Two theories attempt to answer this question: One theory views hypnosis as
dissociation and the other theory views it as the performance of a social role. According to the dissociation
view, hypnosis is effectively a dissociated state of consciousness, much like our earlier example where you
may drive to work, but you are only minimally aware of the process of driving because your attention
is focused elsewhere. This theory is supported by Ernest Hilgard’s research into hypnosis and pain. In
Hilgard’s experiments, he induced participants into a state of hypnosis, and placed their arms into ice
water. Participants were told they would not feel pain, but they could press a button if they did; while they
reported not feeling pain, they did, in fact, press the button, suggesting a dissociation of consciousness
while in the hypnotic state (Hilgard & Hilgard, 1994).

Taking a different approach to explain hypnosis, the social-cognitive theory of hypnosis sees people

144 Chapter 4 | States of Consciousness

This OpenStax book is available for free at

in hypnotic states as performing the social role of a hypnotized person. As you will learn when you
study social roles, people’s behavior can be shaped by their expectations of how they should act in
a given situation. Some view a hypnotized person’s behavior not as an altered or dissociated state of
consciousness, but as their fulfillment of the social expectations for that role (Coe, 2009; Coe & Sarbin,


Meditation is the act of focusing on a single target (such as the breath or a repeated sound) to increase
awareness of the moment. While hypnosis is generally achieved through the interaction of a therapist and
the person being treated, an individual can perform meditation alone. Often, however, people wishing to
learn to meditate receive some training in techniques to achieve a meditative state.

Although there are a number of different techniques in use, the central feature of all meditation is clearing
the mind in order to achieve a state of relaxed awareness and focus (Chen et al., 2013; Lang et al.,
2012). Mindfulness meditation has recently become popular. In the variation of mindful meditation, the
meditator’s attention is focused on some internal process or an external object (Zeidan, Grant, Brown,
McHaffie, & Coghill, 2012).

Meditative techniques have their roots in religious practices (Figure 4.21), but their use has grown in
popularity among practitioners of alternative medicine. Research indicates that meditation may help
reduce blood pressure, and the American Heart Association suggests that meditation might be used in
conjunction with more traditional treatments as a way to manage hypertension, although there is not
sufficient data for a recommendation to be made (Brook et al., 2013). Like hypnosis, meditation also
shows promise in stress management, sleep quality (Caldwell, Harrison, Adams, Quin, & Greeson, 2010),
treatment of mood and anxiety disorders (Chen et al., 2013; Freeman et al., 2010; Vøllestad, Nielsen, &
Nielsen, 2012), and pain management (Reiner, Tibi, & Lipsitz, 2013).

Figure 4.21 (a) This is a statue of a meditating Buddha, representing one of the many religious traditions of which
meditation plays a part. (b) People practicing meditation may experience an alternate state of consciousness. (credit
a: modification of work by Jim Epler; credit b: modification of work by Caleb Roenigk)

Feeling stressed? Think meditation might help? Watch this instructional video about using Buddhist
meditation techniques to alleviate stress ( to learn more.


Chapter 4 | States of Consciousness 145

Watch this video about the results of a brain imaging study in individuals who underwent specific
mindfulness meditative techniques ( to learn more.


146 Chapter 4 | States of Consciousness

This OpenStax book is available for free at

alpha wave

biological rhythm


central sleep apnea

circadian rhythm


cognitive-behavioral therapy

collective unconscious


continuous positive airway pressure (CPAP)

delta wave


euphoric high

evolutionary psychology





jet lag


latent content

lucid dream

Key Terms

type of relatively low frequency, relatively high amplitude brain wave that becomes
synchronized; characteristic of the beginning of stage 1 sleep

internal cycle of biological activity

lack of muscle tone or muscle weakness, and in some cases complete paralysis of the voluntary

sleep disorder with periods of interrupted breathing due to a disruption in signals
sent from the brain that regulate breathing

biological rhythm that occurs over approximately 24 hours

opiate with relatively low potency often prescribed for minor pain

psychotherapy that focuses on cognitive processes and problem behaviors
that is sometimes used to treat sleep disorders such as insomnia

theoretical repository of information shared by all people across cultures, as
described by Carl Jung

awareness of internal and external stimuli

device used to treat sleep apnea; includes a mask that fits
over the sleeper’s nose and mouth, which is connected to a pump that pumps air into the person’s
airways, forcing them to remain open

type of low frequency, high amplitude brain wave characteristic of stage 3 and stage 4 sleep

drug that tends to suppress central nervous system activity

feelings of intense elation and pleasure from drug use

discipline that studies how universal patterns of behavior and cognitive
processes have evolved over time as a result of natural selection

one of a class of drugs that results in profound alterations in sensory and perceptual
experiences, often with vivid hallucinations

tendency to maintain a balance, or optimal level, within a biological system

state of extreme self-focus and attention in which minimal attention is given to external stimuli

consistent difficulty in falling or staying asleep for at least three nights a week over a month’s

collection of symptoms brought on by travel from one time zone to another that results from the
mismatch between our internal circadian cycles and our environment

very high amplitude pattern of brain activity associated with stage 2 sleep that may occur in
response to environmental stimuli

hidden meaning of a dream, per Sigmund Freud’s view of the function of dreams

people become aware that they are dreaming and can control the dream’s content

Chapter 4 | States of Consciousness 147

manifest content





methadone clinic



night terror

non-REM (NREM)

obstructive sleep apnea



physical dependence

pineal gland

psychological dependence

rapid eye movement (REM) sleep

REM sleep behavior disorder (RBD)

restless leg syndrome

rotating shift work


storyline of events that occur during a dream, per Sigmund Freud’s view of the
function of dreams

clearing the mind in order to achieve a state of relaxed awareness and focus

hormone secreted by the endocrine gland that serves as an important regulator of the sleep-
wake cycle

study that combines the results of several related studies

synthetic opioid that is less euphorogenic than heroin and similar drugs; used to manage
withdrawal symptoms in opiate users

uses methadone to treat withdrawal symptoms in opiate users

type of amphetamine that can be made from pseudoephedrine, an over-the-counter
drug; widely manufactured and abused

sleep disorder in which the sufferer cannot resist falling to sleep at inopportune times

sleep disorder in which the sleeper experiences a sense of panic and may scream or attempt
to escape from the immediate environment

period of sleep outside periods of rapid eye movement (REM) sleep

sleep disorder defined by episodes when breathing stops during sleep as a
result of blockage of the airway

one of a category of drugs that has strong analgesic properties; opiates are produced from
the resin of the opium poppy; includes heroin, morphine, methadone, and codeine

one of a group of sleep disorders characterized by unwanted, disruptive motor activity
and/or experiences during sleep

changes in normal bodily functions that cause a drug user to experience
withdrawal symptoms upon cessation of use

endocrine structure located inside the brain that releases melatonin

emotional, rather than a physical, need for a drug which may be used to
relieve psychological distress

period of sleep characterized by brain waves very similar to those
during wakefulness and by darting movements of the eyes under closed eyelids

sleep disorder in which the muscle paralysis associated with the
REM sleep phase does not occur; sleepers have high levels of physical activity during REM sleep,
especially during disturbing dreams

sleep disorder in which the sufferer has uncomfortable sensations in the legs
when trying to fall asleep that are relieved by moving the legs

work schedule that changes from early to late on a daily or weekly basis

state marked by relatively low levels of physical activity and reduced sensory awareness that is
distinct from periods of rest that occur during wakefulness

148 Chapter 4 | States of Consciousness

This OpenStax book is available for free at

sleep apnea

sleep debt

sleep rebound

sleep regulation

sleep spindle


stage 1 sleep

stage 2 sleep

stage 3 sleep

stage 4 sleep


sudden infant death syndrome (SIDS)

suprachiasmatic nucleus (SCN)

theta wave




sleep disorder defined by episodes during which breathing stops during sleep

result of insufficient sleep on a chronic basis

sleep-deprived individuals will experience shorter sleep latencies during subsequent
opportunities for sleep

brain’s control of switching between sleep and wakefulness as well as coordinating this
cycle with the outside world

rapid burst of high frequency brain waves during stage 2 sleep that may be important for
learning and memory

(also, somnambulism) sleep disorder in which the sleeper engages in relatively complex

first stage of sleep; transitional phase that occurs between wakefulness and sleep; the
period during which a person drifts off to sleep

second stage of sleep; the body goes into deep relaxation; characterized by the appearance
of sleep spindles

third stage of sleep; deep sleep characterized by low frequency, high amplitude delta waves

fourth stage of sleep; deep sleep characterized by low frequency, high amplitude delta

drug that tends to increase overall levels of neural activity; includes caffeine, nicotine,
amphetamines, and cocaine

infant (one year old or younger) with no apparent medical
condition suddenly dies during sleep

area of the hypothalamus in which the body’s biological clock is located

type of low frequency, high amplitude brain wave characteristic of stage 1 and stage 2 sleep

state of requiring increasing quantities of the drug to gain the desired effect

characterized by high levels of sensory awareness, thought, and behavior

variety of negative symptoms experienced when drug use is discontinued


4.1 What Is Consciousness?
States of consciousness vary over the course of the day and throughout our lives. Important factors
in these changes are the biological rhythms, and, more specifically, the circadian rhythms generated
by the suprachiasmatic nucleus (SCN). Typically, our biological clocks are aligned with our external
environment, and light tends to be an important cue in setting this clock. When people travel across
multiple time zones or work rotating shifts, they can experience disruptions of their circadian cycles that
can lead to insomnia, sleepiness, and decreased alertness. Bright light therapy has shown to be promising
in dealing with circadian disruptions. If people go extended periods of time without sleep, they will
accrue a sleep debt and potentially experience a number of adverse psychological and physiological

Chapter 4 | States of Consciousness 149

4.2 Sleep and Why We Sleep
We devote a very large portion of time to sleep, and our brains have complex systems that control various
aspects of sleep. Several hormones important for physical growth and maturation are secreted during
sleep. While the reason we sleep remains something of a mystery, there is some evidence to suggest that
sleep is very important to learning and memory.

4.3 Stages of Sleep
The different stages of sleep are characterized by the patterns of brain waves associated with each stage.
As a person transitions from being awake to falling asleep, alpha waves are replaced by theta waves.
Sleep spindles and K-complexes emerge in stage 2 sleep. Stage 3 and stage 4 are described as slow-wave
sleep that is marked by a predominance of delta waves. REM sleep involves rapid movements of the
eyes, paralysis of voluntary muscles, and dreaming. Both NREM and REM sleep appear to play important
roles in learning and memory. Dreams may represent life events that are important to the dreamer.
Alternatively, dreaming may represent a state of protoconsciousness, or a virtual reality, in the mind that
helps a person during consciousness.

4.4 Sleep Problems and Disorders
Many individuals suffer from some type of sleep disorder or disturbance at some point in their lives.
Insomnia is a common experience in which people have difficulty falling or staying asleep. Parasomnias
involve unwanted motor behavior or experiences throughout the sleep cycle and include RBD,
sleepwalking, restless leg syndrome, and night terrors. Sleep apnea occurs when individuals stop
breathing during their sleep, and in the case of sudden infant death syndrome, infants will stop breathing
during sleep and die. Narcolepsy involves an irresistible urge to fall asleep during waking hours and is
often associated with cataplexy and hallucination.

4.5 Substance Use and Abuse
Substance use disorder is defined in DSM-5 as a compulsive pattern of drug use despite negative
consequences. Both physical and psychological dependence are important parts of this disorder. Alcohol,
barbiturates, and benzodiazepines are central nervous system depressants that affect GABA
neurotransmission. Cocaine, amphetamine, cathinones, and MDMA are all central nervous stimulants
that agonize dopamine neurotransmission, while nicotine and caffeine affect acetylcholine and adenosine,
respectively. Opiate drugs serve as powerful analgesics through their effects on the endogenous opioid
neurotransmitter system, and hallucinogenic drugs cause pronounced changes in sensory and perceptual
experiences. The hallucinogens are variable with regards to the specific neurotransmitter systems they

4.6 Other States of Consciousness
Hypnosis is a focus on the self that involves suggested changes of behavior and experience. Meditation
involves relaxed, yet focused, awareness. Both hypnotic and meditative states may involve altered states of
consciousness that have potential application for the treatment of a variety of physical and psychological

Review Questions

1. The body’s biological clock is located in the

a. hippocampus
b. thalamus
c. hypothalamus
d. pituitary gland

2. ________ occurs when there is a chronic
deficiency in sleep.

a. jet lag
b. rotating shift work
c. circadian rhythm
d. sleep debt

150 Chapter 4 | States of Consciousness

This OpenStax book is available for free at

3. ________ cycles occur roughly once every 24

a. biological
b. circadian
c. rotating
d. conscious

4. ________ is one way in which people can help
reset their biological clocks.

a. Light-dark exposure
b. coffee consumption
c. alcohol consumption
d. napping

5. Growth hormone is secreted by the ________
while we sleep.

a. pineal gland
b. thyroid
c. pituitary gland
d. pancreas

6. The ________ plays a role in controlling slow-
wave sleep.

a. hypothalamus
b. thalamus
c. pons
d. both a and b

7. ________ is a hormone secreted by the pineal
gland that plays a role in regulating biological
rhythms and immune function.

a. growth hormone
b. melatonin
c. LH
d. FSH

8. ________ appears to be especially important for
enhanced performance on recently learned tasks.

a. melatonin
b. slow-wave sleep
c. sleep deprivation
d. growth hormone

9. ________ is(are) described as slow-wave sleep.
a. stage 1
b. stage 2
c. stage 3 and stage 4
d. REM sleep

10. Sleep spindles and K-complexes are most
often associated with ________ sleep.

a. stage 1
b. stage 2
c. stage 3 and stage 4
d. REM

11. Symptoms of ________ may be improved by
REM deprivation.

a. schizophrenia
b. Parkinson’s disease
c. depression
d. generalized anxiety disorder

12. The ________ content of a dream refers to the
true meaning of the dream.

a. latent
b. manifest
c. collective unconscious
d. important

13. ________ is loss of muscle tone or control that
is often associated with narcolepsy.

a. RBD
c. cataplexy
d. insomnia

14. An individual may suffer from ________ if
there is a disruption in the brain signals that are
sent to the muscles that regulate breathing.

a. central sleep apnea
b. obstructive sleep apnea
c. narcolepsy

15. The most common treatment for ________
involves the use of amphetamine-like medications.

a. sleep apnea
b. RBD
d. narcolepsy

16. ________ is another word for sleepwalking.
a. insomnia
b. somnambulism
c. cataplexy
d. narcolepsy

Chapter 4 | States of Consciousness 151

17. ________ occurs when a drug user requires
more and more of a given drug in order to
experience the same effects of the drug.

a. withdrawal
b. psychological dependence
c. tolerance
d. reuptake

18. Cocaine blocks the reuptake of ________.
b. glutamate
c. acetylcholine
d. dopamine

19. ________ refers to drug craving.
a. psychological dependence
b. antagonism
c. agonism
d. physical dependence

20. LSD affects ________ neurotransmission.
a. dopamine
b. serotonin
c. acetylcholine
d. norepinephrine

21. ________ is most effective in individuals that
are very open to the power of suggestion.

a. hypnosis
b. meditation
c. mindful awareness
d. cognitive therapy

22. ________ has its roots in religious practice.
a. hypnosis
b. meditation
c. cognitive therapy
d. behavioral therapy

23. Meditation may be helpful in ________.
a. pain management
b. stress control
c. treating the flu
d. both a and b

24. Research suggests that cognitive processes,
such as learning, may be affected by ________.

a. hypnosis
b. meditation
c. mindful awareness
d. progressive relaxation

Critical Thinking Questions

25. Healthcare professionals often work rotating shifts. Why is this problematic? What can be done to deal
with potential problems?

26. Generally, humans are considered diurnal which means we are awake during the day and asleep
during the night. Many rodents, on the other hand, are nocturnal. Why do you think different animals
have such different sleep-wake cycles?

27. If theories that assert sleep is necessary for restoration and recovery from daily energetic demands
are correct, what do you predict about the relationship that would exist between individuals’ total sleep
duration and their level of activity?

28. How could researchers determine if given areas of the brain are involved in the regulation of sleep?

29. Differentiate the evolutionary theories of sleep and make a case for the one with the most compelling

30. Freud believed that dreams provide important insight into the unconscious mind. He maintained that
a dream’s manifest content could provide clues into an individual’s unconscious. What potential criticisms
exist for this particular perspective?

31. Some people claim that sleepwalking and talking in your sleep involve individuals acting out their
dreams. Why is this particular explanation unlikely?

152 Chapter 4 | States of Consciousness

This OpenStax book is available for free at

32. One of the recommendations that therapists will make to people who suffer from insomnia is to spend
less waking time in bed. Why do you think spending waking time in bed might interfere with the ability
to fall asleep later?

33. How is narcolepsy with cataplexy similar to and different from REM sleep?

34. The negative health consequences of both alcohol and tobacco products are well-documented. A drug
like marijuana, on the other hand, is generally considered to be as safe, if not safer than these legal drugs.
Why do you think marijuana use continues to be illegal in many parts of the United States?

35. Why are programs designed to educate people about the dangers of using tobacco products just as
important as developing tobacco cessation programs?

36. What advantages exist for researching the potential health benefits of hypnosis?

37. What types of studies would be most convincing regarding the effectiveness of meditation in the
treatment for some type of physical or mental disorder?

Personal Application Questions

38. We experience shifts in our circadian clocks in the fall and spring of each year with time changes
associated with daylight saving time. Is springing ahead or falling back easier for you to adjust to, and
why do you think that is?

39. What do you do to adjust to the differences in your daily schedule throughout the week? Are you
running a sleep debt when daylight saving time begins or ends?

40. Have you (or someone you know) ever experienced significant periods of sleep deprivation because of
simple insomnia, high levels of stress, or as a side effect from a medication? What were the consequences
of missing out on sleep?

41. Researchers believe that one important function of sleep is to facilitate learning and memory. How
does knowing this help you in your college studies? What changes could you make to your study and
sleep habits to maximize your mastery of the material covered in class?

42. What factors might contribute to your own experiences with insomnia?

43. Many people experiment with some sort of psychoactive substance at some point in their lives. Why
do you think people are motivated to use substances that alter consciousness?

44. Under what circumstances would you be willing to consider hypnosis and/or meditation as a
treatment option? What kind of information would you need before you made a decision to use these

Chapter 4 | States of Consciousness 153

154 Chapter 4 | States of Consciousness

This OpenStax book is available for free at

Chapter 5

Sensation and Perception

Figure 5.1 If you were standing in the midst of this street scene, you would be absorbing and processing numerous
pieces of sensory input. (credit: modification of work by Cory Zanker)

Chapter Outline

5.1 Sensation versus Perception

5.2 Waves and Wavelengths

5.3 Vision

5.4 Hearing

5.5 The Other Senses

5.6 Gestalt Principles of Perception


Imagine standing on a city street corner. You might be struck by movement everywhere as cars and people
go about their business, by the sound of a street musician’s melody or a horn honking in the distance,
by the smell of exhaust fumes or of food being sold by a nearby vendor, and by the sensation of hard
pavement under your feet.

We rely on our sensory systems to provide important information about our surroundings. We use this
information to successfully navigate and interact with our environment so that we can find nourishment,
seek shelter, maintain social relationships, and avoid potentially dangerous situations.

This chapter will provide an overview of how sensory information is received and processed by the
nervous system and how that affects our conscious experience of the world. We begin by learning the
distinction between sensation and perception. Then we consider the physical properties of light and sound
stimuli, along with an overview of the basic structure and function of the major sensory systems. The
chapter will close with a discussion of a historically important theory of perception called Gestalt.

Chapter 5 | Sensation and Perception 155

5.1 Sensation versus Perception

Learning Objectives

By the end of this section, you will be able to:
• Distinguish between sensation and perception
• Describe the concepts of absolute threshold and difference threshold
• Discuss the roles attention, motivation, and sensory adaptation play in perception


What does it mean to sense something? Sensory receptors are specialized neurons that respond to specific
types of stimuli. When sensory information is detected by a sensory receptor, sensation has occurred. For
example, light that enters the eye causes chemical changes in cells that line the back of the eye. These
cells relay messages, in the form of action potentials (as you learned when studying biopsychology), to
the central nervous system. The conversion from sensory stimulus energy to action potential is known as

You have probably known since elementary school that we have five senses: vision, hearing (audition),
smell (olfaction), taste (gustation), and touch (somatosensation). It turns out that this notion of five
senses is oversimplified. We also have sensory systems that provide information about balance (the
vestibular sense), body position and movement (proprioception and kinesthesia), pain (nociception), and
temperature (thermoception).

The sensitivity of a given sensory system to the relevant stimuli can be expressed as an absolute threshold.
Absolute threshold refers to the minimum amount of stimulus energy that must be present for the
stimulus to be detected 50% of the time. Another way to think about this is by asking how dim can a light
be or how soft can a sound be and still be detected half of the time. The sensitivity of our sensory receptors
can be quite amazing. It has been estimated that on a clear night, the most sensitive sensory cells in the
back of the eye can detect a candle flame 30 miles away (Okawa & Sampath, 2007). Under quiet conditions,
the hair cells (the receptor cells of the inner ear) can detect the tick of a clock 20 feet away (Galanter, 1962).

It is also possible for us to get messages that are presented below the threshold for conscious
awareness—these are called subliminal messages. A stimulus reaches a physiological threshold when it
is strong enough to excite sensory receptors and send nerve impulses to the brain: This is an absolute
threshold. A message below that threshold is said to be subliminal: We receive it, but we are not
consciously aware of it. Over the years there has been a great deal of speculation about the use of
subliminal messages in advertising, rock music, and self-help audio programs. Research evidence shows
that in laboratory settings, people can process and respond to information outside of awareness. But
this does not mean that we obey these messages like zombies; in fact, hidden messages have little effect
on behavior outside the laboratory (Kunst-Wilson & Zajonc, 1980; Rensink, 2004; Nelson, 2008; Radel,
Sarrazin, Legrain, & Gobancé, 2009; Loersch, Durso, & Petty, 2013).

Absolute thresholds are generally measured under incredibly controlled conditions in situations that are
optimal for sensitivity. Sometimes, we are more interested in how much difference in stimuli is required
to detect a difference between them. This is known as the just noticeable difference (jnd) or difference
threshold. Unlike the absolute threshold, the difference threshold changes depending on the stimulus
intensity. As an example, imagine yourself in a very dark movie theater. If an audience member were to
receive a text message that caused the cell phone screen to light up, chances are that many people would
notice the change in illumination in the theater. However, if the same thing happened in a brightly lit
arena during a basketball game, very few people would notice. The cell phone brightness does not change,
but its ability to be detected as a change in illumination varies dramatically between the two contexts.
Ernst Weber proposed this theory of change in difference threshold in the 1830s, and it has become known
as Weber’s law: The difference threshold is a constant fraction of the original stimulus, as the example

156 Chapter 5 | Sensation and Perception

This OpenStax book is available for free at



While our sensory receptors are constantly collecting information from the environment, it is ultimately
how we interpret that information that affects how we interact with the world. Perception refers to the
way sensory information is organized, interpreted, and consciously experienced. Perception involves both
bottom-up and top-down processing. Bottom-up processing refers to sensory information from a stimulus
in the environment driving a process, and top-down processing refers to knowledge and expectancy
driving a process, as shown in Figure 5.2 (Egeth & Yantis, 1997; Fine & Minnery, 2009; Yantis & Egeth,

Figure 5.2 Top-down and bottom-up are ways we process our perceptions.

Imagine that you and some friends are sitting in a crowded restaurant eating lunch and talking. It is
very noisy, and you are concentrating on your friend’s face to hear what she is saying, then the sound
of breaking glass and clang of metal pans hitting the floor rings out. The server dropped a large tray of
food. Although you were attending to your meal and conversation, that crashing sound would likely get
through your attentional filters and capture your attention. You would have no choice but to notice it. That
attentional capture would be caused by the sound from the environment: it would be bottom-up.

Alternatively, top-down processes are generally goal directed, slow, deliberate, effortful, and under your
control (Fine & Minnery, 2009; Miller & Cohen, 2001; Miller & D’Esposito, 2005). For instance, if you
misplaced your keys, how would you look for them? If you had a yellow key fob, you would probably look
for yellowness of a certain size in specific locations, such as on the counter, coffee table, and other similar
places. You would not look for yellowness on your ceiling fan, because you know keys are not normally
lying on top of a ceiling fan. That act of searching for a certain size of yellowness in some locations and not
others would be top-down—under your control and based on your experience.

One way to think of this concept is that sensation is a physical process, whereas perception is
psychological. For example, upon walking into a kitchen and smelling the scent of baking cinnamon rolls,
the sensation is the scent receptors detecting the odor of cinnamon, but the perception may be “Mmm, this
smells like the bread Grandma used to bake when the family gathered for holidays.”

Although our perceptions are built from sensations, not all sensations result in perception. In fact, we often
don’t perceive stimuli that remain relatively constant over prolonged periods of time. This is known as
sensory adaptation. Imagine going to a city that you have never visited. You check in to the hotel, but
when you get to your room, there is a road construction sign with a bright flashing light outside your
window. Unfortunately, there are no other rooms available, so you are stuck with a flashing light. You
decide to watch television to unwind. The flashing light was extremely annoying when you first entered
your room. It was as if someone was continually turning a bright yellow spotlight on and off in your
room, but after watching television for a short while, you no longer notice the light flashing. The light
is still flashing and filling your room with yellow light every few seconds, and the photoreceptors in
your eyes still sense the light, but you no longer perceive the rapid changes in lighting conditions. That

Chapter 5 | Sensation and Perception 157

you no longer perceive the flashing light demonstrates sensory adaptation and shows that while closely
associated, sensation and perception are different.

There is another factor that affects sensation and perception: attention. Attention plays a significant role
in determining what is sensed versus what is perceived. Imagine you are at a party full of music, chatter,
and laughter. You get involved in an interesting conversation with a friend, and you tune out all the
background noise. If someone interrupted you to ask what song had just finished playing, you would
probably be unable to answer that question.

See for yourself how inattentional blindness works by checking out this selective attention test
( from Simons and Chabris (1999).

One of the most interesting demonstrations of how important attention is in determining our perception of
the environment occurred in a famous study conducted by Daniel Simons and Christopher Chabris (1999).
In this study, participants watched a video of people dressed in black and white passing basketballs.
Participants were asked to count the number of times the team dressed in white passed the ball. During
the video, a person dressed in a black gorilla costume walks among the two teams. You would think that
someone would notice the gorilla, right? Nearly half of the people who watched the video didn’t notice
the gorilla at all, despite the fact that he was clearly visible for nine seconds. Because participants were
so focused on the number of times the team dressed in white was passing the ball, they completely tuned
out other visual information. Inattentional blindness is the failure to notice something that is completely
visible because the person was actively attending to something else and did not pay attention to other
things (Mack & Rock, 1998; Simons & Chabris, 1999).

In a similar experiment, researchers tested inattentional blindness by asking participants to observe
images moving across a computer screen. They were instructed to focus on either white or black objects,
disregarding the other color. When a red cross passed across the screen, about one third of subjects did not
notice it (Figure 5.3) (Most, Simons, Scholl, & Chabris, 2000).

Figure 5.3 Nearly one third of participants in a study did not notice that a red cross passed on the screen because
their attention was focused on the black or white figures. (credit: Cory Zanker)

Motivation can also affect perception. Have you ever been expecting a really important phone call and,
while taking a shower, you think you hear the phone ringing, only to discover that it is not? If so, then
you have experienced how motivation to detect a meaningful stimulus can shift our ability to discriminate
between a true sensory stimulus and background noise. The ability to identify a stimulus when it is
embedded in a distracting background is called signal detection theory. This might also explain why a


158 Chapter 5 | Sensation and Perception

This OpenStax book is available for free at

mother is awakened by a quiet murmur from her baby but not by other sounds that occur while she is
asleep. Signal detection theory has practical applications, such as increasing air traffic controller accuracy.
Controllers need to be able to detect planes among many signals (blips) that appear on the radar screen
and follow those planes as they move through the sky. In fact, the original work of the researcher who
developed signal detection theory was focused on improving the sensitivity of air traffic controllers to
plane blips (Swets, 1964).

Our perceptions can also be affected by our beliefs, values, prejudices, expectations, and life experiences.
As you will see later in this chapter, individuals who are deprived of the experience of binocular vision
during critical periods of development have trouble perceiving depth (Fawcett, Wang, & Birch, 2005). The
shared experiences of people within a given cultural context can have pronounced effects on perception.
For example, Marshall Segall, Donald Campbell, and Melville Herskovits (1963) published the results of a
multinational study in which they demonstrated that individuals from Western cultures were more prone
to experience certain types of visual illusions than individuals from non-Western cultures, and vice versa.
One such illusion that Westerners were more likely to experience was the Müller-Lyer illusion (Figure
5.4): The lines appear to be different lengths, but they are actually the same length.

Figure 5.4 In the Müller-Lyer illusion, lines appear to be different lengths although they are identical. (a) Arrows at
the ends of lines may make the line on the right appear longer, although the lines are the same length. (b) When
applied to a three-dimensional image, the line on the right again may appear longer although both black lines are the
same length.

These perceptual differences were consistent with differences in the types of environmental features
experienced on a regular basis by people in a given cultural context. People in Western cultures, for
example, have a perceptual context of buildings with straight lines, what Segall’s study called a
carpentered world (Segall et al., 1966). In contrast, people from certain non-Western cultures with an
uncarpentered view, such as the Zulu of South Africa, whose villages are made up of round huts arranged
in circles, are less susceptible to this illusion (Segall et al., 1999). It is not just vision that is affected
by cultural factors. Indeed, research has demonstrated that the ability to identify an odor, and rate its
pleasantness and its intensity, varies cross-culturally (Ayabe-Kanamura, Saito, Distel, Martínez-Gómez, &
Hudson, 1998).

Children described as thrill seekers are more likely to show taste preferences for intense sour flavors (Liem,
Westerbeek, Wolterink, Kok, & de Graaf, 2004), which suggests that basic aspects of personality might
affect perception. Furthermore, individuals who hold positive attitudes toward reduced-fat foods are more
likely to rate foods labeled as reduced fat as tasting better than people who have less positive attitudes
about these products (Aaron, Mela, & Evans, 1994).

Chapter 5 | Sensation and Perception 159

5.2 Waves and Wavelengths

Learning Objectives

By the end of this section, you will be able to:
• Describe important physical features of wave forms
• Show how physical properties of light waves are associated with perceptual experience
• Show how physical properties of sound waves are associated with perceptual experience

Visual and auditory stimuli both occur in the form of waves. Although the two stimuli are very different in
terms of composition, wave forms share similar characteristics that are especially important to our visual
and auditory perceptions. In this section, we describe the physical properties of the waves as well as the
perceptual experiences associated with them.


Two physical characteristics of a wave are amplitude and wavelength (Figure 5.5). The amplitude of a
wave is the distance from the center line to the top point of the crest or the bottom point of the trough.
Wavelength refers to the length of a wave from one peak to the next.

Figure 5.5 The amplitude or height of a wave is measured from the peak to the trough. The wavelength is measured
from peak to peak.

Wavelength is directly related to the frequency of a given wave form. Frequency refers to the number of
waves that pass a given point in a given time period and is often expressed in terms of hertz (Hz), or cycles
per second. Longer wavelengths will have lower frequencies, and shorter wavelengths will have higher
frequencies (Figure 5.6).

Figure 5.6 This figure illustrates waves of differing wavelengths/frequencies. At the top of the figure, the red wave
has a long wavelength/short frequency. Moving from top to bottom, the wavelengths decrease and frequencies


The visible spectrum is the portion of the larger electromagnetic spectrum that we can see. As Figure 5.7
shows, the electromagnetic spectrum encompasses all of the electromagnetic radiation that occurs in our

160 Chapter 5 | Sensation and Perception

This OpenStax book is available for free at

environment and includes gamma rays, x-rays, ultraviolet light, visible light, infrared light, microwaves,
and radio waves. The visible spectrum in humans is associated with wavelengths that range from 380 to
740 nm—a very small distance, since a nanometer (nm) is one billionth of a meter. Other species can detect
other portions of the electromagnetic spectrum. For instance, honeybees can see light in the ultraviolet
range (Wakakuwa, Stavenga, & Arikawa, 2007), and some snakes can detect infrared radiation in addition
to more traditional visual light cues (Chen, Deng, Brauth, Ding, & Tang, 2012; Hartline, Kass, & Loop,

Figure 5.7 Light that is visible to humans makes up only a small portion of the electromagnetic spectrum.

In humans, light wavelength is associated with perception of color (Figure 5.8). Within the visible
spectrum, our experience of red is associated with longer wavelengths, greens are intermediate, and blues
and violets are shorter in wavelength. (An easy way to remember this is the mnemonic ROYGBIV: red,
orange, yellow, green, blue, indigo, violet.) The amplitude of light waves is associated with our experience
of brightness or intensity of color, with larger amplitudes appearing brighter.

Figure 5.8 Different wavelengths of light are associated with our perception of different colors. (credit: modification
of work by Johannes Ahlmann)


Like light waves, the physical properties of sound waves are associated with various aspects of our
perception of sound. The frequency of a sound wave is associated with our perception of that sound’s
pitch. High-frequency sound waves are perceived as high-pitched sounds, while low-frequency sound
waves are perceived as low-pitched sounds. The audible range of sound frequencies is between 20 and
20000 Hz, with greatest sensitivity to those frequencies that fall in the middle of this range.

As was the case with the visible spectrum, other species show differences in their audible ranges. For
instance, chickens have a very limited audible range, from 125 to 2000 Hz. Mice have an audible range
from 1000 to 91000 Hz, and the beluga whale’s audible range is from 1000 to 123000 Hz. Our pet dogs and

Chapter 5 | Sensation and Perception 161

cats have audible ranges of about 70–45000 Hz and 45–64000 Hz, respectively (Strain, 2003).

The loudness of a given sound is closely associated with the amplitude of the sound wave. Higher
amplitudes are associated with louder sounds. Loudness is measured in terms of decibels (dB), a
logarithmic unit of sound intensity. A typical conversation would correlate with 60 dB; a rock concert
might check in at 120 dB (Figure 5.9). A whisper 5 feet away or rustling leaves are at the low end of
our hearing range; sounds like a window air conditioner, a normal conversation, and even heavy traffic
or a vacuum cleaner are within a tolerable range. However, there is the potential for hearing damage
from about 80 dB to 130 dB: These are sounds of a food processor, power lawnmower, heavy truck
(25 feet away), subway train (20 feet away), live rock music, and a jackhammer. About one-third of all
hearing loss is due to noise exposure, and the louder the sound, the shorter the exposure needed to
cause hearing damage (Le, Straatman, Lea, & Westerberg, 2017). Listening to music through earbuds at
maximum volume (around 100–105 decibels) can cause noise-induced hearing loss after 15 minutes of
exposure. Although listening to music at maximum volume may not seem to cause damage, it increases
the risk of age-related hearing loss (Kujawa & Liberman, 2006). The threshold for pain is about 130 dB, a
jet plane taking off or a revolver firing at close range (Dunkle, 1982).

Figure 5.9 This figure illustrates the loudness of common sounds. (credit “planes”: modification of work by Max
Pfandl; credit “crowd”: modification of work by Christian Holmér; credit: “earbuds”: modification of work by “Skinny
Guy Lover_Flickr”/Flickr; credit “traffic”: modification of work by “quinntheislander_Pixabay”/Pixabay; credit “talking”:
modification of work by Joi Ito; credit “leaves”: modification of work by Aurelijus Valeiša)

162 Chapter 5 | Sensation and Perception

This OpenStax book is available for free at

Although wave amplitude is generally associated with loudness, there is some interaction between
frequency and amplitude in our perception of loudness within the audible range. For example, a 10 Hz
sound wave is inaudible no matter the amplitude of the wave. A 1000 Hz sound wave, on the other hand,
would vary dramatically in terms of perceived loudness as the amplitude of the wave increased.

Watch this brief video about our perception of frequency and amplitude (
frequency) to learn more.

Of course, different musical instruments can play the same musical note at the same level of loudness, yet
they still sound quite different. This is known as the timbre of a sound. Timbre refers to a sound’s purity,
and it is affected by the complex interplay of frequency, amplitude, and timing of sound waves.

5.3 Vision

Learning Objectives

By the end of this section, you will be able to:
• Describe the basic anatomy of the visual system
• Discuss how rods and cones contribute to different aspects of vision
• Describe how monocular and binocular cues are used in the perception of depth

The visual system constructs a mental representation of the world around us (Figure 5.10). This
contributes to our ability to successfully navigate through physical space and interact with important
individuals and objects in our environments. This section will provide an overview of the basic anatomy
and function of the visual system. In addition, we will explore our ability to perceive color and depth.

Figure 5.10 Our eyes take in sensory information that helps us understand the world around us. (credit “top left”:
modification of work by “rajkumar1220″/Flickr”; credit “top right”: modification of work by Thomas Leuthard; credit
“middle left”: modification of work by Demietrich Baker; credit “middle right”: modification of work by
“kaybee07″/Flickr; credit “bottom left”: modification of work by “Isengardt”/Flickr; credit “bottom right”: modification of
work by Willem Heerbaart)


Chapter 5 | Sensation and Perception 163


The eye is the major sensory organ involved in vision (Figure 5.11). Light waves are transmitted across the
cornea and enter the eye through the pupil. The cornea is the transparent covering over the eye. It serves
as a barrier between the inner eye and the outside world, and it is involved in focusing light waves that
enter the eye. The pupil is the small opening in the eye through which light passes, and the size of the
pupil can change as a function of light levels as well as emotional arousal. When light levels are low, the
pupil will become dilated, or expanded, to allow more light to enter the eye. When light levels are high,
the pupil will constrict, or become smaller, to reduce the amount of light that enters the eye. The pupil’s
size is controlled by muscles that are connected to the iris, which is the colored portion of the eye.

Figure 5.11 The anatomy of the eye is illustrated in this diagram.

After passing through the pupil, light crosses the lens, a curved, transparent structure that serves to
provide additional focus. The lens is attached to muscles that can change its shape to aid in focusing
light that is reflected from near or far objects. In a normal-sighted individual, the lens will focus images
perfectly on a small indentation in the back of the eye known as the fovea, which is part of the retina, the
light-sensitive lining of the eye. The fovea contains densely packed specialized photoreceptor cells (Figure
5.12). These photoreceptor cells, known as cones, are light-detecting cells. The cones are specialized types
of photoreceptors that work best in bright light conditions. Cones are very sensitive to acute detail and
provide tremendous spatial resolution. They also are directly involved in our ability to perceive color.

While cones are concentrated in the fovea, where images tend to be focused, rods, another type of
photoreceptor, are located throughout the remainder of the retina. Rods are specialized photoreceptors
that work well in low light conditions, and while they lack the spatial resolution and color function of the
cones, they are involved in our vision in dimly lit environments as well as in our perception of movement
on the periphery of our visual field.

164 Chapter 5 | Sensation and Perception

This OpenStax book is available for free at

Figure 5.12 The two types of photoreceptors are shown in this image. Cones are colored green and rods are blue.

We have all experienced the different sensitivities of rods and cones when making the transition from
a brightly lit environment to a dimly lit environment. Imagine going to see a blockbuster movie on a
clear summer day. As you walk from the brightly lit lobby into the dark theater, you notice that you
immediately have difficulty seeing much of anything. After a few minutes, you begin to adjust to the
darkness and can see the interior of the theater. In the bright environment, your vision was dominated
primarily by cone activity. As you move to the dark environment, rod activity dominates, but there is a
delay in transitioning between the phases. If your rods do not transform light into nerve impulses as easily
and efficiently as they should, you will have difficulty seeing in dim light, a condition known as night

Rods and cones are connected (via several interneurons) to retinal ganglion cells. Axons from the retinal
ganglion cells converge and exit through the back of the eye to form the optic nerve. The optic nerve carries
visual information from the retina to the brain. There is a point in the visual field called the blind spot:
Even when light from a small object is focused on the blind spot, we do not see it. We are not consciously
aware of our blind spots for two reasons: First, each eye gets a slightly different view of the visual field;
therefore, the blind spots do not overlap. Second, our visual system fills in the blind spot so that although
we cannot respond to visual information that occurs in that portion of the visual field, we are also not
aware that information is missing.

The optic nerve from each eye merges just below the brain at a point called the optic chiasm. As Figure
5.13 shows, the optic chiasm is an X-shaped structure that sits just below the cerebral cortex at the front of
the brain. At the point of the optic chiasm, information from the right visual field (which comes from both
eyes) is sent to the left side of the brain, and information from the left visual field is sent to the right side
of the brain.

Chapter 5 | Sensation and Perception 165

Figure 5.13 This illustration shows the optic chiasm at the front of the brain and the pathways to the occipital lobe at
the back of the brain, where visual sensations are processed into meaningful perceptions.

Once inside the brain, visual information is sent via a number of structures to the occipital lobe at the
back of the brain for processing. Visual information might be processed in parallel pathways which can
generally be described as the “what pathway” and the “where/how” pathway. The “what pathway”
is involved in object recognition and identification, while the “where/how pathway” is involved with
location in space and how one might interact with a particular visual stimulus (Milner & Goodale, 2008;
Ungerleider & Haxby, 1994). For example, when you see a ball rolling down the street, the “what pathway”
identifies what the object is, and the “where/how pathway” identifies its location or movement in space.

The Ethics of Research Using Animals

David Hubel and Torsten Wiesel were awarded the Nobel Prize in Medicine in 1981 for their research on
the visual system. They collaborated for more than twenty years and made significant discoveries about the
neurology of visual perception (Hubel & Wiesel, 1959, 1962, 1963, 1970; Wiesel & Hubel, 1963). They studied
animals, mostly cats and monkeys. Although they used several techniques, they did considerable single unit
recordings, during which tiny electrodes were inserted in the animal’s brain to determine when a single cell
was activated. Among their many discoveries, they found that specific brain cells respond to lines with specific
orientations (called ocular dominance), and they mapped the way those cells are arranged in areas of the
visual cortex known as columns and hypercolumns.

In some of their research, they sutured one eye of newborn kittens closed and followed the development of the
kittens’ vision. They discovered there was a critical period of development for vision. If kittens were deprived
of input from one eye, other areas of their visual cortex filled in the area that was normally used by the eye
that was sewn closed. In other words, neural connections that exist at birth can be lost if they are deprived of
sensory input.

What do you think about sewing a kitten’s eye closed for research? To many animal advocates, this would
seem brutal, abusive, and unethical. What if you could do research that would help ensure babies and children
born with certain conditions could develop normal vision instead of becoming blind? Would you want that
research done? Would you conduct that research, even if it meant causing some harm to cats? Would you
think the same way if you were the parent of such a child? What if you worked at the animal shelter?


166 Chapter 5 | Sensation and Perception

This OpenStax book is available for free at

Like virtually every other industrialized nation, the United States permits medical experimentation on animals,
with few limitations (assuming sufficient scientific justification). The goal of any laws that exist is not to ban
such tests but rather to limit unnecessary animal suffering by establishing standards for the humane treatment
and housing of animals in laboratories.

As explained by Stephen Latham, the director of the Interdisciplinary Center for Bioethics at Yale (2012),
possible legal and regulatory approaches to animal testing vary on a continuum from strong government
regulation and monitoring of all experimentation at one end, to a self-regulated approach that depends on the
ethics of the researchers at the other end. The United Kingdom has the most significant regulatory scheme,
whereas Japan uses the self-regulation approach. The U.S. approach is somewhere in the middle, the result
of a gradual blending of the two approaches.

There is no question that medical research is a valuable and important practice. The question is whether the
use of animals is a necessary or even best practice for producing the most reliable results. Alternatives include
the use of patient-drug databases, virtual drug trials, computer models and simulations, and noninvasive
imaging techniques such as magnetic resonance imaging and computed tomography scans (“Animals in
Science/Alternatives,” n.d.). Other techniques, such as microdosing, use humans not as test animals but as a
means to improve the accuracy and reliability of test results. In vitro methods based on human cell and tissue
cultures, stem cells, and genetic testing methods are also increasingly available.

Today, at the local level, any facility that uses animals and receives federal funding must have an Institutional
Animal Care and Use Committee (IACUC) that ensures that the NIH guidelines are being followed. The IACUC
must include researchers, administrators, a veterinarian, and at least one person with no ties to the institution:
that is, a concerned citizen. This committee also performs inspections of laboratories and protocols.


We do not see the world in black and white; neither do we see it as two-dimensional (2-D) or flat (just
height and width, no depth). Let’s look at how color vision works and how we perceive three dimensions
(height, width, and depth).

Color Vision

Normal-sighted individuals have three different types of cones that mediate color vision. Each of these
cone types is maximally sensitive to a slightly different wavelength of light. According to the trichromatic
theory of color vision, shown in Figure 5.14, all colors in the spectrum can be produced by combining
red, green, and blue. The three types of cones are each receptive to one of the colors.

Chapter 5 | Sensation and Perception 167

Figure 5.14 This figure illustrates the different sensitivities for the three cone types found in a normal-sighted
individual. (credit: modification of work by Vanessa Ezekowitz)


Colorblindness: A Personal Story

Several years ago, I dressed to go to a public function and walked into the kitchen where my 7-year-old daughter
sat. She looked up at me, and in her most stern voice, said, “You can’t wear that.” I asked, “Why not?” and she
informed me the colors of my clothes did not match. She had complained frequently that I was bad at matching
my shirts, pants, and ties, but this time, she sounded especially alarmed. As a single father with no one else to
ask at home, I drove us to the nearest convenience store and asked the store clerk if my clothes matched. She
said my pants were a bright green color, my shirt was a reddish orange, and my tie was brown. She looked at
my quizzically and said, “No way do your clothes match.” Over the next few days, I started asking my coworkers
and friends if my clothes matched. After several days of being told that my coworkers just thought I had “a really
unique style,” I made an appointment with an eye doctor and was tested (Figure 5.15). It was then that I found
out that I was colorblind. I cannot differentiate between most greens, browns, and reds. Fortunately, other than
unknowingly being badly dressed, my colorblindness rarely harms my day-to-day life.

Figure 5.15 The Ishihara test evaluates color perception by assessing whether individuals can discern
numbers that appear in a circle of dots of varying colors and sizes.

Some forms of color deficiency are rare. Seeing in grayscale (only shades of black and white) is extremely
rare, and people who do so only have rods, which means they have very low visual acuity and cannot see very
well. The most common X-linked inherited abnormality is red-green color blindness (Birch, 2012). Approximately
8% of males with European Caucasian decent, 5% of Asian males, 4% of African males, and less than 2% of

168 Chapter 5 | Sensation and Perception

This OpenStax book is available for free at

indigenous American males, Australian males, and Polynesian males have red-green color deficiency (Birch,
2012). Comparatively, only about 0.4% in females from European Caucasian descent have red-green color
deficiency (Birch, 2012).

The trichromatic theory of color vision is not the only theory—another major theory of color vision is
known as the opponent-process theory. According to this theory, color is coded in opponent pairs: black-
white, yellow-blue, and green-red. The basic idea is that some cells of the visual system are excited
by one of the opponent colors and inhibited by the other. So, a cell that was excited by wavelengths
associated with green would be inhibited by wavelengths associated with red, and vice versa. One of
the implications of opponent processing is that we do not experience greenish-reds or yellowish-blues
as colors. Another implication is that this leads to the experience of negative afterimages. An afterimage
describes the continuation of a visual sensation after removal of the stimulus. For example, when you stare
briefly at the sun and then look away from it, you may still perceive a spot of light although the stimulus
(the sun) has been removed. When color is involved in the stimulus, the color pairings identified in the
opponent-process theory lead to a negative afterimage. You can test this concept using the flag in Figure

Figure 5.16 Stare at the white dot for 30–60 seconds and then move your eyes to a blank piece of white paper.
What do you see? This is known as a negative afterimage, and it provides empirical support for the opponent-process
theory of color vision.

But these two theories—the trichromatic theory of color vision and the opponent-process theory—are not
mutually exclusive. Research has shown that they just apply to different levels of the nervous system. For
visual processing on the retina, trichromatic theory applies: the cones are responsive to three different
wavelengths that represent red, blue, and green. But once the signal moves past the retina on its way to
the brain, the cells respond in a way consistent with opponent-process theory (Land, 1959; Kaiser, 1997).

Watch this video about color perception ( to learn more.

Depth Perception

Our ability to perceive spatial relationships in three-dimensional (3-D) space is known as depth
perception. With depth perception, we can describe things as being in front, behind, above, below, or to


Chapter 5 | Sensation and Perception 169

the side of other things.

Our world is three-dimensional, so it makes sense that our mental representation of the world has three-
dimensional properties. We use a variety of cues in a visual scene to establish our sense of depth. Some of
these are binocular cues, which means that they rely on the use of both eyes. One example of a binocular
depth cue is binocular disparity, the slightly different view of the world that each of our eyes receives. To
experience this slightly different view, do this simple exercise: extend your arm fully and extend one of
your fingers and focus on that finger. Now, close your left eye without moving your head, then open your
left eye and close your right eye without moving your head. You will notice that your finger seems to shift
as you alternate between the two eyes because of the slightly different view each eye has of your finger.

A 3-D movie works on the same principle: the special glasses you wear allow the two slightly different
images projected onto the screen to be seen separately by your left and your right eye. As your brain
processes these images, you have the illusion that the leaping animal or running person is coming right
toward you.

Although we rely on binocular cues to experience depth in our 3-D world, we can also perceive depth in
2-D arrays. Think about all the paintings and photographs you have seen. Generally, you pick up on depth
in these images even though the visual stimulus is 2-D. When we do this, we are relying on a number of
monocular cues, or cues that require only one eye. If you think you can’t see depth with one eye, note
that you don’t bump into things when using only one eye while walking—and, in fact, we have more
monocular cues than binocular cues.

An example of a monocular cue would be what is known as linear perspective. Linear perspective refers to
the fact that we perceive depth when we see two parallel lines that seem to converge in an image (Figure
5.17). Some other monocular depth cues are interposition, the partial overlap of objects, and the relative
size and closeness of images to the horizon.

Figure 5.17 We perceive depth in a two-dimensional figure like this one through the use of monocular cues like
linear perspective, like the parallel lines converging as the road narrows in the distance. (credit: Marc Dalmulder)


Bruce Bridgeman was born with an extreme case of lazy eye that resulted in him being stereoblind, or unable
to respond to binocular cues of depth. He relied heavily on monocular depth cues, but he never had a true


170 Chapter 5 | Sensation and Perception

This OpenStax book is available for free at

appreciation of the 3-D nature of the world around him. This all changed one night in 2012 while Bruce was
seeing a movie with his wife.

The movie the couple was going to see was shot in 3-D, and even though he thought it was a waste of money,
Bruce paid for the 3-D glasses when he purchased his ticket. As soon as the film began, Bruce put on the
glasses and experienced something completely new. For the first time in his life he appreciated the true depth
of the world around him. Remarkably, his ability to perceive depth persisted outside of the movie theater.

There are cells in the nervous system that respond to binocular depth cues. Normally, these cells require
activation during early development in order to persist, so experts familiar with Bruce’s case (and others like
his) assume that at some point in his development, Bruce must have experienced at least a fleeting moment of
binocular vision. It was enough to ensure the survival of the cells in the visual system tuned to binocular cues.
The mystery now is why it took Bruce nearly 70 years to have these cells activated (Peck, 2012).

5.4 Hearing

Learning Objectives

By the end of this section, you will be able to:
• Describe the basic anatomy and function of the auditory system
• Explain how we encode and perceive pitch
• Discuss how we localize sound

Our auditory system converts pressure waves into meaningful sounds. This translates into our ability
to hear the sounds of nature, to appreciate the beauty of music, and to communicate with one another
through spoken language. This section will provide an overview of the basic anatomy and function of the
auditory system. It will include a discussion of how the sensory stimulus is translated into neural impulses,
where in the brain that information is processed, how we perceive pitch, and how we know where sound
is coming from.


The ear can be separated into multiple sections. The outer ear includes the pinna, which is the visible
part of the ear that protrudes from our heads, the auditory canal, and the tympanic membrane, or
eardrum. The middle ear contains three tiny bones known as the ossicles, which are named the malleus
(or hammer), incus (or anvil), and the stapes (or stirrup). The inner ear contains the semi-circular canals,
which are involved in balance and movement (the vestibular sense), and the cochlea. The cochlea is a fluid-
filled, snail-shaped structure that contains the sensory receptor cells (hair cells) of the auditory system
(Figure 5.18).

Chapter 5 | Sensation and Perception 171

Figure 5.18 The ear is divided into outer (pinna and tympanic membrane), middle (the three ossicles: malleus,
incus, and stapes), and inner (cochlea and basilar membrane) divisions.

Sound waves travel along the auditory canal and strike the tympanic membrane, causing it to vibrate. This
vibration results in movement of the three ossicles. As the ossicles move, the stapes presses into a thin
membrane of the cochlea known as the oval window. As the stapes presses into the oval window, the fluid
inside the cochlea begins to move, which in turn stimulates hair cells, which are auditory receptor cells of
the inner ear embedded in the basilar membrane. The basilar membrane is a thin strip of tissue within the

The activation of hair cells is a mechanical process: the stimulation of the hair cell ultimately leads to
activation of the cell. As hair cells become activated, they generate neural impulses that travel along
the auditory nerve to the brain. Auditory information is shuttled to the inferior colliculus, the medial
geniculate nucleus of the thalamus, and finally to the auditory cortex in the temporal lobe of the brain
for processing. Like the visual system, there is also evidence suggesting that information about auditory
recognition and localization is processed in parallel streams (Rauschecker & Tian, 2000; Renier et al., 2009).


Different frequencies of sound waves are associated with differences in our perception of the pitch of those
sounds. Low-frequency sounds are lower pitched, and high-frequency sounds are higher pitched. How
does the auditory system differentiate among various pitches?

Several theories have been proposed to account for pitch perception. We’ll discuss two of them here:
temporal theory and place theory. The temporal theory of pitch perception asserts that frequency is coded
by the activity level of a sensory neuron. This would mean that a given hair cell would fire action potentials
related to the frequency of the sound wave. While this is a very intuitive explanation, we detect such a
broad range of frequencies (20–20,000 Hz) that the frequency of action potentials fired by hair cells cannot
account for the entire range. Because of properties related to sodium channels on the neuronal membrane
that are involved in action potentials, there is a point at which a cell cannot fire any faster (Shamma, 2001).

The place theory of pitch perception suggests that different portions of the basilar membrane are sensitive
to sounds of different frequencies. More specifically, the base of the basilar membrane responds best to
high frequencies and the tip of the basilar membrane responds best to low frequencies. Therefore, hair
cells that are in the base portion would be labeled as high-pitch receptors, while those in the tip of basilar
membrane would be labeled as low-pitch receptors (Shamma, 2001).

In reality, both theories explain different aspects of pitch perception. At frequencies up to about 4000 Hz,
it is clear that both the rate of action potentials and place contribute to our perception of pitch. However,

172 Chapter 5 | Sensation and Perception

This OpenStax book is available for free at

much higher frequency sounds can only be encoded using place cues (Shamma, 2001).


The ability to locate sound in our environments is an important part of hearing. Localizing sound could be
considered similar to the way that we perceive depth in our visual fields. Like the monocular and binocular
cues that provided information about depth, the auditory system uses both monaural (one-eared) and
binaural (two-eared) cues to localize sound.

Each pinna interacts with incoming sound waves differently, depending on the sound’s source relative to
our bodies. This interaction provides a monaural cue that is helpful in locating sounds that occur above or
below and in front or behind us. The sound waves received by your two ears from sounds that come from
directly above, below, in front, or behind you would be identical; therefore, monaural cues are essential
(Grothe, Pecka, & McAlpine, 2010).

Binaural cues, on the other hand, provide information on the location of a sound along a horizontal axis
by relying on differences in patterns of vibration of the eardrum between our two ears. If a sound comes
from an off-center location, it creates two types of binaural cues: interaural level differences and interaural
timing differences. Interaural level difference refers to the fact that a sound coming from the right side of
your body is more intense at your right ear than at your left ear because of the attenuation of the sound
wave as it passes through your head. Interaural timing difference refers to the small difference in the
time at which a given sound wave arrives at each ear (Figure 5.19). Certain brain areas monitor these
differences to construct where along a horizontal axis a sound originates (Grothe et al., 2010).

Figure 5.19 Localizing sound involves the use of both monaural and binaural cues. (credit “plane”: modification of
work by Max Pfandl)


Deafness is the partial or complete inability to hear. Some people are born without hearing, which is
known as congenital deafness. Other people suffer from conductive hearing loss, which is due to a
problem delivering sound energy to the cochlea. Causes for conductive hearing loss include blockage
of the ear canal, a hole in the tympanic membrane, problems with the ossicles, or fluid in the space
between the eardrum and cochlea. Another group of people suffer from sensorineural hearing loss, which

Chapter 5 | Sensation and Perception 173

is the most common form of hearing loss. Sensorineural hearing loss can be caused by many factors,
such as aging, head or acoustic trauma, infections and diseases (such as measles or mumps), medications,
environmental effects such as noise exposure (noise-induced hearing loss, as shown in Figure 5.20),
tumors, and toxins (such as those found in certain solvents and metals).

Figure 5.20 Environmental factors that can lead to sensorineural hearing loss include regular exposure to loud
music or construction equipment. (a) Musical performers and (b) construction workers are at risk for this type of
hearing loss. (credit a: modification of work by “GillyBerlin_Flickr”/Flickr; credit b: modification of work by Nick Allen)

Given the mechanical nature by which the sound wave stimulus is transmitted from the eardrum through
the ossicles to the oval window of the cochlea, some degree of hearing loss is inevitable. With conductive
hearing loss, hearing problems are associated with a failure in the vibration of the eardrum and/or
movement of the ossicles. These problems are often dealt with through devices like hearing aids that
amplify incoming sound waves to make vibration of the eardrum and movement of the ossicles more likely
to occur.

When the hearing problem is associated with a failure to transmit neural signals from the cochlea to the
brain, it is called sensorineural hearing loss. One disease that results in sensorineural hearing loss is
Ménière’s disease. Although not well understood, Ménière’s disease results in a degeneration of inner ear
structures that can lead to hearing loss, tinnitus (constant ringing or buzzing), vertigo (a sense of spinning),
and an increase in pressure within the inner ear (Semaan & Megerian, 2011). This kind of loss cannot be
treated with hearing aids, but some individuals might be candidates for a cochlear implant as a treatment
option. Cochlear implants are electronic devices that consist of a microphone, a speech processor, and
an electrode array. The device receives incoming sound information and directly stimulates the auditory
nerve to transmit information to the brain.

Watch this video about cochlear implant surgeries ( to learn more.

Deaf Culture

In the United States and other places around the world, deaf people have their own language, schools, and



174 Chapter 5 | Sensation and Perception

This OpenStax book is available for free at

customs. This is called deaf culture. In the United States, deaf individuals often communicate using American
Sign Language (ASL); ASL has no verbal component and is based entirely on visual signs and gestures. The
primary mode of communication is signing. One of the values of deaf culture is to continue traditions like using
sign language rather than teaching deaf children to try to speak, read lips, or have cochlear implant surgery.

When a child is diagnosed as deaf, parents have difficult decisions to make. Should the child be enrolled in
mainstream schools and taught to verbalize and read lips? Or should the child be sent to a school for deaf
children to learn ASL and have significant exposure to deaf culture? Do you think there might be differences in
the way that parents approach these decisions depending on whether or not they are also deaf?

5.5 The Other Senses

Learning Objectives

By the end of this section, you will be able to:
• Describe the basic functions of the chemical senses
• Explain the basic functions of the somatosensory, nociceptive, and thermoceptive sensory

• Describe the basic functions of the vestibular, proprioceptive, and kinesthetic sensory


Vision and hearing have received an incredible amount of attention from researchers over the years.
While there is still much to be learned about how these sensory systems work, we have a much better
understanding of them than of our other sensory modalities. In this section, we will explore our chemical
senses (taste and smell) and our body senses (touch, temperature, pain, balance, and body position).


Taste (gustation) and smell (olfaction) are called chemical senses because both have sensory receptors that
respond to molecules in the food we eat or in the air we breathe. There is a pronounced interaction between
our chemical senses. For example, when we describe the flavor of a given food, we are really referring to
both gustatory and olfactory properties of the food working in combination.

Taste (Gustation)

You have learned since elementary school that there are four basic groupings of taste: sweet, salty, sour,
and bitter. Research demonstrates, however, that we have at least six taste groupings. Umami is our fifth
taste. Umami is actually a Japanese word that roughly translates to yummy, and it is associated with
a taste for monosodium glutamate (Kinnamon & Vandenbeuch, 2009). There is also a growing body of
experimental evidence suggesting that we possess a taste for the fatty content of a given food (Mizushige,
Inoue, & Fushiki, 2007).

Molecules from the food and beverages we consume dissolve in our saliva and interact with taste receptors
on our tongue and in our mouth and throat. Taste buds are formed by groupings of taste receptor cells
with hair-like extensions that protrude into the central pore of the taste bud (Figure 5.21). Taste buds
have a life cycle of ten days to two weeks, so even destroying some by burning your tongue won’t have
any long-term effect; they just grow right back. Taste molecules bind to receptors on this extension and
cause chemical changes within the sensory cell that result in neural impulses being transmitted to the brain
via different nerves, depending on where the receptor is located. Taste information is transmitted to the
medulla, thalamus, and limbic system, and to the gustatory cortex, which is tucked underneath the overlap

Chapter 5 | Sensation and Perception 175

between the frontal and temporal lobes (Maffei, Haley, & Fontanini, 2012; Roper, 2013).

Figure 5.21 (a) Taste buds are composed of a number of individual taste receptors cells that transmit information to
nerves. (b) This micrograph shows a close-up view of the tongue’s surface. (credit a: modification of work by Jonas
Töle; credit b: scale-bar data from Matt Russell)

Smell (Olfaction)

Olfactory receptor cells are located in a mucous membrane at the top of the nose. Small hair-like
extensions from these receptors serve as the sites for odor molecules dissolved in the mucus to interact
with chemical receptors located on these extensions (Figure 5.22). Once an odor molecule has bound a
given receptor, chemical changes within the cell result in signals being sent to the olfactory bulb: a bulb-
like structure at the tip of the frontal lobe where the olfactory nerves begin. From the olfactory bulb,
information is sent to regions of the limbic system and to the primary olfactory cortex, which is located
very near the gustatory cortex (Lodovichi & Belluscio, 2012; Spors et al., 2013).

Figure 5.22 Olfactory receptors are the hair-like parts that extend from the olfactory bulb into the mucous membrane
of the nasal cavity.

There is tremendous variation in the sensitivity of the olfactory systems of different species. We often think
of dogs as having far superior olfactory systems than our own, and indeed, dogs can do some remarkable
things with their noses. There is some evidence to suggest that dogs can “smell” dangerous drops in blood

176 Chapter 5 | Sensation and Perception

This OpenStax book is available for free at

glucose levels as well as cancerous tumors (Wells, 2010). Dogs’ extraordinary olfactory abilities may be
due to the increased number of functional genes for olfactory receptors (between 800 and 1200), compared
to the fewer than 400 observed in humans and other primates (Niimura & Nei, 2007).

Many species respond to chemical messages, known as pheromones, sent by another individual (Wysocki
& Preti, 2004). Pheromonal communication often involves providing information about the reproductive
status of a potential mate. So, for example, when a female rat is ready to mate, she secretes pheromonal
signals that draw attention from nearby male rats. Pheromonal activation is actually an important
component in eliciting sexual behavior in the male rat (Furlow, 1996, 2012; Purvis & Haynes, 1972; Sachs,
1997). There has also been a good deal of research (and controversy) about pheromones in humans
(Comfort, 1971; Russell, 1976; Wolfgang-Kimball, 1992; Weller, 1998).


A number of receptors are distributed throughout the skin to respond to various touch-related stimuli
(Figure 5.23). These receptors include Meissner’s corpuscles, Pacinian corpuscles, Merkel’s disks, and
Ruffini corpuscles. Meissner’s corpuscles respond to pressure and lower frequency vibrations, and
Pacinian corpuscles detect transient pressure and higher frequency vibrations. Merkel’s disks respond to
light pressure, while Ruffini corpuscles detect stretch (Abraira & Ginty, 2013).

Figure 5.23 There are many types of sensory receptors located in the skin, each attuned to specific touch-related

In addition to the receptors located in the skin, there are also a number of free nerve endings that
serve sensory functions. These nerve endings respond to a variety of different types of touch-related
stimuli and serve as sensory receptors for both thermoception (temperature perception) and nociception
(a signal indicating potential harm and maybe pain) (Garland, 2012; Petho & Reeh, 2012; Spray, 1986).
Sensory information collected from the receptors and free nerve endings travels up the spinal cord and is
transmitted to regions of the medulla, thalamus, and ultimately to somatosensory cortex, which is located
in the postcentral gyrus of the parietal lobe.

Pain Perception

Pain is an unpleasant experience that involves both physical and psychological components. Feeling pain
is quite adaptive because it makes us aware of an injury, and it motivates us to remove ourselves from the
cause of that injury. In addition, pain also makes us less likely to suffer additional injury because we will
be gentler with our injured body parts.

Generally speaking, pain can be considered to be neuropathic or inflammatory in nature. Pain that signals
some type of tissue damage is known as inflammatory pain. In some situations, pain results from damage
to neurons of either the peripheral or central nervous system. As a result, pain signals that are sent to the

Chapter 5 | Sensation and Perception 177

brain get exaggerated. This type of pain is known as neuropathic pain. Multiple treatment options for pain
relief range from relaxation therapy to the use of analgesic medications to deep brain stimulation. The most
effective treatment option for a given individual will depend on a number of considerations, including the
severity and persistence of the pain and any medical/psychological conditions.

Some individuals are born without the ability to feel pain. This very rare genetic disorder is known as
congenital insensitivity to pain (or congenital analgesia). While those with congenital analgesia can
detect differences in temperature and pressure, they cannot experience pain. As a result, they often suffer
significant injuries. Young children have serious mouth and tongue injuries because they have bitten
themselves repeatedly. Not surprisingly, individuals suffering from this disorder have much shorter life
expectancies due to their injuries and secondary infections of injured sites (U.S. National Library of
Medicine, 2013).

Watch this video about congenital insensitivity to pain ( to learn


The vestibular sense contributes to our ability to maintain balance and body posture. As Figure 5.24
shows, the major sensory organs (utricle, saccule, and the three semicircular canals) of this system are
located next to the cochlea in the inner ear. The vestibular organs are fluid-filled and have hair cells, similar
to the ones found in the auditory system, which respond to movement of the head and gravitational forces.
When these hair cells are stimulated, they send signals to the brain via the vestibular nerve. Although we
may not be consciously aware of our vestibular system’s sensory information under normal circumstances,
its importance is apparent when we experience motion sickness and/or dizziness related to infections of
the inner ear (Khan & Chang, 2013).

Figure 5.24 The major sensory organs of the vestibular system are located next to the cochlea in the inner ear.
These include the utricle, saccule, and the three semicircular canals (posterior, superior, and horizontal).

In addition to maintaining balance, the vestibular system collects information critical for controlling
movement and the reflexes that move various parts of our bodies to compensate for changes in body


178 Chapter 5 | Sensation and Perception

This OpenStax book is available for free at

position. Therefore, both proprioception (perception of body position) and kinesthesia (perception of the
body’s movement through space) interact with information provided by the vestibular system.

These sensory systems also gather information from receptors that respond to stretch and tension in
muscles, joints, skin, and tendons (Lackner & DiZio, 2005; Proske, 2006; Proske & Gandevia, 2012).
Proprioceptive and kinesthetic information travels to the brain via the spinal column. Several cortical
regions in addition to the cerebellum receive information from and send information to the sensory organs
of the proprioceptive and kinesthetic systems.

5.6 Gestalt Principles of Perception

Learning Objectives

By the end of this section, you will be able to:
• Explain the figure-ground relationship
• Define Gestalt principles of grouping
• Describe how perceptual set is influenced by an individual’s characteristics and mental state

In the early part of the 20th century, Max Wertheimer published a paper demonstrating that individuals
perceived motion in rapidly flickering static images—an insight that came to him as he used a child’s toy
tachistoscope. Wertheimer, and his assistants Wolfgang Köhler and Kurt Koffka, who later became his
partners, believed that perception involved more than simply combining sensory stimuli. This belief led to
a new movement within the field of psychology known as Gestalt psychology. The word gestalt literally
means form or pattern, but its use reflects the idea that the whole is different from the sum of its parts. In
other words, the brain creates a perception that is more than simply the sum of available sensory inputs,
and it does so in predictable ways. Gestalt psychologists translated these predictable ways into principles
by which we organize sensory information. As a result, Gestalt psychology has been extremely influential
in the area of sensation and perception (Rock & Palmer, 1990).

One Gestalt principle is the figure-ground relationship. According to this principle, we tend to segment
our visual world into figure and ground. Figure is the object or person that is the focus of the visual
field, while the ground is the background. As Figure 5.25 shows, our perception can vary tremendously,
depending on what is perceived as figure and what is perceived as ground. Presumably, our ability to
interpret sensory information depends on what we label as figure and what we label as ground in any
particular case, although this assumption has been called into question (Peterson & Gibson, 1994; Vecera
& O’Reilly, 1998).

Chapter 5 | Sensation and Perception 179

Figure 5.25 The concept of figure-ground relationship explains why this image can be perceived either as a vase or
as a pair of faces.

Another Gestalt principle for organizing sensory stimuli into meaningful perception is proximity. This
principle asserts that things that are close to one another tend to be grouped together, as Figure 5.26

Figure 5.26 The Gestalt principle of proximity suggests that you see (a) one block of dots on the left side and (b)
three columns on the right side.

How we read something provides another illustration of the proximity concept. For example, we read this
sentence like this, notl iket hiso rt hat. We group the letters of a given word together because there are no
spaces between the letters, and we perceive words because there are spaces between each word. Here are
some more examples: Cany oum akes enseo ft hiss entence? What doth es e wor dsmea n?

We might also use the principle of similarity to group things in our visual fields. According to this
principle, things that are alike tend to be grouped together (Figure 5.27). For example, when watching
a football game, we tend to group individuals based on the colors of their uniforms. When watching an
offensive drive, we can get a sense of the two teams simply by grouping along this dimension.

180 Chapter 5 | Sensation and Perception

This OpenStax book is available for free at

Figure 5.27 When looking at this array of dots, we likely perceive alternating rows of colors. We are grouping these
dots according to the principle of similarity.

Two additional Gestalt principles are the law of continuity (or good continuation) and closure. The law
of continuity suggests that we are more likely to perceive continuous, smooth flowing lines rather than
jagged, broken lines (Figure 5.28). The principle of closure states that we organize our perceptions into
complete objects rather than as a series of parts (Figure 5.29).

Figure 5.28 Good continuation would suggest that we are more likely to perceive this as two overlapping lines,
rather than four lines meeting in the center.

Figure 5.29 Closure suggests that we will perceive a complete circle and rectangle rather than a series of

Chapter 5 | Sensation and Perception 181

Watch this video showing real world examples of Gestalt principles ( to
learn more.

According to Gestalt theorists, pattern perception, or our ability to discriminate among different figures
and shapes, occurs by following the principles described above. You probably feel fairly certain that
your perception accurately matches the real world, but this is not always the case. Our perceptions are
based on perceptual hypotheses: educated guesses that we make while interpreting sensory information.
These hypotheses are informed by a number of factors, including our personalities, experiences, and
expectations. We use these hypotheses to generate our perceptual set. For instance, research has
demonstrated that those who are given verbal priming produce a biased interpretation of complex
ambiguous figures (Goolkasian & Woodbury, 2010).

The Depths of Perception: Bias, Prejudice, and Cultural Factors

In this chapter, you have learned that perception is a complex process. Built from sensations, but influenced
by our own experiences, biases, prejudices, and cultures, perceptions can be very different from person
to person. Research suggests that implicit racial prejudice and stereotypes affect perception. For instance,
several studies have demonstrated that non-Black participants identify weapons faster and are more likely to
identify non-weapons as weapons when the image of the weapon is paired with the image of a Black person
(Payne, 2001; Payne, Shimizu, & Jacoby, 2005). Furthermore, White individuals’ decisions to shoot an armed
target in a video game is made more quickly when the target is Black (Correll, Park, Judd, & Wittenbrink, 2002;
Correll, Urland, & Ito, 2006). This research is important, considering the number of very high-profile cases in
the last few decades in which young Blacks were killed by people who claimed to believe that the unarmed
individuals were armed and/or represented some threat to their personal safety.



182 Chapter 5 | Sensation and Perception

This OpenStax book is available for free at

absolute threshold



basilar membrane

binaural cue

binocular cue

binocular disparity

blind spot

bottom-up processing



cochlear implant

conductive hearing loss


congenital deafness

congenital insensitivity to pain (congenital analgesia)



decibel (dB)

depth perception

electromagnetic spectrum

figure-ground relationship



Gestalt psychology

good continuation

Key Terms

minimum amount of stimulus energy that must be present for the stimulus to be
detected 50% of the time

continuation of a visual sensation after removal of the stimulus

height of a wave

thin strip of tissue within the cochlea that contains the hair cells which serve as the
sensory receptors for the auditory system

two-eared cue to localize sound

cue that relies on the use of both eyes

slightly different view of the world that each eye receives

point where we cannot respond to visual information in that portion of the visual field

system in which perceptions are built from sensory input

organizing our perceptions into complete objects rather than as a series of parts

fluid-filled, snail-shaped structure that contains the sensory receptor cells of the auditory system

electronic device that consists of a microphone, a speech processor, and an electrode
array to directly stimulate the auditory nerve to transmit information to the brain

failure in the vibration of the eardrum and/or movement of the ossicles

specialized photoreceptor that works best in bright light conditions and detects color

deafness from birth

genetic disorder that results in the inability to
experience pain

transparent covering over the eye

partial or complete inability to hear

logarithmic unit of sound intensity

ability to perceive depth

all the electromagnetic radiation that occurs in our environment

segmenting our visual world into figure and ground

small indentation in the retina that contains cones

number of waves that pass a given point in a given time period

field of psychology based on the idea that the whole is different from the sum of its

(also, continuity) we are more likely to perceive continuous, smooth flowing lines

Chapter 5 | Sensation and Perception 183

hair cell

hertz (Hz)

inattentional blindness


inflammatory pain

interaural level difference

interaural timing difference


just noticeable difference



linear perspective


Meissner’s corpuscle

Merkel’s disk

monaural cue

monocular cue

Ménière’s disease

neuropathic pain


olfactory bulb

olfactory receptor

opponent-process theory of color perception

optic chiasm

optic nerve

Pacinian corpuscle

rather than jagged, broken lines

auditory receptor cell of the inner ear

cycles per second; measure of frequency

failure to notice something that is completely visible because of a lack of

middle ear ossicle; also known as the anvil

signal that some type of tissue damage has occurred

sound coming from one side of the body is more intense at the closest ear
because of the attenuation of the sound wave as it passes through the head

small difference in the time at which a given sound wave arrives at each ear

colored portion of the eye

difference in stimuli required to detect a difference between the stimuli

perception of the body’s movement through space

curved, transparent structure that provides additional focus for light entering the eye

perceive depth in an image when two parallel lines seem to converge

middle ear ossicle; also known as the hammer

touch receptor that responds to pressure and lower frequency vibrations

touch receptor that responds to light touch

one-eared cue to localize sound

cue that requires only one eye

results in a degeneration of inner ear structures that can lead to hearing loss, tinnitus,
vertigo, and an increase in pressure within the inner ear

pain from damage to neurons of either the peripheral or central nervous system

sensory signal indicating potential harm and maybe pain

bulb-like structure at the tip of the frontal lobe, where the olfactory nerves begin

sensory cell for the olfactory system

color is coded in opponent pairs: black-white, yellow-blue,
and red-green

X-shaped structure that sits just below the brain’s ventral surface; represents the merging of
the optic nerves from the two eyes and the separation of information from the two sides of the visual field
to the opposite side of the brain

carries visual information from the retina to the brain

touch receptor that detects transient pressure and higher frequency vibrations

184 Chapter 5 | Sensation and Perception

This OpenStax book is available for free at

pattern perception



perceptual hypothesis





place theory of pitch perception

principle of closure






Ruffini corpuscle


sensorineural hearing loss

sensory adaptation

signal detection theory



subliminal message

taste bud

temporal theory of pitch perception



top-down processing

ability to discriminate among different figures and shapes

(also, crest) highest point of a wave

way that sensory information is interpreted and consciously experienced

educated guess used to interpret sensory information

chemical message sent by another individual

light-detecting cell

visible part of the ear that protrudes from the head

perception of a sound’s frequency

different portions of the basilar membrane are sensitive to sounds of
different frequencies

organize perceptions into complete objects rather than as a series of parts

perception of body position

things that are close to one another tend to be grouped together

small opening in the eye through which light passes

light-sensitive lining of the eye

specialized photoreceptor that works well in low light conditions

touch receptor that detects stretch

what happens when sensory information is detected by a sensory receptor

failure to transmit neural signals from the cochlea to the brain

not perceiving stimuli that remain relatively constant over prolonged periods of time

change in stimulus detection as a function of current mental state

things that are alike tend to be grouped together

middle ear ossicle; also known as the stirrup

message presented below the threshold of conscious awareness

grouping of taste receptor cells with hair-like extensions that protrude into the central pore of
the taste bud

sound’s frequency is coded by the activity level of a sensory neuron

temperature perception

sound’s purity

interpretation of sensations is influenced by available knowledge, experiences, and

Chapter 5 | Sensation and Perception 185


trichromatic theory of color perception


tympanic membrane



vestibular sense

visible spectrum


conversion from sensory stimulus energy to action potential

color vision is mediated by the activity across the three groups
of cones

lowest point of a wave


taste for monosodium glutamate

spinning sensation

contributes to our ability to maintain balance and body posture

portion of the electromagnetic spectrum that we can see

length of a wave from one peak to the next peak


5.1 Sensation versus Perception
Sensation occurs when sensory receptors detect sensory stimuli. Perception involves the organization,
interpretation, and conscious experience of those sensations. All sensory systems have both absolute and
difference thresholds, which refer to the minimum amount of stimulus energy or the minimum amount
of difference in stimulus energy required to be detected about 50% of the time, respectively. Sensory
adaptation, selective attention, and signal detection theory can help explain what is perceived and what is
not. In addition, our perceptions are affected by a number of factors, including beliefs, values, prejudices,
culture, and life experiences.

5.2 Waves and Wavelengths
Both light and sound can be described in terms of wave forms with physical characteristics like amplitude,
wavelength, and timbre. Wavelength and frequency are inversely related so that longer waves have lower
frequencies, and shorter waves have higher frequencies. In the visual system, a light wave’s wavelength is
generally associated with color, and its amplitude is associated with brightness. In the auditory system, a
sound’s frequency is associated with pitch, and its amplitude is associated with loudness.

5.3 Vision
Light waves cross the cornea and enter the eye at the pupil. The eye’s lens focuses this light so that the
image is focused on a region of the retina known as the fovea. The fovea contains cones that possess
high levels of visual acuity and operate best in bright light conditions. Rods are located throughout the
retina and operate best under dim light conditions. Visual information leaves the eye via the optic nerve.
Information from each visual field is sent to the opposite side of the brain at the optic chiasm. Visual
information then moves through a number of brain sites before reaching the occipital lobe, where it is

Two theories explain color perception. The trichromatic theory asserts that three distinct cone groups are
tuned to slightly different wavelengths of light, and it is the combination of activity across these cone
types that results in our perception of all the colors we see. The opponent-process theory of color vision
asserts that color is processed in opponent pairs and accounts for the interesting phenomenon of a negative
afterimage. We perceive depth through a combination of monocular and binocular depth cues.

5.4 Hearing
Sound waves are funneled into the auditory canal and cause vibrations of the eardrum; these vibrations
move the ossicles. As the ossicles move, the stapes presses against the oval window of the cochlea, which

186 Chapter 5 | Sensation and Perception

This OpenStax book is available for free at

causes fluid inside the cochlea to move. As a result, hair cells embedded in the basilar membrane become
enlarged, which sends neural impulses to the brain via the auditory nerve.

Pitch perception and sound localization are important aspects of hearing. Our ability to perceive pitch
relies on both the firing rate of the hair cells in the basilar membrane as well as their location within the
membrane. In terms of sound localization, both monaural and binaural cues are used to locate where
sounds originate in our environment.

Individuals can be born deaf, or they can develop deafness as a result of age, genetic predisposition, and/
or environmental causes. Hearing loss that results from a failure of the vibration of the eardrum or the
resultant movement of the ossicles is called conductive hearing loss. Hearing loss that involves a failure of
the transmission of auditory nerve impulses to the brain is called sensorineural hearing loss.

5.5 The Other Senses
Taste (gustation) and smell (olfaction) are chemical senses that employ receptors on the tongue and in the
nose that bind directly with taste and odor molecules in order to transmit information to the brain for
processing. Our ability to perceive touch, temperature, and pain is mediated by a number of receptors
and free nerve endings that are distributed throughout the skin and various tissues of the body. The
vestibular sense helps us maintain a sense of balance through the response of hair cells in the utricle,
saccule, and semi-circular canals that respond to changes in head position and gravity. Our proprioceptive
and kinesthetic systems provide information about body position and body movement through receptors
that detect stretch and tension in the muscles, joints, tendons, and skin of the body.

5.6 Gestalt Principles of Perception
Gestalt theorists have been incredibly influential in the areas of sensation and perception. Gestalt
principles such as figure-ground relationship, grouping by proximity or similarity, the law of good
continuation, and closure are all used to help explain how we organize sensory information. Our
perceptions are not infallible, and they can be influenced by bias, prejudice, and other factors.

Review Questions

1. ________ refers to the minimum amount of
stimulus energy required to be detected 50% of the

a. absolute threshold
b. difference threshold
c. just noticeable difference
d. transduction

2. Decreased sensitivity to an unchanging
stimulus is known as ________.

a. transduction
b. difference threshold
c. sensory adaptation
d. inattentional blindness

3. ________ involves the conversion of sensory
stimulus energy into neural impulses.

a. sensory adaptation
b. inattentional blindness
c. difference threshold
d. transduction

4. ________ occurs when sensory information is
organized, interpreted, and consciously

a. sensation
b. perception
c. transduction
d. sensory adaptation

5. Which of the following correctly matches the
pattern in our perception of color as we move
from short wavelengths to long wavelengths?

a. red to orange to yellow
b. yellow to orange to red
c. yellow to red to orange
d. orange to yellow to red

6. The visible spectrum includes light that ranges
from about ________.

a. 400–700 nm
b. 200–900 nm
c. 20–20000 Hz
d. 10–20 dB

Chapter 5 | Sensation and Perception 187

7. The electromagnetic spectrum includes

a. radio waves
b. x-rays
c. infrared light
d. all of the above

8. The audible range for humans is ________.
a. 380–740 Hz
b. 10–20 dB
c. less than 300 dB
d. 20-20,000 Hz

9. The quality of a sound that is affected by
frequency, amplitude, and timing of the sound
wave is known as ________.

a. pitch
b. tone
c. electromagnetic
d. timbre

10. The ________ is a small indentation of the
retina that contains cones.

a. optic chiasm
b. optic nerve
c. fovea
d. iris

11. ________ operate best under bright light

a. cones
b. rods
c. retinal ganglion cells
d. striate cortex

12. ________ depth cues require the use of both

a. monocular
b. binocular
c. linear perspective
d. accommodating

13. If you were to stare at a green dot for a
relatively long period of time and then shift your
gaze to a blank white screen, you would see a
________ negative afterimage.

a. blue
b. yellow
c. black
d. red

14. Hair cells located near the base of the basilar
membrane respond best to ________ sounds.

a. low-frequency
b. high-frequency
c. low-amplitude
d. high-amplitude

15. The three ossicles of the middle ear are
known as ________.

a. malleus, incus, and stapes
b. hammer, anvil, and stirrup
c. pinna, cochlea, and utricle
d. both a and b

16. Hearing aids might be effective for treating

a. Ménière’s disease
b. sensorineural hearing loss
c. conductive hearing loss
d. interaural time differences

17. Cues that require two ears are referred to as
________ cues.

a. monocular
b. monaural
c. binocular
d. binaural

18. Chemical messages often sent between two
members of a species to communicate something
about reproductive status are called ________.

a. hormones
b. pheromones
c. Merkel’s disks
d. Meissner’s corpuscles

19. Which taste is associated with monosodium

a. sweet
b. bitter
c. umami
d. sour

20. ________ serve as sensory receptors for
temperature and pain stimuli.

a. free nerve endings
b. Pacinian corpuscles
c. Ruffini corpuscles
d. Meissner’s corpuscles

188 Chapter 5 | Sensation and Perception

This OpenStax book is available for free at

21. Which of the following is involved in
maintaining balance and body posture?

a. auditory nerve
b. nociceptors
c. olfactory bulb
d. vestibular system

22. According to the principle of ________,
objects that occur close to one another tend to be
grouped together.

a. similarity
b. good continuation
c. proximity
d. closure

23. Our tendency to perceive things as complete
objects rather than as a series of parts is known as
the principle of ________.

a. closure
b. good continuation
c. proximity
d. similarity

24. According to the law of ________, we are
more likely to perceive smoothly flowing lines
rather than choppy or jagged lines.

a. closure
b. good continuation
c. proximity
d. similarity

25. The main point of focus in a visual display is
known as the ________.

a. closure
b. perceptual set
c. ground
d. figure

Critical Thinking Questions

26. Not everything that is sensed is perceived. Do you think there could ever be a case where something
could be perceived without being sensed?

27. Please generate a novel example of how just noticeable difference can change as a function of stimulus

28. Why do you think other species have such different ranges of sensitivity for both visual and auditory
stimuli compared to humans?

29. Why do you think humans are especially sensitive to sounds with frequencies that fall in the middle
portion of the audible range?

30. Compare the two theories of color perception. Are they completely different?

31. Color is not a physical property of our environment. What function (if any) do you think color vision

32. Given what you’ve read about sound localization, from an evolutionary perspective, how does sound
localization facilitate survival?

33. How can temporal and place theories both be used to explain our ability to perceive the pitch of sound
waves with frequencies up to 4000 Hz?

34. Many people experience nausea while traveling in a car, plane, or boat. How might you explain this
as a function of sensory interaction?

Chapter 5 | Sensation and Perception 189

35. If you heard someone say that they would do anything not to feel the pain associated with significant
injury, how would you respond given what you’ve just read?

36. Do you think women experience pain differently than men? Why do you think this is?

37. The central tenet of Gestalt psychology is that the whole is different from the sum of its parts. What
does this mean in the context of perception?

38. Take a look at the following figure. How might you influence whether people see a duck or a rabbit?

Figure 5.30

Personal Application Questions

39. Think about a time when you failed to notice something around you because your attention was
focused elsewhere. If someone pointed it out, were you surprised that you hadn’t noticed it right away?

40. If you grew up with a family pet, then you have surely noticed that they often seem to hear things that
you don’t hear. Now that you’ve read this section, you probably have some insight as to why this may be.
How would you explain this to a friend who never had the opportunity to take a class like this?

41. Take a look at a few of your photos or personal works of art. Can you find examples of linear
perspective as a potential depth cue?

42. If you had to choose to lose either your vision or your hearing, which would you choose and why?

43. As mentioned earlier, a food’s flavor represents an interaction of both gustatory and olfactory
information. Think about the last time you were seriously congested due to a cold or the flu. What changes
did you notice in the flavors of the foods that you ate during this time?

44. Have you ever listened to a song on the radio and sung along only to find out later that you have been
singing the wrong lyrics? Once you found the correct lyrics, did your perception of the song change?

190 Chapter 5 | Sensation and Perception

This OpenStax book is available for free at

Chapter 6


Figure 6.1 Loggerhead sea turtle hatchlings are born knowing how to find the ocean and how to swim. Unlike the
sea turtle, humans must learn how to swim (and surf). (credit “turtle”: modification of work by Becky Skiba, USFWS;
credit “surfer”: modification of work by Mike Baird)

Chapter Outline

6.1 What Is Learning?

6.2 Classical Conditioning

6.3 Operant Conditioning

6.4 Observational Learning (Modeling)


The summer sun shines brightly on a deserted stretch of beach. Suddenly, a tiny grey head emerges
from the sand, then another and another. Soon the beach is teeming with loggerhead sea turtle hatchlings
(Figure 6.1). Although only minutes old, the hatchlings know exactly what to do. Their flippers are not
very efficient for moving across the hot sand, yet they continue onward, instinctively. Some are quickly
snapped up by gulls circling overhead and others become lunch for hungry ghost crabs that dart out of
their holes. Despite these dangers, the hatchlings are driven to leave the safety of their nest and find the

Not far down this same beach, Ben and his son, Julian, paddle out into the ocean on surfboards. A wave
approaches. Julian crouches on his board, then jumps up and rides the wave for a few seconds before
losing his balance. He emerges from the water in time to watch his father ride the face of the wave.

Unlike baby sea turtles, which know how to find the ocean and swim with no help from their parents, we
are not born knowing how to swim (or surf). Yet we humans pride ourselves on our ability to learn. In fact,
over thousands of years and across cultures, we have created institutions devoted entirely to learning. But
have you ever asked yourself how exactly it is that we learn? What processes are at work as we come to
know what we know? This chapter focuses on the primary ways in which learning occurs.

Chapter 6 | Learning 191

6.1 What Is Learning?

Learning Objectives

By the end of this section, you will be able to:
• Explain how learned behaviors are different from instincts and reflexes
• Define learning
• Recognize and define three basic forms of learning—classical conditioning, operant

conditioning, and observational learning

Birds build nests and migrate as winter approaches. Infants suckle at their mother’s breast. Dogs shake
water off wet fur. Salmon swim upstream to spawn, and spiders spin intricate webs. What do these
seemingly unrelated behaviors have in common? They all are unlearned behaviors. Both instincts and
reflexes are innate (unlearned) behaviors that organisms are born with. Reflexes are a motor or neural
reaction to a specific stimulus in the environment. They tend to be simpler than instincts, involve the
activity of specific body parts and systems (e.g., the knee-jerk reflex and the contraction of the pupil in
bright light), and involve more primitive centers of the central nervous system (e.g., the spinal cord and the
medulla). In contrast, instincts are innate behaviors that are triggered by a broader range of events, such
as maturation and the change of seasons. They are more complex patterns of behavior, involve movement
of the organism as a whole (e.g., sexual activity and migration), and involve higher brain centers.

Both reflexes and instincts help an organism adapt to its environment and do not have to be learned. For
example, every healthy human baby has a sucking reflex, present at birth. Babies are born knowing how to
suck on a nipple, whether artificial (from a bottle) or human. Nobody teaches the baby to suck, just as no
one teaches a sea turtle hatchling to move toward the ocean. Learning, like reflexes and instincts, allows an
organism to adapt to its environment. But unlike instincts and reflexes, learned behaviors involve change
and experience: learning is a relatively permanent change in behavior or knowledge that results from
experience. In contrast to the innate behaviors discussed above, learning involves acquiring knowledge
and skills through experience. Looking back at our surfing scenario, Julian will have to spend much more
time training with his surfboard before he learns how to ride the waves like his father.

Learning to surf, as well as any complex learning process (e.g., learning about the discipline of
psychology), involves a complex interaction of conscious and unconscious processes. Learning has
traditionally been studied in terms of its simplest components—the associations our minds automatically
make between events. Our minds have a natural tendency to connect events that occur closely together or
in sequence. Associative learning occurs when an organism makes connections between stimuli or events
that occur together in the environment. You will see that associative learning is central to all three basic
learning processes discussed in this chapter; classical conditioning tends to involve unconscious processes,
operant conditioning tends to involve conscious processes, and observational learning adds social and
cognitive layers to all the basic associative processes, both conscious and unconscious. These learning
processes will be discussed in detail later in the chapter, but it is helpful to have a brief overview of each
as you begin to explore how learning is understood from a psychological perspective.

In classical conditioning, also known as Pavlovian conditioning, organisms learn to associate events—or
stimuli—that repeatedly happen together. We experience this process throughout our daily lives. For
example, you might see a flash of lightning in the sky during a storm and then hear a loud boom of
thunder. The sound of the thunder naturally makes you jump (loud noises have that effect by reflex).
Because lightning reliably predicts the impending boom of thunder, you may associate the two and jump
when you see lightning. Psychological researchers study this associative process by focusing on what can
be seen and measured—behaviors. Researchers ask if one stimulus triggers a reflex, can we train a different
stimulus to trigger that same reflex? In operant conditioning, organisms learn, again, to associate events—a
behavior and its consequence (reinforcement or punishment). A pleasant consequence encourages more

192 Chapter 6 | Learning

This OpenStax book is available for free at

of that behavior in the future, whereas a punishment deters the behavior. Imagine you are teaching your
dog, Hodor, to sit. You tell Hodor to sit, and give him a treat when he does. After repeated experiences,
Hodor begins to associate the act of sitting with receiving a treat. He learns that the consequence of sitting
is that he gets a doggie biscuit (Figure 6.2). Conversely, if the dog is punished when exhibiting a behavior,
it becomes conditioned to avoid that behavior (e.g., receiving a small shock when crossing the boundary
of an invisible electric fence).

Figure 6.2 In operant conditioning, a response is associated with a consequence. This dog has learned that certain
behaviors result in receiving a treat. (credit: Crystal Rolfe)

Observational learning extends the effective range of both classical and operant conditioning. In contrast to
classical and operant conditioning, in which learning occurs only through direct experience, observational
learning is the process of watching others and then imitating what they do. A lot of learning among
humans and other animals comes from observational learning. To get an idea of the extra effective range
that observational learning brings, consider Ben and his son Julian from the introduction. How might
observation help Julian learn to surf, as opposed to learning by trial and error alone? By watching his
father, he can imitate the moves that bring success and avoid the moves that lead to failure. Can you think
of something you have learned how to do after watching someone else?

All of the approaches covered in this chapter are part of a particular tradition in psychology, called
behaviorism, which we discuss in the next section. However, these approaches do not represent the entire
study of learning. Separate traditions of learning have taken shape within different fields of psychology,
such as memory and cognition, so you will find that other chapters will round out your understanding
of the topic. Over time these traditions tend to converge. For example, in this chapter you will see how
cognition has come to play a larger role in behaviorism, whose more extreme adherents once insisted that
behaviors are triggered by the environment with no intervening thought.

6.2 Classical Conditioning

Learning Objectives

By the end of this section, you will be able to:
• Explain how classical conditioning occurs
• Summarize the processes of acquisition, extinction, spontaneous recovery, generalization,

and discrimination

Does the name Ivan Pavlov ring a bell? Even if you are new to the study of psychology, chances are that
you have heard of Pavlov and his famous dogs.

Chapter 6 | Learning 193

Pavlov (1849–1936), a Russian scientist, performed extensive research on dogs and is best known for
his experiments in classical conditioning (Figure 6.3). As we discussed briefly in the previous section,
classical conditioning is a process by which we learn to associate stimuli and, consequently, to anticipate

Figure 6.3 Ivan Pavlov’s research on the digestive system of dogs unexpectedly led to his discovery of the learning
process now known as classical conditioning.

Pavlov came to his conclusions about how learning occurs completely by accident. Pavlov was a
physiologist, not a psychologist. Physiologists study the life processes of organisms, from the molecular
level to the level of cells, organ systems, and entire organisms. Pavlov’s area of interest was the digestive
system (Hunt, 2007). In his studies with dogs, Pavlov measured the amount of saliva produced in response
to various foods. Over time, Pavlov (1927) observed that the dogs began to salivate not only at the taste
of food, but also at the sight of food, at the sight of an empty food bowl, and even at the sound of the
laboratory assistants’ footsteps. Salivating to food in the mouth is reflexive, so no learning is involved.
However, dogs don’t naturally salivate at the sight of an empty bowl or the sound of footsteps.

These unusual responses intrigued Pavlov, and he wondered what accounted for what he called the dogs’
“psychic secretions” (Pavlov, 1927). To explore this phenomenon in an objective manner, Pavlov designed
a series of carefully controlled experiments to see which stimuli would cause the dogs to salivate. He was
able to train the dogs to salivate in response to stimuli that clearly had nothing to do with food, such as the
sound of a bell, a light, and a touch on the leg. Through his experiments, Pavlov realized that an organism
has two types of responses to its environment: (1) unconditioned (unlearned) responses, or reflexes, and
(2) conditioned (learned) responses.

In Pavlov’s experiments, the dogs salivated each time meat powder was presented to them. The meat
powder in this situation was an unconditioned stimulus (UCS): a stimulus that elicits a reflexive response
in an organism. The dogs’ salivation was an unconditioned response (UCR): a natural (unlearned)
reaction to a given stimulus. Before conditioning, think of the dogs’ stimulus and response like this:

Meat powder (UCS) → Salivation (UCR)

In classical conditioning, a neutral stimulus is presented immediately before an unconditioned stimulus.
Pavlov would sound a tone (like ringing a bell) and then give the dogs the meat powder (Figure 6.4). The
tone was the neutral stimulus (NS), which is a stimulus that does not naturally elicit a response. Prior to
conditioning, the dogs did not salivate when they just heard the tone because the tone had no association
for the dogs.

Tone (NS) + Meat Powder (UCS) → Salivation (UCR)

When Pavlov paired the tone with the meat powder over and over again, the previously neutral stimulus
(the tone) also began to elicit salivation from the dogs. Thus, the neutral stimulus became the conditioned

194 Chapter 6 | Learning

This OpenStax book is available for free at

stimulus (CS), which is a stimulus that elicits a response after repeatedly being paired with an
unconditioned stimulus. Eventually, the dogs began to salivate to the tone alone, just as they previously
had salivated at the sound of the assistants’ footsteps. The behavior caused by the conditioned stimulus is
called the conditioned response (CR). In the case of Pavlov’s dogs, they had learned to associate the tone
(CS) with being fed, and they began to salivate (CR) in anticipation of food.

Tone (CS) → Salivation (CR)

Figure 6.4 Before conditioning, an unconditioned stimulus (food) produces an unconditioned response (salivation),
and a neutral stimulus (bell) does not produce a response. During conditioning, the unconditioned stimulus (food) is
presented repeatedly just after the presentation of the neutral stimulus (bell). After conditioning, the neutral stimulus
alone produces a conditioned response (salivation), thus becoming a conditioned stimulus.

View this video about Pavlov and his dogs ( to learn more.


How does classical conditioning work in the real world? Consider the case of Moisha, who was diagnosed
with cancer. When she received her first chemotherapy treatment, she vomited shortly after the chemicals
were injected. In fact, every trip to the doctor for chemotherapy treatment shortly after the drugs were
injected, she vomited. Moisha’s treatment was a success and her cancer went into remission. Now, when
she visits her oncologist’s office every 6 months for a check-up, she becomes nauseous. In this case,
the chemotherapy drugs are the unconditioned stimulus (UCS), vomiting is the unconditioned response
(UCR), the doctor’s office is the conditioned stimulus (CS) after being paired with the UCS, and nausea
is the conditioned response (CR). Let’s assume that the chemotherapy drugs that Moisha takes are given
through a syringe injection. After entering the doctor’s office, Moisha sees a syringe, and then gets
her medication. In addition to the doctor’s office, Moisha will learn to associate the syringe will the
medication and will respond to syringes with nausea. This is an example of higher-order (or second-order)


Chapter 6 | Learning 195

conditioning, when the conditioned stimulus (the doctor’s office) serves to condition another stimulus (the
syringe). It is hard to achieve anything above second-order conditioning. For example, if someone rang a
bell every time Moisha received a syringe injection of chemotherapy drugs in the doctor’s office, Moisha
likely will never get sick in response to the bell.

Consider another example of classical conditioning. Let’s say you have a cat named Tiger, who is quite
spoiled. You keep her food in a separate cabinet, and you also have a special electric can opener that you
use only to open cans of cat food. For every meal, Tiger hears the distinctive sound of the electric can
opener (“zzhzhz”) and then gets her food. Tiger quickly learns that when she hears “zzhzhz” she is about
to get fed. What do you think Tiger does when she hears the electric can opener? She will likely get excited
and run to where you are preparing her food. This is an example of classical conditioning. In this case,
what are the UCS, CS, UCR, and CR?

What if the cabinet holding Tiger’s food becomes squeaky? In that case, Tiger hears “squeak” (the cabinet),
“zzhzhz” (the electric can opener), and then she gets her food. Tiger will learn to get excited when she
hears the “squeak” of the cabinet. Pairing a new neutral stimulus (“squeak”) with the conditioned stimulus
(“zzhzhz”) is called higher-order conditioning, or second-order conditioning. This means you are using
the conditioned stimulus of the can opener to condition another stimulus: the squeaky cabinet (Figure 6.5).
It is hard to achieve anything above second-order conditioning. For example, if you ring a bell, open the
cabinet (“squeak”), use the can opener (“zzhzhz”), and then feed Tiger, Tiger will likely never get excited
when hearing the bell alone.

196 Chapter 6 | Learning

This OpenStax book is available for free at

Figure 6.5 In higher-order conditioning, an established conditioned stimulus is paired with a new neutral stimulus
(the second-order stimulus), so that eventually the new stimulus also elicits the conditioned response, without the
initial conditioned stimulus being presented.

Classical Conditioning at Stingray City

Kate and her spouse recently vacationed in the Cayman Islands, and booked a boat tour to Stingray City,
where they could feed and swim with the southern stingrays. The boat captain explained how the normally
solitary stingrays have become accustomed to interacting with humans. About 40 years ago, fishermen began
to clean fish and conch (unconditioned stimulus) at a particular sandbar near a barrier reef, and large numbers
of stingrays would swim in to eat (unconditioned response) what the fishermen threw into the water; this
continued for years. By the late 1980s, word of the large group of stingrays spread among scuba divers, who
then started feeding them by hand. Over time, the southern stingrays in the area were classically conditioned
much like Pavlov’s dogs. When they hear the sound of a boat engine (neutral stimulus that becomes a
conditioned stimulus), they know that they will get to eat (conditioned response).

As soon as they reached Stingray City, over two dozen stingrays surrounded their tour boat. The couple slipped
into the water with bags of squid, the stingrays’ favorite treat. The swarm of stingrays bumped and rubbed
up against their legs like hungry cats (Figure 6.6). Kate was able to feed, pet, and even kiss (for luck) these
amazing creatures. Then all the squid was gone, and so were the stingrays.


Chapter 6 | Learning 197

Figure 6.6 Kate holds a southern stingray at Stingray City in the Cayman Islands. These stingrays have
been classically conditioned to associate the sound of a boat motor with food provided by tourists. (credit:
Kathryn Dumper)

Classical conditioning also applies to humans, even babies. For example, Sara buys formula in blue
canisters for her six-month-old daughter, Angelina. Whenever Sara takes out a formula container,
Angelina gets excited, tries to reach toward the food, and most likely salivates. Why does Angelina get
excited when she sees the formula canister? What are the UCS, CS, UCR, and CR here?

So far, all of the examples have involved food, but classical conditioning extends beyond the basic need
to be fed. Consider our earlier example of a dog whose owners install an invisible electric dog fence.
A small electrical shock (unconditioned stimulus) elicits discomfort (unconditioned response). When the
unconditioned stimulus (shock) is paired with a neutral stimulus (the edge of a yard), the dog associates
the discomfort (unconditioned response) with the edge of the yard (conditioned stimulus) and stays within
the set boundaries. In this example, the edge of the yard elicits fear and anxiety in the dog. Fear and anxiety
are the conditioned response.

Watch this video clip from the television show, The Office, for a humorous look at conditioning
( in which Jim conditions Dwight to expect a breath mint every time Jim’s
computer makes a specific sound.


Now that you know how classical conditioning works and have seen several examples, let’s take a look at
some of the general processes involved. In classical conditioning, the initial period of learning is known
as acquisition, when an organism learns to connect a neutral stimulus and an unconditioned stimulus.
During acquisition, the neutral stimulus begins to elicit the conditioned response, and eventually the
neutral stimulus becomes a conditioned stimulus capable of eliciting the conditioned response by itself.
Timing is important for conditioning to occur. Typically, there should only be a brief interval between
presentation of the conditioned stimulus and the unconditioned stimulus. Depending on what is being


198 Chapter 6 | Learning

This OpenStax book is available for free at

conditioned, sometimes this interval is as little as five seconds (Chance, 2009). However, with other types
of conditioning, the interval can be up to several hours.

Taste aversion is a type of conditioning in which an interval of several hours may pass between the
conditioned stimulus (something ingested) and the unconditioned stimulus (nausea or illness). Here’s how
it works. Between classes, you and a friend grab a quick lunch from a food cart on campus. You share a
dish of chicken curry and head off to your next class. A few hours later, you feel nauseous and become ill.
Although your friend is fine and you determine that you have intestinal flu (the food is not the culprit),
you’ve developed a taste aversion; the next time you are at a restaurant and someone orders curry, you
immediately feel ill. While the chicken dish is not what made you sick, you are experiencing taste aversion:
you’ve been conditioned to be averse to a food after a single, bad experience.

How does this occur—conditioning based on a single instance and involving an extended time lapse
between the event and the negative stimulus? Research into taste aversion suggests that this response
may be an evolutionary adaptation designed to help organisms quickly learn to avoid harmful foods
(Garcia & Rusiniak, 1980; Garcia & Koelling, 1966). Not only may this contribute to species survival via
natural selection, but it may also help us develop strategies for challenges such as helping cancer patients
through the nausea induced by certain treatments (Holmes, 1993; Jacobsen et al., 1993; Hutton, Baracos, &
Wismer, 2007; Skolin et al., 2006). Garcia and Koelling (1966) showed not only that taste aversions could
be conditioned, but also that there were biological constraints to learning. In their study, separate groups
of rats were conditioned to associate either a flavor with illness, or lights and sounds with illness. Results
showed that all rats exposed to flavor-illness pairings learned to avoid the flavor, but none of the rats
exposed to lights and sounds with illness learned to avoid lights or sounds. This added evidence to the
idea that classical conditioning could contribute to species survival by helping organisms learn to avoid
stimuli that posed real dangers to health and welfare.

Robert Rescorla demonstrated how powerfully an organism can learn to predict the UCS from the CS.
Take, for example, the following two situations. Ari’s dad always has dinner on the table every day at 6:00.
Soraya’s mom switches it up so that some days they eat dinner at 6:00, some days they eat at 5:00, and
other days they eat at 7:00. For Ari, 6:00 reliably and consistently predicts dinner, so Ari will likely start
feeling hungry every day right before 6:00, even if he’s had a late snack. Soraya, on the other hand, will be
less likely to associate 6:00 with dinner, since 6:00 does not always predict that dinner is coming. Rescorla,
along with his colleague at Yale University, Alan Wagner, developed a mathematical formula that could
be used to calculate the probability that an association would be learned given the ability of a conditioned
stimulus to predict the occurrence of an unconditioned stimulus and other factors; today this is known as
the Rescorla-Wagner model (Rescorla & Wagner, 1972)

Once we have established the connection between the unconditioned stimulus and the conditioned
stimulus, how do we break that connection and get the dog, cat, or child to stop responding? In Tiger’s
case, imagine what would happen if you stopped using the electric can opener for her food and began to
use it only for human food. Now, Tiger would hear the can opener, but she would not get food. In classical
conditioning terms, you would be giving the conditioned stimulus, but not the unconditioned stimulus.
Pavlov explored this scenario in his experiments with dogs: sounding the tone without giving the dogs the
meat powder. Soon the dogs stopped responding to the tone. Extinction is the decrease in the conditioned
response when the unconditioned stimulus is no longer presented with the conditioned stimulus. When
presented with the conditioned stimulus alone, the dog, cat, or other organism would show a weaker and
weaker response, and finally no response. In classical conditioning terms, there is a gradual weakening
and disappearance of the conditioned response.

What happens when learning is not used for a while—when what was learned lies dormant? As we
just discussed, Pavlov found that when he repeatedly presented the bell (conditioned stimulus) without
the meat powder (unconditioned stimulus), extinction occurred; the dogs stopped salivating to the bell.
However, after a couple of hours of resting from this extinction training, the dogs again began to salivate
when Pavlov rang the bell. What do you think would happen with Tiger’s behavior if your electric can
opener broke, and you did not use it for several months? When you finally got it fixed and started using

Chapter 6 | Learning 199

it to open Tiger’s food again, Tiger would remember the association between the can opener and her
food—she would get excited and run to the kitchen when she heard the sound. The behavior of Pavlov’s
dogs and Tiger illustrates a concept Pavlov called spontaneous recovery: the return of a previously
extinguished conditioned response following a rest period (Figure 6.7).

Figure 6.7 This is the curve of acquisition, extinction, and spontaneous recovery. The rising curve shows the
conditioned response quickly getting stronger through the repeated pairing of the conditioned stimulus and the
unconditioned stimulus (acquisition). Then the curve decreases, which shows how the conditioned response weakens
when only the conditioned stimulus is presented (extinction). After a break or pause from conditioning, the
conditioned response reappears (spontaneous recovery).

Of course, these processes also apply in humans. For example, let’s say that every day when you walk to
campus, an ice cream truck passes your route. Day after day, you hear the truck’s music (neutral stimulus),
so you finally stop and purchase a chocolate ice cream bar. You take a bite (unconditioned stimulus) and
then your mouth waters (unconditioned response). This initial period of learning is known as acquisition,
when you begin to connect the neutral stimulus (the sound of the truck) and the unconditioned stimulus
(the taste of the chocolate ice cream in your mouth). During acquisition, the conditioned response gets
stronger and stronger through repeated pairings of the conditioned stimulus and unconditioned stimulus.
Several days (and ice cream bars) later, you notice that your mouth begins to water (conditioned response)
as soon as you hear the truck’s musical jingle—even before you bite into the ice cream bar. Then one day
you head down the street. You hear the truck’s music (conditioned stimulus), and your mouth waters
(conditioned response). However, when you get to the truck, you discover that they are all out of ice cream.
You leave disappointed. The next few days you pass by the truck and hear the music, but don’t stop to
get an ice cream bar because you’re running late for class. You begin to salivate less and less when you
hear the music, until by the end of the week, your mouth no longer waters when you hear the tune. This
illustrates extinction. The conditioned response weakens when only the conditioned stimulus (the sound
of the truck) is presented, without being followed by the unconditioned stimulus (chocolate ice cream in
the mouth). Then the weekend comes. You don’t have to go to class, so you don’t pass the truck. Monday
morning arrives and you take your usual route to campus. You round the corner and hear the truck again.
What do you think happens? Your mouth begins to water again. Why? After a break from conditioning,
the conditioned response reappears, which indicates spontaneous recovery.

Acquisition and extinction involve the strengthening and weakening, respectively, of a learned
association. Two other learning processes—stimulus discrimination and stimulus generalization—are
involved in determining which stimuli will trigger learned responses. Animals (including humans) need
to distinguish between stimuli—for example, between sounds that predict a threatening event and sounds
that do not—so that they can respond appropriately (such as running away if the sound is threatening).
When an organism learns to respond differently to various stimuli that are similar, it is called stimulus
discrimination. In classical conditioning terms, the organism demonstrates the conditioned response only

200 Chapter 6 | Learning

This OpenStax book is available for free at

to the conditioned stimulus. Pavlov’s dogs discriminated between the basic tone that sounded before they
were fed and other tones (e.g., the doorbell), because the other sounds did not predict the arrival of food.
Similarly, Tiger, the cat, discriminated between the sound of the can opener and the sound of the electric
mixer. When the electric mixer is going, Tiger is not about to be fed, so she does not come running to
the kitchen looking for food. In our other example, Moisha, the cancer patient, discriminated between
oncologists and other types of doctors. She learned not to feel ill when visiting doctors for other types of
appointments, such as her annual physical.

On the other hand, when an organism demonstrates the conditioned response to stimuli that are similar to
the condition stimulus, it is called stimulus generalization, the opposite of stimulus discrimination. The
more similar a stimulus is to the condition stimulus, the more likely the organism is to give the conditioned
response. For instance, if the electric mixer sounds very similar to the electric can opener, Tiger may come
running after hearing its sound. But if you do not feed her following the electric mixer sound, and you
continue to feed her consistently after the electric can opener sound, she will quickly learn to discriminate
between the two sounds (provided they are sufficiently dissimilar that she can tell them apart). In our
other example, Moisha continued to feel ill whenever visiting other oncologists or other doctors in the
same building as her oncologist.


John B. Watson, shown in Figure 6.8, is considered the founder of behaviorism. Behaviorism is a school
of thought that arose during the first part of the 20th century, which incorporates elements of Pavlov’s
classical conditioning (Hunt, 2007). In stark contrast with Freud, who considered the reasons for behavior
to be hidden in the unconscious, Watson championed the idea that all behavior can be studied as a
simple stimulus-response reaction, without regard for internal processes. Watson argued that in order for
psychology to become a legitimate science, it must shift its concern away from internal mental processes
because mental processes cannot be seen or measured. Instead, he asserted that psychology must focus on
outward observable behavior that can be measured.

Figure 6.8 John B. Watson used the principles of classical conditioning in the study of human emotion.

Watson’s ideas were influenced by Pavlov’s work. According to Watson, human behavior, just like animal
behavior, is primarily the result of conditioned responses. Whereas Pavlov’s work with dogs involved the
conditioning of reflexes, Watson believed the same principles could be extended to the conditioning of
human emotions (Watson, 1919). Thus began Watson’s work with his graduate student Rosalie Rayner
and a baby called Little Albert. Through their experiments with Little Albert, Watson and Rayner (1920)
demonstrated how fears can be conditioned.

In 1920, Watson was the chair of the psychology department at Johns Hopkins University. Through his
position at the university he came to meet Little Albert’s mother, Arvilla Merritte, who worked at a campus

Chapter 6 | Learning 201

hospital (DeAngelis, 2010). Watson offered her a dollar to allow her son to be the subject of his experiments
in classical conditioning. Through these experiments, Little Albert was exposed to and conditioned to fear
certain things. Initially he was presented with various neutral stimuli, including a rabbit, a dog, a monkey,
masks, cotton wool, and a white rat. He was not afraid of any of these things. Then Watson, with the
help of Rayner, conditioned Little Albert to associate these stimuli with an emotion—fear. For example,
Watson handed Little Albert the white rat, and Little Albert enjoyed playing with it. Then Watson made
a loud sound, by striking a hammer against a metal bar hanging behind Little Albert’s head, each time
Little Albert touched the rat. Little Albert was frightened by the sound—demonstrating a reflexive fear of
sudden loud noises—and began to cry. Watson repeatedly paired the loud sound with the white rat. Soon
Little Albert became frightened by the white rat alone. In this case, what are the UCS, CS, UCR, and CR?
Days later, Little Albert demonstrated stimulus generalization—he became afraid of other furry things:
a rabbit, a furry coat, and even a Santa Claus mask (Figure 6.9). Watson had succeeded in conditioning
a fear response in Little Albert, thus demonstrating that emotions could become conditioned responses.
It had been Watson’s intention to produce a phobia—a persistent, excessive fear of a specific object or
situation— through conditioning alone, thus countering Freud’s view that phobias are caused by deep,
hidden conflicts in the mind. However, there is no evidence that Little Albert experienced phobias in later
years. Little Albert’s mother moved away, ending the experiment. While Watson’s research provided new
insight into conditioning, it would be considered unethical by today’s standards.

Figure 6.9 Through stimulus generalization, Little Albert came to fear furry things, including Watson in a Santa
Claus mask.

View scenes from this video on John Watson’s experiment in which Little Albert was conditioned to
respond in fear to furry objects ( to learn more.

As you watch the video, look closely at Little Albert’s reactions and the manner in which Watson and
Rayner present the stimuli before and after conditioning. Based on what you see, would you come to the
same conclusions as the researchers?

Advertising and Associative Learning

Advertising executives are pros at applying the principles of associative learning. Think about the car
commercials you have seen on television. Many of them feature an attractive model. By associating the model
with the car being advertised, you come to see the car as being desirable (Cialdini, 2008). You may be asking
yourself, does this advertising technique actually work? According to Cialdini (2008), men who viewed a car
commercial that included an attractive model later rated the car as being faster, more appealing, and better



202 Chapter 6 | Learning

This OpenStax book is available for free at

designed than did men who viewed an advertisement for the same car minus the model.

Have you ever noticed how quickly advertisers cancel contracts with a famous athlete following a scandal?
As far as the advertiser is concerned, that athlete is no longer associated with positive feelings; therefore, the
athlete cannot be used as an unconditioned stimulus to condition the public to associate positive feelings (the
unconditioned response) with their product (the conditioned stimulus).

Now that you are aware of how associative learning works, see if you can find examples of these types of
advertisements on television, in magazines, or on the Internet.

6.3 Operant Conditioning

Learning Objectives

By the end of this section, you will be able to:
• Define operant conditioning
• Explain the difference between reinforcement and punishment
• Distinguish between reinforcement schedules

The previous section of this chapter focused on the type of associative learning known as classical
conditioning. Remember that in classical conditioning, something in the environment triggers a reflex
automatically, and researchers train the organism to react to a different stimulus. Now we turn to the
second type of associative learning, operant conditioning. In operant conditioning, organisms learn to
associate a behavior and its consequence (Table 6.1). A pleasant consequence makes that behavior more
likely to be repeated in the future. For example, Spirit, a dolphin at the National Aquarium in Baltimore,
does a flip in the air when her trainer blows a whistle. The consequence is that she gets a fish.

Classical and Operant Conditioning Compared

Classical Conditioning Operant Conditioning


An unconditioned stimulus (such as
food) is paired with a neutral
stimulus (such as a bell). The neutral
stimulus eventually becomes the
conditioned stimulus, which brings
about the conditioned response

The target behavior is followed by
reinforcement or punishment to
either strengthen or weaken it, so
that the learner is more likely to
exhibit the desired behavior in the

Stimulus timing The stimulus occurs immediately
before the response.

The stimulus (either reinforcement
or punishment) occurs soon after the

Table 6.1

Psychologist B. F. Skinner saw that classical conditioning is limited to existing behaviors that are
reflexively elicited, and it doesn’t account for new behaviors such as riding a bike. He proposed a theory
about how such behaviors come about. Skinner believed that behavior is motivated by the consequences
we receive for the behavior: the reinforcements and punishments. His idea that learning is the result of

Chapter 6 | Learning 203

consequences is based on the law of effect, which was first proposed by psychologist Edward Thorndike.
According to the law of effect, behaviors that are followed by consequences that are satisfying to the
organism are more likely to be repeated, and behaviors that are followed by unpleasant consequences are
less likely to be repeated (Thorndike, 1911). Essentially, if an organism does something that brings about
a desired result, the organism is more likely to do it again. If an organism does something that does not
bring about a desired result, the organism is less likely to do it again. An example of the law of effect is in
employment. One of the reasons (and often the main reason) we show up for work is because we get paid
to do so. If we stop getting paid, we will likely stop showing up—even if we love our job.

Working with Thorndike’s law of effect as his foundation, Skinner began conducting scientific experiments
on animals (mainly rats and pigeons) to determine how organisms learn through operant conditioning
(Skinner, 1938). He placed these animals inside an operant conditioning chamber, which has come to be
known as a “Skinner box” (Figure 6.10). A Skinner box contains a lever (for rats) or disk (for pigeons) that
the animal can press or peck for a food reward via the dispenser. Speakers and lights can be associated
with certain behaviors. A recorder counts the number of responses made by the animal.

Figure 6.10 (a) B. F. Skinner developed operant conditioning for systematic study of how behaviors are
strengthened or weakened according to their consequences. (b) In a Skinner box, a rat presses a lever in an operant
conditioning chamber to receive a food reward. (credit a: modification of work by “Silly rabbit”/Wikimedia Commons)

Watch this brief video to see Skinner’s interview and a demonstration of operant conditioning of
pigeons ( to learn more.

In discussing operant conditioning, we use several everyday words—positive, negative, reinforcement,
and punishment—in a specialized manner. In operant conditioning, positive and negative do not mean
good and bad. Instead, positive means you are adding something, and negative means you are taking
something away. Reinforcement means you are increasing a behavior, and punishment means you are
decreasing a behavior. Reinforcement can be positive or negative, and punishment can also be positive
or negative. All reinforcers (positive or negative) increase the likelihood of a behavioral response. All
punishers (positive or negative) decrease the likelihood of a behavioral response. Now let’s combine
these four terms: positive reinforcement, negative reinforcement, positive punishment, and negative
punishment (Table 6.2).


204 Chapter 6 | Learning

This OpenStax book is available for free at

Positive and Negative Reinforcement and Punishment

Reinforcement Punishment

Positive Something is added to increase the
likelihood of a behavior.

Something is added to decrease the
likelihood of a behavior.

Negative Something is removed to increase the
likelihood of a behavior.

Something is removed to decrease the
likelihood of a behavior.

Table 6.2


The most effective way to teach a person or animal a new behavior is with positive reinforcement. In
positive reinforcement, a desirable stimulus is added to increase a behavior.

For example, you tell your five-year-old son, Jerome, that if he cleans his room, he will get a toy. Jerome
quickly cleans his room because he wants a new art set. Let’s pause for a moment. Some people might
say, “Why should I reward my child for doing what is expected?” But in fact we are constantly and
consistently rewarded in our lives. Our paychecks are rewards, as are high grades and acceptance into
our preferred school. Being praised for doing a good job and for passing a driver’s test is also a reward.
Positive reinforcement as a learning tool is extremely effective. It has been found that one of the most
effective ways to increase achievement in school districts with below-average reading scores was to pay
the children to read. Specifically, second-grade students in Dallas were paid $2 each time they read a book
and passed a short quiz about the book. The result was a significant increase in reading comprehension
(Fryer, 2010). What do you think about this program? If Skinner were alive today, he would probably
think this was a great idea. He was a strong proponent of using operant conditioning principles to
influence students’ behavior at school. In fact, in addition to the Skinner box, he also invented what
he called a teaching machine that was designed to reward small steps in learning (Skinner, 1961)—an
early forerunner of computer-assisted learning. His teaching machine tested students’ knowledge as
they worked through various school subjects. If students answered questions correctly, they received
immediate positive reinforcement and could continue; if they answered incorrectly, they did not receive
any reinforcement. The idea was that students would spend additional time studying the material to
increase their chance of being reinforced the next time (Skinner, 1961).

In negative reinforcement, an undesirable stimulus is removed to increase a behavior. For example, car
manufacturers use the principles of negative reinforcement in their seatbelt systems, which go “beep,
beep, beep” until you fasten your seatbelt. The annoying sound stops when you exhibit the desired
behavior, increasing the likelihood that you will buckle up in the future. Negative reinforcement is also
used frequently in horse training. Riders apply pressure—by pulling the reins or squeezing their legs—and
then remove the pressure when the horse performs the desired behavior, such as turning or speeding up.
The pressure is the negative stimulus that the horse wants to remove.


Many people confuse negative reinforcement with punishment in operant conditioning, but they are two
very different mechanisms. Remember that reinforcement, even when it is negative, always increases a
behavior. In contrast, punishment always decreases a behavior. In positive punishment, you add an
undesirable stimulus to decrease a behavior. An example of positive punishment is scolding a student
to get the student to stop texting in class. In this case, a stimulus (the reprimand) is added in order
to decrease the behavior (texting in class). In negative punishment, you remove a pleasant stimulus to
decrease behavior. For example, when a child misbehaves, a parent can take away a favorite toy. In this
case, a stimulus (the toy) is removed in order to decrease the behavior.

Chapter 6 | Learning 205

Punishment, especially when it is immediate, is one way to decrease undesirable behavior. For example,
imagine your four-year-old son, Brandon, hit his younger brother. You have Brandon write 100 times
“I will not hit my brother” (positive punishment). Chances are he won’t repeat this behavior. While
strategies like this are common today, in the past children were often subject to physical punishment,
such as spanking. It’s important to be aware of some of the drawbacks in using physical punishment on
children. First, punishment may teach fear. Brandon may become fearful of the street, but he also may
become fearful of the person who delivered the punishment—you, his parent. Similarly, children who
are punished by teachers may come to fear the teacher and try to avoid school (Gershoff et al., 2010).
Consequently, most schools in the United States have banned corporal punishment. Second, punishment
may cause children to become more aggressive and prone to antisocial behavior and delinquency
(Gershoff, 2002). They see their parents resort to spanking when they become angry and frustrated, so, in
turn, they may act out this same behavior when they become angry and frustrated. For example, because
you spank Brenda when you are angry with her for her misbehavior, she might start hitting her friends
when they won’t share their toys.

While positive punishment can be effective in some cases, Skinner suggested that the use of punishment
should be weighed against the possible negative effects. Today’s psychologists and parenting experts favor
reinforcement over punishment—they recommend that you catch your child doing something good and
reward her for it.


In his operant conditioning experiments, Skinner often used an approach called shaping. Instead of
rewarding only the target behavior, in shaping, we reward successive approximations of a target behavior.
Why is shaping needed? Remember that in order for reinforcement to work, the organism must first
display the behavior. Shaping is needed because it is extremely unlikely that an organism will display
anything but the simplest of behaviors spontaneously. In shaping, behaviors are broken down into many
small, achievable steps. The specific steps used in the process are the following:

1. Reinforce any response that resembles the desired behavior.

2. Then reinforce the response that more closely resembles the desired behavior. You will no longer
reinforce the previously reinforced response.

3. Next, begin to reinforce the response that even more closely resembles the desired behavior.

4. Continue to reinforce closer and closer approximations of the desired behavior.

5. Finally, only reinforce the desired behavior.

Shaping is often used in teaching a complex behavior or chain of behaviors. Skinner used shaping to
teach pigeons not only such relatively simple behaviors as pecking a disk in a Skinner box, but also many
unusual and entertaining behaviors, such as turning in circles, walking in figure eights, and even playing
ping pong; the technique is commonly used by animal trainers today. An important part of shaping is
stimulus discrimination. Recall Pavlov’s dogs—he trained them to respond to the tone of a bell, and not
to similar tones or sounds. This discrimination is also important in operant conditioning and in shaping

Watch this brief video of Skinner’s pigeons playing ping pong ( to
learn more.


206 Chapter 6 | Learning

This OpenStax book is available for free at

It’s easy to see how shaping is effective in teaching behaviors to animals, but how does shaping work with
humans? Let’s consider parents whose goal is to have their child learn to clean his room. They use shaping
to help him master steps toward the goal. Instead of performing the entire task, they set up these steps and
reinforce each step. First, he cleans up one toy. Second, he cleans up five toys. Third, he chooses whether
to pick up ten toys or put his books and clothes away. Fourth, he cleans up everything except two toys.
Finally, he cleans his entire room.


Rewards such as stickers, praise, money, toys, and more can be used to reinforce learning. Let’s go back
to Skinner’s rats again. How did the rats learn to press the lever in the Skinner box? They were rewarded
with food each time they pressed the lever. For animals, food would be an obvious reinforcer.

What would be a good reinforcer for humans? For your child Chris, it was the promise of a toy when they
cleaned their room. How about Sydney, the soccer player? If you gave Sydney a piece of candy every time
Sydney scored a goal, you would be using a primary reinforcer. Primary reinforcers are reinforcers that
have innate reinforcing qualities. These kinds of reinforcers are not learned. Water, food, sleep, shelter,
sex, and touch, among others, are primary reinforcers. Pleasure is also a primary reinforcer. Organisms
do not lose their drive for these things. For most people, jumping in a cool lake on a very hot day would
be reinforcing and the cool lake would be innately reinforcing—the water would cool the person off (a
physical need), as well as provide pleasure.

A secondary reinforcer has no inherent value and only has reinforcing qualities when linked with a
primary reinforcer. Praise, linked to affection, is one example of a secondary reinforcer, as when you called
out “Great shot!” every time Sydney made a goal. Another example, money, is only worth something
when you can use it to buy other things—either things that satisfy basic needs (food, water, shelter—all
primary reinforcers) or other secondary reinforcers. If you were on a remote island in the middle of the
Pacific Ocean and you had stacks of money, the money would not be useful if you could not spend it. What
about the stickers on the behavior chart? They also are secondary reinforcers.

Sometimes, instead of stickers on a sticker chart, a token is used. Tokens, which are also secondary
reinforcers, can then be traded in for rewards and prizes. Entire behavior management systems, known
as token economies, are built around the use of these kinds of token reinforcers. Token economies have
been found to be very effective at modifying behavior in a variety of settings such as schools, prisons,
and mental hospitals. For example, a study by Cangi and Daly (2013) found that use of a token economy
increased appropriate social behaviors and reduced inappropriate behaviors in a group of autistic school
children. Autistic children tend to exhibit disruptive behaviors such as pinching and hitting. When the
children in the study exhibited appropriate behavior (not hitting or pinching), they received a “quiet
hands” token. When they hit or pinched, they lost a token. The children could then exchange specified
amounts of tokens for minutes of playtime.

Behavior Modification in Children

Parents and teachers often use behavior modification to change a child’s behavior. Behavior modification
uses the principles of operant conditioning to accomplish behavior change so that undesirable behaviors are
switched for more socially acceptable ones. Some teachers and parents create a sticker chart, in which several
behaviors are listed (Figure 6.11). Sticker charts are a form of token economies, as described in the text. Each
time children perform the behavior, they get a sticker, and after a certain number of stickers, they get a prize,
or reinforcer. The goal is to increase acceptable behaviors and decrease misbehavior. Remember, it is best
to reinforce desired behaviors, rather than to use punishment. In the classroom, the teacher can reinforce a
wide range of behaviors, from students raising their hands, to walking quietly in the hall, to turning in their


Chapter 6 | Learning 207

homework. At home, parents might create a behavior chart that rewards children for things such as putting
away toys, brushing their teeth, and helping with dinner. In order for behavior modification to be effective, the
reinforcement needs to be connected with the behavior; the reinforcement must matter to the child and be
done consistently.

Figure 6.11 Sticker charts are a form of positive reinforcement and a tool for behavior modification. Once
this child earns a certain number of stickers for demonstrating a desired behavior, she will be rewarded with a
trip to the ice cream parlor. (credit: Abigail Batchelder)

Time-out is another popular technique used in behavior modification with children. It operates on the principle
of negative punishment. When a child demonstrates an undesirable behavior, she is removed from the
desirable activity at hand (Figure 6.12). For example, say that Sophia and her brother Mario are playing with
building blocks. Sophia throws some blocks at her brother, so you give her a warning that she will go to time-
out if she does it again. A few minutes later, she throws more blocks at Mario. You remove Sophia from the
room for a few minutes. When she comes back, she doesn’t throw blocks.

There are several important points that you should know if you plan to implement time-out as a behavior
modification technique. First, make sure the child is being removed from a desirable activity and placed in a
less desirable location. If the activity is something undesirable for the child, this technique will backfire because
it is more enjoyable for the child to be removed from the activity. Second, the length of the time-out is important.
The general rule of thumb is one minute for each year of the child’s age. Sophia is five; therefore, she sits in
a time-out for five minutes. Setting a timer helps children know how long they have to sit in time-out. Finally,
as a caregiver, keep several guidelines in mind over the course of a time-out: remain calm when directing your
child to time-out; ignore your child during time-out (because caregiver attention may reinforce misbehavior);
and give the child a hug or a kind word when time-out is over.

208 Chapter 6 | Learning

This OpenStax book is available for free at

Figure 6.12 Time-out is a popular form of negative punishment used by caregivers. When a child
misbehaves, he or she is removed from a desirable activity in an effort to decrease the unwanted behavior.
For example, (a) a child might be playing on the playground with friends and push another child; (b) the child
who misbehaved would then be removed from the activity for a short period of time. (credit a: modification of
work by Simone Ramella; credit b: modification of work by “Spring Dew”/Flickr)


Remember, the best way to teach a person or animal a behavior is to use positive reinforcement. For
example, Skinner used positive reinforcement to teach rats to press a lever in a Skinner box. At first, the rat
might randomly hit the lever while exploring the box, and out would come a pellet of food. After eating
the pellet, what do you think the hungry rat did next? It hit the lever again, and received another pellet
of food. Each time the rat hit the lever, a pellet of food came out. When an organism receives a reinforcer
each time it displays a behavior, it is called continuous reinforcement. This reinforcement schedule is the
quickest way to teach someone a behavior, and it is especially effective in training a new behavior. Let’s
look back at the dog that was learning to sit earlier in the chapter. Now, each time he sits, you give him
a treat. Timing is important here: you will be most successful if you present the reinforcer immediately
after he sits, so that he can make an association between the target behavior (sitting) and the consequence
(getting a treat).

Watch this video clip of veterinarian Dr. Sophia Yin shaping a dog’s behavior using the steps
outlined above ( to learn more.

Once a behavior is trained, researchers and trainers often turn to another type of reinforcement
schedule—partial reinforcement. In partial reinforcement, also referred to as intermittent reinforcement,
the person or animal does not get reinforced every time they perform the desired behavior. There are
several different types of partial reinforcement schedules (Table 6.3). These schedules are described as
either fixed or variable, and as either interval or ratio. Fixed refers to the number of responses between
reinforcements, or the amount of time between reinforcements, which is set and unchanging. Variable
refers to the number of responses or amount of time between reinforcements, which varies or changes.
Interval means the schedule is based on the time between reinforcements, and ratio means the schedule is
based on the number of responses between reinforcements.


Chapter 6 | Learning 209

Reinforcement Schedules


Description Result Example

Fixed interval Reinforcement is
delivered at predictable
time intervals (e.g., after
5, 10, 15, and 20

Moderate response rate
with significant pauses
after reinforcement

Hospital patient uses
doctor-timed pain relief


Reinforcement is
delivered at
unpredictable time
intervals (e.g., after 5, 7,
10, and 20 minutes).

Moderate yet steady
response rate

Checking Facebook

Fixed ratio Reinforcement is
delivered after a
predictable number of
responses (e.g., after 2, 4,
6, and 8 responses).

High response rate with
pauses after

worker getting paid for
every x number of items

Variable ratio Reinforcement is
delivered after an
unpredictable number of
responses (e.g., after 1, 4,
5, and 9 responses).

High and steady
response rate


Table 6.3

Now let’s combine these four terms. A fixed interval reinforcement schedule is when behavior is
rewarded after a set amount of time. For example, June undergoes major surgery in a hospital. During
recovery, she is expected to experience pain and will require prescription medications for pain relief. June
is given an IV drip with a patient-controlled painkiller. Her doctor sets a limit: one dose per hour. June
pushes a button when pain becomes difficult, and she receives a dose of medication. Since the reward
(pain relief) only occurs on a fixed interval, there is no point in exhibiting the behavior when it will not be

With a variable interval reinforcement schedule, the person or animal gets the reinforcement based
on varying amounts of time, which are unpredictable. Say that Manuel is the manager at a fast-food
restaurant. Every once in a while someone from the quality control division comes to Manuel’s restaurant.
If the restaurant is clean and the service is fast, everyone on that shift earns a $20 bonus. Manuel never
knows when the quality control person will show up, so he always tries to keep the restaurant clean and
ensures that his employees provide prompt and courteous service. His productivity regarding prompt
service and keeping a clean restaurant are steady because he wants his crew to earn the bonus.

With a fixed ratio reinforcement schedule, there are a set number of responses that must occur before
the behavior is rewarded. Carla sells glasses at an eyeglass store, and she earns a commission every time
she sells a pair of glasses. She always tries to sell people more pairs of glasses, including prescription
sunglasses or a backup pair, so she can increase her commission. She does not care if the person really
needs the prescription sunglasses, Carla just wants her bonus. The quality of what Carla sells does not

210 Chapter 6 | Learning

This OpenStax book is available for free at

matter because her commission is not based on quality; it’s only based on the number of pairs sold.
This distinction in the quality of performance can help determine which reinforcement method is most
appropriate for a particular situation. Fixed ratios are better suited to optimize the quantity of output,
whereas a fixed interval, in which the reward is not quantity based, can lead to a higher quality of output.

In a variable ratio reinforcement schedule, the number of responses needed for a reward varies. This is
the most powerful partial reinforcement schedule. An example of the variable ratio reinforcement schedule
is gambling. Imagine that Sarah—generally a smart, thrifty woman—visits Las Vegas for the first time.
She is not a gambler, but out of curiosity she puts a quarter into the slot machine, and then another, and
another. Nothing happens. Two dollars in quarters later, her curiosity is fading, and she is just about to
quit. But then, the machine lights up, bells go off, and Sarah gets 50 quarters back. That’s more like it!
Sarah gets back to inserting quarters with renewed interest, and a few minutes later she has used up all
her gains and is $10 in the hole. Now might be a sensible time to quit. And yet, she keeps putting money
into the slot machine because she never knows when the next reinforcement is coming. She keeps thinking
that with the next quarter she could win $50, or $100, or even more. Because the reinforcement schedule
in most types of gambling has a variable ratio schedule, people keep trying and hoping that the next time
they will win big. This is one of the reasons that gambling is so addictive—and so resistant to extinction.

In operant conditioning, extinction of a reinforced behavior occurs at some point after reinforcement stops,
and the speed at which this happens depends on the reinforcement schedule. In a variable ratio schedule,
the point of extinction comes very slowly, as described above. But in the other reinforcement schedules,
extinction may come quickly. For example, if June presses the button for the pain relief medication before
the allotted time her doctor has approved, no medication is administered. She is on a fixed interval
reinforcement schedule (dosed hourly), so extinction occurs quickly when reinforcement doesn’t come at
the expected time. Among the reinforcement schedules, variable ratio is the most productive and the most
resistant to extinction. Fixed interval is the least productive and the easiest to extinguish (Figure 6.13).

Figure 6.13 The four reinforcement schedules yield different response patterns. The variable ratio schedule is
unpredictable and yields high and steady response rates, with little if any pause after reinforcement (e.g., gambler). A
fixed ratio schedule is predictable and produces a high response rate, with a short pause after reinforcement (e.g.,
eyeglass saleswoman). The variable interval schedule is unpredictable and produces a moderate, steady response
rate (e.g., restaurant manager). The fixed interval schedule yields a scallop-shaped response pattern, reflecting a
significant pause after reinforcement (e.g., surgery patient).


Gambling and the Brain

Skinner (1953) stated, “If the gambling establishment cannot persuade a patron to turn over money with no return,
it may achieve the same effect by returning part of the patron’s money on a variable-ratio schedule” (p. 397).

Skinner uses gambling as an example of the power of the variable-ratio reinforcement schedule for maintaining
behavior even during long periods without any reinforcement. In fact, Skinner was so confident in his knowledge

Chapter 6 | Learning 211

of gambling addiction that he even claimed he could turn a pigeon into a pathological gambler (“Skinner’s Utopia,”
1971). It is indeed true that variable-ratio schedules keep behavior quite persistent—just imagine the frequency
of a child’s tantrums if a parent gives in even once to the behavior. The occasional reward makes it almost
impossible to stop the behavior.

Recent research in rats has failed to support Skinner’s idea that training on variable-ratio schedules alone causes
pathological gambling (Laskowski et al., 2019). However, other research suggests that gambling does seem to
work on the brain in the same way as most addictive drugs, and so there may be some combination of brain
chemistry and reinforcement schedule that could lead to problem gambling (Figure 6.14). Specifically, modern
research shows the connection between gambling and the activation of the reward centers of the brain that
use the neurotransmitter (brain chemical) dopamine (Murch & Clark, 2016). Interestingly, gamblers don’t even
have to win to experience the “rush” of dopamine in the brain. “Near misses,” or almost winning but not actually
winning, also have been shown to increase activity in the ventral striatum and other brain reward centers that use
dopamine (Chase & Clark, 2010). These brain effects are almost identical to those produced by addictive drugs
like cocaine and heroin (Murch & Clark, 2016). Based on the neuroscientific evidence showing these similarities,
the DSM-5 now considers gambling an addiction, while earlier versions of the DSM classified gambling as an
impulse control disorder.

Figure 6.14 Some research suggests that pathological gamblers use gambling to compensate for abnormally
low levels of the hormone norepinephrine, which is associated with stress and is secreted in moments of arousal
and thrill. (credit: Ted Murphy)

In addition to dopamine, gambling also appears to involve other neurotransmitters, including norepinephrine and
serotonin (Potenza, 2013). Norepinephrine is secreted when a person feels stress, arousal, or thrill. It may be
that pathological gamblers use gambling to increase their levels of this neurotransmitter. Deficiencies in serotonin
might also contribute to compulsive behavior, including a gambling addiction (Potenza, 2013).

It may be that pathological gamblers’ brains are different than those of other people, and perhaps this difference
may somehow have led to their gambling addiction, as these studies seem to suggest. However, it is very difficult
to ascertain the cause because it is impossible to conduct a true experiment (it would be unethical to try to turn
randomly assigned participants into problem gamblers). Therefore, it may be that causation actually moves in the
opposite direction—perhaps the act of gambling somehow changes neurotransmitter levels in some gamblers’
brains. It also is possible that some overlooked factor, or confounding variable, played a role in both the gambling
addiction and the differences in brain chemistry.


Strict behaviorists like Watson and Skinner focused exclusively on studying behavior rather than cognition
(such as thoughts and expectations). In fact, Skinner was such a staunch believer that cognition didn’t
matter that his ideas were considered radical behaviorism. Skinner considered the mind a “black
box”—something completely unknowable—and, therefore, something not to be studied. However, another
behaviorist, Edward C. Tolman, had a different opinion. Tolman’s experiments with rats demonstrated

212 Chapter 6 | Learning

This OpenStax book is available for free at

that organisms can learn even if they do not receive immediate reinforcement (Tolman & Honzik, 1930;
Tolman, Ritchie, & Kalish, 1946). This finding was in conflict with the prevailing idea at the time that
reinforcement must be immediate in order for learning to occur, thus suggesting a cognitive aspect to

In the experiments, Tolman placed hungry rats in a maze with no reward for finding their way through
it. He also studied a comparison group that was rewarded with food at the end of the maze. As the
unreinforced rats explored the maze, they developed a cognitive map: a mental picture of the layout of
the maze (Figure 6.15). After 10 sessions in the maze without reinforcement, food was placed in a goal
box at the end of the maze. As soon as the rats became aware of the food, they were able to find their way
through the maze quickly, just as quickly as the comparison group, which had been rewarded with food all
along. This is known as latent learning: learning that occurs but is not observable in behavior until there
is a reason to demonstrate it.

Figure 6.15 Psychologist Edward Tolman found that rats use cognitive maps to navigate through a maze. Have you
ever worked your way through various levels on a video game? You learned when to turn left or right, move up or
down. In that case you were relying on a cognitive map, just like the rats in a maze. (credit: modification of work by

Latent learning also occurs in humans. Children may learn by watching the actions of their parents but
only demonstrate it at a later date, when the learned material is needed. For example, suppose that Ravi’s
dad drives him to school every day. In this way, Ravi learns the route from his house to his school, but
he’s never driven there himself, so he has not had a chance to demonstrate that he’s learned the way. One
morning Ravi’s dad has to leave early for a meeting, so he can’t drive Ravi to school. Instead, Ravi follows
the same route on his bike that his dad would have taken in the car. This demonstrates latent learning.
Ravi had learned the route to school, but had no need to demonstrate this knowledge earlier.

Chapter 6 | Learning 213

This Place Is Like a Maze

Have you ever gotten lost in a building and couldn’t find your way back out? While that can be frustrating,
you’re not alone. At one time or another we’ve all gotten lost in places like a museum, hospital, or university
library. Whenever we go someplace new, we build a mental representation—or cognitive map—of the location,
as Tolman’s rats built a cognitive map of their maze. However, some buildings are confusing because they
include many areas that look alike or have short lines of sight. Because of this, it’s often difficult to predict
what’s around a corner or decide whether to turn left or right to get out of a building. Psychologist Laura Carlson
(2010) suggests that what we place in our cognitive map can impact our success in navigating through the
environment. She suggests that paying attention to specific features upon entering a building, such as a picture
on the wall, a fountain, a statue, or an escalator, adds information to our cognitive map that can be used later
to help find our way out of the building.

Watch this video about Carlson’s studies on cognitive maps and navigation in buildings
( to learn more.

6.4 Observational Learning (Modeling)

Learning Objectives

By the end of this section, you will be able to:
• Define observational learning
• Discuss the steps in the modeling process
• Explain the prosocial and antisocial effects of observational learning

Previous sections of this chapter focused on classical and operant conditioning, which are forms of
associative learning. In observational learning, we learn by watching others and then imitating, or
modeling, what they do or say. For instance, have you ever gone to YouTube to find a video showing
you how to do something? The individuals performing the imitated behavior are called models. Research
suggests that this imitative learning involves a specific type of neuron, called a mirror neuron (Hickock,
2010; Rizzolatti, Fadiga, Fogassi, & Gallese, 2002; Rizzolatti, Fogassi, & Gallese, 2006).

Humans and other animals are capable of observational learning. As you will see, the phrase “monkey see,
monkey do” really is accurate (Figure 6.16). The same could be said about other animals. For example,
in a study of social learning in chimpanzees, researchers gave juice boxes with straws to two groups of
captive chimpanzees. The first group dipped the straw into the juice box, and then sucked on the small
amount of juice at the end of the straw. The second group sucked through the straw directly, getting much
more juice. When the first group, the “dippers,” observed the second group, “the suckers,” what do you
think happened? All of the “dippers” in the first group switched to sucking through the straws directly. By
simply observing the other chimps and modeling their behavior, they learned that this was a more efficient
method of getting juice (Yamamoto, Humle, and Tanaka, 2013).



214 Chapter 6 | Learning

This OpenStax book is available for free at

Figure 6.16 This spider monkey learned to drink water from a plastic bottle by seeing the behavior modeled by a
human. (credit: U.S. Air Force, Senior Airman Kasey Close)

Imitation is much more obvious in humans, but is imitation really the sincerest form of flattery? Consider
Claire’s experience with observational learning. Claire’s nine-year-old son, Jay, was getting into trouble at
school and was defiant at home. Claire feared that Jay would end up like her brothers, two of whom were
in prison. One day, after yet another bad day at school and another negative note from the teacher, Claire,
at her wit’s end, beat her son with a belt to get him to behave. Later that night, as she put her children to
bed, Claire witnessed her four-year-old daughter, Anna, take a belt to her teddy bear and whip it. Claire
was horrified, realizing that Anna was imitating her mother. It was then that Claire knew she wanted to
discipline her children in a different manner.

Like Tolman, whose experiments with rats suggested a cognitive component to learning, psychologist
Albert Bandura’s ideas about learning were different from those of strict behaviorists. Bandura and other
researchers proposed a brand of behaviorism called social learning theory, which took cognitive processes
into account. According to Bandura, pure behaviorism could not explain why learning can take place in
the absence of external reinforcement. He felt that internal mental states must also have a role in learning
and that observational learning involves much more than imitation. In imitation, a person simply copies
what the model does. Observational learning is much more complex. According to Lefrançois (2012) there
are several ways that observational learning can occur:

1. You learn a new response. After watching your coworker get chewed out by your boss for coming
in late, you start leaving home 10 minutes earlier so that you won’t be late.

2. You choose whether or not to imitate the model depending on what you saw happen to the model.
Remember Julian and his father? When learning to surf, Julian might watch how his father pops
up successfully on his surfboard and then attempt to do the same thing. On the other hand, Julian
might learn not to touch a hot stove after watching his father get burned on a stove.

3. You learn a general rule that you can apply to other situations.

Bandura identified three kinds of models: live, verbal, and symbolic. A live model demonstrates a behavior
in person, as when Ben stood up on his surfboard so that Julian could see how he did it. A verbal
instructional model does not perform the behavior, but instead explains or describes the behavior, as when
a soccer coach tells his young players to kick the ball with the side of the foot, not with the toe. A symbolic
model can be fictional characters or real people who demonstrate behaviors in books, movies, television
shows, video games, or Internet sources (Figure 6.17).

Chapter 6 | Learning 215

Figure 6.17 (a) Yoga students learn by observation as their yoga instructor demonstrates the correct stance and
movement for her students (live model). (b) Models don’t have to be present for learning to occur: through symbolic
modeling, this child can learn a behavior by watching someone demonstrate it on television. (credit a: modification of
work by Tony Cecala; credit b: modification of work by Andrew Hyde)

Latent learning and modeling are used all the time in the world of marketing and advertising. This Ford
commercial starring Derek Jeter ( played for months across the New York,
New Jersey, and Connecticut areas. Jeter is an award-winning baseball player for the New York Yankees.
The commercial aired in a part of the country where Jeter is an incredibly well-known athlete. He is
wealthy, and considered very loyal and good looking. What message are the advertisers sending by
having him featured in the ad? How effective do you think it is?


Of course, we don’t learn a behavior simply by observing a model. Bandura described specific steps in the
process of modeling that must be followed if learning is to be successful: attention, retention, reproduction,
and motivation. First, you must be focused on what the model is doing—you have to pay attention. Next,
you must be able to retain, or remember, what you observed; this is retention. Then, you must be able to
perform the behavior that you observed and committed to memory; this is reproduction. Finally, you must
have motivation. You need to want to copy the behavior, and whether or not you are motivated depends
on what happened to the model. If you saw that the model was reinforced for her behavior, you will be
more motivated to copy her. This is known as vicarious reinforcement. On the other hand, if you observed
the model being punished, you would be less motivated to copy her. This is called vicarious punishment.
For example, imagine that four-year-old Allison watched her older sister Kaitlyn playing in their mother’s
makeup, and then saw Kaitlyn get a time out when their mother came in. After their mother left the room,
Allison was tempted to play in the make-up, but she did not want to get a time-out from her mother. What
do you think she did? Once you actually demonstrate the new behavior, the reinforcement you receive
plays a part in whether or not you will repeat the behavior.

Bandura researched modeling behavior, particularly children’s modeling of adults’ aggressive and violent
behaviors (Bandura, Ross, & Ross, 1961). He conducted an experiment with a five-foot inflatable doll that
he called a Bobo doll. In the experiment, children’s aggressive behavior was influenced by whether the
teacher was punished for her behavior. In one scenario, a teacher acted aggressively with the doll, hitting,
throwing, and even punching the doll, while a child watched. There were two types of responses by the
children to the teacher’s behavior. When the teacher was punished for her bad behavior, the children


216 Chapter 6 | Learning

This OpenStax book is available for free at

decreased their tendency to act as she had. When the teacher was praised or ignored (and not punished
for her behavior), the children imitated what she did, and even what she said. They punched, kicked, and
yelled at the doll.

Watch this video clip about the famous Bobo doll experiment ( to see
a portion of the experiment and an interview with Albert Bandura.

What are the implications of this study? Bandura concluded that we watch and learn, and that this learning
can have both prosocial and antisocial effects. Prosocial (positive) models can be used to encourage socially
acceptable behavior. Parents in particular should take note of this finding. If you want your children to
read, then read to them. Let them see you reading. Keep books in your home. Talk about your favorite
books. If you want your children to be healthy, then let them see you eat right and exercise, and spend time
engaging in physical fitness activities together. The same holds true for qualities like kindness, courtesy,
and honesty. The main idea is that children observe and learn from their parents, even their parents’
morals, so be consistent and toss out the old adage “Do as I say, not as I do,” because children tend to copy
what you do instead of what you say. Besides parents, many public figures, such as Martin Luther King,
Jr. and Mahatma Gandhi, are viewed as prosocial models who are able to inspire global social change. Can
you think of someone who has been a prosocial model in your life?

The antisocial effects of observational learning are also worth mentioning. As you saw from the example
of Claire at the beginning of this section, her daughter viewed Claire’s aggressive behavior and copied
it. Research suggests that this may help to explain why abused children often grow up to be abusers
themselves (Murrell, Christoff, & Henning, 2007). In fact, about 30% of abused children become abusive
parents (U.S. Department of Health & Human Services, 2013). We tend to do what we know. Abused
children, who grow up witnessing their parents deal with anger and frustration through violent and
aggressive acts, often learn to behave in that manner themselves. Sadly, it’s a vicious cycle that’s difficult
to break.

Some studies suggest that violent television shows, movies, and video games may also have antisocial
effects (Figure 6.18) although further research needs to be done to understand the correlational and
causational aspects of media violence and behavior. Some studies have found a link between viewing
violence and aggression seen in children (Anderson & Gentile, 2008; Kirsch, 2010; Miller, Grabell, Thomas,
Bermann, & Graham-Bermann, 2012). These findings may not be surprising, given that a child graduating
from high school has been exposed to around 200,000 violent acts including murder, robbery, torture,
bombings, beatings, and rape through various forms of media (Huston et al., 1992). Not only might
viewing media violence affect aggressive behavior by teaching people to act that way in real life situations,
but it has also been suggested that repeated exposure to violent acts also desensitizes people to it.
Psychologists are working to understand this dynamic.


Chapter 6 | Learning 217

Figure 6.18 Can video games make us violent? Psychological researchers study this topic. (credit:

View this video about the connection between violent video games and violent behavior
( to learn more.

Violent Media and Aggression

Does watching violent media or playing violent video games cause aggression? Albert Bandura’s early
studies suggested television violence increased aggression in children, and more recent studies support
these findings. For example, research by Craig Anderson and colleagues (Anderson, Bushman, Donnerstein,
Hummer, & Warbuten, 2015; Anderson et al., 2010; Bushman et al., 2016) found extensive evidence to suggest
a causal link between hours of exposure to violent media and aggressive thoughts and behaviors. However,
studies by Christopher Ferguson and others suggests that while there may be a link between violent media
exposure and aggression, research to date has not accounted for other risk factors for aggression including
mental health and family life (Ferguson, 2011; Gentile, 2016). What do think?



218 Chapter 6 | Learning

This OpenStax book is available for free at


associative learning

classical conditioning

cognitive map

conditioned response (CR)

conditioned stimulus (CS)

continuous reinforcement


fixed interval reinforcement schedule

fixed ratio reinforcement schedule

higher-order conditioning


latent learning

law of effect



negative punishment

negative reinforcement

neutral stimulus (NS)

observational learning

operant conditioning

partial reinforcement

positive punishment

Key Terms

period of initial learning in classical conditioning in which a human or an animal begins to
connect a neutral stimulus and an unconditioned stimulus so that the neutral stimulus will begin to elicit
the conditioned response

form of learning that involves connecting certain stimuli or events that occur
together in the environment (classical and operant conditioning)

learning in which the stimulus or experience occurs before the behavior and then
gets paired or associated with the behavior

mental picture of the layout of the environment

response caused by the conditioned stimulus

stimulus that elicits a response due to its being paired with an unconditioned

rewarding a behavior every time it occurs

decrease in the conditioned response when the unconditioned stimulus is no longer paired
with the conditioned stimulus

behavior is rewarded after a set amount of time

set number of responses must occur before a behavior is rewarded

(also, second-order conditioning) using a conditioned stimulus to condition a
neutral stimulus

unlearned knowledge, involving complex patterns of behavior; instincts are thought to be more
prevalent in lower animals than in humans

learning that occurs, but it may not be evident until there is a reason to demonstrate it

behavior that is followed by consequences satisfying to the organism will be repeated and
behaviors that are followed by unpleasant consequences will be discouraged

change in behavior or knowledge that is the result of experience

person who performs a behavior that serves as an example (in observational learning)

taking away a pleasant stimulus to decrease or stop a behavior

taking away an undesirable stimulus to increase a behavior

stimulus that does not initially elicit a response

type of learning that occurs by watching others

form of learning in which the stimulus/experience happens after the behavior is

rewarding behavior only some of the time

adding an undesirable stimulus to stop or decrease a behavior

Chapter 6 | Learning 219

positive reinforcement

primary reinforcer


radical behaviorism



secondary reinforcer


spontaneous recovery

stimulus discrimination

stimulus generalization

unconditioned response (UCR)

unconditioned stimulus (UCS)

variable interval reinforcement schedule

variable ratio reinforcement schedule

vicarious punishment

vicarious reinforcement

adding a desirable stimulus to increase a behavior

has innate reinforcing qualities (e.g., food, water, shelter, sex)

implementation of a consequence in order to decrease a behavior

staunch form of behaviorism developed by B. F. Skinner that suggested that even
complex higher mental functions like human language are nothing more than stimulus-outcome

unlearned, automatic response by an organism to a stimulus in the environment

implementation of a consequence in order to increase a behavior

has no inherent value unto itself and only has reinforcing qualities when linked
with something else (e.g., money, gold stars, poker chips)

rewarding successive approximations toward a target behavior

return of a previously extinguished conditioned response

ability to respond differently to similar stimuli

demonstrating the conditioned response to stimuli that are similar to the
conditioned stimulus

natural (unlearned) behavior to a given stimulus

stimulus that elicits a reflexive response

behavior is rewarded after unpredictable amounts of time
have passed

number of responses differ before a behavior is rewarded

process where the observer sees the model punished, making the observer less
likely to imitate the model’s behavior

process where the observer sees the model rewarded, making the observer
more likely to imitate the model’s behavior


6.1 What Is Learning?
Instincts and reflexes are innate behaviors—they occur naturally and do not involve learning. In contrast,
learning is a change in behavior or knowledge that results from experience. There are three main types
of learning: classical conditioning, operant conditioning, and observational learning. Both classical and
operant conditioning are forms of associative learning where associations are made between events that
occur together. Observational learning is just as it sounds: learning by observing others.

6.2 Classical Conditioning
Pavlov’s pioneering work with dogs contributed greatly to what we know about learning. His experiments
explored the type of associative learning we now call classical conditioning. In classical conditioning,
organisms learn to associate events that repeatedly happen together, and researchers study how a reflexive
response to a stimulus can be mapped to a different stimulus—by training an association between the
two stimuli. Pavlov’s experiments show how stimulus-response bonds are formed. Watson, the founder

220 Chapter 6 | Learning

This OpenStax book is available for free at

of behaviorism, was greatly influenced by Pavlov’s work. He tested humans by conditioning fear in an
infant known as Little Albert. His findings suggest that classical conditioning can explain how some fears

6.3 Operant Conditioning
Operant conditioning is based on the work of B. F. Skinner. Operant conditioning is a form of learning in
which the motivation for a behavior happens after the behavior is demonstrated. An animal or a human
receives a consequence after performing a specific behavior. The consequence is either a reinforcer or
a punisher. All reinforcement (positive or negative) increases the likelihood of a behavioral response.
All punishment (positive or negative) decreases the likelihood of a behavioral response. Several types of
reinforcement schedules are used to reward behavior depending on either a set or variable period of time.

6.4 Observational Learning (Modeling)
According to Bandura, learning can occur by watching others and then modeling what they do or say.
This is known as observational learning. There are specific steps in the process of modeling that must
be followed if learning is to be successful. These steps include attention, retention, reproduction, and
motivation. Through modeling, Bandura has shown that children learn many things both good and bad
simply by watching their parents, siblings, and others.

Review Questions

1. Which of the following is an example of a
reflex that occurs at some point in the
development of a human being?

a. child riding a bike
b. teen socializing
c. infant sucking on a nipple
d. toddler walking

2. Learning is best defined as a relatively
permanent change in behavior that ________.

a. is innate
b. occurs as a result of experience
c. is found only in humans
d. occurs by observing others

3. Two forms of associative learning are ________
and ________.

a. classical conditioning; operant conditioning
b. classical conditioning; Pavlovian

c. operant conditioning; observational

d. operant conditioning; learning conditioning

4. In ________ the stimulus or experience occurs
before the behavior and then gets paired with the

a. associative learning
b. observational learning
c. operant conditioning
d. classical conditioning

5. A stimulus that does not initially elicit a
response in an organism is a(n) ________.

a. unconditioned stimulus
b. neutral stimulus
c. conditioned stimulus
d. unconditioned response

6. In Watson and Rayner’s experiments, Little
Albert was conditioned to fear a white rat, and
then he began to be afraid of other furry white
objects. This demonstrates ________.

a. higher order conditioning
b. acquisition
c. stimulus discrimination
d. stimulus generalization

Chapter 6 | Learning 221

7. Extinction occurs when ________.
a. the conditioned stimulus is presented

repeatedly without being paired with an
unconditioned stimulus

b. the unconditioned stimulus is presented
repeatedly without being paired with a
conditioned stimulus

c. the neutral stimulus is presented repeatedly
without being paired with an
unconditioned stimulus

d. the neutral stimulus is presented repeatedly
without being paired with a conditioned

8. In Pavlov’s work with dogs, the psychic
secretions were ________.

a. unconditioned responses
b. conditioned responses
c. unconditioned stimuli
d. conditioned stimuli

9. ________ is when you take away a pleasant
stimulus to stop a behavior.

a. positive reinforcement
b. negative reinforcement
c. positive punishment
d. negative punishment

10. Which of the following is not an example of a
primary reinforcer?

a. food
b. money
c. water
d. sex

11. Rewarding successive approximations toward
a target behavior is ________.

a. shaping
b. extinction
c. positive reinforcement
d. negative reinforcement

12. Slot machines reward gamblers with money
according to which reinforcement schedule?

a. fixed ratio
b. variable ratio
c. fixed interval
d. variable interval

13. The person who performs a behavior that
serves as an example is called a ________.

a. teacher
b. model
c. instructor
d. coach

14. In Bandura’s Bobo doll study, when the
children who watched the aggressive model were
placed in a room with the doll and other toys, they

a. ignored the doll
b. played nicely with the doll
c. played with tinker toys
d. kicked and threw the doll

15. Which is the correct order of steps in the
modeling process?

a. attention, retention, reproduction,

b. motivation, attention, reproduction,

c. attention, motivation, retention,

d. motivation, attention, retention,

16. Who proposed observational learning?
a. Ivan Pavlov
b. John Watson
c. Albert Bandura
d. B. F. Skinner

Critical Thinking Questions

17. Compare and contrast classical and operant conditioning. How are they alike? How do they differ?

18. What is the difference between a reflex and a learned behavior?

19. If the sound of your toaster popping up toast causes your mouth to water, what are the UCS, CS, and

222 Chapter 6 | Learning

This OpenStax book is available for free at

20. Explain how the processes of stimulus generalization and stimulus discrimination are considered

21. How does a neutral stimulus become a conditioned stimulus?

22. What is a Skinner box and what is its purpose?

23. What is the difference between negative reinforcement and punishment?

24. What is shaping and how would you use shaping to teach a dog to roll over?

25. What is the effect of prosocial modeling and antisocial modeling?

26. Cara is 17 years old. Cara’s mother and father both drink alcohol every night. They tell Cara that
drinking is bad and she shouldn’t do it. Cara goes to a party where beer is being served. What do you think
Cara will do? Why?

Personal Application Questions

27. What is your personal definition of learning? How do your ideas about learning compare with the
definition of learning presented in this text?

28. What kinds of things have you learned through the process of classical conditioning? Operant
conditioning? Observational learning? How did you learn them?

29. Can you think of an example in your life of how classical conditioning has produced a positive
emotional response, such as happiness or excitement? How about a negative emotional response, such as
fear, anxiety, or anger?

30. Explain the difference between negative reinforcement and punishment, and provide several
examples of each based on your own experiences.

31. Think of a behavior that you have that you would like to change. How could you use behavior
modification, specifically positive reinforcement, to change your behavior? What is your positive

32. What is something you have learned how to do after watching someone else?

Chapter 6 | Learning 223

224 Chapter 6 | Learning

This OpenStax book is available for free at

Chapter 7

Thinking and Intelligence

Figure 7.1 Thinking is an important part of our human experience, and one that has captivated people for centuries.
Today, it is one area of psychological study. The 19th-century Girl with a Book by José Ferraz de Almeida Júnior, the
20th-century sculpture The Thinker by August Rodin, and Shi Ke’s 10th-century painting Huike Thinking all reflect the
fascination with the process of human thought. (credit “middle”: modification of work by Jason Rogers; credit “right”:
modification of work by Tang Zu-Ming)

Chapter Outline

7.1 What Is Cognition?

7.2 Language

7.3 Problem Solving

7.4 What Are Intelligence and Creativity?

7.5 Measures of Intelligence

7.6 The Source of Intelligence


What is the best way to solve a problem? How does a person who has never seen or touched snow in real
life develop an understanding of the concept of snow? How do young children acquire the ability to learn
language with no formal instruction? Psychologists who study thinking explore questions like these and
are called cognitive psychologists.

Cognitive psychologists also study intelligence. What is intelligence, and how does it vary from person
to person? Are “street smarts” a kind of intelligence, and if so, how do they relate to other types of
intelligence? What does an IQ test really measure? These questions and more will be explored in this
chapter as you study thinking and intelligence.

In other chapters, we discussed the cognitive processes of perception, learning, and memory. In this
chapter, we will focus on high-level cognitive processes. As a part of this discussion, we will consider
thinking and briefly explore the development and use of language. We will also discuss problem solving
and creativity before ending with a discussion of how intelligence is measured and how our biology
and environments interact to affect intelligence. After finishing this chapter, you will have a greater
appreciation of the higher-level cognitive processes that contribute to our distinctiveness as a species.

Chapter 7 | Thinking and Intelligence 225

7.1 What Is Cognition?

Learning Objectives

By the end of this section, you will be able to:
• Describe cognition
• Distinguish concepts and prototypes
• Explain the difference between natural and artificial concepts
• Describe how schemata are organized and constructed

Imagine all of your thoughts as if they were physical entities, swirling rapidly inside your mind. How is it
possible that the brain is able to move from one thought to the next in an organized, orderly fashion? The
brain is endlessly perceiving, processing, planning, organizing, and remembering—it is always active. Yet,
you don’t notice most of your brain’s activity as you move throughout your daily routine. This is only one
facet of the complex processes involved in cognition. Simply put, cognition is thinking, and it encompasses
the processes associated with perception, knowledge, problem solving, judgment, language, and memory.
Scientists who study cognition are searching for ways to understand how we integrate, organize, and
utilize our conscious cognitive experiences without being aware of all of the unconscious work that our
brains are doing (for example, Kahneman, 2011).


Upon waking each morning, you begin thinking—contemplating the tasks that you must complete that
day. In what order should you run your errands? Should you go to the bank, the cleaners, or the grocery
store first? Can you get these things done before you head to class or will they need to wait until school
is done? These thoughts are one example of cognition at work. Exceptionally complex, cognition is an
essential feature of human consciousness, yet not all aspects of cognition are consciously experienced.

Cognitive psychology is the field of psychology dedicated to examining how people think. It attempts
to explain how and why we think the way we do by studying the interactions among human thinking,
emotion, creativity, language, and problem solving, in addition to other cognitive processes. Cognitive
psychologists strive to determine and measure different types of intelligence, why some people are better
at problem solving than others, and how emotional intelligence affects success in the workplace, among
countless other topics. They also sometimes focus on how we organize thoughts and information gathered
from our environments into meaningful categories of thought, which will be discussed later.


The human nervous system is capable of handling endless streams of information. The senses serve as
the interface between the mind and the external environment, receiving stimuli and translating it into
nervous impulses that are transmitted to the brain. The brain then processes this information and uses the
relevant pieces to create thoughts, which can then be expressed through language or stored in memory
for future use. To make this process more complex, the brain does not gather information from external
environments only. When thoughts are formed, the mind synthesizes information from emotions and
memories (Figure 7.2). Emotion and memory are powerful influences on both our thoughts and behaviors.

226 Chapter 7 | Thinking and Intelligence

This OpenStax book is available for free at

Figure 7.2 Sensations and information are received by our brains, filtered through emotions and memories, and
processed to become thoughts.

In order to organize this staggering amount of information, the mind has developed a “file cabinet” of sorts
in the mind. The different files stored in the file cabinet are called concepts. Concepts are categories or
groupings of linguistic information, images, ideas, or memories, such as life experiences. Concepts are,
in many ways, big ideas that are generated by observing details, and categorizing and combining these
details into cognitive structures. You use concepts to see the relationships among the different elements of
your experiences and to keep the information in your mind organized and accessible.

Concepts are informed by our semantic memory (you will learn more about semantic memory in a later
chapter) and are present in every aspect of our lives; however, one of the easiest places to notice concepts
is inside a classroom, where they are discussed explicitly. When you study United States history, for
example, you learn about more than just individual events that have happened in America’s past. You
absorb a large quantity of information by listening to and participating in discussions, examining maps,
and reading first-hand accounts of people’s lives. Your brain analyzes these details and develops an overall
understanding of American history. In the process, your brain gathers details that inform and refine your
understanding of related concepts like democracy, power, and freedom.

Concepts can be complex and abstract, like justice, or more concrete, like types of birds. In psychology,
for example, Piaget’s stages of development are abstract concepts. Some concepts, like tolerance, are
agreed upon by many people, because they have been used in various ways over many years. Other
concepts, like the characteristics of your ideal friend or your family’s birthday traditions, are personal and
individualized. In this way, concepts touch every aspect of our lives, from our many daily routines to the
guiding principles behind the way governments function.

Another technique used by your brain to organize information is the identification of prototypes for the
concepts you have developed. A prototype is the best example or representation of a concept. For example,
what comes to your mind when you think of a dog? Most likely your early experiences with dogs will
shape what you imagine. If your first pet was a Golden Retriever, there is a good chance that this would
be your prototype for the category of dogs.


In psychology, concepts can be divided into two categories, natural and artificial. Natural concepts
are created “naturally” through your experiences and can be developed from either direct or indirect
experiences. For example, if you live in Essex Junction, Vermont, you have probably had a lot of direct
experience with snow. You’ve watched it fall from the sky, you’ve seen lightly falling snow that barely
covers the windshield of your car, and you’ve shoveled out 18 inches of fluffy white snow as you’ve

Chapter 7 | Thinking and Intelligence 227

thought, “This is perfect for skiing.” You’ve thrown snowballs at your best friend and gone sledding down
the steepest hill in town. In short, you know snow. You know what it looks like, smells like, tastes like,
and feels like. If, however, you’ve lived your whole life on the island of Saint Vincent in the Caribbean,
you may never have actually seen snow, much less tasted, smelled, or touched it. You know snow from
the indirect experience of seeing pictures of falling snow—or from watching films that feature snow as
part of the setting. Either way, snow is a natural concept because you can construct an understanding of it
through direct observations, experiences with snow, or indirect knowledge (such as from films or books)
(Figure 7.3).

Figure 7.3 (a) Our concept of snow is an example of a natural concept—one that we understand through direct
observation and experience. (b) In contrast, artificial concepts are ones that we know by a specific set of
characteristics that they always exhibit, such as what defines different basic shapes. (credit a: modification of work by
Maarten Takens; credit b: modification of work by “Shayan (USA)”/Flickr)

An artificial concept, on the other hand, is a concept that is defined by a specific set of characteristics.
Various properties of geometric shapes, like squares and triangles, serve as useful examples of artificial
concepts. A triangle always has three angles and three sides. A square always has four equal sides and
four right angles. Mathematical formulas, like the equation for area (length × width) are artificial concepts
defined by specific sets of characteristics that are always the same. Artificial concepts can enhance the
understanding of a topic by building on one another. For example, before learning the concept of “area of
a square” (and the formula to find it), you must understand what a square is. Once the concept of “area
of a square” is understood, an understanding of area for other geometric shapes can be built upon the
original understanding of area. The use of artificial concepts to define an idea is crucial to communicating
with others and engaging in complex thought. According to Goldstone and Kersten (2003), concepts act as
building blocks and can be connected in countless combinations to create complex thoughts.


A schema is a mental construct consisting of a cluster or collection of related concepts (Bartlett, 1932).
There are many different types of schemata, and they all have one thing in common: schemata are a
method of organizing information that allows the brain to work more efficiently. When a schema is
activated, the brain makes immediate assumptions about the person or object being observed.

There are several types of schemata. A role schema makes assumptions about how individuals in certain
roles will behave (Callero, 1994). For example, imagine you meet someone who introduces himself as a
firefighter. When this happens, your brain automatically activates the “firefighter schema” and begins
making assumptions that this person is brave, selfless, and community-oriented. Despite not knowing
this person, already you have unknowingly made judgments about him. Schemata also help you fill in
gaps in the information you receive from the world around you. While schemata allow for more efficient
information processing, there can be problems with schemata, regardless of whether they are accurate:
Perhaps this particular firefighter is not brave, he just works as a firefighter to pay the bills while studying
to become a children’s librarian.

228 Chapter 7 | Thinking and Intelligence

This OpenStax book is available for free at

An event schema, also known as a cognitive script, is a set of behaviors that can feel like a routine. Think
about what you do when you walk into an elevator (Figure 7.4). First, the doors open and you wait to
let exiting passengers leave the elevator car. Then, you step into the elevator and turn around to face
the doors, looking for the correct button to push. You never face the back of the elevator, do you? And
when you’re riding in a crowded elevator and you can’t face the front, it feels uncomfortable, doesn’t it?
Interestingly, event schemata can vary widely among different cultures and countries. For example, while
it is quite common for people to greet one another with a handshake in the United States, in Tibet, you
greet someone by sticking your tongue out at them, and in Belize, you bump fists (Cairns Regional Council,

Figure 7.4 What event schema do you perform when riding in an elevator? (credit: “Gideon”/Flickr)

Because event schemata are automatic, they can be difficult to change. Imagine that you are driving home
from work or school. This event schema involves getting in the car, shutting the door, and buckling your
seatbelt before putting the key in the ignition. You might perform this script two or three times each day.
As you drive home, you hear your phone’s ring tone. Typically, the event schema that occurs when you
hear your phone ringing involves locating the phone and answering it or responding to your latest text
message. So without thinking, you reach for your phone, which could be in your pocket, in your bag, or
on the passenger seat of the car. This powerful event schema is informed by your pattern of behavior and
the pleasurable stimulation that a phone call or text message gives your brain. Because it is a schema, it is
extremely challenging for us to stop reaching for the phone, even though we know that we endanger our
own lives and the lives of others while we do it (Neyfakh, 2013) (Figure 7.5).

Figure 7.5 Texting while driving is dangerous, but it is a difficult event schema for some people to resist.

Remember the elevator? It feels almost impossible to walk in and not face the door. Our powerful event
schema dictates our behavior in the elevator, and it is no different with our phones. Current research
suggests that it is the habit, or event schema, of checking our phones in many different situations that
makes refraining from checking them while driving especially difficult (Bayer & Campbell, 2012). Because
texting and driving has become a dangerous epidemic in recent years, psychologists are looking at ways
to help people interrupt the “phone schema” while driving. Event schemata like these are the reason why
many habits are difficult to break once they have been acquired. As we continue to examine thinking, keep

Chapter 7 | Thinking and Intelligence 229

in mind how powerful the forces of concepts and schemata are to our understanding of the world.

7.2 Language

Learning Objectives

By the end of this section, you will be able to:
• Define language and demonstrate familiarity with the components of language
• Understand the development of language
• Explain the relationship between language and thinking

Language is a communication system that involves using words and systematic rules to organize those
words to transmit information from one individual to another. While language is a form of
communication, not all communication is language. Many species communicate with one another through
their postures, movements, odors, or vocalizations. This communication is crucial for species that need to
interact and develop social relationships with their conspecifics. However, many people have asserted that
it is language that makes humans unique among all of the animal species (Corballis & Suddendorf, 2007;
Tomasello & Rakoczy, 2003). This section will focus on what distinguishes language as a special form of
communication, how the use of language develops, and how language affects the way we think.


Language, be it spoken, signed, or written, has specific components: a lexicon and grammar. Lexicon refers
to the words of a given language. Thus, lexicon is a language’s vocabulary. Grammar refers to the set
of rules that are used to convey meaning through the use of the lexicon (Fernández & Cairns, 2011). For
instance, English grammar dictates that most verbs receive an “-ed” at the end to indicate past tense.

Words are formed by combining the various phonemes that make up the language. A phoneme (e.g., the
sounds “ah” vs. “eh”) is a basic sound unit of a given language, and different languages have different
sets of phonemes. Phonemes are combined to form morphemes, which are the smallest units of language
that convey some type of meaning (e.g., “I” is both a phoneme and a morpheme). We use semantics and
syntax to construct language. Semantics and syntax are part of a language’s grammar. Semantics refers to
the process by which we derive meaning from morphemes and words. Syntax refers to the way words are
organized into sentences (Chomsky, 1965; Fernández & Cairns, 2011).

We apply the rules of grammar to organize the lexicon in novel and creative ways, which allow us to
communicate information about both concrete and abstract concepts. We can talk about our immediate
and observable surroundings as well as the surface of unseen planets. We can share our innermost
thoughts, our plans for the future, and debate the value of a college education. We can provide detailed
instructions for cooking a meal, fixing a car, or building a fire. Through our use of words and language,
we are able to form, organize, and express ideas, schema, and artificial concepts.


Given the remarkable complexity of a language, one might expect that mastering a language would
be an especially arduous task; indeed, for those of us trying to learn a second language as adults, this
might seem to be true. However, young children master language very quickly with relative ease. B. F.
Skinner (1957) proposed that language is learned through reinforcement. Noam Chomsky (1965) criticized
this behaviorist approach, asserting instead that the mechanisms underlying language acquisition are
biologically determined. The use of language develops in the absence of formal instruction and appears
to follow a very similar pattern in children from vastly different cultures and backgrounds. It would
seem, therefore, that we are born with a biological predisposition to acquire a language (Chomsky, 1965;

230 Chapter 7 | Thinking and Intelligence

This OpenStax book is available for free at

Fernández & Cairns, 2011). Moreover, it appears that there is a critical period for language acquisition,
such that this proficiency at acquiring language is maximal early in life; generally, as people age, the ease
with which they acquire and master new languages diminishes (Johnson & Newport, 1989; Lenneberg,
1967; Singleton, 1995).

Children begin to learn about language from a very early age (Table 7.1). In fact, it appears that this is
occurring even before we are born. Newborns show preference for their mother’s voice and appear to be
able to discriminate between the language spoken by their mother and other languages. Babies are also
attuned to the languages being used around them and show preferences for videos of faces that are moving
in synchrony with the audio of spoken language versus videos that do not synchronize with the audio
(Blossom & Morgan, 2006; Pickens, 1994; Spelke & Cortelyou, 1981).

Stages of Language and Communication Development

Stage Age Developmental Language and Communication

1 0–3 months Reflexive communication

2 3–8 months Reflexive communication; interest in others

3 8–13 months Intentional communication; sociability

4 12–18 months First words

5 18–24 months Simple sentences of two words

6 2–3 years Sentences of three or more words

7 3–5 years Complex sentences; has conversations

Table 7.1

The Case of Genie

In the fall of 1970, a social worker in the Los Angeles area found a 13-year-old girl who was being raised in
extremely neglectful and abusive conditions. The girl, who came to be known as Genie, had lived most of her
life tied to a potty chair or confined to a crib in a small room that was kept closed with the curtains drawn. For a
little over a decade, Genie had virtually no social interaction and no access to the outside world. As a result of
these conditions, Genie was unable to stand up, chew solid food, or speak (Fromkin, Krashen, Curtiss, Rigler,
& Rigler, 1974; Rymer, 1993). The police took Genie into protective custody.

Genie’s abilities improved dramatically following her removal from her abusive environment, and early on, it
appeared she was acquiring language—much later than would be predicted by critical period hypotheses that
had been posited at the time (Fromkin et al., 1974). Genie managed to amass an impressive vocabulary in
a relatively short amount of time. However, she never developed a mastery of the grammatical aspects of
language (Curtiss, 1981). Perhaps being deprived of the opportunity to learn language during a critical period
impeded Genie’s ability to fully acquire and use language.

You may recall that each language has its own set of phonemes that are used to generate morphemes,
words, and so on. Babies can discriminate among the sounds that make up a language (for example, they
can tell the difference between the “s” in vision and the “ss” in fission); early on, they can differentiate


Chapter 7 | Thinking and Intelligence 231

between the sounds of all human languages, even those that do not occur in the languages that are used in
their environments. However, by the time that they are about 1 year old, they can only discriminate among
those phonemes that are used in the language or languages in their environments (Jensen, 2011; Werker &
Lalonde, 1988; Werker & Tees, 1984).

Watch this video about how babies lose the ability to discriminate among all possible human
phonemes as they age ( to learn more.

After the first few months of life, babies enter what is known as the babbling stage, during which time they
tend to produce single syllables that are repeated over and over. As time passes, more variations appear in
the syllables that they produce. During this time, it is unlikely that the babies are trying to communicate;
they are just as likely to babble when they are alone as when they are with their caregivers (Fernández &
Cairns, 2011). Interestingly, babies who are raised in environments in which sign language is used will also
begin to show babbling in the gestures of their hands during this stage (Petitto, Holowka, Sergio, Levy, &
Ostry, 2004).

Generally, a child’s first word is uttered sometime between the ages of 1 year to 18 months, and for the
next few months, the child will remain in the “one word” stage of language development. During this
time, children know a number of words, but they only produce one-word utterances. The child’s early
vocabulary is limited to familiar objects or events, often nouns. Although children in this stage only make
one-word utterances, these words often carry larger meaning (Fernández & Cairns, 2011). So, for example,
a child saying “cookie” could be identifying a cookie or asking for a cookie.

As a child’s lexicon grows, she begins to utter simple sentences and to acquire new vocabulary at a very
rapid pace. In addition, children begin to demonstrate a clear understanding of the specific rules that
apply to their language(s). Even the mistakes that children sometimes make provide evidence of just how
much they understand about those rules. This is sometimes seen in the form of overgeneralization. In
this context, overgeneralization refers to an extension of a language rule to an exception to the rule. For
example, in English, it is usually the case that an “s” is added to the end of a word to indicate plurality.
For example, we speak of one dog versus two dogs. Young children will overgeneralize this rule to cases
that are exceptions to the “add an s to the end of the word” rule and say things like “those two gooses” or
“three mouses.” Clearly, the rules of the language are understood, even if the exceptions to the rules are
still being learned (Moskowitz, 1978).


When we speak one language, we agree that words are representations of ideas, people, places, and events.
The given language that children learn is connected to their culture and surroundings. But can words
themselves shape the way we think about things? Psychologists have long investigated the question of
whether language shapes thoughts and actions, or whether our thoughts and beliefs shape our language.
Two researchers, Edward Sapir and Benjamin Lee Whorf, began this investigation in the 1940s. They
wanted to understand how the language habits of a community encourage members of that community
to interpret language in a particular manner (Sapir, 1941/1964). Sapir and Whorf proposed that language
determines thought. For example, in some languages there are many different words for love. However,
in English we use the word love for all types of love. Does this affect how we think about love depending
on the language that we speak (Whorf, 1956)? Researchers have since identified this view as too absolute,
pointing out a lack of empiricism behind what Sapir and Whorf proposed (Abler, 2013; Boroditsky, 2011;
van Troyer, 1994). Today, psychologists continue to study and debate the relationship between language


232 Chapter 7 | Thinking and Intelligence

This OpenStax book is available for free at

and thought.

The Meaning of Language

Think about what you know of other languages; perhaps you even speak multiple languages. Imagine for
a moment that your closest friend fluently speaks more than one language. Do you think that friend thinks
differently, depending on which language is being spoken? You may know a few words that are not translatable
from their original language into English. For example, the Portuguese word saudade originated during the
15th century, when Portuguese sailors left home to explore the seas and travel to Africa or Asia. Those left
behind described the emptiness and fondness they felt as saudade (Figure 7.6). The word came to express
many meanings, including loss, nostalgia, yearning, warm memories, and hope. There is no single word in
English that includes all of those emotions in a single description. Do words such as saudade indicate that
different languages produce different patterns of thought in people? What do you think??

Figure 7.6 These two works of art depict saudade. (a) Saudade de Nápoles, which is translated into
“missing Naples,” was painted by Bertha Worms in 1895. (b) Almeida Júnior painted Saudade in 1899.

Language may indeed influence the way that we think, an idea known as linguistic determinism. One
recent demonstration of this phenomenon involved differences in the way that English and Mandarin
Chinese speakers talk and think about time. English speakers tend to talk about time using terms that
describe changes along a horizontal dimension, for example, saying something like “I’m running behind
schedule” or “Don’t get ahead of yourself.” While Mandarin Chinese speakers also describe time in
horizontal terms, it is not uncommon to also use terms associated with a vertical arrangement. For
example, the past might be described as being “up” and the future as being “down.” It turns out that these
differences in language translate into differences in performance on cognitive tests designed to measure
how quickly an individual can recognize temporal relationships. Specifically, when given a series of
tasks with vertical priming, Mandarin Chinese speakers were faster at recognizing temporal relationships
between months. Indeed, Boroditsky (2001) sees these results as suggesting that “habits in language
encourage habits in thought” (p. 12).

One group of researchers who wanted to investigate how language influences thought compared how


Chapter 7 | Thinking and Intelligence 233

English speakers and the Dani people of Papua New Guinea think and speak about color. The Dani have
two words for color: one word for light and one word for dark. In contrast, the English language has 11
color words. Researchers hypothesized that the number of color terms could limit the ways that the Dani
people conceptualized color. However, the Dani were able to distinguish colors with the same ability as
English speakers, despite having fewer words at their disposal (Berlin & Kay, 1969). A recent review of
research aimed at determining how language might affect something like color perception suggests that
language can influence perceptual phenomena, especially in the left hemisphere of the brain. You may
recall from earlier chapters that the left hemisphere is associated with language for most people. However,
the right (less linguistic hemisphere) of the brain is less affected by linguistic influences on perception
(Regier & Kay, 2009)

7.3 Problem Solving

Learning Objectives

By the end of this section, you will be able to:
• Describe problem solving strategies
• Define algorithm and heuristic
• Explain some common roadblocks to effective problem solving and decision making

People face problems every day—usually, multiple problems throughout the day. Sometimes these
problems are straightforward: To double a recipe for pizza dough, for example, all that is required is
that each ingredient in the recipe be doubled. Sometimes, however, the problems we encounter are more
complex. For example, say you have a work deadline, and you must mail a printed copy of a report to your
supervisor by the end of the business day. The report is time-sensitive and must be sent overnight. You
finished the report last night, but your printer will not work today. What should you do? First, you need
to identify the problem and then apply a strategy for solving the problem.


When you are presented with a problem—whether it is a complex mathematical problem or a broken
printer, how do you solve it? Before finding a solution to the problem, the problem must first be clearly
identified. After that, one of many problem solving strategies can be applied, hopefully resulting in a

A problem-solving strategy is a plan of action used to find a solution. Different strategies have different
action plans associated with them (Table 7.2). For example, a well-known strategy is trial and error. The
old adage, “If at first you don’t succeed, try, try again” describes trial and error. In terms of your broken
printer, you could try checking the ink levels, and if that doesn’t work, you could check to make sure the
paper tray isn’t jammed. Or maybe the printer isn’t actually connected to your laptop. When using trial
and error, you would continue to try different solutions until you solved your problem. Although trial and
error is not typically one of the most time-efficient strategies, it is a commonly used one.

Problem-Solving Strategies

Method Description Example

Trial and

Continue trying different
solutions until problem is

Restarting phone, turning off WiFi, turning off
bluetooth in order to determine why your phone is

234 Chapter 7 | Thinking and Intelligence

This OpenStax book is available for free at

Problem-Solving Strategies

Method Description Example

Algorithm Step-by-step problem-
solving formula

Instruction manual for installing new software on your

Heuristic General problem-solving

Working backwards; breaking a task into steps

Table 7.2

Another type of strategy is an algorithm. An algorithm is a problem-solving formula that provides you
with step-by-step instructions used to achieve a desired outcome (Kahneman, 2011). You can think of an
algorithm as a recipe with highly detailed instructions that produce the same result every time they are
performed. Algorithms are used frequently in our everyday lives, especially in computer science. When
you run a search on the Internet, search engines like Google use algorithms to decide which entries will
appear first in your list of results. Facebook also uses algorithms to decide which posts to display on your
newsfeed. Can you identify other situations in which algorithms are used?

A heuristic is another type of problem solving strategy. While an algorithm must be followed exactly
to produce a correct result, a heuristic is a general problem-solving framework (Tversky & Kahneman,
1974). You can think of these as mental shortcuts that are used to solve problems. A “rule of thumb” is an
example of a heuristic. Such a rule saves the person time and energy when making a decision, but despite
its time-saving characteristics, it is not always the best method for making a rational decision. Different
types of heuristics are used in different types of situations, but the impulse to use a heuristic occurs when
one of five conditions is met (Pratkanis, 1989):

• When one is faced with too much information

• When the time to make a decision is limited

• When the decision to be made is unimportant

• When there is access to very little information to use in making the decision

• When an appropriate heuristic happens to come to mind in the same moment

Working backwards is a useful heuristic in which you begin solving the problem by focusing on the end
result. Consider this example: You live in Washington, D.C. and have been invited to a wedding at 4 PM
on Saturday in Philadelphia. Knowing that Interstate 95 tends to back up any day of the week, you need to
plan your route and time your departure accordingly. If you want to be at the wedding service by 3:30 PM,
and it takes 2.5 hours to get to Philadelphia without traffic, what time should you leave your house? You
use the working backwards heuristic to plan the events of your day on a regular basis, probably without
even thinking about it.

Another useful heuristic is the practice of accomplishing a large goal or task by breaking it into a series
of smaller steps. Students often use this common method to complete a large research project or long
essay for school. For example, students typically brainstorm, develop a thesis or main topic, research the
chosen topic, organize their information into an outline, write a rough draft, revise and edit the rough
draft, develop a final draft, organize the references list, and proofread their work before turning in the
project. The large task becomes less overwhelming when it is broken down into a series of small steps.

Chapter 7 | Thinking and Intelligence 235

Solving Puzzles

Problem-solving abilities can improve with practice. Many people challenge themselves every day with puzzles
and other mental exercises to sharpen their problem-solving skills. Sudoku puzzles appear daily in most
newspapers. Typically, a sudoku puzzle is a 9×9 grid. The simple sudoku below (Figure 7.7) is a 4×4 grid. To
solve the puzzle, fill in the empty boxes with a single digit: 1, 2, 3, or 4. Here are the rules: The numbers must
total 10 in each bolded box, each row, and each column; however, each digit can only appear once in a bolded
box, row, and column. Time yourself as you solve this puzzle and compare your time with a classmate.

Figure 7.7 How long did it take you to solve this sudoku puzzle? (You can see the answer at the end of this

Here is another popular type of puzzle (Figure 7.8) that challenges your spatial reasoning skills. Connect all
nine dots with four connecting straight lines without lifting your pencil from the paper:


236 Chapter 7 | Thinking and Intelligence

This OpenStax book is available for free at

Figure 7.8 Did you figure it out? (The answer is at the end of this section.) Once you understand how to
crack this puzzle, you won’t forget.

Take a look at the “Puzzling Scales” logic puzzle below (Figure 7.9). Sam Loyd, a well-known puzzle master,
created and refined countless puzzles throughout his lifetime (Cyclopedia of Puzzles, n.d.).

Chapter 7 | Thinking and Intelligence 237

Figure 7.9 What steps did you take to solve this puzzle? You can read the solution at the end of this section.


Not all problems are successfully solved, however. What challenges stop us from successfully solving a
problem? Albert Einstein once said, “Insanity is doing the same thing over and over again and expecting a
different result.” Imagine a person in a room that has four doorways. One doorway that has always been
open in the past is now locked. The person, accustomed to exiting the room by that particular doorway,
keeps trying to get out through the same doorway even though the other three doorways are open. The
person is stuck—but she just needs to go to another doorway, instead of trying to get out through the
locked doorway. A mental set is where you persist in approaching a problem in a way that has worked in
the past but is clearly not working now.

Functional fixedness is a type of mental set where you cannot perceive an object being used for something
other than what it was designed for. Duncker (1945) conducted foundational research on functional
fixedness. He created an experiment in which participants were given a candle, a book of matches, and a
box of thumbtacks. They were instructed to use those items to attach the candle to the wall so that it did not
drip wax onto the table below. Participants had to use functional fixedness to solve the problem (Figure
7.10). During the Apollo 13 mission to the moon, NASA engineers at Mission Control had to overcome
functional fixedness to save the lives of the astronauts aboard the spacecraft. An explosion in a module
of the spacecraft damaged multiple systems. The astronauts were in danger of being poisoned by rising
levels of carbon dioxide because of problems with the carbon dioxide filters. The engineers found a way
for the astronauts to use spare plastic bags, tape, and air hoses to create a makeshift air filter, which saved

238 Chapter 7 | Thinking and Intelligence

This OpenStax book is available for free at

the lives of the astronauts.

Figure 7.10 In Duncker’s classic study, participants were provided the three objects in the top panel and asked to
solve the problem. The solution is shown in the bottom portion.

Check out this Apollo 13 scene about NASA engineers overcoming functional fixedness
( to learn more.

Researchers have investigated whether functional fixedness is affected by culture. In one experiment,
individuals from the Shuar group in Ecuador were asked to use an object for a purpose other than that
for which the object was originally intended. For example, the participants were told a story about a bear
and a rabbit that were separated by a river and asked to select among various objects, including a spoon,
a cup, erasers, and so on, to help the animals. The spoon was the only object long enough to span the
imaginary river, but if the spoon was presented in a way that reflected its normal usage, it took participants
longer to choose the spoon to solve the problem. (German & Barrett, 2005). The researchers wanted to
know if exposure to highly specialized tools, as occurs with individuals in industrialized nations, affects
their ability to transcend functional fixedness. It was determined that functional fixedness is experienced
in both industrialized and nonindustrialized cultures (German & Barrett, 2005).

In order to make good decisions, we use our knowledge and our reasoning. Often, this knowledge and
reasoning is sound and solid. Sometimes, however, we are swayed by biases or by others manipulating a
situation. For example, let’s say you and three friends wanted to rent a house and had a combined target
budget of $1,600. The realtor shows you only very run-down houses for $1,600 and then shows you a
very nice house for $2,000. Might you ask each person to pay more in rent to get the $2,000 home? Why
would the realtor show you the run-down houses and the nice house? The realtor may be challenging your
anchoring bias. An anchoring bias occurs when you focus on one piece of information when making a
decision or solving a problem. In this case, you’re so focused on the amount of money you are willing to
spend that you may not recognize what kinds of houses are available at that price point.

The confirmation bias is the tendency to focus on information that confirms your existing beliefs. For
example, if you think that your professor is not very nice, you notice all of the instances of rude behavior
exhibited by the professor while ignoring the countless pleasant interactions he is involved in on a daily
basis. Hindsight bias leads you to believe that the event you just experienced was predictable, even
though it really wasn’t. In other words, you knew all along that things would turn out the way they did.
Representative bias describes a faulty way of thinking, in which you unintentionally stereotype someone


Chapter 7 | Thinking and Intelligence 239

or something; for example, you may assume that your professors spend their free time reading books and
engaging in intellectual conversation, because the idea of them spending their time playing volleyball or
visiting an amusement park does not fit in with your stereotypes of professors.

Finally, the availability heuristic is a heuristic in which you make a decision based on an example,
information, or recent experience that is that readily available to you, even though it may not be the best
example to inform your decision. Biases tend to “preserve that which is already established—to maintain
our preexisting knowledge, beliefs, attitudes, and hypotheses” (Aronson, 1995; Kahneman, 2011). These
biases are summarized in Table 7.3.

Summary of Decision Biases

Bias Description

Anchoring Tendency to focus on one particular piece of information when making decisions
or problem-solving

Confirmation Focuses on information that confirms existing beliefs

Hindsight Belief that the event just experienced was predictable

Representative Unintentional stereotyping of someone or something

Availability Decision is based upon either an available precedent or an example that may be

Table 7.3

Watch this teacher-made music video about cognitive biases ( to
learn more.

Were you able to determine how many marbles are needed to balance the scales in Figure 7.9? You need
nine. Were you able to solve the problems in Figure 7.7 and Figure 7.8? Here are the answers (Figure


240 Chapter 7 | Thinking and Intelligence

This OpenStax book is available for free at

Figure 7.11

7.4 What Are Intelligence and Creativity?

Learning Objectives

By the end of this section, you will be able to:
• Define intelligence
• Explain the triarchic theory of intelligence
• Identify the difference between intelligence theories
• Explain emotional intelligence
• Define creativity

A four-and-a-half-year-old boy sits at the kitchen table with his father, who is reading a new story aloud
to him. He turns the page to continue reading, but before he can begin, the boy says, “Wait, Daddy!” He
points to the words on the new page and reads aloud, “Go, Pig! Go!” The father stops and looks at his son.
“Can you read that?” he asks. “Yes, Daddy!” And he points to the words and reads again, “Go, Pig! Go!”

This father was not actively teaching his son to read, even though the child constantly asked questions
about letters, words, and symbols that they saw everywhere: in the car, in the store, on the television. The
dad wondered about what else his son might understand and decided to try an experiment. Grabbing a
sheet of blank paper, he wrote several simple words in a list: mom, dad, dog, bird, bed, truck, car, tree. He
put the list down in front of the boy and asked him to read the words. “Mom, dad, dog, bird, bed, truck,
car, tree,” he read, slowing down to carefully pronounce bird and truck. Then, “Did I do it, Daddy?” “You
sure did! That is very good.” The father gave his little boy a warm hug and continued reading the story
about the pig, all the while wondering if his son’s abilities were an indication of exceptional intelligence
or simply a normal pattern of linguistic development. Like the father in this example, psychologists have
wondered what constitutes intelligence and how it can be measured.


What exactly is intelligence? The way that researchers have defined the concept of intelligence has been
modified many times since the birth of psychology. British psychologist Charles Spearman believed
intelligence consisted of one general factor, called g, which could be measured and compared among
individuals. Spearman focused on the commonalities among various intellectual abilities and de-

Chapter 7 | Thinking and Intelligence 241

emphasized what made each unique. Long before modern psychology developed, however, ancient
philosophers, such as Aristotle, held a similar view (Cianciolo & Sternberg, 2004).

Others psychologists believe that instead of a single factor, intelligence is a collection of distinct abilities.
In the 1940s, Raymond Cattell proposed a theory of intelligence that divided general intelligence into
two components: crystallized intelligence and fluid intelligence (Cattell, 1963). Crystallized intelligence
is characterized as acquired knowledge and the ability to retrieve it. When you learn, remember, and
recall information, you are using crystallized intelligence. You use crystallized intelligence all the time in
your coursework by demonstrating that you have mastered the information covered in the course. Fluid
intelligence encompasses the ability to see complex relationships and solve problems. Navigating your
way home after being detoured onto an unfamiliar route because of road construction would draw upon
your fluid intelligence. Fluid intelligence helps you tackle complex, abstract challenges in your daily life,
whereas crystallized intelligence helps you overcome concrete, straightforward problems (Cattell, 1963).

Other theorists and psychologists believe that intelligence should be defined in more practical terms. For
example, what types of behaviors help you get ahead in life? Which skills promote success? Think about
this for a moment. Being able to recite all 45 presidents of the United States in order is an excellent party
trick, but will knowing this make you a better person?

Robert Sternberg developed another theory of intelligence, which he titled the triarchic theory of
intelligence because it sees intelligence as comprised of three parts (Sternberg, 1988): practical, creative,
and analytical intelligence (Figure 7.12).

Figure 7.12 Sternberg’s theory identifies three types of intelligence: practical, creative, and analytical.

Practical intelligence, as proposed by Sternberg, is sometimes compared to “street smarts.” Being practical
means you find solutions that work in your everyday life by applying knowledge based on your
experiences. This type of intelligence appears to be separate from traditional understanding of IQ;
individuals who score high in practical intelligence may or may not have comparable scores in creative
and analytical intelligence (Sternberg, 1988).

This story about the 2007 Virginia Tech shootings illustrates both high and low practical intelligences.
During the incident, one student left her class to go get a soda in an adjacent building. She planned to
return to class, but when she returned to her building after getting her soda, she saw that the door she used
to leave was now chained shut from the inside. Instead of thinking about why there was a chain around
the door handles, she went to her class’s window and crawled back into the room. She thus potentially
exposed herself to the gunman. Thankfully, she was not shot. On the other hand, a pair of students was
walking on campus when they heard gunshots nearby. One friend said, “Let’s go check it out and see what
is going on.” The other student said, “No way, we need to run away from the gunshots.” They did just
that. As a result, both avoided harm. The student who crawled through the window demonstrated some
creative intelligence but did not use common sense. She would have low practical intelligence. The student
who encouraged his friend to run away from the sound of gunshots would have much higher practical

242 Chapter 7 | Thinking and Intelligence

This OpenStax book is available for free at


Analytical intelligence is closely aligned with academic problem solving and computations. Sternberg
says that analytical intelligence is demonstrated by an ability to analyze, evaluate, judge, compare, and
contrast. When reading a classic novel for literature class, for example, it is usually necessary to compare
the motives of the main characters of the book or analyze the historical context of the story. In a science
course such as anatomy, you must study the processes by which the body uses various minerals in
different human systems. In developing an understanding of this topic, you are using analytical
intelligence. When solving a challenging math problem, you would apply analytical intelligence to analyze
different aspects of the problem and then solve it section by section.

Creative intelligence is marked by inventing or imagining a solution to a problem or situation. Creativity
in this realm can include finding a novel solution to an unexpected problem or producing a beautiful work
of art or a well-developed short story. Imagine for a moment that you are camping in the woods with some
friends and realize that you’ve forgotten your camp coffee pot. The person in your group who figures out
a way to successfully brew coffee for everyone would be credited as having higher creative intelligence.

Multiple Intelligences Theory was developed by Howard Gardner, a Harvard psychologist and former
student of Erik Erikson. Gardner’s theory, which has been refined for more than 30 years, is a more
recent development among theories of intelligence. In Gardner’s theory, each person possesses at least
eight intelligences. Among these eight intelligences, a person typically excels in some and falters in others
(Gardner, 1983). Table 7.4 describes each type of intelligence.

Multiple Intelligences




Perceives different functions of language, different
sounds and meanings of words, may easily learn
multiple languages

Journalist, novelist,
poet, teacher


Capable of seeing numerical patterns, strong ability to
use reason and logic



Understands and appreciates rhythm, pitch, and tone;
may play multiple instruments or perform as a vocalist

Composer, performer


High ability to control the movements of the body and
use the body to perform various physical tasks

Dancer, athlete,
athletic coach, yoga


Ability to perceive the relationship between objects and
how they move in space

sculptor, architect,
aviator, sailor


Ability to understand and be sensitive to the various
emotional states of others

Counselor, social
worker, salesperson


Ability to access personal feelings and motivations, and
use them to direct behavior and reach personal goals

Key component of
personal success over

Chapter 7 | Thinking and Intelligence 243

Multiple Intelligences




High capacity to appreciate the natural world and
interact with the species within it

Biologist, ecologist,

Table 7.4

Gardner’s theory is relatively new and needs additional research to better establish empirical support. At
the same time, his ideas challenge the traditional idea of intelligence to include a wider variety of abilities,
although it has been suggested that Gardner simply relabeled what other theorists called “cognitive styles”
as “intelligences” (Morgan, 1996). Furthermore, developing traditional measures of Gardner’s intelligences
is extremely difficult (Furnham, 2009; Gardner & Moran, 2006; Klein, 1997).

Gardner’s inter- and intrapersonal intelligences are often combined into a single type: emotional
intelligence. Emotional intelligence encompasses the ability to understand the emotions of yourself and
others, show empathy, understand social relationships and cues, and regulate your own emotions and
respond in culturally appropriate ways (Parker, Saklofske, & Stough, 2009). People with high emotional
intelligence typically have well-developed social skills. Some researchers, including Daniel Goleman, the
author of Emotional Intelligence: Why It Can Matter More than IQ, argue that emotional intelligence is a better
predictor of success than traditional intelligence (Goleman, 1995). However, emotional intelligence has
been widely debated, with researchers pointing out inconsistencies in how it is defined and described,
as well as questioning results of studies on a subject that is difficulty to measure and study emperically
(Locke, 2005; Mayer, Salovey, & Caruso, 2004)

The most comprehensive theory of intelligence to date is the Cattell-Horn-Carroll (CHC) theory of
cognitive abilities (Schneider & McGrew, 2018). In this theory, abilities are related and arranged in a
hierarchy with general abilities at the top, broad abilities in the middle, and narrow (specific) abilities
at the bottom. The narrow abilities are the only ones that can be directly measured; however, they are
integrated within the other abilities. At the general level is general intelligence. Next, the broad level
consists of general abilities such as fluid reasoning, short-term memory, and processing speed. Finally, as
the hierarchy continues, the narrow level includes specific forms of cognitive abilities. For example, short-
term memory would further break down into memory span and working memory capacity.

Intelligence can also have different meanings and values in different cultures. If you live on a small island,
where most people get their food by fishing from boats, it would be important to know how to fish
and how to repair a boat. If you were an exceptional angler, your peers would probably consider you
intelligent. If you were also skilled at repairing boats, your intelligence might be known across the whole
island. Think about your own family’s culture. What values are important for Latinx families? Italian
families? In Irish families, hospitality and telling an entertaining story are marks of the culture. If you are
a skilled storyteller, other members of Irish culture are likely to consider you intelligent.

Some cultures place a high value on working together as a collective. In these cultures, the importance of
the group supersedes the importance of individual achievement. When you visit such a culture, how well
you relate to the values of that culture exemplifies your cultural intelligence, sometimes referred to as
cultural competence.

244 Chapter 7 | Thinking and Intelligence

This OpenStax book is available for free at

Watch this video that compares different theories of intelligence (
to learn more.


Creativity is the ability to generate, create, or discover new ideas, solutions, and possibilities. Very creative
people often have intense knowledge about something, work on it for years, look at novel solutions, seek
out the advice and help of other experts, and take risks. Although creativity is often associated with the
arts, it is actually a vital form of intelligence that drives people in many disciplines to discover something
new. Creativity can be found in every area of life, from the way you decorate your residence to a new way
of understanding how a cell works.

Creativity is often assessed as a function of one’s ability to engage in divergent thinking. Divergent
thinking can be described as thinking “outside the box;” it allows an individual to arrive at unique,
multiple solutions to a given problem. In contrast, convergent thinking describes the ability to provide a
correct or well-established answer or solution to a problem (Cropley, 2006; Gilford, 1967)


Dr. Tom Steitz, former Sterling Professor of Biochemistry and Biophysics at Yale University, spent his career
looking at the structure and specific aspects of RNA molecules and how their interactions could help produce
antibiotics and ward off diseases. As a result of his lifetime of work, he won the Nobel Prize in Chemistry in
2009. He wrote, “Looking back over the development and progress of my career in science, I am reminded
how vitally important good mentorship is in the early stages of one’s career development and constant face-to-
face conversations, debate and discussions with colleagues at all stages of research. Outstanding discoveries,
insights and developments do not happen in a vacuum” (Steitz, 2010, para. 39). Based on Steitz’s comment, it
becomes clear that someone’s creativity, although an individual strength, benefits from interactions with others.
Think of a time when your creativity was sparked by a conversation with a friend or classmate. How did that
person influence you and what problem did you solve using creativity?

7.5 Measures of Intelligence

Learning Objectives

By the end of this section, you will be able to:
• Explain how intelligence tests are developed
• Describe the history of the use of IQ tests
• Describe the purposes and benefits of intelligence testing

While you’re likely familiar with the term “IQ” and associate it with the idea of intelligence, what does
IQ really mean? IQ stands for intelligence quotient and describes a score earned on a test designed to
measure intelligence. You’ve already learned that there are many ways psychologists describe intelligence
(or more aptly, intelligences). Similarly, IQ tests—the tools designed to measure intelligence—have been
the subject of debate throughout their development and use.



Chapter 7 | Thinking and Intelligence 245

When might an IQ test be used? What do we learn from the results, and how might people use this
information? While there are certainly many benefits to intelligence testing, it is important to also note
the limitations and controversies surrounding these tests. For example, IQ tests have sometimes been
used as arguments in support of insidious purposes, such as the eugenics movement (Severson, 2011).
The infamous Supreme Court Case, Buck v. Bell, legalized the forced sterilization of some people deemed
“feeble-minded” through this type of testing, resulting in about 65,000 sterilizations (Buck v. Bell, 274 U.S.
200; Ko, 2016). Today, only professionals trained in psychology can administer IQ tests, and the purchase
of most tests requires an advanced degree in psychology. Other professionals in the field, such as social
workers and psychiatrists, cannot administer IQ tests. In this section, we will explore what intelligence
tests measure, how they are scored, and how they were developed.


It seems that the human understanding of intelligence is somewhat limited when we focus on traditional or
academic-type intelligence. How then, can intelligence be measured? And when we measure intelligence,
how do we ensure that we capture what we’re really trying to measure (in other words, that IQ tests
function as valid measures of intelligence)? In the following paragraphs, we will explore the how
intelligence tests were developed and the history of their use.

The IQ test has been synonymous with intelligence for over a century. In the late 1800s, Sir Francis
Galton developed the first broad test of intelligence (Flanagan & Kaufman, 2004). Although he was not
a psychologist, his contributions to the concepts of intelligence testing are still felt today (Gordon, 1995).
Reliable intelligence testing (you may recall from earlier chapters that reliability refers to a test’s ability to
produce consistent results) began in earnest during the early 1900s with a researcher named Alfred Binet
(Figure 7.13). Binet was asked by the French government to develop an intelligence test to use on children
to determine which ones might have difficulty in school; it included many verbally based tasks. American
researchers soon realized the value of such testing. Louis Terman, a Stanford professor, modified Binet’s
work by standardizing the administration of the test and tested thousands of different-aged children to
establish an average score for each age. As a result, the test was normed and standardized, which means
that the test was administered consistently to a large enough representative sample of the population that
the range of scores resulted in a bell curve (bell curves will be discussed later). Standardization means that
the manner of administration, scoring, and interpretation of results is consistent. Norming involves giving
a test to a large population so data can be collected comparing groups, such as age groups. The resulting
data provide norms, or referential scores, by which to interpret future scores. Norms are not expectations
of what a given group should know but a demonstration of what that group does know. Norming and
standardizing the test ensures that new scores are reliable. This new version of the test was called the
Stanford-Binet Intelligence Scale (Terman, 1916). Remarkably, an updated version of this test is still widely
used today.

246 Chapter 7 | Thinking and Intelligence

This OpenStax book is available for free at

Figure 7.13 French psychologist Alfred Binet helped to develop intelligence testing. (b) This page is from a 1908
version of the Binet-Simon Intelligence Scale. Children being tested were asked which face, of each pair, was prettier.

In 1939, David Wechsler, a psychologist who spent part of his career working with World War I veterans,
developed a new IQ test in the United States. Wechsler combined several subtests from other intelligence
tests used between 1880 and World War I. These subtests tapped into a variety of verbal and nonverbal
skills, because Wechsler believed that intelligence encompassed “the global capacity of a person to act
purposefully, to think rationally, and to deal effectively with his environment” (Wechsler, 1958, p. 7). He
named the test the Wechsler-Bellevue Intelligence Scale (Wechsler, 1981). This combination of subtests
became one of the most extensively used intelligence tests in the history of psychology. Although its name
was later changed to the Wechsler Adult Intelligence Scale (WAIS) and has been revised several times,
the aims of the test remain virtually unchanged since its inception (Boake, 2002). Today, there are three
intelligence tests credited to Wechsler, the Wechsler Adult Intelligence Scale-fourth edition (WAIS-IV),
the Wechsler Intelligence Scale for Children (WISC-V), and the Wechsler Preschool and Primary Scale of
Intelligence—IV (WPPSI-IV) (Wechsler, 2012). These tests are used widely in schools and communities
throughout the United States, and they are periodically normed and standardized as a means of
recalibration. As a part of the recalibration process, the WISC-V was given to thousands of children across
the country, and children taking the test today are compared with their same-age peers (Figure 7.13).

The WISC-V is composed of 14 subtests, which comprise five indices, which then render an IQ score. The
five indices are Verbal Comprehension, Visual Spatial, Fluid Reasoning, Working Memory, and Processing
Speed. When the test is complete, individuals receive a score for each of the five indices and a Full Scale IQ
score. The method of scoring reflects the understanding that intelligence is comprised of multiple abilities
in several cognitive realms and focuses on the mental processes that the child used to arrive at his or her
answers to each test item.

Interestingly, the periodic recalibrations have led to an interesting observation known as the Flynn effect.
Named after James Flynn, who was among the first to describe this trend, the Flynn effect refers to the
observation that each generation has a significantly higher IQ than the last. Flynn himself argues, however,
that increased IQ scores do not necessarily mean that younger generations are more intelligent per se
(Flynn, Shaughnessy, & Fulgham, 2012).

Ultimately, we are still left with the question of how valid intelligence tests are. Certainly, the most modern
versions of these tests tap into more than verbal competencies, yet the specific skills that should be assessed

Chapter 7 | Thinking and Intelligence 247

in IQ testing, the degree to which any test can truly measure an individual’s intelligence, and the use of the
results of IQ tests are still issues of debate (Gresham & Witt, 1997; Flynn, Shaughnessy, & Fulgham, 2012;
Richardson, 2002; Schlinger, 2003).

Capital Punishment and Criminals with Intellectual Disabilities

The case of Atkins v. Virginia was a landmark case in the United States Supreme Court. On August 16, 1996,
two men, Daryl Atkins and William Jones, robbed, kidnapped, and then shot and killed Eric Nesbitt, a local
airman from the U.S. Air Force. A clinical psychologist evaluated Atkins and testified at the trial that Atkins had
an IQ of 59. The mean IQ score is 100. The psychologist concluded that Atkins was mildly mentally retarded.

The jury found Atkins guilty, and he was sentenced to death. Atkins and his attorneys appealed to the Supreme
Court. In June 2002, the Supreme Court reversed a previous decision and ruled that executions of mentally
retarded criminals are ‘cruel and unusual punishments’ prohibited by the Eighth Amendment. The court wrote
in their decision:

Clinical definitions of mental retardation require not only subaverage intellectual functioning, but
also significant limitations in adaptive skills. Mentally retarded persons frequently know the
difference between right and wrong and are competent to stand trial. Because of their impairments,
however, by definition they have diminished capacities to understand and process information, to
communicate, to abstract from mistakes and learn from experience, to engage in logical reasoning,
to control impulses, and to understand others’ reactions. Their deficiencies do not warrant an
exemption from criminal sanctions, but diminish their personal culpability (Atkins v. Virginia, 2002,
par. 5).

The court also decided that there was a state legislature consensus against the execution of the mentally
retarded and that this consensus should stand for all of the states. The Supreme Court ruling left it up to
the states to determine their own definitions of mental retardation and intellectual disability. The definitions
vary among states as to who can be executed. In the Atkins case, a jury decided that because he had many
contacts with his lawyers and thus was provided with intellectual stimulation, his IQ had reportedly increased,
and he was now smart enough to be executed. He was given an execution date and then received a stay of
execution after it was revealed that lawyers for co-defendant, William Jones, coached Jones to “produce a
testimony against Mr. Atkins that did match the evidence” (Liptak, 2008). After the revelation of this misconduct,
Atkins was re-sentenced to life imprisonment.

Atkins v. Virginia (2002) highlights several issues regarding society’s beliefs around intelligence. In the Atkins
case, the Supreme Court decided that intellectual disability does affect decision making and therefore should
affect the nature of the punishment such criminals receive. Where, however, should the lines of intellectual
disability be drawn? In May 2014, the Supreme Court ruled in a related case (Hall v. Florida) that IQ scores
cannot be used as a final determination of a prisoner’s eligibility for the death penalty (Roberts, 2014).


The results of intelligence tests follow the bell curve, a graph in the general shape of a bell. When the bell
curve is used in psychological testing, the graph demonstrates a normal distribution of a trait, in this case,
intelligence, in the human population. Many human traits naturally follow the bell curve. For example,
if you lined up all your female schoolmates according to height, it is likely that a large cluster of them
would be the average height for an American woman: 5’4”–5’6”. This cluster would fall in the center of
the bell curve, representing the average height for American women (Figure 7.14). There would be fewer
women who stand closer to 4’11”. The same would be true for women of above-average height: those who
stand closer to 5’11”. The trick to finding a bell curve in nature is to use a large sample size. Without a
large sample size, it is less likely that the bell curve will represent the wider population. A representative
sample is a subset of the population that accurately represents the general population. If, for example, you


248 Chapter 7 | Thinking and Intelligence

This OpenStax book is available for free at

measured the height of the women in your classroom only, you might not actually have a representative
sample. Perhaps the women’s basketball team wanted to take this course together, and they are all in your
class. Because basketball players tend to be taller than average, the women in your class may not be a good
representative sample of the population of American women. But if your sample included all the women
at your school, it is likely that their heights would form a natural bell curve.

Figure 7.14 Are you of below-average, average, or above-average height?

The same principles apply to intelligence tests scores. Individuals earn a score called an intelligence
quotient (IQ). Over the years, different types of IQ tests have evolved, but the way scores are interpreted
remains the same. The average IQ score on an IQ test is 100. Standard deviations describe how data are
dispersed in a population and give context to large data sets. The bell curve uses the standard deviation
to show how all scores are dispersed from the average score (Figure 7.15). In modern IQ testing, one
standard deviation is 15 points. So a score of 85 would be described as “one standard deviation below
the mean.” How would you describe a score of 115 and a score of 70? Any IQ score that falls within one
standard deviation above and below the mean (between 85 and 115) is considered average, and 68% of the
population has IQ scores in this range. An IQ score of 130 or above is considered a superior level.

Chapter 7 | Thinking and Intelligence 249

Figure 7.15 The majority of people have an IQ score between 85 and 115.

Only 2.2% of the population has an IQ score below 70 (American Psychological Association [APA], 2013).
A score of 70 or below indicates significant cognitive delays. When these are combined with major deficits
in adaptive functioning, a person is diagnosed with having an intellectual disability (American Association
on Intellectual and Developmental Disabilities, 2013). Formerly known as mental retardation, the accepted
term now is intellectual disability, and it has four subtypes: mild, moderate, severe, and profound (Table
7.5). The Diagnostic and Statistical Manual of Psychological Disorders lists criteria for each subgroup (APA,

Characteristics of Cognitive Disorders


Percentage of Population
with Intellectual


Mild 85% 3rd- to 6th-grade skill level in reading, writing,
and math; may be employed and live

Moderate 10% Basic reading and writing skills; functional self-
care skills; requires some oversight

Severe 5% Functional self-care skills; requires oversight of
daily environment and activities

Profound <1% May be able to communicate verbally or
nonverbally; requires intensive oversight

Table 7.5

On the other end of the intelligence spectrum are those individuals whose IQs fall into the highest
ranges. Consistent with the bell curve, about 2% of the population falls into this category. People are
considered gifted if they have an IQ score of 130 or higher, or superior intelligence in a particular
area. Long ago, popular belief suggested that people of high intelligence were maladjusted. This idea
was disproven through a groundbreaking study of gifted children. In 1921, Lewis Terman began a

250 Chapter 7 | Thinking and Intelligence

This OpenStax book is available for free at

longitudinal study of over 1500 children with IQs over 135 (Terman, 1925). His findings showed that
these children became well-educated, successful adults who were, in fact, well-adjusted (Terman & Oden,
1947). Additionally, Terman’s study showed that the subjects were above average in physical build and
attractiveness, dispelling an earlier popular notion that highly intelligent people were “weaklings.” Some
people with very high IQs elect to join Mensa, an organization dedicated to identifying, researching, and
fostering intelligence. Members must have an IQ score in the top 2% of the population, and they may be
required to pass other exams in their application to join the group.

What’s in a Name? Mental Retardation

In the past, individuals with IQ scores below 70 and significant adaptive and social functioning delays were
diagnosed with mental retardation. When this diagnosis was first named, the title held no social stigma. In
time, however, the degrading word “retard” sprang from this diagnostic term. “Retard” was frequently used as
a taunt, especially among young people, until the words “mentally retarded” and “retard” became an insult. As
such, the DSM-5 now labels this diagnosis as “intellectual disability.” Many states once had a Department of
Mental Retardation to serve those diagnosed with such cognitive delays, but most have changed their name to
Department of Developmental Disabilities or something similar in language. The Social Security Administration
still uses the term “mental retardation” but is considering eliminating it from its programming (Goad, 2013).
Earlier in the chapter, we discussed how language affects how we think. Do you think changing the title of
this department has any impact on how people regard those with developmental disabilities? Does a different
name give people more dignity, and if so, how? Does it change the expectations for those with developmental
or cognitive disabilities? Why or why not?


The value of IQ testing is most evident in educational or clinical settings. Children who seem to be
experiencing learning difficulties or severe behavioral problems can be tested to ascertain whether the
child’s difficulties can be partly attributed to an IQ score that is significantly different from the mean for
her age group. Without IQ testing—or another measure of intelligence—children and adults needing extra
support might not be identified effectively. In addition, IQ testing is used in courts to determine whether a
defendant has special or extenuating circumstances that preclude him from participating in some way in a
trial. People also use IQ testing results to seek disability benefits from the Social Security Administration.

The following case study demonstrates the usefulness and benefits of IQ testing. Candace, a 14-year-
old girl experiencing problems at school in Connecticut, was referred for a court-ordered psychological
evaluation. She was in regular education classes in ninth grade and was failing every subject. Candace
had never been a stellar student but had always been passed to the next grade. Frequently, she would
curse at any of her teachers who called on her in class. She also got into fights with other students and
occasionally shoplifted. When she arrived for the evaluation, Candace immediately said that she hated
everything about school, including the teachers, the rest of the staff, the building, and the homework. Her
parents stated that they felt their daughter was picked on, because she was of a different race than the
teachers and most of the other students. When asked why she cursed at her teachers, Candace replied,
“They only call on me when I don’t know the answer. I don’t want to say, ‘I don’t know’ all of the time
and look like an idiot in front of my friends. The teachers embarrass me.” She was given a battery of tests,
including an IQ test. Her score on the IQ test was 68. What does Candace’s score say about her ability
to excel or even succeed in regular education classes without assistance? Why were her difficulties never
noticed or addressed?


Chapter 7 | Thinking and Intelligence 251

7.6 The Source of Intelligence

Learning Objectives

By the end of this section, you will be able to:
• Describe how genetics and environment affect intelligence
• Explain the relationship between IQ scores and socioeconomic status
• Describe the difference between a learning disability and a developmental disorder

A young girl, born of teenage parents, lives with her grandmother in rural Mississippi. They are poor—in
serious poverty—but they do their best to get by with what they have. She learns to read when she is just
3 years old. As she grows older, she longs to live with her mother, who now resides in Wisconsin. She
moves there at the age of 6 years. At 9 years of age, she is raped. During the next several years, several
different male relatives repeatedly molest her. Her life unravels. She turns to drugs and sex to fill the deep,
lonely void inside her. Her mother then sends her to Nashville to live with her father, who imposes strict
behavioral expectations upon her, and over time, her wild life settles once again. She begins to experience
success in school, and at 19 years old, becomes the youngest and first African-American female news
anchor (“Dates and Events,” n.d.). The woman—Oprah Winfrey—goes on to become a media giant known
for both her intelligence and her empathy.


Where does high intelligence come from? Some researchers believe that intelligence is a trait inherited
from a person’s parents. Scientists who research this topic typically use twin studies to determine the
heritability of intelligence. The Minnesota Study of Twins Reared Apart is one of the most well-known
twin studies. In this investigation, researchers found that identical twins raised together and identical
twins raised apart exhibit a higher correlation between their IQ scores than siblings or fraternal twins
raised together (Bouchard, Lykken, McGue, Segal, & Tellegen, 1990). The findings from this study reveal
a genetic component to intelligence (Figure 7.15). At the same time, other psychologists believe that
intelligence is shaped by a child’s developmental environment. If parents were to provide their children
with intellectual stimuli from before they are born, it is likely that they would absorb the benefits of that
stimulation, and it would be reflected in intelligence levels.

252 Chapter 7 | Thinking and Intelligence

This OpenStax book is available for free at

Figure 7.16 The correlations of IQs of unrelated versus related persons reared apart or together suggest a genetic
component to intelligence.

The reality is that aspects of each idea are probably correct. In fact, one study suggests that although
genetics seem to be in control of the level of intelligence, the environmental influences provide both
stability and change to trigger manifestation of cognitive abilities (Bartels, Rietveld, Van Baal, & Boomsma,
2002). Certainly, there are behaviors that support the development of intelligence, but the genetic
component of high intelligence should not be ignored. As with all heritable traits, however, it is not always
possible to isolate how and when high intelligence is passed on to the next generation.

Range of Reaction is the theory that each person responds to the environment in a unique way based
on his or her genetic makeup. According to this idea, your genetic potential is a fixed quantity, but
whether you reach your full intellectual potential is dependent upon the environmental stimulation you
experience, especially in childhood. Think about this scenario: A couple adopts a child who has average
genetic intellectual potential. They raise her in an extremely stimulating environment. What will happen
to the couple’s new daughter? It is likely that the stimulating environment will improve her intellectual
outcomes over the course of her life. But what happens if this experiment is reversed? If a child with
an extremely strong genetic background is placed in an environment that does not stimulate him: What
happens? Interestingly, according to a longitudinal study of highly gifted individuals, it was found that
“the two extremes of optimal and pathological experience are both represented disproportionately in the
backgrounds of creative individuals”; however, those who experienced supportive family environments
were more likely to report being happy (Csikszentmihalyi & Csikszentmihalyi, 1993, p. 187).

Another challenge to determining origins of high intelligence is the confounding nature of our human
social structures. It is troubling to note that some ethnic groups perform better on IQ tests than others—and
it is likely that the results do not have much to do with the quality of each ethnic group’s intellect.
The same is true for socioeconomic status. Children who live in poverty experience more pervasive,
daily stress than children who do not worry about the basic needs of safety, shelter, and food. These
worries can negatively affect how the brain functions and develops, causing a dip in IQ scores. Mark
Kishiyama and his colleagues determined that children living in poverty demonstrated reduced prefrontal
brain functioning comparable to children with damage to the lateral prefrontal cortex (Kishyama, Boyce,
Jimenez, Perry, & Knight, 2009).

The debate around the foundations and influences on intelligence exploded in 1969, when an educational
psychologist named Arthur Jensen published the article “How Much Can We Boost I.Q. and Achievement”
in the Harvard Educational Review. Jensen had administered IQ tests to diverse groups of students, and

Chapter 7 | Thinking and Intelligence 253

his results led him to the conclusion that IQ is determined by genetics. He also posited that intelligence
was made up of two types of abilities: Level I and Level II. In his theory, Level I is responsible for rote
memorization, whereas Level II is responsible for conceptual and analytical abilities. According to his
findings, Level I remained consistent among the human race. Level II, however, exhibited differences
among ethnic groups (Modgil & Routledge, 1987). Jensen’s most controversial conclusion was that Level
II intelligence is prevalent among Asians, then Caucasians, then African Americans. Robert Williams was
among those who called out racial bias in Jensen’s results (Williams, 1970).

Obviously, Jensen’s interpretation of his own data caused an intense response in a nation that continued to
grapple with the effects of racism (Fox, 2012). However, Jensen’s ideas were not solitary or unique; rather,
they represented one of many examples of psychologists asserting racial differences in IQ and cognitive
ability. In fact, Rushton and Jensen (2005) reviewed three decades worth of research on the relationship
between race and cognitive ability. Jensen’s belief in the inherited nature of intelligence and the validity
of the IQ test to be the truest measure of intelligence are at the core of his conclusions. If, however, you
believe that intelligence is more than Levels I and II, or that IQ tests do not control for socioeconomic and
cultural differences among people, then perhaps you can dismiss Jensen’s conclusions as a single window
that looks out on the complicated and varied landscape of human intelligence.

In a related story, parents of African American students filed a case against the State of California in
1979, because they believed that the testing method used to identify students with learning disabilities
was culturally unfair as the tests were normed and standardized using white children (Larry P. v. Riles).
The testing method used by the state disproportionately identified African American children as mentally
retarded. This resulted in many students being incorrectly classified as “mentally retarded.” According to
a summary of the case, Larry P. v. Riles:

In violation of Title VI of the Civil Rights Act of 1964, the Rehabilitation Act of 1973, and the
Education for All Handicapped Children Act of 1975, defendants have utilized standardized
intelligence tests that are racially and culturally biased, have a discriminatory impact against
black children, and have not been validated for the purpose of essentially permanent placements
of black children into educationally dead-end, isolated, and stigmatizing classes for the so-
called educable mentally retarded. Further, these federal laws have been violated by defendants’
general use of placement mechanisms that, taken together, have not been validated and result in
a large over-representation of black children in the special E.M.R. classes. (Larry P. v. Riles, par.

Once again, the limitations of intelligence testing were revealed.


Learning disabilities are cognitive disorders that affect different areas of cognition, particularly language
or reading. It should be pointed out that learning disabilities are not the same thing as intellectual
disabilities. Learning disabilities are considered specific neurological impairments rather than global
intellectual or developmental disabilities. A person with a language disability has difficulty understanding
or using spoken language, whereas someone with a reading disability, such as dyslexia, has difficulty
processing what he or she is reading.

Often, learning disabilities are not recognized until a child reaches school age. One confounding aspect of
learning disabilities is that they most often affect children with average to above-average intelligence. In
other words, the disability is specific to a particular area and not a measure of overall intellectual ability.
At the same time, learning disabilities tend to exhibit comorbidity with other disorders, like attention-
deficit hyperactivity disorder (ADHD). Anywhere between 30–70% of individuals with diagnosed cases
of ADHD also have some sort of learning disability (Riccio, Gonzales, & Hynd, 1994). Let’s take a look at
three examples of common learning disabilities: dysgraphia, dyslexia, and dyscalculia.

254 Chapter 7 | Thinking and Intelligence

This OpenStax book is available for free at


Children with dysgraphia have a learning disability that results in a struggle to write legibly. The physical
task of writing with a pen and paper is extremely challenging for the person. These children often have
extreme difficulty putting their thoughts down on paper (Smits-Engelsman & Van Galen, 1997). This
difficulty is inconsistent with a person’s IQ. That is, based on the child’s IQ and/or abilities in other
areas, a child with dysgraphia should be able to write, but can’t. Children with dysgraphia may also have
problems with spatial abilities.

Students with dysgraphia need academic accommodations to help them succeed in school. These
accommodations can provide students with alternative assessment opportunities to demonstrate what
they know (Barton, 2003). For example, a student with dysgraphia might be permitted to take an oral exam
rather than a traditional paper-and-pencil test. Treatment is usually provided by an occupational therapist,
although there is some question as to how effective such treatment is (Zwicker, 2005).


Dyslexia is the most common learning disability in children. An individual with dyslexia exhibits an
inability to correctly process letters. The neurological mechanism for sound processing does not work
properly in someone with dyslexia. As a result, dyslexic children may not understand sound-letter
correspondence. A child with dyslexia may mix up letters within words and sentences—letter reversals,
such as those shown in Figure 7.17, are a hallmark of this learning disability—or skip whole words
while reading. A dyslexic child may have difficulty spelling words correctly while writing. Because of the
disordered way that the brain processes letters and sound, learning to read is a frustrating experience.
Some dyslexic individuals cope by memorizing the shapes of most words, but they never actually learn to
read (Berninger, 2008).

Figure 7.17 These written words show variations of the word “teapot” as written by individuals with dyslexia.


Dyscalculia is difficulty in learning or comprehending arithmetic. This learning disability is often first
evident when children exhibit difficulty discerning how many objects are in a small group without
counting them. Other symptoms may include struggling to memorize math facts, organize numbers, or
fully differentiate between numerals, math symbols, and written numbers (such as “3” and “three”).

Chapter 7 | Thinking and Intelligence 255


analytical intelligence

anchoring bias

artificial concept

availability heuristic


cognitive psychology

cognitive script


confirmation bias

convergent thinking

creative intelligence


crystallized intelligence

cultural intelligence

divergent thinking




emotional intelligence

event schema

fluid intelligence

Flynn effect

functional fixedness



Key Terms

problem-solving strategy characterized by a specific set of instructions

aligned with academic problem solving and computations

faulty heuristic in which you fixate on a single aspect of a problem to find a solution

concept that is defined by a very specific set of characteristics

faulty heuristic in which you make a decision based on information readily
available to you

thinking, including perception, learning, problem solving, judgment, and memory

field of psychology dedicated to studying every aspect of how people think

set of behaviors that are performed the same way each time; also referred to as an event

category or grouping of linguistic information, objects, ideas, or life experiences

faulty heuristic in which you focus on information that confirms your beliefs

providing correct or established answers to problems

ability to produce new products, ideas, or inventing a new, novel solution to a

ability to generate, create, or discover new ideas, solutions, and possibilities

characterized by acquired knowledge and the ability to retrieve it

ability with which people can understand and relate to those in another culture

ability to think “outside the box” to arrive at novel solutions to a problem

learning disability that causes difficulty in learning or comprehending mathematics

learning disability that causes extreme difficulty in writing legibly

common learning disability in which letters are not processed properly by the brain

ability to understand emotions and motivations in yourself and others

set of behaviors that are performed the same way each time; also referred to as a cognitive

ability to see complex relationships and solve problems

observation that each generation has a significantly higher IQ than the previous generation

inability to see an object as useful for any other use other than the one for which it
was intended

set of rules that are used to convey meaning through the use of a lexicon

mental shortcut that saves time when solving a problem

256 Chapter 7 | Thinking and Intelligence

This OpenStax book is available for free at

hindsight bias

intelligence quotient



mental set


Multiple Intelligences Theory

natural concept




practical intelligence

problem-solving strategy


range of reaction

representative bias

representative sample

role schema



standard deviation



trial and error

triarchic theory of intelligence

belief that the event just experienced was predictable, even though it really wasn’t

(also, IQ) score on a test designed to measure intelligence

communication system that involves using words to transmit information from one individual
to another

the words of a given language

continually using an old solution to a problem without results

smallest unit of language that conveys some type of meaning

Gardner’s theory that each person possesses at least eight types of

mental groupings that are created “naturally” through your experiences

administering a test to a large population so data can be collected to reference the normal scores
for a population and its groups

extension of a rule that exists in a given language to an exception to the rule

basic sound unit of a given language

aka “street smarts”

method for solving problems

best representation of a concept

each person’s response to the environment is unique based on his or her genetic make-

faulty heuristic in which you stereotype someone or something without a valid basis
for your judgment

subset of the population that accurately represents the general population

set of expectations that define the behaviors of a person occupying a particular role

(plural = schemata) mental construct consisting of a cluster or collection of related concepts

process by which we derive meaning from morphemes and words

measure of variability that describes the difference between a set of scores and their

method of testing in which administration, scoring, and interpretation of results are

manner by which words are organized into sentences

problem-solving strategy in which multiple solutions are attempted until the correct one
is found

Sternberg’s theory of intelligence; three facets of intelligence: practical,
creative, and analytical

Chapter 7 | Thinking and Intelligence 257

working backwards heuristic in which you begin to solve a problem by focusing on the end result


7.1 What Is Cognition?
In this section, you were introduced to cognitive psychology, which is the study of cognition, or the brain’s
ability to think, perceive, plan, analyze, and remember. Concepts and their corresponding prototypes help
us quickly organize our thinking by creating categories into which we can sort new information. We also
develop schemata, which are clusters of related concepts. Some schemata involve routines of thought and
behavior, and these help us function properly in various situations without having to “think twice” about
them. Schemata show up in social situations and routines of daily behavior.

7.2 Language
Language is a communication system that has both a lexicon and a system of grammar. Language
acquisition occurs naturally and effortlessly during the early stages of life, and this acquisition occurs in a
predictable sequence for individuals around the world. Language has a strong influence on thought, and
the concept of how language may influence cognition remains an area of study and debate in psychology.

7.3 Problem Solving
Many different strategies exist for solving problems. Typical strategies include trial and error, applying
algorithms, and using heuristics. To solve a large, complicated problem, it often helps to break the problem
into smaller steps that can be accomplished individually, leading to an overall solution. Roadblocks to
problem solving include a mental set, functional fixedness, and various biases that can cloud decision
making skills.

7.4 What Are Intelligence and Creativity?
Intelligence is a complex characteristic of cognition. Many theories have been developed to explain what
intelligence is and how it works. Sternberg generated his triarchic theory of intelligence, whereas Gardner
posits that intelligence is comprised of many factors. Still others focus on the importance of emotional
intelligence. Finally, creativity seems to be a facet of intelligence, but it is extremely difficult to measure

7.5 Measures of Intelligence
In this section, we learned about the history of intelligence testing and some of the challenges regarding
intelligence testing. Intelligence tests began in earnest with Binet; Wechsler later developed intelligence
tests that are still in use today: the WAIS-IV and WISC-V. The Bell curve shows the range of scores that
encompass average intelligence as well as standard deviations.

7.6 The Source of Intelligence
Genetics and environment affect intelligence and the challenges of certain learning disabilities. The
intelligence levels of all individuals seem to benefit from rich stimulation in their early environments.
Highly intelligent individuals, however, may have a built-in resiliency that allows them to overcome
difficult obstacles in their upbringing. Learning disabilities can cause major challenges for children who
are learning to read and write. Unlike developmental disabilities, learning disabilities are strictly
neurological in nature and are not related to intelligence levels. Students with dyslexia, for example,
may have extreme difficulty learning to read, but their intelligence levels are typically average or above

258 Chapter 7 | Thinking and Intelligence

This OpenStax book is available for free at

Review Questions

1. Cognitive psychology is the branch of
psychology that focuses on the study of ________.

a. human development
b. human thinking
c. human behavior
d. human society

2. Which of the following is an example of a
prototype for the concept of leadership on an
athletic team?

a. the equipment manager
b. the scorekeeper
c. the team captain
d. the quietest member of the team

3. Which of the following is an example of an
artificial concept?

a. mammals
b. a triangle’s area
c. gemstones
d. teachers

4. An event schema is also known as a cognitive

a. stereotype
b. concept
c. script
d. prototype

5. ________ provides general principles for
organizing words into meaningful sentences.

a. Linguistic determinism
b. Lexicon
c. Semantics
d. Syntax

6. ________ are the smallest unit of language that
carry meaning.

a. Lexicon
b. Phonemes
c. Morphemes
d. Syntax

7. The meaning of words and phrases is
determined by applying the rules of ________.

a. lexicon
b. phonemes
c. overgeneralization
d. semantics

8. ________ is (are) the basic sound units of a
spoken language.

a. Syntax
b. Phonemes
c. Morphemes
d. Grammar

9. A specific formula for solving a problem is
called ________.

a. an algorithm
b. a heuristic
c. a mental set
d. trial and error

10. A mental shortcut in the form of a general
problem-solving framework is called ________.

a. an algorithm
b. a heuristic
c. a mental set
d. trial and error

11. Which type of bias involves becoming fixated
on a single trait of a problem?

a. anchoring bias
b. confirmation bias
c. representative bias
d. availability bias

12. Which type of bias involves relying on a false
stereotype to make a decision?

a. anchoring bias
b. confirmation bias
c. representative bias
d. availability bias

13. Fluid intelligence is characterized by

a. being able to recall information
b. being able to create new products
c. being able to understand and communicate

with different cultures
d. being able to see complex relationships and

solve problems

Chapter 7 | Thinking and Intelligence 259

14. Which of the following is not one of
Gardner’s Multiple Intelligences?

a. creative
b. spatial
c. linguistic
d. musical

15. Which theorist put forth the triarchic theory
of intelligence?

a. Goleman
b. Gardner
c. Sternberg
d. Steitz

16. When you are examining data to look for
trends, which type of intelligence are you using

a. practical
b. analytical
c. emotional
d. creative

17. In order for a test to be normed and
standardized it must be tested on ________.

a. a group of same-age peers
b. a representative sample
c. children with mental disabilities
d. children of average intelligence

18. The mean score for a person with an average
IQ is ________.

a. 70
b. 130
c. 85
d. 100

19. Who developed the IQ test most widely used

a. Sir Francis Galton
b. Alfred Binet
c. Louis Terman
d. David Wechsler

20. The DSM-5 now uses ________ as a diagnostic
label for what was once referred to as mental

a. autism and developmental disabilities
b. lowered intelligence
c. intellectual disability
d. cognitive disruption

21. Where does high intelligence come from?
a. genetics
b. environment
c. both A and B
d. neither A nor B

22. Arthur Jensen believed that ________.
a. genetics was solely responsible for

b. environment was solely responsible for

c. intelligence level was determined by race
d. IQ tests do not take socioeconomic status

into account

23. What is a learning disability?
a. a developmental disorder
b. a neurological disorder
c. an emotional disorder
d. an intellectual disorder

24. Which of the following statements is true?
a. Poverty always affects whether individuals

are able to reach their full intellectual

b. An individual’s intelligence is determined
solely by the intelligence levels of his

c. The environment in which an individual is
raised is the strongest predictor of her
future intelligence

d. There are many factors working together to
influence an individual’s intelligence level.

Critical Thinking Questions

25. Describe an event schema that you would notice at a sporting event.

26. Explain why event schemata have so much power over human behavior.

27. How do words not only represent our thoughts but also represent our values?

260 Chapter 7 | Thinking and Intelligence

This OpenStax book is available for free at

28. How could grammatical errors actually be indicative of language acquisition in children?

29. How do words not only represent our thoughts but also represent our values?

30. What is functional fixedness and how can overcoming it help you solve problems?

31. How does an algorithm save you time and energy when solving a problem?

32. Describe a situation in which you would need to use practical intelligence.

33. Describe a situation in which cultural intelligence would help you communicate better.

34. Why do you think different theorists have defined intelligence in different ways?

35. Compare and contrast the benefits of the Stanford-Binet IQ test and Wechsler’s IQ tests.

36. What evidence exists for a genetic component to an individual’s IQ?

37. Describe the relationship between learning disabilities and intellectual disabilities to intelligence.

Personal Application Questions

38. Describe a natural concept that you know fully but that would be difficult for someone else to
understand and explain why it would be difficult.

39. Can you think of examples of how language affects cognition?

40. Which type of bias do you recognize in your own decision making processes? How has this bias
affected how you’ve made decisions in the past and how can you use your awareness of it to improve your
decisions making skills in the future?

41. What influence do you think emotional intelligence plays in your personal life?

42. In thinking about the case of Candace described earlier, do you think that Candace benefitted or
suffered as a result of consistently being passed on to the next grade?

43. Do you believe your level of intelligence was improved because of the stimuli in your childhood
environment? Why or why not?

Chapter 7 | Thinking and Intelligence 261

262 Chapter 7 | Thinking and Intelligence

This OpenStax book is available for free at

Chapter 8


Figure 8.1 Photographs can trigger our memories and bring past experiences back to life. (credit: modification of
work by Cory Zanker)

Chapter Outline

8.1 How Memory Functions

8.2 Parts of the Brain Involved with Memory

8.3 Problems with Memory

8.4 Ways to Enhance Memory


We may be top-notch learners, but if we don’t have a way to store what we’ve learned, what good is the
knowledge we’ve gained?

Take a few minutes to imagine what your day might be like if you could not remember anything you had
learned. You would have to figure out how to get dressed. What clothing should you wear, and how do
buttons and zippers work? You would need someone to teach you how to brush your teeth and tie your
shoes. Who would you ask for help with these tasks, since you wouldn’t recognize the faces of these people
in your house? Wait . . . is this even your house? Uh oh, your stomach begins to rumble and you feel
hungry. You’d like something to eat, but you don’t know where the food is kept or even how to prepare it.
Oh dear, this is getting confusing. Maybe it would be best just go back to bed. A bed . . . what is a bed?

We have an amazing capacity for memory, but how, exactly, do we process and store information? Are
there different kinds of memory, and if so, what characterizes the different types? How, exactly, do we
retrieve our memories? And why do we forget? This chapter will explore these questions as we learn about

Chapter 8 | Memory 263

8.1 How Memory Functions

Learning Objectives

By the end of this section, you will be able to:
• Discuss the three basic functions of memory
• Describe the three stages of memory storage
• Describe and distinguish between procedural and declarative memory and semantic and

episodic memory

Memory is an information processing system; therefore, we often compare it to a computer. Memory is the
set of processes used to encode, store, and retrieve information over different periods of time (Figure 8.2).

Figure 8.2 Encoding involves the input of information into the memory system. Storage is the retention of the
encoded information. Retrieval, or getting the information out of memory and back into awareness, is the third

Watch this video of unexpected facts about memory ( to learn


We get information into our brains through a process called encoding, which is the input of information
into the memory system. Once we receive sensory information from the environment, our brains label or
code it. We organize the information with other similar information and connect new concepts to existing
concepts. Encoding information occurs through automatic processing and effortful processing.

If someone asks you what you ate for lunch today, more than likely you could recall this information quite
easily. This is known as automatic processing, or the encoding of details like time, space, frequency, and
the meaning of words. Automatic processing is usually done without any conscious awareness. Recalling
the last time you studied for a test is another example of automatic processing. But what about the actual
test material you studied? It probably required a lot of work and attention on your part in order to encode
that information. This is known as effortful processing (Figure 8.3).


264 Chapter 8 | Memory

This OpenStax book is available for free at

Figure 8.3 When you first learn new skills such as driving a car, you have to put forth effort and attention to encode
information about how to start a car, how to brake, how to handle a turn, and so on. Once you know how to drive, you
can encode additional information about this skill automatically. (credit: Robert Couse-Baker)

What are the most effective ways to ensure that important memories are well encoded? Even a simple
sentence is easier to recall when it is meaningful (Anderson, 1984). Read the following sentences
(Bransford & McCarrell, 1974), then look away and count backwards from 30 by threes to zero, and then
try to write down the sentences (no peeking back at this page!).

1. The notes were sour because the seams split.

2. The voyage wasn’t delayed because the bottle shattered.

3. The haystack was important because the cloth ripped.

How well did you do? By themselves, the statements that you wrote down were most likely confusing
and difficult for you to recall. Now, try writing them again, using the following prompts: bagpipe, ship
christening, and parachutist. Next count backwards from 40 by fours, then check yourself to see how
well you recalled the sentences this time. You can see that the sentences are now much more memorable
because each of the sentences was placed in context. Material is far better encoded when you make it

There are three types of encoding. The encoding of words and their meaning is known as semantic
encoding. It was first demonstrated by William Bousfield (1935) in an experiment in which he asked
people to memorize words. The 60 words were actually divided into 4 categories of meaning, although
the participants did not know this because the words were randomly presented. When they were asked
to remember the words, they tended to recall them in categories, showing that they paid attention to the
meanings of the words as they learned them.

Visual encoding is the encoding of images, and acoustic encoding is the encoding of sounds, words in
particular. To see how visual encoding works, read over this list of words: car, level, dog, truth, book, value.
If you were asked later to recall the words from this list, which ones do you think you’d most likely
remember? You would probably have an easier time recalling the words car, dog, and book, and a more
difficult time recalling the words level, truth, and value. Why is this? Because you can recall images (mental
pictures) more easily than words alone. When you read the words car, dog, and book you created images
of these things in your mind. These are concrete, high-imagery words. On the other hand, abstract words
like level, truth, and value are low-imagery words. High-imagery words are encoded both visually and
semantically (Paivio, 1986), thus building a stronger memory.

Now let’s turn our attention to acoustic encoding. You are driving in your car and a song comes on the
radio that you haven’t heard in at least 10 years, but you sing along, recalling every word. In the United
States, children often learn the alphabet through song, and they learn the number of days in each month
through rhyme: “Thirty days hath September, / April, June, and November; / All the rest have thirty-
one, / Save February, with twenty-eight days clear, / And twenty-nine each leap year.” These lessons are

Chapter 8 | Memory 265

easy to remember because of acoustic encoding. We encode the sounds the words make. This is one of the
reasons why much of what we teach young children is done through song, rhyme, and rhythm.

Which of the three types of encoding do you think would give you the best memory of verbal information?
Some years ago, psychologists Fergus Craik and Endel Tulving (1975) conducted a series of experiments
to find out. Participants were given words along with questions about them. The questions required the
participants to process the words at one of the three levels. The visual processing questions included such
things as asking the participants about the font of the letters. The acoustic processing questions asked
the participants about the sound or rhyming of the words, and the semantic processing questions asked
the participants about the meaning of the words. After participants were presented with the words and
questions, they were given an unexpected recall or recognition task.

Words that had been encoded semantically were better remembered than those encoded visually or
acoustically. Semantic encoding involves a deeper level of processing than the shallower visual or acoustic
encoding. Craik and Tulving concluded that we process verbal information best through semantic
encoding, especially if we apply what is called the self-reference effect. The self-reference effect is the
tendency for an individual to have better memory for information that relates to oneself in comparison
to material that has less personal relevance (Rogers, Kuiper, & Kirker, 1977). Could semantic encoding be
beneficial to you as you attempt to memorize the concepts in this chapter?


Once the information has been encoded, we have to somehow retain it. Our brains take the encoded
information and place it in storage. Storage is the creation of a permanent record of information.

In order for a memory to go into storage (i.e., long-term memory), it has to pass through three distinct
stages: Sensory Memory, Short-Term Memory, and finally Long-Term Memory. These stages were first
proposed by Richard Atkinson and Richard Shiffrin (1968). Their model of human memory (Figure 8.4),
called Atkinson and Shiffrin’s model, is based on the belief that we process memories in the same way that
a computer processes information.

Figure 8.4 According to the Atkinson-Shiffrin model of memory, information passes through three distinct stages in
order for it to be stored in long-term memory.

Atkinson and Shiffrin’s model is not the only model of memory. Baddeley and Hitch (1974) proposed
a working memory model in which short-term memory has different forms. In their model, storing
memories in short-term memory is like opening different files on a computer and adding information. The
working memory files hold a limited amount of information. The type of short-term memory (or computer
file) depends on the type of information received. There are memories in visual-spatial form, as well as
memories of spoken or written material, and they are stored in three short-term systems: a visuospatial
sketchpad, an episodic buffer (Baddeley, 2000), and a phonological loop. According to Baddeley and

266 Chapter 8 | Memory

This OpenStax book is available for free at

Hitch, a central executive part of memory supervises or controls the flow of information to and from the
three short-term systems, and the central executive is responsible for moving information into long-term

Sensory Memory

In the Atkinson-Shiffrin model, stimuli from the environment are processed first in sensory memory:
storage of brief sensory events, such as sights, sounds, and tastes. It is very brief storage—up to a couple
of seconds. We are constantly bombarded with sensory information. We cannot absorb all of it, or even
most of it. And most of it has no impact on our lives. For example, what was your professor wearing the
last class period? As long as the professor was dressed appropriately, it does not really matter what she
was wearing. Sensory information about sights, sounds, smells, and even textures, which we do not view
as valuable information, we discard. If we view something as valuable, the information will move into our
short-term memory system.

Short-Term Memory

Short-term memory (STM) is a temporary storage system that processes incoming sensory memory. The
terms short-term and working memory are sometimes used interchangeably, but they are not exactly the
same. Short-term memory is more accurately described as a component of working memory. Short-term
memory takes information from sensory memory and sometimes connects that memory to something
already in long-term memory. Short-term memory storage lasts 15 to 30 seconds. Think of it as the
information you have displayed on your computer screen, such as a document, spreadsheet, or website.
Then, information in STM goes to long-term memory (you save it to your hard drive), or it is discarded
(you delete a document or close a web browser).

Rehearsal moves information from short-term memory to long-term memory. Active rehearsal is a way of
attending to information to move it from short-term to long-term memory. During active rehearsal, you
repeat (practice) the information to be remembered. If you repeat it enough, it may be moved into long-
term memory. For example, this type of active rehearsal is the way many children learn their ABCs by
singing the alphabet song. Alternatively, elaborative rehearsal is the act of linking new information you are
trying to learn to existing information that you already know. For example, if you meet someone at a party
and your phone is dead but you want to remember his phone number, which starts with area code 203,
you might remember that your uncle Abdul lives in Connecticut and has a 203 area code. This way, when
you try to remember the phone number of your new prospective friend, you will easily remember the area
code. Craik and Lockhart (1972) proposed the levels of processing hypothesis that states the deeper you
think about something, the better you remember it.

You may find yourself asking, “How much information can our memory handle at once?” To explore the
capacity and duration of your short-term memory, have a partner read the strings of random numbers
(Figure 8.5) out loud to you, beginning each string by saying, “Ready?” and ending each by saying,
“Recall,” at which point you should try to write down the string of numbers from memory.

Figure 8.5 Work through this series of numbers using the recall exercise explained above to determine the longest
string of digits that you can store.

Note the longest string at which you got the series correct. For most people, the capacity will probably
be close to 7 plus or minus 2. In 1956, George Miller reviewed most of the research on the capacity of
short-term memory and found that people can retain between 5 and 9 items, so he reported the capacity of
short-term memory was the “magic number” 7 plus or minus 2. However, more contemporary research has
found working memory capacity is 4 plus or minus 1 (Cowan, 2010). Generally, recall is somewhat better

Chapter 8 | Memory 267

for random numbers than for random letters (Jacobs, 1887) and also often slightly better for information
we hear (acoustic encoding) rather than information we see (visual encoding) (Anderson, 1969).

Memory trace decay and interference are two factors that affect short-term memory retention. Peterson
and Peterson (1959) investigated short-term memory using the three letter sequences called trigrams
(e.g., CLS) that had to be recalled after various time intervals between 3 and 18 seconds. Participants
remembered about 80% of the trigrams after a 3-second delay, but only 10% after a delay of 18 seconds,
which caused them to conclude that short-term memory decayed in 18 seconds. During decay, the memory
trace becomes less activated over time, and the information is forgotten. However, Keppel and Underwood
(1962) examined only the first trials of the trigram task and found that proactive interference also affected
short-term memory retention. During proactive interference, previously learned information interferes
with the ability to learn new information. Both memory trace decay and proactive interference affect short-
term memory. Once the information reaches long-term memory, it has to be consolidated at both the
synaptic level, which takes a few hours, and into the memory system, which can take weeks or longer.

Long-term Memory

Long-term memory (LTM) is the continuous storage of information. Unlike short-term memory, long-term
memory storage capacity is believed to be unlimited. It encompasses all the things you can remember
that happened more than just a few minutes ago. One cannot really consider long-term memory without
thinking about the way it is organized. Really quickly, what is the first word that comes to mind when
you hear “peanut butter”? Did you think of jelly? If you did, you probably have associated peanut butter
and jelly in your mind. It is generally accepted that memories are organized in semantic (or associative)
networks (Collins & Loftus, 1975). A semantic network consists of concepts, and as you may recall
from what you’ve learned about memory, concepts are categories or groupings of linguistic information,
images, ideas, or memories, such as life experiences. Although individual experiences and expertise can
affect concept arrangement, concepts are believed to be arranged hierarchically in the mind (Anderson &
Reder, 1999; Johnson & Mervis, 1997, 1998; Palmer, Jones, Hennessy, Unze, & Pick, 1989; Rosch, Mervis,
Gray, Johnson, & Boyes-Braem, 1976; Tanaka & Taylor, 1991). Related concepts are linked, and the strength
of the link depends on how often two concepts have been associated.

Semantic networks differ depending on personal experiences. Importantly for memory, activating any part
of a semantic network also activates the concepts linked to that part to a lesser degree. The process is
known as spreading activation (Collins & Loftus, 1975). If one part of a network is activated, it is easier to
access the associated concepts because they are already partially activated. When you remember or recall
something, you activate a concept, and the related concepts are more easily remembered because they
are partially activated. However, the activations do not spread in just one direction. When you remember
something, you usually have several routes to get the information you are trying to access, and the more
links you have to a concept, the better your chances of remembering.

There are two types of long-term memory: explicit and implicit (Figure 8.6). Understanding the difference
between explicit memory and implicit memory is important because aging, particular types of brain
trauma, and certain disorders can impact explicit and implicit memory in different ways. Explicit
memories are those we consciously try to remember, recall, and report. For example, if you are studying
for your chemistry exam, the material you are learning will be part of your explicit memory. In keeping
with the computer analogy, some information in your long-term memory would be like the information
you have saved on the hard drive. It is not there on your desktop (your short-term memory), but most
of the time you can pull up this information when you want it. Not all long-term memories are strong
memories, and some memories can only be recalled using prompts. For example, you might easily recall a
fact, such as the capital of the United States, but you might struggle to recall the name of the restaurant at
which you had dinner when you visited a nearby city last summer. A prompt, such as that the restaurant
was named after its owner, might help you recall the name of the restaurant. Explicit memory is sometimes
referred to as declarative memory, because it can be put into words. Explicit memory is divided into

268 Chapter 8 | Memory

This OpenStax book is available for free at

episodic memory and semantic memory.

View this video that explains short-term and long-term memory ( to
learn more about how memories are stored and retrieved.

Episodic memory is information about events we have personally experienced (i.e., an episode). For
instance, the memory of your last birthday is an episodic memory. Usually, episodic memory is reported as
a story. The concept of episodic memory was first proposed about in the 1970s (Tulving, 1972). Since then,
Tulving and others have reformulated the theory, and currently scientists believe that episodic memory is
memory about happenings in particular places at particular times—the what, where, and when of an event
(Tulving, 2002). It involves recollection of visual imagery as well as the feeling of familiarity (Hassabis &
Maguire, 2007). Semantic memory is knowledge about words, concepts, and language-based knowledge
and facts. Semantic memory is typically reported as facts. Semantic means having to do with language and
knowledge about language. For example, answers to the following questions like “what is the definition of
psychology” and “who was the first African American president of the United States” are stored in your
semantic memory.

Implicit memories are long-term memories that are not part of our consciousness. Although implicit
memories are learned outside of our awareness and cannot be consciously recalled, implicit memory is
demonstrated in the performance of some task (Roediger, 1990; Schacter, 1987). Implicit memory has been
studied with cognitive demand tasks, such as performance on artificial grammars (Reber, 1976), word
memory (Jacoby, 1983; Jacoby & Witherspoon, 1982), and learning unspoken and unwritten contingencies
and rules (Greenspoon, 1955; Giddan & Eriksen, 1959; Krieckhaus & Eriksen, 1960). Returning to the
computer metaphor, implicit memories are like a program running in the background, and you are not
aware of their influence. Implicit memories can influence observable behaviors as well as cognitive tasks.
In either case, you usually cannot put the memory into words that adequately describe the task. There are
several types of implicit memories, including procedural, priming, and emotional conditioning.


Chapter 8 | Memory 269

Figure 8.6 There are two components of long-term memory: explicit and implicit. Explicit memory includes episodic
and semantic memory. Implicit memory includes procedural memory and things learned through conditioning.

Implicit procedural memory is often studied using observable behaviors (Adams, 1957; Lacey & Smith,
1954; Lazarus & McCleary, 1951). Implicit procedural memory stores information about the way to do
something, and it is the memory for skilled actions, such as brushing your teeth, riding a bicycle, or driving
a car. You were probably not that good at riding a bicycle or driving a car the first time you tried, but you
were much better after doing those things for a year. Your improved bicycle riding was due to learning
balancing abilities. You likely thought about staying upright in the beginning, but now you just do it.
Moreover, you probably are good at staying balanced, but cannot tell someone the exact way you do it.
Similarly, when you first learned to drive, you probably thought about a lot of things that you just do now
without much thought. When you first learned to do these tasks, someone may have told you how to do
them, but everything you learned since those instructions that you cannot readily explain to someone else
as the way to do it is implicit memory.

Implicit priming is another type of implicit memory (Schacter, 1992). During priming exposure to a
stimulus affects the response to a later stimulus. Stimuli can vary and may include words, pictures, and
other stimuli to elicit a response or increase recognition. For instance, some people really enjoy picnics.
They love going into nature, spreading a blanket on the ground, and eating a delicious meal. Now,
unscramble the following letters to make a word.


What word did you come up with? Chances are good that it was “plate.”

Had you read, “Some people really enjoy growing flowers. They love going outside to their garden,
fertilizing their plants, and watering their flowers,” you probably would have come up with the word
“petal” instead of plate.

Do you recall the earlier discussion of semantic networks? The reason people are more likely to come up
with “plate” after reading about a picnic is that plate is associated (linked) with picnic. Plate was primed
by activating the semantic network. Similarly, “petal” is linked to flower and is primed by flower. Priming
is also the reason you probably said jelly in response to peanut butter.

Implicit emotional conditioning is the type of memory involved in classically conditioned emotion
responses (Olson & Fazio, 2001). These emotional relationships cannot be reported or recalled but can be

270 Chapter 8 | Memory

This OpenStax book is available for free at

associated with different stimuli. For example, specific smells can cause specific emotional responses for
some people. If there is a smell that makes you feel positive and nostalgic, and you don’t know where that
response comes from, it is an implicit emotional response. Similarly, most people have a song that causes a
specific emotional response. That song’s effect could be an implicit emotional memory (Yang, Xu, Du, Shi,
& Fang, 2011).

Can You Remember Everything You Ever Did or Said?

Episodic memories are also called autobiographical memories. Let’s quickly test your autobiographical
memory. What were you wearing exactly five years ago today? What did you eat for lunch on April 10, 2009?
You probably find it difficult, if not impossible, to answer these questions. Can you remember every event you
have experienced over the course of your life—meals, conversations, clothing choices, weather conditions,
and so on? Most likely none of us could even come close to answering these questions; however, American
actress Marilu Henner, best known for the television show Taxi, can remember. She has an amazing and highly
superior autobiographical memory (Figure 8.7).

Figure 8.7 Marilu Henner’s super autobiographical memory is known as hyperthymesia. (credit: Mark

Very few people can recall events in this way; right now, fewer than 20 have been identified as having this
ability, and only a few have been studied (Parker, Cahill & McGaugh 2006). And although hyperthymesia
normally appears in adolescence, two children in the United States appear to have memories from well before
their tenth birthdays.

Watch this video about superior autobiographical memory ( from
the television news show 60 Minutes to learn more.


So you have worked hard to encode (via effortful processing) and store some important information for
your upcoming final exam. How do you get that information back out of storage when you need it? The
act of getting information out of memory storage and back into conscious awareness is known as retrieval.
This would be similar to finding and opening a paper you had previously saved on your computer’s hard
drive. Now it’s back on your desktop, and you can work with it again. Our ability to retrieve information
from long-term memory is vital to our everyday functioning. You must be able to retrieve information



Chapter 8 | Memory 271

from memory in order to do everything from knowing how to brush your hair and teeth, to driving to
work, to knowing how to perform your job once you get there.

There are three ways you can retrieve information out of your long-term memory storage system: recall,
recognition, and relearning. Recall is what we most often think about when we talk about memory
retrieval: it means you can access information without cues. For example, you would use recall for an
essay test. Recognition happens when you identify information that you have previously learned after
encountering it again. It involves a process of comparison. When you take a multiple-choice test, you
are relying on recognition to help you choose the correct answer. Here is another example. Let’s say you
graduated from high school 10 years ago, and you have returned to your hometown for your 10-year
reunion. You may not be able to recall all of your classmates, but you recognize many of them based on
their yearbook photos.

The third form of retrieval is relearning, and it’s just what it sounds like. It involves learning information
that you previously learned. Whitney took Spanish in high school, but after high school she did not have
the opportunity to speak Spanish. Whitney is now 31, and her company has offered her an opportunity
to work in their Mexico City office. In order to prepare herself, she enrolls in a Spanish course at the local
community center. She’s surprised at how quickly she’s able to pick up the language after not speaking it
for 13 years; this is an example of relearning.

8.2 Parts of the Brain Involved with Memory

Learning Objectives

By the end of this section, you will be able to:
• Explain the brain functions involved in memory
• Recognize the roles of the hippocampus, amygdala, and cerebellum

Are memories stored in just one part of the brain, or are they stored in many different parts of the brain?
Karl Lashley began exploring this problem, about 100 years ago, by making lesions in the brains of animals
such as rats and monkeys. He was searching for evidence of the engram: the group of neurons that serve
as the “physical representation of memory” (Josselyn, 2010). First, Lashley (1950) trained rats to find their
way through a maze. Then, he used the tools available at the time—in this case a soldering iron—to create
lesions in the rats’ brains, specifically in the cerebral cortex. He did this because he was trying to erase the
engram, or the original memory trace that the rats had of the maze.

Lashley did not find evidence of the engram, and the rats were still able to find their way through the
maze, regardless of the size or location of the lesion. Based on his creation of lesions and the animals’
reaction, he formulated the equipotentiality hypothesis: if part of one area of the brain involved in
memory is damaged, another part of the same area can take over that memory function (Lashley, 1950).
Although Lashley’s early work did not confirm the existence of the engram, modern psychologists are
making progress locating it. For example, Eric Kandel has spent decades studying the synapse and its
role in controlling the flow of information through neural circuits needed to store memories (Mayford,
Siegelbaum, & Kandel, 2012).

Many scientists believe that the entire brain is involved with memory. However, since Lashley’s research,
other scientists have been able to look more closely at the brain and memory. They have argued that
memory is located in specific parts of the brain, and specific neurons can be recognized for their
involvement in forming memories. The main parts of the brain involved with memory are the amygdala,
the hippocampus, the cerebellum, and the prefrontal cortex (Figure 8.8).

272 Chapter 8 | Memory

This OpenStax book is available for free at

Figure 8.8 The amygdala is involved in fear and fear memories. The hippocampus is associated with declarative
and episodic memory as well as recognition memory. The cerebellum plays a role in processing procedural
memories, such as how to play the piano. The prefrontal cortex appears to be involved in remembering semantic


First, let’s look at the role of the amygdala in memory formation. The main job of the amygdala is to
regulate emotions, such as fear and aggression (Figure 8.8). The amygdala plays a part in how memories
are stored because storage is influenced by stress hormones. For example, one researcher experimented
with rats and the fear response (Josselyn, 2010). Using Pavlovian conditioning, a neutral tone was paired
with a foot shock to the rats. This produced a fear memory in the rats. After being conditioned, each time
they heard the tone, they would freeze (a defense response in rats), indicating a memory for the impending
shock. Then the researchers induced cell death in neurons in the lateral amygdala, which is the specific area
of the brain responsible for fear memories. They found the fear memory faded (became extinct). Because of
its role in processing emotional information, the amygdala is also involved in memory consolidation: the
process of transferring new learning into long-term memory. The amygdala seems to facilitate encoding
memories at a deeper level when the event is emotionally arousing.

In this TED Talk called “A Mouse. A Laser Beam. A Manipulated Memory,” (
mousebeam) Steve Ramirez and Xu Liu from MIT talk about using laser beams to manipulate fear
memory in rats. Find out why their work caused a media frenzy once it was published in Science.


Another group of researchers also experimented with rats to learn how the hippocampus functions in
memory processing (Figure 8.8). They created lesions in the hippocampi of the rats, and found that the
rats demonstrated memory impairment on various tasks, such as object recognition and maze running.
They concluded that the hippocampus is involved in memory, specifically normal recognition memory as
well as spatial memory (when the memory tasks are like recall tests) (Clark, Zola, & Squire, 2000). Another
job of the hippocampus is to project information to cortical regions that give memories meaning and
connect them with other memories. It also plays a part in memory consolidation: the process of transferring


Chapter 8 | Memory 273

new learning into long-term memory.

Injury to this area leaves us unable to process new declarative memories. One famous patient, known for
years only as H. M., had both his left and right temporal lobes (hippocampi) removed in an attempt to help
control the seizures he had been suffering from for years (Corkin, Amaral, González, Johnson, & Hyman,
1997). As a result, his declarative memory was significantly affected, and he could not form new semantic
knowledge. He lost the ability to form new memories, yet he could still remember information and events
that had occurred prior to the surgery.


Although the hippocampus seems to be more of a processing area for explicit memories, you could
still lose it and be able to create implicit memories (procedural memory, motor learning, and classical
conditioning), thanks to your cerebellum (Figure 8.8). For example, one classical conditioning experiment
is to accustom subjects to blink when they are given a puff of air to the eyes. When researchers damaged
the cerebellums of rabbits, they discovered that the rabbits were not able to learn the conditioned eye-blink
response (Steinmetz, 1999; Green & Woodruff-Pak, 2000).

Other researchers have used brain scans, including positron emission tomography (PET) scans, to learn
how people process and retain information. From these studies, it seems the prefrontal cortex is involved.
In one study, participants had to complete two different tasks: either looking for the letter a in words
(considered a perceptual task) or categorizing a noun as either living or non-living (considered a semantic
task) (Kapur et al., 1994). Participants were then asked which words they had previously seen. Recall was
much better for the semantic task than for the perceptual task. According to PET scans, there was much
more activation in the left inferior prefrontal cortex in the semantic task. In another study, encoding was
associated with left frontal activity, while retrieval of information was associated with the right frontal
region (Craik et al., 1999).


There also appear to be specific neurotransmitters involved with the process of memory, such as
epinephrine, dopamine, serotonin, glutamate, and acetylcholine (Myhrer, 2003). There continues to be
discussion and debate among researchers as to which neurotransmitter plays which specific role
(Blockland, 1996). Although we don’t yet know which role each neurotransmitter plays in memory, we do
know that communication among neurons via neurotransmitters is critical for developing new memories.
Repeated activity by neurons leads to increased neurotransmitters in the synapses and more efficient and
more synaptic connections. This is how memory consolidation occurs.

It is also believed that strong emotions trigger the formation of strong memories, and weaker emotional
experiences form weaker memories; this is called arousal theory (Christianson, 1992). For example, strong
emotional experiences can trigger the release of neurotransmitters, as well as hormones, which strengthen
memory; therefore, our memory for an emotional event is usually better than our memory for a non-
emotional event. When humans and animals are stressed, the brain secretes more of the neurotransmitter
glutamate, which helps them remember the stressful event (McGaugh, 2003). This is clearly evidenced by
what is known as the flashbulb memory phenomenon.

A flashbulb memory is an exceptionally clear recollection of an important event (Figure 8.9). Where were
you when you first heard about the 9/11 terrorist attacks? Most likely you can remember where you were
and what you were doing. In fact, a Pew Research Center (2011) survey found that for those Americans
who were age 8 or older at the time of the event, 97% can recall the moment they learned of this event,
even a decade after it happened.

274 Chapter 8 | Memory

This OpenStax book is available for free at

Figure 8.9 Most people can remember where they were when they first heard about the 9/11 terrorist attacks. This
is an example of a flashbulb memory: a record of an atypical and unusual event that has very strong emotional
associations. (credit: Michael Foran)

Inaccurate and False Memories

Even flashbulb memories for important events can have decreased accuracy with the passage of time. For
example, on at least three occasions, when asked how he heard about the terrorist attacks of 9/11, President
George W. Bush responded inaccurately. In January 2002, less than 4 months after the attacks, the then sitting
President Bush was asked how he heard about the attacks. He responded:

I was sitting there, and my Chief of Staff—well, first of all, when we walked into the classroom, I
had seen this plane fly into the first building. There was a TV set on. And you know, I thought it was
pilot error and I was amazed that anybody could make such a terrible mistake. (Greenberg, 2004,
p. 2)

Contrary to what President Bush stated, no one saw the first plane hit, except people on the ground near the
twin towers. Video footage of the first plane was not recorded because it was a normal Tuesday morning, until
the first plane hit.

Memory is not like a video recording. Human memory, even flashbulb memories, can be frail. Different parts
of them, such as the time, visual elements, and smells, are stored in different places. When something is
remembered, these components have to be put back together for the complete memory, which is known as
memory reconstruction. Each component creates a chance for an error to occur. False memory is remembering
something that did not happen. Research participants have recalled hearing a word, even though they never
heard the word (Roediger & McDermott, 2000).

Do you remember where you were when you heard about the school shooting at Marjorie Douglas High
School? Who were you with and what were you doing? What did you talk about? Can you contact those people
you were with? Do they have the same memories as you or do they have different memories?


Chapter 8 | Memory 275

8.3 Problems with Memory

Learning Objectives

By the end of this section, you will be able to:
• Compare and contrast the two types of amnesia
• Discuss the unreliability of eyewitness testimony
• Discuss encoding failure
• Discuss the various memory errors
• Compare and contrast the two types of interference

You may pride yourself on your amazing ability to remember the birthdates and ages of all of your friends
and family members, or you may be able recall vivid details of your 5th birthday party at Chuck E.
Cheese’s. However, all of us have at times felt frustrated, and even embarrassed, when our memories have
failed us. There are several reasons why this happens.


Amnesia is the loss of long-term memory that occurs as the result of disease, physical trauma, or
psychological trauma. Endel Tulving (2002) and his colleagues at the University of Toronto studied K. C.
for years. K. C. suffered a traumatic head injury in a motorcycle accident and then had severe amnesia.
Tulving writes,

the outstanding fact about K.C.’s mental make-up is his utter inability to remember any events,
circumstances, or situations from his own life. His episodic amnesia covers his whole life, from
birth to the present. The only exception is the experiences that, at any time, he has had in the last
minute or two. (Tulving, 2002, p. 14)

Anterograde Amnesia

There are two common types of amnesia: anterograde amnesia and retrograde amnesia (Figure 8.10).
Anterograde amnesia is commonly caused by brain trauma, such as a blow to the head. With anterograde
amnesia, you cannot remember new information, although you can remember information and events
that happened prior to your injury. The hippocampus is usually affected (McLeod, 2011). This suggests
that damage to the brain has resulted in the inability to transfer information from short-term to long-term
memory; that is, the inability to consolidate memories.

Many people with this form of amnesia are unable to form new episodic or semantic memories, but are
still able to form new procedural memories (Bayley & Squire, 2002). This was true of H. M., which was
discussed earlier. The brain damage caused by his surgery resulted in anterograde amnesia. H. M. would
read the same magazine over and over, having no memory of ever reading it—it was always new to him.
He also could not remember people he had met after his surgery. If you were introduced to H. M. and
then you left the room for a few minutes, he would not know you upon your return and would introduce
himself to you again. However, when presented the same puzzle several days in a row, although he did
not remember having seen the puzzle before, his speed at solving it became faster each day (because of
relearning) (Corkin, 1965, 1968).

276 Chapter 8 | Memory

This OpenStax book is available for free at

Figure 8.10 This diagram illustrates the timeline of retrograde and anterograde amnesia. Memory problems that
extend back in time before the injury and prevent retrieval of information previously stored in long-term memory are
known as retrograde amnesia. Conversely, memory problems that extend forward in time from the point of injury and
prevent the formation of new memories are called anterograde amnesia.

Retrograde Amnesia

Retrograde amnesia is loss of memory for events that occurred prior to the trauma. People with retrograde
amnesia cannot remember some or even all of their past. They have difficulty remembering episodic
memories. What if you woke up in the hospital one day and there were people surrounding your bed
claiming to be your spouse, your children, and your parents? The trouble is you don’t recognize any of
them. You were in a car accident, suffered a head injury, and now have retrograde amnesia. You don’t
remember anything about your life prior to waking up in the hospital. This may sound like the stuff of
Hollywood movies, and Hollywood has been fascinated with the amnesia plot for nearly a century, going
all the way back to the film Garden of Lies from 1915 to more recent movies such as the Jason Bourne
spy thrillers. However, for real-life sufferers of retrograde amnesia, like former NFL football player Scott
Bolzan, the story is not a Hollywood movie. Bolzan fell, hit his head, and deleted 46 years of his life in an
instant. He is now living with one of the most extreme cases of retrograde amnesia on record.

View the video story about Scott Bolzan’s amnesia and his attempts to get his life back
( to learn more.


The formulation of new memories is sometimes called construction, and the process of bringing up old
memories is called reconstruction. Yet as we retrieve our memories, we also tend to alter and modify
them. A memory pulled from long-term storage into short-term memory is flexible. New events can be
added and we can change what we think we remember about past events, resulting in inaccuracies and
distortions. People may not intend to distort facts, but it can happen in the process of retrieving old
memories and combining them with new memories (Roediger & DeSoto, 2015).


When someone witnesses a crime, that person’s memory of the details of the crime is very important in
catching the suspect. Because memory is so fragile, witnesses can be easily (and often accidentally) misled
due to the problem of suggestibility. Suggestibility describes the effects of misinformation from external
sources that leads to the creation of false memories. In the fall of 2002, a sniper in the DC area shot people
at a gas station, leaving Home Depot, and walking down the street. These attacks went on in a variety of
places for over three weeks and resulted in the deaths of ten people. During this time, as you can imagine,
people were terrified to leave their homes, go shopping, or even walk through their neighborhoods. Police
officers and the FBI worked frantically to solve the crimes, and a tip hotline was set up. Law enforcement
received over 140,000 tips, which resulted in approximately 35,000 possible suspects (Newseum, n.d.).


Chapter 8 | Memory 277

Most of the tips were dead ends, until a white van was spotted at the site of one of the shootings. The police
chief went on national television with a picture of the white van. After the news conference, several other
eyewitnesses called to say that they too had seen a white van fleeing from the scene of the shooting. At
the time, there were more than 70,000 white vans in the area. Police officers, as well as the general public,
focused almost exclusively on white vans because they believed the eyewitnesses. Other tips were ignored.
When the suspects were finally caught, they were driving a blue sedan.

As illustrated by this example, we are vulnerable to the power of suggestion, simply based on something
we see on the news. Or we can claim to remember something that in fact is only a suggestion someone
made. It is the suggestion that is the cause of the false memory.

Eyewitness Misidentification

Even though memory and the process of reconstruction can be fragile, police officers, prosecutors, and
the courts often rely on eyewitness identification and testimony in the prosecution of criminals. However,
faulty eyewitness identification and testimony can lead to wrongful convictions (Figure 8.11).

Figure 8.11 In studying cases where DNA evidence has exonerated people from crimes, the Innocence Project
discovered that eyewitness misidentification is the leading cause of wrongful convictions (Benjamin N. Cardozo
School of Law, Yeshiva University, 2009).

How does this happen? In 1984, Jennifer Thompson, then a 22-year-old college student in North Carolina,
was brutally raped at knifepoint. As she was being raped, she tried to memorize every detail of her rapist’s
face and physical characteristics, vowing that if she survived, she would help get him convicted. After the
police were contacted, a composite sketch was made of the suspect, and Jennifer was shown six photos.
She chose two, one of which was of Ronald Cotton. After looking at the photos for 4–5 minutes, she said,
“Yeah. This is the one,” and then she added, “I think this is the guy.” When questioned about this by the
detective who asked, “You’re sure? Positive?” She said that it was him. Then she asked the detective if
she did OK, and he reinforced her choice by telling her she did great. These kinds of unintended cues and
suggestions by police officers can lead witnesses to identify the wrong suspect. The district attorney was
concerned about her lack of certainty the first time, so she viewed a lineup of seven men. She said she was
trying to decide between numbers 4 and 5, finally deciding that Cotton, number 5, “Looks most like him.”
He was 22 years old.

By the time the trial began, Jennifer Thompson had absolutely no doubt that she was raped by Ronald
Cotton. She testified at the court hearing, and her testimony was compelling enough that it helped convict
him. How did she go from, “I think it’s the guy” and it “Looks most like him,” to such certainty? Gary
Wells and Deah Quinlivan (2009) assert it’s suggestive police identification procedures, such as stacking

278 Chapter 8 | Memory

This OpenStax book is available for free at

lineups to make the defendant stand out, telling the witness which person to identify, and confirming
witnesses choices by telling them “Good choice,” or “You picked the guy.”

After Cotton was convicted of the rape, he was sent to prison for life plus 50 years. After 4 years in prison,
he was able to get a new trial. Jennifer Thompson once again testified against him. This time Ronald Cotton
was given two life sentences. After serving 11 years in prison, DNA evidence finally demonstrated that
Ronald Cotton did not commit the rape, was innocent, and had served over a decade in prison for a crime
he did not commit.

Watch this first video about Ronald Cotton who was falsely convicted (
Cotton1) and then watch this second video about the task of his accuser (
Cotton2) to learn more about the fallibility of memory.

Ronald Cotton’s story, unfortunately, is not unique. There are also people who were convicted and placed
on death row, who were later exonerated. The Innocence Project is a non-profit group that works to
exonerate falsely convicted people, including those convicted by eyewitness testimony. To learn more, you
can visit

Preserving Eyewitness Memory: The Elizabeth Smart Case

Contrast the Cotton case with what happened in the Elizabeth Smart case. When Elizabeth was 14 years old
and fast asleep in her bed at home, she was abducted at knifepoint. Her nine-year-old sister, Mary Katherine,
was sleeping in the same bed and watched, terrified, as her beloved older sister was abducted. Mary Katherine
was the sole eyewitness to this crime and was very fearful. In the coming weeks, the Salt Lake City police
and the FBI proceeded with caution with Mary Katherine. They did not want to implant any false memories or
mislead her in any way. They did not show her police line-ups or push her to do a composite sketch of the
abductor. They knew if they corrupted her memory, Elizabeth might never be found. For several months, there
was little or no progress on the case. Then, about 4 months after the kidnapping, Mary Katherine first recalled
that she had heard the abductor’s voice prior to that night (he had worked exactly one day as a handyman at
the family’s home) and then she was able to name the person whose voice it was. The family contacted the
press and others recognized him—after a total of nine months, the suspect was caught and Elizabeth Smart
was returned to her family.

The Misinformation Effect

Cognitive psychologist Elizabeth Loftus has conducted extensive research on memory. She has studied
false memories as well as recovered memories of childhood sexual abuse. Loftus also developed the
misinformation effect paradigm, which holds that after exposure to additional and possibly inaccurate
information, a person may misremember the original event.

According to Loftus, an eyewitness’s memory of an event is very flexible due to the misinformation effect.
To test this theory, Loftus and John Palmer (1974) asked 45 U.S. college students to estimate the speed of
cars using different forms of questions (Figure 8.12). The participants were shown films of car accidents
and were asked to play the role of the eyewitness and describe what happened. They were asked, “About
how fast were the cars going when they (smashed, collided, bumped, hit, contacted) each other?” The



Chapter 8 | Memory 279

participants estimated the speed of the cars based on the verb used.

Participants who heard the word “smashed” estimated that the cars were traveling at a much higher
speed than participants who heard the word “contacted.” The implied information about speed, based on
the verb they heard, had an effect on the participants’ memory of the accident. In a follow-up one week
later, participants were asked if they saw any broken glass (none was shown in the accident pictures).
Participants who had been in the “smashed” group were more than twice as likely to indicate that they did
remember seeing glass. Loftus and Palmer demonstrated that a leading question encouraged them to not
only remember the cars were going faster, but to also falsely remember that they saw broken glass.

Figure 8.12 When people are asked leading questions about an event, their memory of the event may be altered.
(credit a: modification of work by Rob Young)

Controversies over Repressed and Recovered Memories

Other researchers have described how whole events, not just words, can be falsely recalled, even when
they did not happen. The idea that memories of traumatic events could be repressed has been a theme
in the field of psychology, beginning with Sigmund Freud, and the controversy surrounding the idea
continues today.

Recall of false autobiographical memories is called false memory syndrome. This syndrome has received
a lot of publicity, particularly as it relates to memories of events that do not have independent
witnesses—often the only witnesses to the abuse are the perpetrator and the victim (e.g., sexual abuse).

On one side of the debate are those who have recovered memories of childhood abuse years after
it occurred. These researchers argue that some children’s experiences have been so traumatizing and
distressing that they must lock those memories away in order to lead some semblance of a normal life.
They believe that repressed memories can be locked away for decades and later recalled intact through
hypnosis and guided imagery techniques (Devilly, 2007).

Research suggests that having no memory of childhood sexual abuse is quite common in adults. For
instance, one large-scale study conducted by John Briere and Jon Conte (1993) revealed that 59% of
450 men and women who were receiving treatment for sexual abuse that had occurred before age 18
had forgotten their experiences. Ross Cheit (2007) suggested that repressing these memories created
psychological distress in adulthood. The Recovered Memory Project was created so that victims of
childhood sexual abuse can recall these memories and allow the healing process to begin (Cheit, 2007;
Devilly, 2007).

280 Chapter 8 | Memory

This OpenStax book is available for free at

On the other side, Loftus has challenged the idea that individuals can repress memories of traumatic
events from childhood, including sexual abuse, and then recover those memories years later through
therapeutic techniques such as hypnosis, guided visualization, and age regression.

Loftus is not saying that childhood sexual abuse doesn’t happen, but she does question whether or
not those memories are accurate, and she is skeptical of the questioning process used to access these
memories, given that even the slightest suggestion from the therapist can lead to misinformation effects.
For example, researchers Stephen Ceci and Maggie Brucks (1993, 1995) asked three-year-old children to
use an anatomically correct doll to show where their pediatricians had touched them during an exam.
Fifty-five percent of the children pointed to the genital/anal area on the dolls, even when they had not
received any form of genital exam.

Ever since Loftus published her first studies on the suggestibility of eyewitness testimony in the 1970s,
social scientists, police officers, therapists, and legal practitioners have been aware of the flaws in interview
practices. Consequently, steps have been taken to decrease suggestibility of witnesses. One way is to
modify how witnesses are questioned. When interviewers use neutral and less leading language, children
more accurately recall what happened and who was involved (Goodman, 2006; Pipe, 1996; Pipe, Lamb,
Orbach, & Esplin, 2004). Another change is in how police lineups are conducted. It’s recommended that
a blind photo lineup be used. This way the person administering the lineup doesn’t know which photo
belongs to the suspect, minimizing the possibility of giving leading cues. Additionally, judges in some
states now inform jurors about the possibility of misidentification. Judges can also suppress eyewitness
testimony if they deem it unreliable.


“I’ve a grand memory for forgetting,” quipped Robert Louis Stevenson. Forgetting refers to loss of
information from long-term memory. We all forget things, like a loved one’s birthday, someone’s name, or
where we put our car keys. As you’ve come to see, memory is fragile, and forgetting can be frustrating and
even embarrassing. But why do we forget? To answer this question, we will look at several perspectives
on forgetting.

Encoding Failure

Sometimes memory loss happens before the actual memory process begins, which is encoding failure. We
can’t remember something if we never stored it in our memory in the first place. This would be like trying
to find a book on your e-reader that you never actually purchased and downloaded. Often, in order to
remember something, we must pay attention to the details and actively work to process the information
(effortful encoding). Lots of times we don’t do this. For instance, think of how many times in your life
you’ve seen a penny. Can you accurately recall what the front of a U.S. penny looks like? When researchers
Raymond Nickerson and Marilyn Adams (1979) asked this question, they found that most Americans
don’t know which one it is. The reason is most likely encoding failure. Most of us never encode the details
of the penny. We only encode enough information to be able to distinguish it from other coins. If we don’t
encode the information, then it’s not in our long-term memory, so we will not be able to remember it.

Chapter 8 | Memory 281

Figure 8.13 Can you tell which coin, (a), (b), (c), or (d) is the accurate depiction of a US nickel? The correct answer
is (c).

Memory Errors

Psychologist Daniel Schacter (2001), a well-known memory researcher, offers seven ways our memories
fail us. He calls them the seven sins of memory and categorizes them into three groups: forgetting,
distortion, and intrusion (Table 8.1).

Schacter’s Seven Sins of Memory

Sin Type Description Example

Transience Forgetting Accessibility of memory
decreases over time

Forget events that occurred
long ago

absentmindedness Forgetting Forgetting caused by lapses in

Forget where your phone is

Blocking Forgetting Accessibility of information is
temporarily blocked

Tip of the tongue

Misattribution Distortion Source of memory is confused Recalling a dream memory as
a waking memory

Suggestibility Distortion False memories Result from leading questions

Bias Distortion Memories distorted by current
belief system

Align memories to current

Persistence Intrusion Inability to forget undesirable

Traumatic events

Table 8.1

Let’s look at the first sin of the forgetting errors: transience, which means that memories can fade over
time. Here’s an example of how this happens. Nathan’s English teacher has assigned his students to read
the novel To Kill a Mockingbird. Nathan comes home from school and tells his mom he has to read this
book for class. “Oh, I loved that book!” she says. Nathan asks her what the book is about, and after some
hesitation she says, “Well . . . I know I read the book in high school, and I remember that one of the main
characters is named Scout, and her father is an attorney, but I honestly don’t remember anything else.”
Nathan wonders if his mother actually read the book, and his mother is surprised she can’t recall the plot.
What is going on here is storage decay: unused information tends to fade with the passage of time.

282 Chapter 8 | Memory

This OpenStax book is available for free at

In 1885, German psychologist Hermann Ebbinghaus analyzed the process of memorization. First, he
memorized lists of nonsense syllables. Then he measured how much he learned (retained) when he
attempted to relearn each list. He tested himself over different periods of time from 20 minutes later to 30
days later. The result is his famous forgetting curve (Figure 8.14). Due to storage decay, an average person
will lose 50% of the memorized information after 20 minutes and 70% of the information after 24 hours
(Ebbinghaus, 1885/1964). Your memory for new information decays quickly and then eventually levels

Figure 8.14 The Ebbinghaus forgetting curve shows how quickly memory for new information decays.

Are you constantly losing your cell phone? Have you ever driven back home to make sure you turned
off the stove? Have you ever walked into a room for something, but forgotten what it was? You probably
answered yes to at least one, if not all, of these examples—but don’t worry, you are not alone. We are all
prone to committing the memory error known as absentmindedness, which describes lapses in memory
caused by breaks in attention or our focus being somewhere else.

Cynthia, a psychologist, recalls a time when she recently committed the memory error of

When I was completing court-ordered psychological evaluations, each time I went to the court,
I was issued a temporary identification card with a magnetic strip which would open otherwise
locked doors. As you can imagine, in a courtroom, this identification is valuable and important
and no one wanted it to be lost or be picked up by a criminal. At the end of the day, I would
hand in my temporary identification. One day, when I was almost done with an evaluation, my
daughter’s day care called and said she was sick and needed to be picked up. It was flu season, I
didn’t know how sick she was, and I was concerned. I finished up the evaluation in the next ten
minutes, packed up my briefcase, and rushed to drive to my daughter’s day care. After I picked
up my daughter, I could not remember if I had handed back my identification or if I had left it
sitting out on a table. I immediately called the court to check. It turned out that I had handed
back my identification. Why could I not remember that? (personal communication, September
5, 2013)

When have you experienced absentmindedness?

“I just streamed this movie called Oblivion, and it had that famous actor in it. Oh, what’s his name? He’s
been in all of those movies, like The Shawshank Redemption and The Dark Knight trilogy. I think he’s even
won an Oscar. Oh gosh, I can picture his face in my mind, and hear his distinctive voice, but I just can’t
think of his name! This is going to bug me until I can remember it!” This particular error can be so
frustrating because you have the information right on the tip of your tongue. Have you ever experienced
this? If so, you’ve committed the error known as blocking: you can’t access stored information (Figure

Chapter 8 | Memory 283

Figure 8.15 Blocking is also known as tip-of-the-tongue (TOT) phenomenon. The memory is right there, but you
can’t seem to recall it, just like not being able to remember the name of that very famous actor, Morgan Freeman.
(credit: modification of work by D. Miller)

Now let’s take a look at the three errors of distortion: misattribution, suggestibility, and bias.
Misattribution happens when you confuse the source of your information. Let’s say Alejandra was dating
Lucia and they saw the first Hobbit movie together. Then they broke up and Alejandra saw the second
Hobbit movie with someone else. Later that year, Alejandra and Lucia get back together. One day, they are
discussing how the Hobbit books and movies are different and Alejandra says to Lucia, “I loved watching
the second movie with you and seeing you jump out of your seat during that super scary part.” When
Lucia responded with a puzzled and then angry look, Alejandra realized she’d committed the error of

What if someone is a victim of rape shortly after watching a television program? Is it possible that the
victim could actually blame the rape on the person she saw on television because of misattribution? This
is exactly what happened to Donald Thomson.

Australian eyewitness expert Donald Thomson appeared on a live TV discussion about the
unreliability of eyewitness memory. He was later arrested, placed in a lineup and identified by
a victim as the man who had raped her. The police charged Thomson although the rape had
occurred at the time he was on TV. They dismissed his alibi that he was in plain view of a TV
audience and in the company of the other discussants, including an assistant commissioner of
police. . . . Eventually, the investigators discovered that the rapist had attacked the woman as she
was watching TV—the very program on which Thomson had appeared. Authorities eventually
cleared Thomson. The woman had confused the rapist’s face with the face that she had seen on
TV. (Baddeley, 2004, p. 133)

The second distortion error is suggestibility. Suggestibility is similar to misattribution, since it also
involves false memories, but it’s different. With misattribution you create the false memory entirely on
your own, which is what the victim did in the Donald Thomson case above. With suggestibility, it comes
from someone else, such as a therapist or police interviewer asking leading questions of a witness during
an interview.

Memories can also be affected by bias, which is the final distortion error. Schacter (2001) says that your

284 Chapter 8 | Memory

This OpenStax book is available for free at

feelings and view of the world can actually distort your memory of past events. There are several types of

• Stereotypical bias involves racial and gender biases. For example, when Asian American and
European American research participants were presented with a list of names, they more frequently
incorrectly remembered typical African American names such as Jamal and Tyrone to be associated
with the occupation basketball player, and they more frequently incorrectly remembered typical
White names such as Greg and Howard to be associated with the occupation of politician (Payne,
Jacoby, & Lambert, 2004).

• Egocentric bias involves enhancing our memories of the past (Payne et al., 2004). Did you really
score the winning goal in that big soccer match, or did you just assist?

• Hindsight bias happens when we think an outcome was inevitable after the fact. This is the “I knew
it all along” phenomenon. The reconstructive nature of memory contributes to hindsight bias (Carli,
1999). We remember untrue events that seem to confirm that we knew the outcome all along.

Have you ever had a song play over and over in your head? How about a memory of a traumatic event,
something you really do not want to think about? When you keep remembering something, to the point
where you can’t “get it out of your head” and it interferes with your ability to concentrate on other
things, it is called persistence. It’s Schacter’s seventh and last memory error. It’s actually a failure of our
memory system because we involuntarily recall unwanted memories, particularly unpleasant ones (Figure
8.16). For instance, you witness a horrific car accident on the way to work one morning, and you can’t
concentrate on work because you keep remembering the scene.

Figure 8.16 Many veterans of military conflicts involuntarily recall unwanted, unpleasant memories. (credit:
Department of Defense photo by U.S. Air Force Tech. Sgt. Michael R. Holzworth)


Sometimes information is stored in our memory, but for some reason it is inaccessible. This is known as
interference, and there are two types: proactive interference and retroactive interference (Figure 8.17).
Have you ever gotten a new phone number or moved to a new address, but right after you tell people the
old (and wrong) phone number or address? When the new year starts, do you find you accidentally write
the previous year? These are examples of proactive interference: when old information hinders the recall
of newly learned information. Retroactive interference happens when information learned more recently
hinders the recall of older information. For example, this week you are studying about memory and
learn about the Ebbinghaus forgetting curve. Next week you study lifespan development and learn about
Erikson’s theory of psychosocial development, but thereafter have trouble remembering Ebbinghaus’s
work because you can only remember Erickson’s theory.

Chapter 8 | Memory 285

Figure 8.17 Sometimes forgetting is caused by a failure to retrieve information. This can be due to interference,
either retroactive or proactive.

8.4 Ways to Enhance Memory

Learning Objectives

By the end of this section, you will be able to:
• Recognize and apply memory-enhancing strategies
• Recognize and apply effective study techniques

Most of us suffer from memory failures of one kind or another, and most of us would like to improve our
memories so that we don’t forget where we put the car keys or, more importantly, the material we need
to know for an exam. In this section, we’ll look at some ways to help you remember better, and at some
strategies for more effective studying.


What are some everyday ways we can improve our memory, including recall? To help make sure
information goes from short-term memory to long-term memory, you can use memory-enhancing
strategies. One strategy is rehearsal, or the conscious repetition of information to be remembered (Craik &
Watkins, 1973). Think about how you learned your multiplication tables as a child. You may recall that 6 x
6 = 36, 6 x 7 = 42, and 6 x 8 = 48. Memorizing these facts is rehearsal.

Another strategy is chunking: you organize information into manageable bits or chunks (Bodie, Powers,
& Fitch-Hauser, 2006). Chunking is useful when trying to remember information like dates and phone
numbers. Instead of trying to remember 5205550467, you remember the number as 520-555-0467. So, if you
met an interesting person at a party and you wanted to remember his phone number, you would naturally
chunk it, and you could repeat the number over and over, which is the rehearsal strategy.

286 Chapter 8 | Memory

This OpenStax book is available for free at

Try this fun activity that employs a memory-enchancing strategy (
to learn more.

You could also enhance memory by using elaborative rehearsal: a technique in which you think about the
meaning of new information and its relation to knowledge already stored in your memory (Tigner, 1999).
Elaborative rehearsal involves both linking the information to knowledge already stored and repeating the
information. For example, in this case, you could remember that 520 is an area code for Arizona and the
person you met is from Arizona. This would help you better remember the 520 prefix. If the information is
retained, it goes into long-term memory.

Mnemonic devices are memory aids that help us organize information for encoding (Figure 8.18). They
are especially useful when we want to recall larger bits of information such as steps, stages, phases, and
parts of a system (Bellezza, 1981). Brian needs to learn the order of the planets in the solar system, but he’s
having a hard time remembering the correct order. His friend Kelly suggests a mnemonic device that can
help him remember. Kelly tells Brian to simply remember the name Mr. VEM J. SUN, and he can easily
recall the correct order of the planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
You might use a mnemonic device to help you remember someone’s name, a mathematical formula, or the
order of mathematical operations.

Figure 8.18 This is a knuckle mnemonic to help you remember the number of days in each month. Months with 31
days are represented by the protruding knuckles and shorter months fall in the spots between knuckles. (credit:
modification of work by Cory Zanker)

If you have ever watched the television show Modern Family, you might have seen Phil Dunphy explain
how he remembers names:

The other day I met this guy named Carl. Now, I might forget that name, but he was wearing
a Grateful Dead t-shirt. What’s a band like the Grateful Dead? Phish. Where do fish live? The
ocean. What else lives in the ocean? Coral. Hello, Co-arl. (Wrubel & Spiller, 2010)

It seems the more vivid or unusual the mnemonic, the easier it is to remember. The key to using any
mnemonic successfully is to find a strategy that works for you.


Chapter 8 | Memory 287

Joshua Foer is a science writer who “accidentally” won the U.S. Memory Championships. Watch his
TEDTalk, titled “Feats of Memory Anyone Can Do,” in which he explains a mnemonic device called
the memory palace ( to learn more.

Some other strategies that are used to improve memory include expressive writing and saying words
aloud. Expressive writing helps boost your short-term memory, particularly if you write about a traumatic
experience in your life. Masao Yogo and Shuji Fujihara (2008) had participants write for 20-minute
intervals several times per month. The participants were instructed to write about a traumatic experience,
their best possible future selves, or a trivial topic. The researchers found that this simple writing task
increased short-term memory capacity after five weeks, but only for the participants who wrote about
traumatic experiences. Psychologists can’t explain why this writing task works, but it does.

What if you want to remember items you need to pick up at the store? Simply say them out loud to
yourself. A series of studies (MacLeod, Gopie, Hourihan, Neary, & Ozubko, 2010) found that saying a
word out loud improves your memory for the word because it increases the word’s distinctiveness. Feel
silly, saying random grocery items aloud? This technique works equally well if you just mouth the words.
Using these techniques increased participants’ memory for the words by more than 10%. These techniques
can also be used to help you study.


Based on the information presented in this chapter, here are some strategies and suggestions to help you
hone your study techniques (Figure 8.19). The key with any of these strategies is to figure out what works
best for you.

Figure 8.19 Memory techniques can be useful when studying for class. (credit: Barry Pousman)

• Use elaborative rehearsal: In a famous article, Fergus Craik and Robert Lockhart (1972) discussed
their belief that information we process more deeply goes into long-term memory. Their theory is
called levels of processing. If we want to remember a piece of information, we should think about
it more deeply and link it to other information and memories to make it more meaningful. For
example, if we are trying to remember that the hippocampus is involved with memory processing,
we might envision a hippopotamus with excellent memory and then we could better remember the


288 Chapter 8 | Memory

This OpenStax book is available for free at

• Apply the self-reference effect: As you go through the process of elaborative rehearsal, it would
be even more beneficial to make the material you are trying to memorize personally meaningful
to you. In other words, make use of the self-reference effect. Write notes in your own words.
Write definitions from the text, and then rewrite them in your own words. Relate the material to
something you have already learned for another class, or think how you can apply the concepts to
your own life. When you do this, you are building a web of retrieval cues that will help you access
the material when you want to remember it.

• Use distributed practice: Study across time in short durations rather than trying to cram it all in
at once. Memory consolidation takes time, and studying across time allows time for memories to
consolidate. In addition, cramming can cause the links between concepts to become so active that
you get stuck in a link, and it prevents you from accessing the rest of the information that you

• Rehearse, rehearse, rehearse: Review the material over time, in spaced and organized study
sessions. Organize and study your notes, and take practice quizzes/exams. Link the new
information to other information you already know well.

• Study efficiently: Students are great highlighters, but highlighting is not very efficient because
students spend too much time studying the things they already learned. Instead of highlighting,
use index cards. Write the question on one side and the answer on the other side. When you study,
separate your cards into those you got right and those you got wrong. Study the ones you got wrong
and keep sorting. Eventually, all your cards will be in the pile you answered correctly.

• Be aware of interference: To reduce the likelihood of interference, study during a quiet time
without interruptions or distractions (like television or music).

• Keep moving: Of course you already know that exercise is good for your body, but did you also
know it’s also good for your mind? Research suggests that regular aerobic exercise (anything that
gets your heart rate elevated) is beneficial for memory (van Praag, 2008). Aerobic exercise promotes
neurogenesis: the growth of new brain cells in the hippocampus, an area of the brain known to play
a role in memory and learning.

• Get enough sleep: While you are sleeping, your brain is still at work. During sleep the brain
organizes and consolidates information to be stored in long-term memory (Abel & Bäuml, 2013).

• Make use of mnemonic devices: As you learned earlier in this chapter, mnemonic devices often
help us to remember and recall information. There are different types of mnemonic devices, such
as the acronym. An acronym is a word formed by the first letter of each of the words you want to
remember. For example, even if you live near one, you might have difficulty recalling the names
of all five Great Lakes. What if I told you to think of the word Homes? HOMES is an acronym
that represents Huron, Ontario, Michigan, Erie, and Superior: the five Great Lakes. Another type of
mnemonic device is an acrostic: you make a phrase of all the first letters of the words. For example,
if you are taking a math test and you are having difficulty remembering the order of operations,
recalling the following sentence will help you: “Please Excuse My Dear Aunt Sally,” because the
order of mathematical operations is Parentheses, Exponents, Multiplication, Division, Addition,
Subtraction. There also are jingles, which are rhyming tunes that contain key words related to the
concept, such as i before e, except after c.

Chapter 8 | Memory 289


acoustic encoding


anterograde amnesia

arousal theory

Atkinson-Shiffrin model

automatic processing





declarative memory

effortful processing

elaborative rehearsal



episodic memory

equipotentiality hypothesis

explicit memory

false memory syndrome

flashbulb memory


implicit memory

levels of processing

Key Terms

lapses in memory that are caused by breaks in attention or our focus being
somewhere else

input of sounds, words, and music

loss of long-term memory that occurs as the result of disease, physical trauma, or psychological

loss of memory for events that occur after the brain trauma

strong emotions trigger the formation of strong memories and weaker emotional
experiences form weaker memories

memory model that states we process information through three systems:
sensory memory, short-term memory, and long-term memory

encoding of informational details like time, space, frequency, and the meaning of

how feelings and view of the world distort memory of past events

memory error in which you cannot access stored information

organizing information into manageable bits or chunks

formulation of new memories

type of long-term memory of facts and events we personally experience

encoding of information that takes effort and attention

thinking about the meaning of new information and its relation to knowledge
already stored in your memory

input of information into the memory system

physical trace of memory

type of declarative memory that contains information about events we have personally
experienced, also known as autobiographical memory

some parts of the brain can take over for damaged parts in forming and
storing memories

memories we consciously try to remember and recall

recall of false autobiographical memories

exceptionally clear recollection of an important event

loss of information from long-term memory

memories that are not part of our consciousness

information that is thought of more deeply becomes more meaningful and thus
better committed to memory

290 Chapter 8 | Memory

This OpenStax book is available for free at

long-term memory (LTM)


memory-enhancing strategy


misinformation effect paradigm

mnemonic device


proactive interference

procedural memory







retroactive interference

retrograde amnesia

self-reference effect

semantic encoding

semantic memory

sensory memory

short-term memory (STM)




continuous storage of information

set of processes used to encode, store, and retrieve information over different periods of time

technique to help make sure information goes from short-term memory to
long-term memory

memory error in which you confuse the source of your information

after exposure to additional and possibly inaccurate information, a
person may misremember the original event

memory aids that help organize information for encoding

failure of the memory system that involves the involuntary recall of unwanted memories,
particularly unpleasant ones

old information hinders the recall of newly learned information

type of long-term memory for making skilled actions, such as how to brush your
teeth, how to drive a car, and how to swim

accessing information without cues

identifying previously learned information after encountering it again, usually in response
to a cue

process of bringing up old memories that might be distorted by new information

repetition of information to be remembered

learning information that was previously learned

act of getting information out of long-term memory storage and back into conscious awareness

information learned more recently hinders the recall of older information

loss of memory for events that occurred prior to brain trauma

tendency for an individual to have better memory for information that relates to
oneself in comparison to material that has less personal relevance

input of words and their meaning

type of declarative memory about words, concepts, and language-based knowledge
and facts

storage of brief sensory events, such as sights, sounds, and tastes

holds about seven bits of information before it is forgotten or stored, as well
as information that has been retrieved and is being used

creation of a permanent record of information

effects of misinformation from external sources that leads to the creation of false memories

memory error in which unused memories fade with the passage of time

Chapter 8 | Memory 291

visual encoding input of images


8.1 How Memory Functions
Memory is a system or process that stores what we learn for future use.

Our memory has three basic functions: encoding, storing, and retrieving information. Encoding is the
act of getting information into our memory system through automatic or effortful processing. Storage is
retention of the information, and retrieval is the act of getting information out of storage and into conscious
awareness through recall, recognition, and relearning. The idea that information is processed through
three memory systems is called the Atkinson-Shiffrin model of memory. First, environmental stimuli enter
our sensory memory for a period of less than a second to a few seconds. Those stimuli that we notice
and pay attention to then move into short-term memory. According to the Atkinson-Shiffrin model, if we
rehearse this information, then it moves into long-term memory for permanent storage. Other models like
that of Baddeley and Hitch suggest there is more of a feedback loop between short-term memory and long-
term memory. Long-term memory has a practically limitless storage capacity and is divided into implicit
and explicit memory.

8.2 Parts of the Brain Involved with Memory
Beginning with Karl Lashley, researchers and psychologists have been searching for the engram, which
is the physical trace of memory. Lashley did not find the engram, but he did suggest that memories
are distributed throughout the entire brain rather than stored in one specific area. Now we know that
three brain areas do play significant roles in the processing and storage of different types of memories:
cerebellum, hippocampus, and amygdala. The cerebellum’s job is to process procedural memories; the
hippocampus is where new memories are encoded; the amygdala helps determine what memories to
store, and it plays a part in determining where the memories are stored based on whether we have a
strong or weak emotional response to the event. Strong emotional experiences can trigger the release
of neurotransmitters, as well as hormones, which strengthen memory, so that memory for an emotional
event is usually stronger than memory for a non-emotional event. This is shown by what is known as the
flashbulb memory phenomenon: our ability to remember significant life events. However, our memory for
life events (autobiographical memory) is not always accurate.

8.3 Problems with Memory
All of us at times have felt dismayed, frustrated, and even embarrassed when our memories have failed us.
Our memory is flexible and prone to many errors, which is why eyewitness testimony has been found to
be largely unreliable. There are several reasons why forgetting occurs. In cases of brain trauma or disease,
forgetting may be due to amnesia. Another reason we forget is due to encoding failure. We can’t remember
something if we never stored it in our memory in the first place. Schacter presents seven memory errors
that also contribute to forgetting. Sometimes, information is actually stored in our memory, but we cannot
access it due to interference. Proactive interference happens when old information hinders the recall of
newly learned information. Retroactive interference happens when information learned more recently
hinders the recall of older information.

8.4 Ways to Enhance Memory
There are many ways to combat the inevitable failures of our memory system. Some common strategies
that can be used in everyday situations include mnemonic devices, rehearsal, self-referencing, and
adequate sleep. These same strategies also can help you to study more effectively.

292 Chapter 8 | Memory

This OpenStax book is available for free at

Review Questions

1. ________ is a memory store with a
phonological loop, visiospatial sketchpad,
episodic buffer, and a central executive.

a. sensory memory
b. episodic memory
c. working memory
d. implicit memory

2. The storage capacity of long-term memory is

a. one or two bits of information
b. seven bits, plus or minus two
c. limited
d. essentially limitless

3. The three functions of memory are ________.
a. automatic processing, effortful processing,

and storage
b. encoding, processing, and storage
c. automatic processing, effortful processing,

and retrieval
d. encoding, storage, and retrieval

4. This physical trace of memory is known as the

a. engram
b. Lashley effect
c. Deese-Roediger-McDermott Paradigm
d. flashbulb memory effect

5. An exceptionally clear recollection of an
important event is a (an) ________.

a. engram
b. arousal theory
c. flashbulb memory
d. equipotentiality hypothesis

6. ________ is when our recollections of the past
are done in a self-enhancing manner.

a. stereotypical bias
b. egocentric bias
c. hindsight bias
d. enhancement bias

7. Tip-of-the-tongue phenomenon is also known
as ________.

a. persistence
b. misattribution
c. transience
d. blocking

8. The formulation of new memories is
sometimes called ________, and the process of
bringing up old memories is called ________.

a. construction; reconstruction
b. reconstruction; construction
c. production; reproduction
d. reproduction; production

9. When you are learning how to play the piano,
the statement “Every good boy does fine” can help
you remember the notes E, G, B, D, and F for the
lines of the treble clef. This is an example of a (an)

a. jingle
b. acronym
c. acrostic
d. acoustic

10. According to a study by Yogo and Fujihara
(2008), if you want to improve your short-term
memory, you should spend time writing about

a. your best possible future self
b. a traumatic life experience
c. a trivial topic
d. your grocery list

11. The self-referencing effect refers to ________.
a. making the material you are trying to

memorize personally meaningful to you
b. making a phrase of all the first letters of the

words you are trying to memorize
c. making a word formed by the first letter of

each of the words you are trying to

d. saying words you want to remember out
loud to yourself

Chapter 8 | Memory 293

12. Memory aids that help organize information
for encoding are ________.

a. mnemonic devices
b. memory-enhancing strategies
c. elaborative rehearsal
d. effortful processing

Critical Thinking Questions

13. Compare and contrast implicit and explicit memory.

14. According to the Atkinson-Shiffrin model, name and describe the three stages of memory.

15. Compare and contrast the two ways in which we encode information.

16. What might happen to your memory system if you sustained damage to your hippocampus?

17. Compare and contrast the two types of interference.

18. Compare and contrast the two types of amnesia.

19. What is the self-reference effect, and how can it help you study more effectively?

20. You and your roommate spent all of last night studying for your psychology test. You think you know
the material; however, you suggest that you study again the next morning an hour prior to the test. Your
roommate asks you to explain why you think this is a good idea. What do you tell her?

Personal Application Questions

21. Describe something you have learned that is now in your procedural memory. Discuss how you
learned this information.

22. Describe something you learned in high school that is now in your semantic memory.

23. Describe a flashbulb memory of a significant event in your life.

24. Which of the seven memory errors presented by Schacter have you committed? Provide an example
of each one.

25. Jurors place a lot of weight on eyewitness testimony. Imagine you are an attorney representing a
defendant who is accused of robbing a convenience store. Several eyewitnesses have been called to testify
against your client. What would you tell the jurors about the reliability of eyewitness testimony?

26. Create a mnemonic device to help you remember a term or concept from this chapter.

27. What is an effective study technique that you have used? How is it similar to/different from the
strategies suggested in this chapter?

294 Chapter 8 | Memory

This OpenStax book is available for free at

Chapter 9

Lifespan Development

Figure 9.1 How have you changed since childhood? How are you the same? What will your life be like 25 years
from now? Fifty years from now? Lifespan development studies how you change as well as how you remain the same
over the course of your life. (credit: modification of work by Giles Cook)

Chapter Outline

9.1 What Is Lifespan Development?

9.2 Lifespan Theories

9.3 Stages of Development

9.4 Death and Dying


Welcome to the story of your life. In this chapter we explore the fascinating tale of how you have grown
and developed into the person you are today. We also look at some ideas about who you will grow into
tomorrow. Yours is a story of lifespan development (Figure 9.1), from the start of life to the end.

The process of human growth and development is more obvious in infancy and childhood, yet your
development is happening this moment and will continue, minute by minute, for the rest of your life. Who
you are today and who you will be in the future depends on a blend of genetics, environment, culture,
relationships, and more, as you continue through each phase of life. You have experienced firsthand much
of what is discussed in this chapter. Now consider what psychological science has to say about your
physical, cognitive, and psychosocial development, from the womb to the tomb.

Chapter 9 | Lifespan Development 295

9.1 What Is Lifespan Development?

Learning Objectives

By the end of this section, you will be able to:
• Define and distinguish between the three domains of development: physical, cognitive and

• Discuss the normative approach to development
• Understand the three major issues in development: continuity and discontinuity, one

common course of development or many unique courses of development, and nature
versus nurture

My heart leaps up when I behold
A rainbow in the sky:
So was it when my life began;
So is it now I am a man;
So be it when I shall grow old,
Or let me die!
The Child is father of the Man;
I could wish my days to be
Bound each to each by natural piety. (Wordsworth, 1802)

In this poem, William Wordsworth writes, “the child is father of the man.” What does this seemingly
incongruous statement mean, and what does it have to do with lifespan development? Wordsworth might
be suggesting that the person he is as an adult depends largely on the experiences he had in childhood.
Consider the following questions: To what extent is the adult you are today influenced by the child you
once were? To what extent is a child fundamentally different from the adult he grows up to be?

These are the types of questions developmental psychologists try to answer, by studying how humans
change and grow from conception through childhood, adolescence, adulthood, and death. They view
development as a lifelong process that can be studied scientifically across three developmental
domains—physical, cognitive, and psychosocial development. Physical development involves growth
and changes in the body and brain, the senses, motor skills, and health and wellness. Cognitive
development involves learning, attention, memory, language, thinking, reasoning, and creativity.
Psychosocial development involves emotions, personality, and social relationships. We refer to these
domains throughout the chapter.


Research Methods in Developmental Psychology

You’ve learned about a variety of research methods used by psychologists. Developmental psychologists use
many of these approaches in order to better understand how individuals change mentally and physically over
time. These methods include naturalistic observations, case studies, surveys, and experiments, among others.

Naturalistic observations involve observing behavior in its natural context. A developmental psychologist might
observe how children behave on a playground, at a daycare center, or in the child’s own home. While this research
approach provides a glimpse into how children behave in their natural settings, researchers have very little control
over the types and/or frequencies of displayed behavior.

In a case study, developmental psychologists collect a great deal of information from one individual in order to
better understand physical and psychological changes over the lifespan. This particular approach is an excellent
way to better understand individuals, who are exceptional in some way, but it is especially prone to researcher

296 Chapter 9 | Lifespan Development

This OpenStax book is available for free at

bias in interpretation, and it is difficult to generalize conclusions to the larger population.

In one classic example of this research method being applied to a study of lifespan development Sigmund Freud
analyzed the development of a child known as “Little Hans” (Freud, 1909/1949). Freud’s findings helped inform
his theories of psychosexual development in children, which you will learn about later in this chapter. Little Genie,
the subject of a case study discussed in the chapter on thinking and intelligence, provides another example
of how psychologists examine developmental milestones through detailed research on a single individual. In
Genie’s case, her neglectful and abusive upbringing led to her being unable to speak until, at age 13, she was
removed from that harmful environment. As she learned to use language, psychologists were able to compare
how her language acquisition abilities differed when occurring in her late-stage development compared to the
typical acquisition of those skills during the ages of infancy through early childhood (Fromkin, Krashen, Curtiss,
Rigler, & Rigler, 1974; Curtiss, 1981).

The survey method asks individuals to self-report important information about their thoughts, experiences, and
beliefs. This particular method can provide large amounts of information in relatively short amounts of time;
however, validity of data collected in this way relies on honest self-reporting, and the data is relatively shallow
when compared to the depth of information collected in a case study. An example of comprehensive survey was
the research done by Ruth W. Howard. In 1947, she obtained her doctorate by surveying 229 sets of triplets, the
most comprehensive research of triplets completed at the time. This pioneering woman was also the first African-
American woman to earn a PhD in psychology (American Psychological Association, 2019).

Experiments involve significant control over extraneous variables and manipulation of the independent variable.
As such, experimental research allows developmental psychologists to make causal statements about certain
variables that are important for the developmental process. Because experimental research must occur in
a controlled environment, researchers must be cautious about whether behaviors observed in the laboratory
translate to an individual’s natural environment.

Later in this chapter, you will learn about several experiments in which toddlers and young children observe
scenes or actions so that researchers can determine at what age specific cognitive abilities develop. For
example, children may observe a quantity of liquid poured from a short, fat glass into a tall, skinny glass. As the
experimenters question the children about what occurred, the subjects’ answers help psychologists understand
at what age a child begins to comprehend that the volume of liquid remained the same although the shapes of
the containers differs.

Across these three domains—physical, cognitive, and psychosocial—the normative approach to
development is also discussed. This approach asks, “What is normal development?” In the early decades of
the 20th century, normative psychologists studied large numbers of children at various ages to determine
norms (i.e., average ages) of when most children reach specific developmental milestones in each of the
three domains (Gesell, 1933, 1939, 1940; Gesell & Ilg, 1946; Hall, 1904). Although children develop at
slightly different rates, we can use these age-related averages as general guidelines to compare children
with same-age peers to determine the approximate ages they should reach specific normative events
called developmental milestones (e.g., crawling, walking, writing, dressing, naming colors, speaking in
sentences, and starting puberty).

Not all normative events are universal, meaning they are not experienced by all individuals across all
cultures. Biological milestones, such as puberty, tend to be universal, but social milestones, such as the age
when children begin formal schooling, are not necessarily universal; instead, they affect most individuals
in a particular culture (Gesell & Ilg, 1946). For example, in developed countries children begin school
around 5 or 6 years old, but in developing countries, like Nigeria, children often enter school at an
advanced age, if at all (Huebler, 2005; United Nations Educational, Scientific, and Cultural Organization
[UNESCO], 2013).

To better understand the normative approach, imagine two new mothers, Louisa and Kimberly, who are
close friends and have children around the same age. Louisa’s daughter is 14 months old, and Kimberly’s
son is 12 months old. According to the normative approach, the average age a child starts to walk is 12
months. However, at 14 months Louisa’s daughter still isn’t walking. She tells Kimberly she is worried that

Chapter 9 | Lifespan Development 297

something might be wrong with her baby. Kimberly is surprised because her son started walking when
he was only 10 months old. Should Louisa be worried? Should she be concerned if her daughter is not
walking by 15 months or 18 months?

The Centers for Disease Control and Prevention (CDC) describes the developmental milestones for
children from 2 months through 5 years old. After reviewing the information, take this Developmental
Milestones Quiz ( to see how well you recall what you’ve learned. If
you are a parent with concerns about your child’s development, contact your pediatrician.


There are many different theoretical approaches regarding human development. As we evaluate them in
this chapter, recall that developmental psychology focuses on how people change, and keep in mind that
all the approaches that we present in this chapter address questions of change: Is the change smooth or
uneven (continuous versus discontinuous)? Is this pattern of change the same for everyone, or are there
many different patterns of change (one course of development versus many courses)? How do genetics
and environment interact to influence development (nature versus nurture)?

Is Development Continuous or Discontinuous?

Continuous development views development as a cumulative process, gradually improving on existing
skills (Figure 9.2). With this type of development, there is gradual change. Consider, for example, a child’s
physical growth: adding inches to height year by year. In contrast, theorists who view development as
discontinuous believe that development takes place in unique stages: It occurs at specific times or ages.
With this type of development, the change is more sudden, such as an infant’s ability to conceive object

Figure 9.2 The concept of continuous development can be visualized as a smooth slope of progression, whereas
discontinuous development sees growth in more discrete stages.

Is There One Course of Development or Many?

Is development essentially the same, or universal, for all children (i.e., there is one course of development)
or does development follow a different course for each child, depending on the child’s specific genetics
and environment (i.e., there are many courses of development)? Do people across the world share more
similarities or more differences in their development? How much do culture and genetics influence a
child’s behavior?


298 Chapter 9 | Lifespan Development

This OpenStax book is available for free at

Stage theories hold that the sequence of development is universal. For example, in cross-cultural studies of
language development, children from around the world reach language milestones in a similar sequence
(Gleitman & Newport, 1995). Infants in all cultures coo before they babble. They begin babbling at about
the same age and utter their first word around 12 months old. Yet we live in diverse contexts that have a
unique effect on each of us. For example, researchers once believed that motor development follows one
course for all children regardless of culture. However, child care practices vary by culture, and different
practices have been found to accelerate or inhibit achievement of developmental milestones such as sitting,
crawling, and walking (Karasik, Adolph, Tamis-LeMonda, & Bornstein, 2010).

For instance, let’s look at the Aché society in Paraguay. They spend a significant amount of time foraging
in forests. While foraging, Aché mothers carry their young children, rarely putting them down in order
to protect them from getting hurt in the forest. Consequently, their children walk much later: They walk
around 23–25 months old, in comparison to infants in Western cultures who begin to walk around 12
months old. However, as Aché children become older, they are allowed more freedom to move about, and
by about age 9, their motor skills surpass those of U.S. children of the same age: Aché children are able to
climb trees up to 25 feet tall and use machetes to chop their way through the forest (Kaplan & Dove, 1987).
As you can see, our development is influenced by multiple contexts, so the timing of basic motor functions
may vary across cultures. However, the functions themselves are present in all societies (Figure 9.3).

Figure 9.3 All children across the world love to play. Whether in (a) Florida or (b) South Africa, children enjoy
exploring sand, sunshine, and the sea. (credit a: modification of work by “Visit St. Pete/Clearwater”/Flickr; credit b:
modification of work by “stringer_bel”/Flickr)

How Do Nature and Nurture Influence Development?

Are we who we are because of nature (biology and genetics), or are we who we are because of nurture
(our environment and culture)? This longstanding question is known in psychology as the nature versus
nurture debate. It seeks to understand how our personalities and traits are the product of our genetic
makeup and biological factors, and how they are shaped by our environment, including our parents, peers,
and culture. For instance, why do biological children sometimes act like their parents—is it because of
genetics or because of early childhood environment and what the child has learned from the parents? What
about children who are adopted—are they more like their biological families or more like their adoptive
families? And how can siblings from the same family be so different?

We are all born with specific genetic traits inherited from our parents, such as eye color, height, and certain
personality traits. Beyond our basic genotype, however, there is a deep interaction between our genes and
our environment: Our unique experiences in our environment influence whether and how particular traits
are expressed, and at the same time, our genes influence how we interact with our environment (Diamond,
2009; Lobo, 2008). This chapter will show that there is a reciprocal interaction between nature and nurture
as they both shape who we become, but the debate continues as to the relative contributions of each.

Chapter 9 | Lifespan Development 299

The Achievement Gap: How Does Socioeconomic Status Affect Development?

The achievement gap refers to the persistent difference in grades, test scores, and graduation rates that exist
among students of different ethnicities, races, and—in certain subjects—sexes (Winerman, 2011). Research
suggests that these achievement gaps are strongly influenced by differences in socioeconomic factors that
exist among the families of these children. While the researchers acknowledge that programs aimed at
reducing such socioeconomic discrepancies would likely aid in equalizing the aptitude and performance of
children from different backgrounds, they recognize that such large-scale interventions would be difficult to
achieve. Therefore, it is recommended that programs aimed at fostering aptitude and achievement among
disadvantaged children may be the best option for dealing with issues related to academic achievement gaps
(Duncan & Magnuson, 2005).

Low-income children perform significantly more poorly than their middle- and high-income peers on a number
of educational variables: They have significantly lower standardized test scores, graduation rates, and college
entrance rates, and they have much higher school dropout rates. There have been attempts to correct the
achievement gap through state and federal legislation, but what if the problems start before the children even
enter school?

Psychologists Betty Hart and Todd Risley (2006) spent their careers looking at early language ability and
progression of children in various income levels. In one longitudinal study, they found that although all the
parents in the study engaged and interacted with their children, middle- and high-income parents interacted
with their children differently than low-income parents. After analyzing 1,300 hours of parent-child interactions,
the researchers found that middle- and high-income parents talk to their children significantly more, starting
when the children are infants. By 3 years old, high-income children knew almost double the number of words
known by their low-income counterparts, and they had heard an estimated total of 30 million more words
than the low-income counterparts (Hart & Risley, 2003). And the gaps only become more pronounced. Before
entering kindergarten, high-income children score 60% higher on achievement tests than their low-income
peers (Lee & Burkam, 2002).

There are solutions to this problem. At the University of Chicago, experts are working with low-income families,
visiting them at their homes, and encouraging them to speak more to their children on a daily and hourly
basis. Other experts are designing preschools in which students from diverse economic backgrounds are
placed in the same classroom. In this research, low-income children made significant gains in their language
development, likely as a result of attending the specialized preschool (Schechter & Byeb, 2007). What other
methods or interventions could be used to decrease the achievement gap? What types of activities could be
implemented to help the children of your community or a neighboring community?

9.2 Lifespan Theories

Learning Objectives

By the end of this section, you will be able to:
• Discuss Freud’s theory of psychosexual development
• Describe the major tasks of child and adult psychosocial development according to Erikson
• Discuss Piaget’s view of cognitive development and apply the stages to understanding

childhood cognition
• Describe Kohlberg’s theory of moral development
• Compare and contrast the strengths and weaknesses of major developmental theories

There are many theories regarding how babies and children grow and develop into happy, healthy adults.
We explore several of these theories in this section.


300 Chapter 9 | Lifespan Development

This OpenStax book is available for free at


Sigmund Freud (1856–1939) believed that personality develops during early childhood. For Freud,
childhood experiences shape our personalities and behavior as adults. Freud viewed development as
discontinuous; he believed that each of us must pass through a series of stages during childhood, and
that if we lack proper nurturance and parenting during a stage, we may become stuck, or fixated, in that
stage. Freud’s stages are called the stages of psychosexual development. According to Freud, children’s
pleasure-seeking urges are focused on a different area of the body, called an erogenous zone, at each of the
five stages of development: oral, anal, phallic, latency, and genital.

While most of Freud’s ideas have not found support in modern research, we cannot discount the
contributions that Freud has made to the field of psychology. Psychologists today dispute Freud’s
psychosexual stages as a legitimate explanation for how one’s personality develops, but what we can take
away from Freud’s theory is that personality is shaped, in some part, by experiences we have in childhood.
These stages are discussed in detail in the chapter on personality.


Erik Erikson (1902–1994) (Figure 9.4), another stage theorist, took Freud’s theory and modified it as
psychosocial theory. Erikson’s psychosocial development theory emphasizes the social nature of our
development rather than its sexual nature. While Freud believed that personality is shaped only in
childhood, Erikson proposed that personality development takes place all through the lifespan. Erikson
suggested that how we interact with others is what affects our sense of self, or what he called the ego

Figure 9.4 Erik Erikson proposed the psychosocial theory of development. In each stage of Erikson’s theory, there is
a psychosocial task that we must master in order to feel a sense of competence.

Erikson proposed that we are motivated by a need to achieve competence in certain areas of our lives.
According to psychosocial theory, we experience eight stages of development over our lifespan, from
infancy through late adulthood. At each stage there is a conflict, or task, that we need to resolve. Successful
completion of each developmental task results in a sense of competence and a healthy personality. Failure
to master these tasks leads to feelings of inadequacy.

According to Erikson (1963), trust is the basis of our development during infancy (birth to 12 months).
Therefore, the primary task of this stage is trust versus mistrust. Infants are dependent upon their
caregivers, so caregivers who are responsive and sensitive to their infant’s needs help their baby to develop
a sense of trust; their baby will see the world as a safe, predictable place. Unresponsive caregivers who do
not meet their baby’s needs can engender feelings of anxiety, fear, and mistrust; their baby may see the
world as unpredictable.

As toddlers (ages 1–3 years) begin to explore their world, they learn that they can control their actions
and act on the environment to get results. They begin to show clear preferences for certain elements of the

Chapter 9 | Lifespan Development 301

environment, such as food, toys, and clothing. A toddler’s main task is to resolve the issue of autonomy
versus shame and doubt, by working to establish independence. This is the “me do it” stage. For example,
we might observe a budding sense of autonomy in a 2-year-old child who wants to choose her clothes
and dress herself. Although her outfits might not be appropriate for the situation, her input in such basic
decisions has an effect on her sense of independence. If denied the opportunity to act on her environment,
she may begin to doubt her abilities, which could lead to low self-esteem and feelings of shame.

Once children reach the preschool stage (ages 3–6 years), they are capable of initiating activities and
asserting control over their world through social interactions and play. According to Erikson, preschool
children must resolve the task of initiative versus guilt. By learning to plan and achieve goals while
interacting with others, preschool children can master this task. Those who do will develop self-confidence
and feel a sense of purpose. Those who are unsuccessful at this stage—with their initiative misfiring or
stifled—may develop feelings of guilt. How might over-controlling parents stifle a child’s initiative?

During the elementary school stage (ages 7–11), children face the task of industry versus inferiority.
Children begin to compare themselves to their peers to see how they measure up. They either develop a
sense of pride and accomplishment in their schoolwork, sports, social activities, and family life, or they
feel inferior and inadequate when they don’t measure up. What are some things parents and teachers can
do to help children develop a sense of competence and a belief in themselves and their abilities?

In adolescence (ages 12–18), children face the task of identity versus role confusion. According to Erikson,
an adolescent’s main task is developing a sense of self. Adolescents struggle with questions such as “Who
am I?” and “What do I want to do with my life?” Along the way, most adolescents try on many different
selves to see which ones fit. Adolescents who are successful at this stage have a strong sense of identity and
are able to remain true to their beliefs and values in the face of problems and other people’s perspectives.
What happens to apathetic adolescents, who do not make a conscious search for identity, or those who are
pressured to conform to their parents’ ideas for the future? These teens will have a weak sense of self and
experience role confusion. They are unsure of their identity and confused about the future.

People in early adulthood (i.e., 20s through early 40s) are concerned with intimacy versus isolation. After
we have developed a sense of self in adolescence, we are ready to share our life with others. Erikson said
that we must have a strong sense of self before developing intimate relationships with others. Adults who
do not develop a positive self-concept in adolescence may experience feelings of loneliness and emotional

When people reach their 40s, they enter the time known as middle adulthood, which extends to the
mid-60s. The social task of middle adulthood is generativity versus stagnation. Generativity involves
finding your life’s work and contributing to the development of others, through activities such as
volunteering, mentoring, and raising children. Those who do not master this task may experience
stagnation, having little connection with others and little interest in productivity and self-improvement.

From the mid-60s to the end of life, we are in the period of development known as late adulthood.
Erikson’s task at this stage is called integrity versus despair. He said that people in late adulthood reflect
on their lives and feel either a sense of satisfaction or a sense of failure. People who feel proud of their
accomplishments feel a sense of integrity, and they can look back on their lives with few regrets. However,
people who are not successful at this stage may feel as if their life has been wasted. They focus on what
“would have,” “should have,” and “could have” been. They face the end of their lives with feelings of
bitterness, depression, and despair. Table 9.1 summarizes the stages of Erikson’s theory.

302 Chapter 9 | Lifespan Development

This OpenStax book is available for free at

Erikson’s Psychosocial Stages of Development




1 0–1 Trust vs.

Trust (or mistrust) that basic needs, such as nourishment and
affection, will be met

2 1–3 Autonomy vs.

Develop a sense of independence in many tasks

3 3–6 Initiative vs.

Take initiative on some activities—may develop guilt when
unsuccessful or boundaries overstepped

4 7–11 Industry vs.

Develop self-confidence in abilities when competent or sense
of inferiority when not

5 12–18 Identity vs.

Experiment with and develop identity and roles

6 19–29 Intimacy vs.

Establish intimacy and relationships with others

7 30–64 Generativity vs.

Contribute to society and be part of a family

8 65– Integrity vs.

Assess and make sense of life and meaning of contributions

Table 9.1


Jean Piaget (1896–1980) is another stage theorist who studied childhood development (Figure 9.5). Instead
of approaching development from a psychoanalytical or psychosocial perspective, Piaget focused on
children’s cognitive growth. He believed that thinking is a central aspect of development and that children
are naturally inquisitive. However, he said that children do not think and reason like adults (Piaget, 1930,
1932). His theory of cognitive development holds that our cognitive abilities develop through specific
stages, which exemplifies the discontinuity approach to development. As we progress to a new stage, there
is a distinct shift in how we think and reason.

Chapter 9 | Lifespan Development 303

Figure 9.5 Jean Piaget spent over 50 years studying children and how their minds develop.

Piaget said that children develop schemata to help them understand the world. Schemata are concepts
(mental models) that are used to help us categorize and interpret information. By the time children
have reached adulthood, they have created schemata for almost everything. When children learn new
information, they adjust their schemata through two processes: assimilation and accommodation. First,
they assimilate new information or experiences in terms of their current schemata: assimilation is when
they take in information that is comparable to what they already know. Accommodation describes when
they change their schemata based on new information. This process continues as children interact with
their environment.

For example, 2-year-old Abdul learned the schema for dogs because his family has a Labrador retriever.
When Abdul sees other dogs in his picture books, he says, “Look mommy, dog!” Thus, he has assimilated
them into his schema for dogs. One day, Abdul sees a sheep for the first time and says, “Look mommy,
dog!” Having a basic schema that a dog is an animal with four legs and fur, Abdul thinks all furry,
four-legged creatures are dogs. When Abdul’s mom tells him that the animal he sees is a sheep, not
a dog, Abdul must accommodate his schema for dogs to include more information based on his new
experiences. Abdul’s schema for dog was too broad, since not all furry, four-legged creatures are dogs. He
now modifies his schema for dogs and forms a new one for sheep.

Like Freud and Erikson, Piaget thought development unfolds in a series of stages approximately
associated with age ranges. He proposed a theory of cognitive development that unfolds in four stages:
sensorimotor, preoperational, concrete operational, and formal operational (Table 9.2).

Piaget’s Stages of Cognitive Development


Stage Description

0–2 Sensorimotor World experienced through senses and actions Object
Stranger anxiety

304 Chapter 9 | Lifespan Development

This OpenStax book is available for free at

Piaget’s Stages of Cognitive Development


Stage Description

2–6 Preoperational Use words and images to represent things, but lack
logical reasoning

Pretend play

7–11 Concrete

Understand concrete events and analogies
logically; perform arithmetical operations


12– Formal

Formal operations
Utilize abstract reasoning

Abstract logic
Moral reasoning

Table 9.2

The first stage is the sensorimotor stage, which lasts from birth to about 2 years old. During this stage,
children learn about the world through their senses and motor behavior. Young children put objects in
their mouths to see if the items are edible, and once they can grasp objects, they may shake or bang them
to see if they make sounds. Between 5 and 8 months old, the child develops object permanence, which is
the understanding that even if something is out of sight, it still exists (Bogartz, Shinskey, & Schilling, 2000).
According to Piaget, young infants do not remember an object after it has been removed from sight. Piaget
studied infants’ reactions when a toy was first shown to an infant and then hidden under a blanket. Infants
who had already developed object permanence would reach for the hidden toy, indicating that they knew
it still existed, whereas infants who had not developed object permanence would appear confused.

Please take a few minutes and view this brief video demonstrating different children’s abilities to
understand object permanence ( to learn more.

In Piaget’s view, around the same time children develop object permanence, they also begin to exhibit
stranger anxiety, which is a fear of unfamiliar people. Babies may demonstrate this by crying and turning
away from a stranger, by clinging to a caregiver, or by attempting to reach their arms toward familiar faces
such as parents. Stranger anxiety results when a child is unable to assimilate the stranger into an existing
schema; therefore, she can’t predict what her experience with that stranger will be like, which results in a
fear response.

Piaget’s second stage is the preoperational stage, which is from approximately 2 to 7 years old. In this
stage, children can use symbols to represent words, images, and ideas, which is why children in this stage
engage in pretend play. A child’s arms might become airplane wings as he zooms around the room, or
a child with a stick might become a brave knight with a sword. Children also begin to use language in
the preoperational stage, but they cannot understand adult logic or mentally manipulate information (the
term operational refers to logical manipulation of information, so children at this stage are considered to be
pre-operational). Children’s logic is based on their own personal knowledge of the world so far, rather than
on conventional knowledge. For example, dad gave a slice of pizza to 10-year-old Keiko and another slice


Chapter 9 | Lifespan Development 305

to her 3-year-old brother, Kenny. Kenny’s pizza slice was cut into five pieces, so Kenny told his sister that
he got more pizza than she did. Children in this stage cannot perform mental operations because they have
not developed an understanding of conservation, which is the idea that even if you change the appearance
of something, it is still equal in size as long as nothing has been removed or added.

Watch this video of a boy in the preoperational stage responding to Piaget’s conservation tasks
( to learn more.

During this stage, we also expect children to display egocentrism, which means that the child is not able to
take the perspective of others. A child at this stage thinks that everyone sees, thinks, and feels just as they
do. Let’s look at Kenny and Keiko again. Keiko’s birthday is coming up, so their mom takes Kenny to the
toy store to choose a present for his sister. He selects an Iron Man action figure for her, thinking that if he
likes the toy, his sister will too. An egocentric child is not able to infer the perspective of other people and
instead attributes his own perspective.

Piaget developed the Three-Mountain Task to determine the level of egocentrism displayed by children.
Children view a 3-dimensional mountain scene from one viewpoint, and are asked what another person at
a different viewpoint would see in the same scene. Watch this short video of the Three Mountain Task
in action ( from the University of Minnesota and the Science
Museum of Minnesota.

Piaget’s third stage is the concrete operational stage, which occurs from about 7 to 11 years old. In
this stage, children can think logically about real (concrete) events; they have a firm grasp on the use
of numbers and start to employ memory strategies. They can perform mathematical operations and
understand transformations, such as addition is the opposite of subtraction, and multiplication is the
opposite of division. In this stage, children also master the concept of conservation: Even if something
changes shape, its mass, volume, and number stay the same. For example, if you pour water from a tall,
thin glass to a short, fat glass, you still have the same amount of water. Remember Keiko and Kenny and
the pizza? How did Keiko know that Kenny was wrong when he said that he had more pizza?

Children in the concrete operational stage also understand the principle of reversibility, which means that
objects can be changed and then returned back to their original form or condition. Take, for example, water
that you poured into the short, fat glass: You can pour water from the fat glass back to the thin glass and
still have the same amount (minus a couple of drops).

The fourth, and last, stage in Piaget’s theory is the formal operational stage, which is from about age 11
to adulthood. Whereas children in the concrete operational stage are able to think logically only about
concrete events, children in the formal operational stage can also deal with abstract ideas and hypothetical
situations. Children in this stage can use abstract thinking to problem solve, look at alternative solutions,
and test these solutions. In adolescence, a renewed egocentrism occurs. For example, a 15-year-old with a
very small pimple on her face might think it is huge and incredibly visible, under the mistaken impression
that others must share her perceptions.



306 Chapter 9 | Lifespan Development

This OpenStax book is available for free at

Beyond Formal Operational Thought

As with other major contributors of theories of development, several of Piaget’s ideas have come under
criticism based on the results of further research. For example, several contemporary studies support a
model of development that is more continuous than Piaget’s discrete stages (Courage & Howe, 2002;
Siegler, 2005, 2006). Many others suggest that children reach cognitive milestones earlier than Piaget
describes (Baillargeon, 2004; de Hevia & Spelke, 2010).

According to Piaget, the highest level of cognitive development is formal operational thought, which
develops between 11 and 20 years old. However, many developmental psychologists disagree with Piaget,
suggesting a fifth stage of cognitive development, known as the postformal stage (Basseches, 1984;
Commons & Bresette, 2006; Sinnott, 1998). In postformal thinking, decisions are made based on situations
and circumstances, and logic is integrated with emotion as adults develop principles that depend on
contexts. One way that we can see the difference between an adult in postformal thought and an adolescent
in formal operations is in terms of how they handle emotionally charged issues.

It seems that once we reach adulthood our problem solving abilities change: As we attempt to solve
problems, we tend to think more deeply about many areas of our lives, such as relationships, work,
and politics (Labouvie-Vief & Diehl, 1999). Because of this, postformal thinkers are able to draw on past
experiences to help them solve new problems. Problem-solving strategies using postformal thought vary,
depending on the situation. What does this mean? Adults can recognize, for example, that what seems to
be an ideal solution to a problem at work involving a disagreement with a colleague may not be the best
solution to a disagreement with a significant other.



The genetic environmental correlation you’ve learned about concerning the bidirectional influence of genes
and the environment has been explored in more recent theories (Newcombe, 2011). One such theory,
neuroconstructivism, suggests that neural brain development influences cognitive development. Experiences that
a child encounters can impact or change the way that neural pathways develop in response to the environment.
An individual’s behavior is based on how one understands the world. There is interaction between neural and
cognitive networks at and between each level, consisting of these:

• genes

• neurons

• brain

• body

• social environment

These interactions shape mental representations in the brain and are dependent on context that individuals
actively explore throughout their lifetimes (Westermann, Mareschal, Johnson, Sirois, Spratling, & Thomas, 2007).

An example of this would be a child who may be genetically predisposed to a difficult temperament. They may
have parents who provide a social environment in which they are encouraged to express themselves in an optimal
manner. The child’s brain would form neural connections enhanced by that environment, thus influencing the
brain. The brain gives information to the body about how it will experience the environment. Thus, neural and
cognitive networks work together to influence genes (i.e., attenuating temperament), body (i.e., may be less prone
to high blood pressure), and social environment (i.e., may seek people who are similar to them).

Chapter 9 | Lifespan Development 307


Lev Vygotsky was a Russian psychologist who proposed a sociocultural theory of development. He
suggested that human development is rooted in one’s culture. A child’s social world, for example, forms
the basis for the formation of language and thought. The language one speaks and the ways a person
thinks about things is dependent on one’s cultural background. Vygotsky also considered historical
influences as key to one’s development. He was interested in the process of development and the
individual’s interactions with their environment (John-Steiner & Mahn, 1996).


A major task beginning in childhood and continuing into adolescence is discerning right from wrong.
Psychologist Lawrence Kohlberg (1927–1987) extended upon the foundation that Piaget built regarding
cognitive development. Kohlberg believed that moral development, like cognitive development, follows a
series of stages. To develop this theory, Kohlberg posed moral dilemmas to people of all ages, and then
he analyzed their answers to find evidence of their particular stage of moral development. Before reading
about the stages, take a minute to consider how you would answer one of Kohlberg’s best-known moral
dilemmas, commonly known as the Heinz dilemma:

In Europe, a woman was near death from a special kind of cancer. There was one drug that the
doctors thought might save her. It was a form of radium that a druggist in the same town had
recently discovered. The drug was expensive to make, but the druggist was charging ten times
what the drug cost him to make. He paid $200 for the radium and charged $2,000 for a small
dose of the drug. The sick woman’s husband, Heinz, went to everyone he knew to borrow the
money, but he could only get together about $1,000, which is half of what it cost. He told the
druggist that his wife was dying and asked him to sell it cheaper or let him pay later. But the
druggist said: “No, I discovered the drug and I’m going to make money from it.” So Heinz got
desperate and broke into the man’s store to steal the drug for his wife. Should the husband have
done that? (Kohlberg, 1969, p. 379)

How would you answer this dilemma? Kohlberg was not interested in whether you answer yes or no to
the dilemma: Instead, he was interested in the reasoning behind your answer.

After presenting people with this and various other moral dilemmas, Kohlberg reviewed people’s
responses and placed them in different stages of moral reasoning (Figure 9.6). According to Kohlberg,
an individual progresses from the capacity for pre-conventional morality (before age 9) to the capacity for
conventional morality (early adolescence), and toward attaining post-conventional morality (once formal
operational thought is attained), which only a few fully achieve. Kohlberg placed in the highest stage
responses that reflected the reasoning that Heinz should steal the drug because his wife’s life is more
important than the pharmacist making money. The value of a human life overrides the pharmacist’s greed.

308 Chapter 9 | Lifespan Development

This OpenStax book is available for free at

Figure 9.6 Kohlberg identified three levels of moral reasoning: pre-conventional, conventional, and post-
conventional: Each level is associated with increasingly complex stages of moral development.

It is important to realize that even those people who have the most sophisticated, post-conventional
reasons for some choices may make other choices for the simplest of pre-conventional reasons. Many
psychologists agree with Kohlberg’s theory of moral development but point out that moral reasoning is
very different from moral behavior. Sometimes what we say we would do in a situation is not what we
actually do in that situation. In other words, we might “talk the talk,” but not “walk the walk.”

How does this theory apply to males and females? Kohlberg (1969) felt that more males than females
move past stage four in their moral development. He went on to note that women seem to be deficient in
their moral reasoning abilities. These ideas were not well received by Carol Gilligan, a research assistant
of Kohlberg, who consequently developed her own ideas of moral development. In her groundbreaking
book, In a Different Voice: Psychological Theory and Women’s Development, Gilligan (1982) criticized her
former mentor’s theory because it was based only on upper class White men and boys. She argued that
women are not deficient in their moral reasoning—she proposed that males and females reason differently.
Girls and women focus more on staying connected and the importance of interpersonal relationships.
Therefore, in the Heinz dilemma, many girls and women respond that Heinz should not steal the medicine.
Their reasoning is that if he steals the medicine, is arrested, and is put in jail, then he and his wife will be
separated, and she could die while he is still in prison.

Chapter 9 | Lifespan Development 309

9.3 Stages of Development

Learning Objectives

By the end of this section, you will be able to:
• Describe the stages of prenatal development and recognize the importance of prenatal care
• Appraise physical, cognitive, and emotional development that occurs from infancy through

• Compare and contrast physical, cognitive, and emotional development that occurs during

• Examine physical, cognitive, and emotional development that occurs in adulthood

From the moment we are born until the moment we die, we continue to develop.

As discussed at the beginning of this chapter, developmental psychologists often divide our development
into three areas: physical development, cognitive development, and psychosocial development. Mirroring
Erikson’s stages, lifespan development is divided into different stages that are based on age. We will
discuss prenatal, infant, child, adolescent, and adult development.


How did you come to be who you are? From beginning as a one-cell structure to your birth, your prenatal
development occurred in an orderly and delicate sequence.

There are three stages of prenatal development: germinal, embryonic, and fetal. Let’s take a look at what
happens to the developing baby in each of these stages.

Germinal Stage (Weeks 1–2)

In the discussion of biopsychology earlier in the book, you learned about genetics and DNA. A mother
and father’s DNA is passed on to the child at the moment of conception. Conception occurs when sperm
fertilizes an egg and forms a zygote (Figure 9.7). A zygote begins as a one-cell structure that is created
when a sperm and egg merge. The genetic makeup and sex of the baby are set at this point. During the
first week after conception, the zygote divides and multiplies, going from a one-cell structure to two cells,
then four cells, then eight cells, and so on. This process of cell division is called mitosis. Mitosis is a fragile
process, and fewer than one-half of all zygotes survive beyond the first two weeks (Hall, 2004). After 5
days of mitosis there are 100 cells, and after 9 months there are billions of cells. As the cells divide, they
become more specialized, forming different organs and body parts. In the germinal stage, the mass of cells
has yet to attach itself to the lining of the mother’s uterus. Once it does, the next stage begins.

Figure 9.7 Sperm and ovum fuse at the point of conception.

Embryonic Stage (Weeks 3–8)

After the zygote divides for about 7–10 days and has 150 cells, it travels down the fallopian tubes and
implants itself in the lining of the uterus. Upon implantation, this multi-cellular organism is called an

310 Chapter 9 | Lifespan Development

This OpenStax book is available for free at

embryo. Now blood vessels grow, forming the placenta. The placenta is a structure connected to the uterus
that provides nourishment and oxygen from the mother to the developing embryo via the umbilical cord.
Basic structures of the embryo start to develop into areas that will become the head, chest, and abdomen.
During the embryonic stage, the heart begins to beat and organs form and begin to function. The neural
tube forms along the back of the embryo, developing into the spinal cord and brain.

Fetal Stage (Weeks 9–40)

When the organism is about nine weeks old, the embryo is called a fetus. At this stage, the fetus is about
the size of a kidney bean and begins to take on the recognizable form of a human being as the “tail” begins
to disappear.

From 9–12 weeks, the sex organs begin to differentiate. At about 16 weeks, the fetus is approximately 4.5
inches long. Fingers and toes are fully developed, and fingerprints are visible. By the time the fetus reaches
the sixth month of development (24 weeks), it weighs up to 1.4 pounds. Hearing has developed, so the
fetus can respond to sounds. The internal organs, such as the lungs, heart, stomach, and intestines, have
formed enough that a fetus born prematurely at this point has a chance to survive outside of the mother’s
womb. Throughout the fetal stage the brain continues to grow and develop, nearly doubling in size from
weeks 16 to 28. Around 36 weeks, the fetus is almost ready for birth. It weighs about 6 pounds and is
about 18.5 inches long, and by week 37 all of the fetus’s organ systems are developed enough that it could
survive outside the mother’s uterus without many of the risks associated with premature birth. The fetus
continues to gain weight and grow in length until approximately 40 weeks. By then, the fetus has very
little room to move around and birth becomes imminent. The progression through the stages is shown in
Figure 9.8.

Chapter 9 | Lifespan Development 311

Figure 9.8 During the fetal stage, the baby’s brain develops and the body adds size and weight, until the fetus
reaches full-term development.

For an amazing look at prenatal development and the process of birth, view the video Life’s Greatest
Miracle ( from Nova and PBS.

Prenatal Influences

During each prenatal stage, genetic and environmental factors can affect development. The developing
fetus is completely dependent on the mother for life. It is important that the mother takes good care of
herself and receives prenatal care, which is medical care during pregnancy that monitors the health of
both the mother and the fetus (Figure 9.9). According to the National Institutes of Health ([NIH], 2013),
routine prenatal care is important because it can reduce the risk of complications to the mother and fetus
during pregnancy. In fact, women who are trying to become pregnant or who may become pregnant
should discuss pregnancy planning with their doctor. They may be advised, for example, to take a vitamin
containing folic acid, which helps prevent certain birth defects, or to monitor aspects of their diet or
exercise routines.


312 Chapter 9 | Lifespan Development

This OpenStax book is available for free at

Figure 9.9 A pregnant woman receives an ultrasound as part of her prenatal care. (credit: “MIKI

Recall that when the zygote attaches to the wall of the mother’s uterus, the placenta is formed. The placenta
provides nourishment and oxygen to the fetus. Most everything the mother ingests, including food, liquid,
and even medication, travels through the placenta to the fetus, hence the common phrase “eating for
two.” Anything the mother is exposed to in the environment affects the fetus; if the mother is exposed to
something harmful, the child can show life-long effects.

A teratogen is any environmental agent—biological, chemical, or physical—that causes damage to the
developing embryo or fetus. There are different types of teratogens. Alcohol and most drugs cross the
placenta and affect the fetus. Alcohol is not safe to drink in any amount during pregnancy. Alcohol use
during pregnancy has been found to be the leading preventable cause of mental retardation in children in
the United States (Maier & West, 2001). Excessive maternal drinking while pregnant can cause fetal alcohol
spectrum disorders with life-long consequences for the child ranging in severity from minor to major
(Table 9.3). Fetal alcohol spectrum disorders (FASD) are a collection of birth defects associated with heavy
consumption of alcohol during pregnancy. Physically, children with FASD may have a small head size
and abnormal facial features. Cognitively, these children may have poor judgment, poor impulse control,
higher rates of ADHD, learning issues, and lower IQ scores. These developmental problems and delays
persist into adulthood (Streissguth et al., 2004). Based on studies conducted on animals, it also has been
suggested that a mother’s alcohol consumption during pregnancy may predispose her child to like alcohol
(Youngentob et al., 2007).

Fetal Alcohol Syndrome Facial Features

Facial Feature Potential Effect of Fetal Alcohol Syndrome

Head size Below-average head circumference

Eyes Smaller than average eye opening, skin folds at corners of eyes

Nose Low nasal bridge, short nose

Midface Smaller than average midface size

Lip and philtrum Thin upper lip, indistinct philtrum

Table 9.3

Smoking is also considered a teratogen because nicotine travels through the placenta to the fetus. When

Chapter 9 | Lifespan Development 313

the mother smokes, the developing baby experiences a reduction in blood oxygen levels. According to the
Centers for Disease Control and Prevention (2013), smoking while pregnant can result in premature birth,
low-birth-weight infants, stillbirth, and sudden infant death syndrome (SIDS).

Heroin, cocaine, methamphetamine, almost all prescription medicines, and most over-the counter
medications are also considered teratogens. Babies born with a heroin addiction need heroin just like an
adult addict. The child will need to be gradually weaned from the heroin under medical supervision;
otherwise, the child could have seizures and die. Other teratogens include radiation, viruses such as HIV
and herpes, and rubella (German measles). Women in the United States are much less likely to be afflicted
with rubella because most women received childhood immunizations or vaccinations that protect the body
from disease.

Each organ of the fetus develops during a specific period in the pregnancy, called the critical or sensitive
period (Figure 9.8). For example, research with primate models of FASD has demonstrated that the time
during which a developing fetus is exposed to alcohol can dramatically affect the appearance of facial
characteristics associated with fetal alcohol syndrome. Specifically, this research suggests that alcohol
exposure that is limited to day 19 or 20 of gestation can lead to significant facial abnormalities in the
offspring (Ashley, Magnuson, Omnell, & Clarren, 1999). Given regions of the brain also show sensitive
periods during which they are most susceptible to the teratogenic effects of alcohol (Tran & Kelly, 2003).

Should Women Who Use Drugs During Pregnancy Be Arrested and Jailed?

As you now know, women who use drugs or alcohol during pregnancy can cause serious lifelong harm to their
child. Some people have advocated mandatory screenings for women who are pregnant and have a history
of drug abuse, and if the women continue using, to arrest, prosecute, and incarcerate them (Figdor & Kaeser,
1998). This policy was tried in Charleston, South Carolina, as recently as 20 years ago. The policy was called
the Interagency Policy on Management of Substance Abuse During Pregnancy, and had disastrous results.

The Interagency Policy applied to patients attending the obstetrics clinic at MUSC, which primarily
serves patients who are indigent or on Medicaid. It did not apply to private obstetrical patients. The
policy required patient education about the harmful effects of substance abuse during pregnancy. . .
. [A] statement also warned patients that protection of unborn and newborn children from the harms
of illegal drug abuse could involve the Charleston police, the Solicitor of the Ninth Judicial Court,
and the Protective Services Division of the Department of Social Services (DSS). (Jos, Marshall, &
Perlmutter, 1995, pp. 120–121)

This policy seemed to deter women from seeking prenatal care, deterred them from seeking other social
services, and was applied solely to low-income women, resulting in lawsuits. The program was canceled after
5 years, during which 42 women were arrested. A federal agency later determined that the program involved
human experimentation without the approval and oversight of an institutional review board (IRB). What were
the flaws in the program and how would you correct them? What are the ethical implications of charging
pregnant women with child abuse?


The average newborn weighs approximately 7.5 pounds. Although small, a newborn is not completely
helpless because his reflexes and sensory capacities help him interact with the environment from the
moment of birth. All healthy babies are born with newborn reflexes: inborn automatic responses to
particular forms of stimulation. Reflexes help the newborn survive until it is capable of more complex
behaviors—these reflexes are crucial to survival. They are present in babies whose brains are developing
normally and usually disappear around 4–5 months old. Let’s take a look at some of these newborn
reflexes. The rooting reflex is the newborn’s response to anything that touches her cheek: When you stroke


314 Chapter 9 | Lifespan Development

This OpenStax book is available for free at

a baby’s cheek, she naturally turns her head in that direction and begins to suck. The sucking reflex is
the automatic, unlearned, sucking motions that infants do with their mouths. Several other interesting
newborn reflexes can be observed. For instance, if you put your finger into a newborn’s hand, you will
witness the grasping reflex, in which a baby automatically grasps anything that touches his palms. The
Moro reflex is the newborn’s response when she feels like she is falling. The baby spreads her arms, pulls
them back in, and then (usually) cries. How do you think these reflexes promote survival in the first
months of life?

Take a few minutes to view this brief video clip about newborn reflexes (
newflexes) to learn more.

What can young infants see, hear, and smell? Newborn infants’ sensory abilities are significant, but their
senses are not yet fully developed. Many of a newborn’s innate preferences facilitate interaction with
caregivers and other humans. Although vision is their least developed sense, newborns already show a
preference for faces. Babies who are just a few days old also prefer human voices, they will listen to voices
longer than sounds that do not involve speech (Vouloumanos & Werker, 2004), and they seem to prefer
their mother’s voice over a stranger’s voice (Mills & Melhuish, 1974). In an interesting experiment, 3-week-
old babies were given pacifiers that played a recording of the infant’s mother’s voice and of a stranger’s
voice. When the infants heard their mother’s voice, they sucked more strongly at the pacifier (Mills &
Melhuish, 1974). Newborns also have a strong sense of smell. For instance, newborn babies can distinguish
the smell of their own mother from that of others. In a study by MacFarlane (1978), 1-week-old babies who
were being breastfed were placed between two gauze pads. One gauze pad was from the bra of a nursing
mother who was a stranger, and the other gauze pad was from the bra of the infant’s own mother. More
than two-thirds of the week-old babies turned toward the gauze pad with their mother’s scent.

Physical Development

In infancy, toddlerhood, and early childhood, the body’s physical development is rapid (Figure 9.10).
On average, newborns weigh between 5 and 10 pounds, and a newborn’s weight typically doubles in six
months and triples in one year. By 2 years old the weight will have quadrupled, so we can expect that
a 2 year old should weigh between 20 and 40 pounds. The average length of a newborn is 19.5 inches,
increasing to 29.5 inches by 12 months and 34.4 inches by 2 years old (WHO Multicentre Growth Reference
Study Group, 2006).

Figure 9.10 Children experience rapid physical changes through infancy and early childhood. (credit “left”:
modification of work by Kerry Ceszyk; credit “middle-left”: modification of work by Kristi Fausel; credit “middle-right”:
modification of work by “devinf”/Flickr; credit “right”: modification of work by Rose Spielman)


Chapter 9 | Lifespan Development 315

During infancy and childhood, growth does not occur at a steady rate (Carel, Lahlou, Roger, & Chaussain,
2004). Growth slows between 4 and 6 years old: During this time children gain 5–7 pounds and grow
about 2–3 inches per year. Once girls reach 8–9 years old, their growth rate outpaces that of boys due to
a pubertal growth spurt. This growth spurt continues until around 12 years old, coinciding with the start
of the menstrual cycle. By 10 years old, the average girl weighs 88 pounds, and the average boy weighs 85

We are born with all of the brain cells that we will ever have—about 100–200 billion neurons (nerve
cells) whose function is to store and transmit information (Huttenlocher & Dabholkar, 1997). However, the
nervous system continues to grow and develop. Each neural pathway forms thousands of new connections
during infancy and toddlerhood. This period of rapid neural growth is called blooming. Neural pathways
continue to develop through puberty. The blooming period of neural growth is then followed by a period
of pruning, where neural connections are reduced. It is thought that pruning causes the brain to function
more efficiently, allowing for mastery of more complex skills (Hutchinson, 2011). Blooming occurs during
the first few years of life, and pruning continues through childhood and into adolescence in various areas
of the brain.

The size of our brains increases rapidly. For example, the brain of a 2-year-old is 55% of its adult size,
and by 6 years old the brain is about 90% of its adult size (Tanner, 1978). During early childhood (ages
3–6), the frontal lobes grow rapidly. Recalling our discussion of the 4 lobes of the brain earlier in this
book, the frontal lobes are associated with planning, reasoning, memory, and impulse control. Therefore,
by the time children reach school age, they are developmentally capable of controlling their attention and
behavior. Through the elementary school years, the frontal, temporal, occipital, and parietal lobes all grow
in size. The brain growth spurts experienced in childhood tend to follow Piaget’s sequence of cognitive
development, so that significant changes in neural functioning account for cognitive advances (Kolb &
Whishaw, 2009; Overman, Bachevalier, Turner, & Peuster, 1992).

Motor development occurs in an orderly sequence as infants move from reflexive reactions (e.g., sucking
and rooting) to more advanced motor functioning. For instance, babies first learn to hold their heads up,
then to sit with assistance, and then to sit unassisted, followed later by crawling and then walking.

Motor skills refer to our ability to move our bodies and manipulate objects. Fine motor skills focus on
the muscles in our fingers, toes, and eyes, and enable coordination of small actions (e.g., grasping a toy,
writing with a pencil, and using a spoon). Gross motor skills focus on large muscle groups that control
our arms and legs and involve larger movements (e.g., balancing, running, and jumping).

As motor skills develop, there are certain developmental milestones that young children should achieve
(Table 9.4). For each milestone there is an average age, as well as a range of ages in which the milestone
should be reached. An example of a developmental milestone is sitting. On average, most babies sit alone
at 7 months old. Sitting involves both coordination and muscle strength, and 90% of babies achieve this
milestone between 5 and 9 months old. In another example, babies on average are able to hold up their
head at 6 weeks old, and 90% of babies achieve this between 3 weeks and 4 months old. If a baby is not
holding up his head by 4 months old, he is showing a delay. If the child is displaying delays on several
milestones, that is reason for concern, and the parent or caregiver should discuss this with the child’s
pediatrician. Some developmental delays can be identified and addressed through early intervention.

316 Chapter 9 | Lifespan Development

This OpenStax book is available for free at

Developmental Milestones, Ages 2–5 Years


Physical Personal/Social Language Cognitive

2 Kicks a ball;
walks up
and down

Plays alongside
other children;
copies adults

Points to objects when
named; puts 2–4 words
together in a sentence

Sorts shapes and
colors; follows 2-step

3 Climbs and
runs; pedals

Takes turns;
expresses many
emotions; dresses

Names familiar things;
uses pronouns

Plays make believe;
works toys with parts
(levers, handles)

4 Catches
balls; uses

Prefers social play
to solo play; knows
likes and interests

Knows songs and
rhymes by memory

Names colors and
numbers; begins
writing letters

5 Hops and
swings; uses
fork and

Distinguishes real
from pretend; likes
to please friends

Speaks clearly; uses full

Counts to 10 or higher;
prints some letters and
copies basic shapes

Table 9.4

Cognitive Development

In addition to rapid physical growth, young children also exhibit significant development of their
cognitive abilities. Piaget thought that children’s ability to understand objects—such as learning that
a rattle makes a noise when shaken—was a cognitive skill that develops slowly as a child matures
and interacts with the environment. Today, developmental psychologists think Piaget was incorrect.
Researchers have found that even very young children understand objects and how they work long before
they have experience with those objects (Baillargeon, 1987; Baillargeon, Li, Gertner, & Wu, 2011). For
example, children as young as 3 months old demonstrated knowledge of the properties of objects that
they had only viewed and did not have prior experience with them. In one study, 3-month-old infants
were shown a truck rolling down a track and behind a screen. The box, which appeared solid but was
actually hollow, was placed next to the track. The truck rolled past the box as would be expected. Then
the box was placed on the track to block the path of the truck. When the truck was rolled down the track
this time, it continued unimpeded. The infants spent significantly more time looking at this impossible
event (Figure 9.11). Baillargeon (1987) concluded that they knew solid objects cannot pass through each
other. Baillargeon’s findings suggest that very young children have an understanding of objects and how
they work, which Piaget (1954) would have said is beyond their cognitive abilities due to their limited
experiences in the world.

Chapter 9 | Lifespan Development 317

Figure 9.11 In Baillargeon’s study, infants observed a truck (a) roll down an unobstructed track, (b) roll down an
unobstructed track with an obstruction (box) beside it, and (c) roll down and pass through what appeared to be an

Just as there are physical milestones that we expect children to reach, there are also cognitive milestones.
It is helpful to be aware of these milestones as children gain new abilities to think, problem solve, and
communicate. For example, infants shake their head “no” around 6–9 months, and they respond to verbal
requests to do things like “wave bye-bye” or “blow a kiss” around 9–12 months. Remember Piaget’s
ideas about object permanence? We can expect children to grasp the concept that objects continue to exist
even when they are not in sight by around 8 months old. Because toddlers (i.e., 12–24 months old) have
mastered object permanence, they enjoy games like hide and seek, and they realize that when someone
leaves the room they will come back (Loop, 2013). Toddlers also point to pictures in books and look in
appropriate places when you ask them to find objects.

Preschool-age children (i.e., 3–5 years old) also make steady progress in cognitive development. Not only
can they count, name colors, and tell you their name and age, but they can also make some decisions on
their own, such as choosing an outfit to wear. Preschool-age children understand basic time concepts and
sequencing (e.g., before and after), and they can predict what will happen next in a story. They also begin
to enjoy the use of humor in stories. Because they can think symbolically, they enjoy pretend play and
inventing elaborate characters and scenarios. One of the most common examples of their cognitive growth
is their blossoming curiosity. Preschool-age children love to ask “Why?”

An important cognitive change occurs in children this age. Recall that Piaget described 2–3 year olds as
egocentric, meaning that they do not have an awareness of others’ points of view. Between 3 and 5 years
old, children come to understand that people have thoughts, feelings, and beliefs that are different from
their own. This is known as theory-of-mind (TOM). Children can use this skill to tease others, persuade
their parents to purchase a candy bar, or understand why a sibling might be angry. When children develop
TOM, they can recognize that others have false beliefs (Dennett, 1987; Callaghan et al., 2005).

False-belief tasks are useful in determining a child’s acquisition of theory-of-mind (TOM). Take a look at
this video clip that shows a false belief task involving a box of crayons (
crayons) to learn more.

Cognitive skills continue to expand in middle and late childhood (6–11 years old). Thought processes
become more logical and organized when dealing with concrete information (Figure 9.12). Children at
this age understand concepts such as the past, present, and future, giving them the ability to plan and
work toward goals. Additionally, they can process complex ideas such as addition and subtraction and
cause-and-effect relationships. However, children’s attention spans tend to be very limited until they are
around 11 years old. After that point, it begins to improve through adulthood.


318 Chapter 9 | Lifespan Development

This OpenStax book is available for free at

Figure 9.12 Because they understand luck and fairness, children in middle and late childhood (6–11 years old) are
able to follow rules for games. (credit: Edwin Martinez)

One well-researched aspect of cognitive development is language acquisition. As mentioned earlier, the
order in which children learn language structures is consistent across children and cultures (Hatch, 1983).
You’ve also learned that some psychological researchers have proposed that children possess a biological
predisposition for language acquisition.

Starting before birth, babies begin to develop language and communication skills. At birth, babies
apparently recognize their mother’s voice and can discriminate between the language(s) spoken by their
mothers and foreign languages, and they show preferences for faces that are moving in synchrony with
audible language (Blossom & Morgan, 2006; Pickens, 1994; Spelke & Cortelyou, 1981).

Children communicate information through gesturing long before they speak, and there is some evidence
that gesture usage predicts subsequent language development (Iverson & Goldin-Meadow, 2005). In
terms of producing spoken language, babies begin to coo almost immediately. Cooing is a one-syllable
combination of a consonant and a vowel sound (e.g., coo or ba). Interestingly, babies replicate sounds from
their own languages. A baby whose parents speak French will coo in a different tone than a baby whose
parents speak Spanish or Urdu. After cooing, the baby starts to babble. Babbling begins with repeating a
syllable, such as ma-ma, da-da, or ba-ba. When a baby is about 12 months old, we expect her to say her
first word for meaning, and to start combining words for meaning at about 18 months.

At about 2 years old, a toddler uses between 50 and 200 words; by 3 years old they have a vocabulary
of up to 1,000 words and can speak in sentences. During the early childhood years, children’s vocabulary
increases at a rapid pace. This is sometimes referred to as the “vocabulary spurt” and has been claimed to
involve an expansion in vocabulary at a rate of 10–20 new words per week. Recent research may indicate
that while some children experience these spurts, it is far from universal (as discussed in Ganger & Brent,
2004). It has been estimated that, 5 year olds understand about 6,000 words, speak 2,000 words, and can
define words and question their meanings. They can rhyme and name the days of the week. Seven year
olds speak fluently and use slang and clichés (Stork & Widdowson, 1974).

What accounts for such dramatic language learning by children? Behaviorist B. F. Skinner thought that we
learn language in response to reinforcement or feedback, such as through parental approval or through
being understood. For example, when a two-year-old child asks for juice, he might say, “me juice,” to
which his mother might respond by giving him a cup of apple juice. Noam Chomsky (1957) criticized
Skinner’s theory and proposed that we are all born with an innate capacity to learn language. Chomsky
called this mechanism a language acquisition device (LAD). Who is correct? Both Chomsky and Skinner
are right. Remember that we are a product of both nature and nurture. Researchers now believe that
language acquisition is partially inborn and partially learned through our interactions with our linguistic
environment (Gleitman & Newport, 1995; Stork & Widdowson, 1974).


Psychosocial development occurs as children form relationships, interact with others, and understand
and manage their feelings. In social and emotional development, forming healthy attachments is very
important and is the major social milestone of infancy. Attachment is a long-standing connection or bond

Chapter 9 | Lifespan Development 319

with others. Developmental psychologists are interested in how infants reach this milestone. They ask such
questions as: How do parent and infant attachment bonds form? How does neglect affect these bonds?
What accounts for children’s attachment differences?

Researchers Harry Harlow, John Bowlby, and Mary Ainsworth conducted studies designed to answer
these questions. In the 1950s, Harlow conducted a series of experiments on monkeys. He separated
newborn monkeys from their mothers. Each monkey was presented with two surrogate mothers. One
surrogate monkey was made out of wire mesh, and she could dispense milk. The other monkey was softer
and made from cloth: This monkey did not dispense milk. Research shows that the monkeys preferred the
soft, cuddly cloth monkey, even though she did not provide any nourishment. The baby monkeys spent
their time clinging to the cloth monkey and only went to the wire monkey when they needed to be fed.
Prior to this study, the medical and scientific communities generally thought that babies become attached
to the people who provide their nourishment. However, Harlow (1958) concluded that there was more to
the mother-child bond than nourishment. Feelings of comfort and security are the critical components to
maternal-infant bonding, which leads to healthy psychosocial development.

Harlow’s studies of monkeys were performed before modern ethics guidelines were in place, and today
his experiments are widely considered to be unethical and even cruel. Watch this video of actual
footage of Harlow’s monkey studies ( to learn more.

Building on the work of Harlow and others, John Bowlby developed the concept of attachment theory.
He defined attachment as the affectional bond or tie that an infant forms with the mother (Bowlby, 1969).
An infant must form this bond with a primary caregiver in order to have normal social and emotional
development. In addition, Bowlby proposed that this attachment bond is very powerful and continues
throughout life. He used the concept of secure base to define a healthy attachment between parent and
child (1988). A secure base is a parental presence that gives the child a sense of safety as he explores his
surroundings. Bowlby said that two things are needed for a healthy attachment: The caregiver must be
responsive to the child’s physical, social, and emotional needs; and the caregiver and child must engage in
mutually enjoyable interactions (Bowlby, 1969) (Figure 9.13).

Figure 9.13 Mutually enjoyable interactions promote the parent-infant bond. (credit:

While Bowlby thought attachment was an all-or-nothing process, Mary Ainsworth’s (1970) research
showed otherwise. Ainsworth wanted to know if children differ in the ways they bond, and if so, why.


320 Chapter 9 | Lifespan Development

This OpenStax book is available for free at

To find the answers, she used the Strange Situation procedure to study attachment between mothers and
their infants (1970). In the Strange Situation, the mother (or primary caregiver) and the infant (age 12-18
months) are placed in a room together. There are toys in the room, and the caregiver and child spend some
time alone in the room. After the child has had time to explore her surroundings, a stranger enters the
room. The mother then leaves her baby with the stranger. After a few minutes, she returns to comfort her

Based on how the infants/toddlers responded to the separation and reunion, Ainsworth identified three
types of parent-child attachments: secure, avoidant, and resistant (Ainsworth & Bell, 1970). A fourth style,
known as disorganized attachment, was later described (Main & Solomon, 1990). The most common
type of attachment—also considered the healthiest—is called secure attachment (Figure 9.14). In this
type of attachment, the toddler prefers his parent over a stranger. The attachment figure is used as a
secure base to explore the environment and is sought out in times of stress. Securely attached children
were distressed when their caregivers left the room in the Strange Situation experiment, but when their
caregivers returned, the securely attached children were happy to see them. Securely attached children
have caregivers who are sensitive and responsive to their needs.

Figure 9.14 In secure attachment, the parent provides a secure base for the toddler, allowing him to securely
explore his environment. (credit: Kerry Ceszyk)

With avoidant attachment, the child is unresponsive to the parent, does not use the parent as a secure
base, and does not care if the parent leaves. The toddler reacts to the parent the same way she reacts to a
stranger. When the parent does return, the child is slow to show a positive reaction. Ainsworth theorized
that these children were most likely to have a caregiver who was insensitive and inattentive to their needs
(Ainsworth, Blehar, Waters, & Wall, 1978).

In cases of resistant attachment, children tend to show clingy behavior, but then they reject the attachment
figure’s attempts to interact with them (Ainsworth & Bell, 1970). These children do not explore the toys
in the room, as they are too fearful. During separation in the Strange Situation, they became extremely
disturbed and angry with the parent. When the parent returns, the children are difficult to comfort.
Resistant attachment is the result of the caregivers’ inconsistent level of response to their child.

Finally, children with disorganized attachment behaved oddly in the Strange Situation. They freeze, run
around the room in an erratic manner, or try to run away when the caregiver returns (Main & Solomon,
1990). This type of attachment is seen most often in kids who have been abused. Research has shown that
abuse disrupts a child’s ability to regulate their emotions.

While Ainsworth’s research has found support in subsequent studies, it has also met criticism. Some
researchers have pointed out that a child’s temperament may have a strong influence on attachment
(Gervai, 2009; Harris, 2009), and others have noted that attachment varies from culture to culture, a

Chapter 9 | Lifespan Development 321

factor not accounted for in Ainsworth’s research (Rothbaum, Weisz, Pott, Miyake, & Morelli, 2000; van
Ijzendoorn & Sagi-Schwartz, 2008).

Watch this video clip of the Strange Situation ( and try to identify
which type of attachment baby Lisa exhibits.


Just as attachment is the main psychosocial milestone of infancy, the primary psychosocial milestone
of childhood is the development of a positive sense of self. How does self-awareness develop? Infants
don’t have a self-concept, which is an understanding of who they are. If you place a baby in front of a
mirror, she will reach out to touch her image, thinking it is another baby. However, by about 18 months
a toddler will recognize that the person in the mirror is herself. How do we know this? In a well-known
experiment, a researcher placed a red dot of paint on children’s noses before putting them in front of a
mirror (Amsterdam, 1972). Commonly known as the mirror test, this behavior is demonstrated by humans
and a few other species and is considered evidence of self-recognition (Archer, 1992). At 18 months old
they would touch their own noses when they saw the paint, surprised to see a spot on their faces. By 24–36
months old children can name and/or point to themselves in pictures, clearly indicating self-recognition.

Children from 2–4 years old display a great increase in social behavior once they have established a self-
concept. They enjoy playing with other children, but they have difficulty sharing their possessions. Also,
through play children explore and come to understand their gender roles and can label themselves as a
girl or boy (Chick, Heilman-Houser, & Hunter, 2002). By 4 years old, children can cooperate with other
children, share when asked, and separate from parents with little anxiety. Children at this age also exhibit
autonomy, initiate tasks, and carry out plans. Success in these areas contributes to a positive sense of self.
Once children reach 6 years old, they can identify themselves in terms of group memberships: “I’m a first
grader!” School-age children compare themselves to their peers and discover that they are competent in
some areas and less so in others (recall Erikson’s task of industry versus inferiority). At this age, children
recognize their own personality traits as well as some other traits they would like to have. For example,
10-year-old Layla says, “I’m kind of shy. I wish I could be more talkative like my friend Alexa.”

Development of a positive self-concept is important to healthy development. Children with a positive self-
concept tend to be more confident, do better in school, act more independently, and are more willing to
try new activities (Maccoby, 1980; Ferrer & Fugate, 2003). Formation of a positive self-concept begins in
Erikson’s toddlerhood stage, when children establish autonomy and become confident in their abilities.
Development of self-concept continues in elementary school, when children compare themselves to others.
When the comparison is favorable, children feel a sense of competence and are motivated to work harder
and accomplish more. Self-concept is re-evaluated in Erikson’s adolescence stage, as teens form an identity.
They internalize the messages they have received regarding their strengths and weaknesses, keeping
some messages and rejecting others. Adolescents who have achieved identity formation are capable of
contributing positively to society (Erikson, 1968).

Phenomenological Variant of Ecological Systems Theory (PVEST)

Kenneth and Mamie Clark were pioneering psychologists responsible for the first psychological study used in



322 Chapter 9 | Lifespan Development

This OpenStax book is available for free at

a Supreme Court case. Their research with African American children and doll choices was used to highlight
the harmful effects of segregation and provided support for the Browns and the NAACP in their lawsuit against
the Board of Education. The finding that African American children were more likely to choose a white doll over
a black doll, in both northern and southern states, led them to theorize that the children did not have a healthy
concept of themselves (Clark & Clark, 1950).

The Clarks’ research differed from that of Inez Beverly Prosser, who also studied African American children
in segregated and integrated schools in Cincinnati. Parents could choose either environment for their children
during the 1930s. She found, among other factors, that the self-concept of children at segregated schools was
more positive versus those in integrated schools, partly due to teachers’ low expectations. Prosser also noted
that the child’s personality should be considered when choosing a segregated school or an integrated school
(Benjamin, Henry, & McMahon, 2005).

Later researchers suggested that African American children choosing a doll that did not look like them was
not an indication of their self-esteem or their self-image. For instance, Rogers and Meltzoff (2017) found
that gender identity was more important than race in their study of diverse children whose average age was
about 10 years old. Thus, for children that young, the meaning of race is an evolving process, as opposed to
adolescents’ search for identity. The ethnic minority children in the study did view racial identity as important,
compared to their white counterparts.

For teenagers who are members of ethnic minority groups, racial/ethnic/cultural identity can be paramount,
depending on the family’s processes. Racial socialization involves teaching them the positive aspects of their
in-group, usually by caregivers. Most of the students in a study by Neblett, Smalls, Ford, Nguyen, and Sellers
(2009) reported having received such messages but a few received no racial socialization messages. They
found that these messages played a role in how they felt about their in-group.

Some theories have been developed to explain the behaviors of ethnic minority youth. One such theory is the
Phenomenological Variant of Ecological Systems Theory (PVEST), put forth by Margaret Beale Spencer. It is
a merging of phenomenology and Bronfenbrenner’s ecological systems theory. A phenomenological approach
is based on how a person makes meaning of their experiences. For example, young African American
boys have different experiences in educational settings compared to African American girls. Consequently,
the meaning they assign to those experiences differs. Bronfenbrenner’s ecological systems theory suggests
that development occurs based on interactions among environments such as school, family, and community
(Bronfenbrenner, 1977).

The research that Spencer, Dupree, and Hartmann (1997) conducted with African American adolescent boys
and girls was explained by PVEST. They found that negative learning attitudes were predicted by unpopularity
with peers for girls and boys. Additionally, for boys, more stress predicted a less negative attitude toward
learning, possibly due to focus on the school environment instead of on personal issues. This occurred along
with perceiving that teachers had positive expectations of African American boys. The researchers surmised
that PVEST accounted for how others’ perceptions and their subsequent attitudes were related and worked
both ways.

What can parents do to nurture a healthy self-concept? Diana Baumrind (1971, 1991) thinks parenting style
may be a factor. The way we parent is an important factor in a child’s socioemotional growth. Baumrind
developed and refined a theory describing four parenting styles: authoritative, authoritarian, permissive,
and uninvolved. With the authoritative style, the parent gives reasonable demands and consistent limits,
expresses warmth and affection, and listens to the child’s point of view. Parents set rules and explain
the reasons behind them. They are also flexible and willing to make exceptions to the rules in certain
cases—for example, temporarily relaxing bedtime rules to allow for a nighttime swim during a family
vacation. Of the four parenting styles, the authoritative style is the one that is most encouraged in modern
American society. American children raised by authoritative parents tend to have high self-esteem and
social skills. However, effective parenting styles vary as a function of culture and, as Small (1999) points
out, the authoritative style is not necessarily preferred or appropriate in all cultures.

Chapter 9 | Lifespan Development 323

In authoritarian style, the parent places high value on conformity and obedience. The parents are often
strict, tightly monitor their children, and express little warmth. In contrast to the authoritative style,
authoritarian parents probably would not relax bedtime rules during a vacation because they consider the
rules to be set, and they expect obedience. This style can create anxious, withdrawn, and unhappy kids.
However, it is important to point out that authoritarian parenting is as beneficial as the authoritative style
in some ethnic groups (Russell, Crockett, & Chao, 2010). For instance, first-generation Chinese American
children raised by authoritarian parents did just as well in school as their peers who were raised by
authoritative parents (Russell et al., 2010).

For parents who employ the permissive style of parenting, the kids run the show and anything goes.
Permissive parents make few demands and rarely use punishment. They tend to be very nurturing and
loving, and may play the role of friend rather than parent. In terms of our example of vacation bedtimes,
permissive parents might not have bedtime rules at all—instead they allow the child to choose his bedtime
whether on vacation or not. Not surprisingly, children raised by permissive parents tend to lack self-
discipline, and the permissive parenting style is negatively associated with grades (Dornbusch, Ritter,
Leiderman, Roberts, & Fraleigh, 1987). The permissive style may also contribute to other risky behaviors
such as alcohol abuse (Bahr & Hoffman, 2010), risky sexual behavior especially among female children
(Donenberg, Wilson, Emerson, & Bryant, 2002), and increased display of disruptive behaviors by male
children (Parent et al., 2011). However, there are some positive outcomes associated with children raised
by permissive parents. They tend to have higher self-esteem, better social skills, and report lower levels of
depression (Darling, 1999).

With the uninvolved style of parenting, the parents are indifferent, uninvolved, and sometimes referred
to as neglectful. They don’t respond to the child’s needs and make relatively few demands. This could
be because of severe depression or substance abuse, or other factors such as the parents’ extreme focus
on work. These parents may provide for the child’s basic needs, but little else. The children raised in this
parenting style are usually emotionally withdrawn, fearful, anxious, perform poorly in school, and are at
an increased risk of substance abuse (Darling, 1999).

As you can see, parenting styles influence childhood adjustment, but could a child’s temperament likewise
influence parenting? Temperament refers to innate traits that influence how one thinks, behaves, and
reacts with the environment. Children with easy temperaments demonstrate positive emotions, adapt well
to change, and are capable of regulating their emotions. Conversely, children with difficult temperaments
demonstrate negative emotions and have difficulty adapting to change and regulating their emotions.
Difficult children are much more likely to challenge parents, teachers, and other caregivers (Thomas, 1984).
Therefore, it’s possible that easy children (i.e., social, adaptable, and easy to soothe) tend to elicit warm
and responsive parenting, while demanding, irritable, withdrawn children evoke irritation in their parents
or cause their parents to withdraw (Sanson & Rothbart, 1995).

The Importance of Play and Recess

According to the American Academy of Pediatrics (2007), unstructured play is an integral part of a child’s
development. It builds creativity, problem solving skills, and social relationships. Play also allows children to
develop a theory-of-mind as they imaginatively take on the perspective of others.

Outdoor play allows children the opportunity to directly experience and sense the world around them. While
doing so, they may collect objects that they come across and develop lifelong interests and hobbies. They
also benefit from increased exercise, and engaging in outdoor play can actually increase how much they enjoy
physical activity. This helps support the development of a healthy heart and brain. Unfortunately, research
suggests that today’s children are engaging in less and less outdoor play (Clements, 2004). Perhaps, it is no
surprise to learn that lowered levels of physical activity in conjunction with easy access to calorie-dense foods


324 Chapter 9 | Lifespan Development

This OpenStax book is available for free at

with little nutritional value are contributing to alarming levels of childhood obesity (Karnik & Kanekar, 2012).

Despite the adverse consequences associated with reduced play, some children are over scheduled and have
little free time to engage in unstructured play. In addition, some schools have taken away recess time for
children in a push for students to do better on standardized tests, and many schools commonly use loss of
recess as a form of punishment. Do you agree with these practices? Why or why not?


Adolescence is a socially constructed concept. In pre-industrial society, children were considered adults
when they reached physical maturity, but today we have an extended time between childhood and
adulthood called adolescence. Adolescence is the period of development that begins at puberty and ends
at emerging adulthood, which is discussed later. In the United States, adolescence is seen as a time to
develop independence from parents while remaining connected to them (Figure 9.15). The typical age
range of adolescence is from 12 to 18 years, and this stage of development also has some predictable
physical, cognitive, and psychosocial milestones.

Figure 9.15 Peers are a primary influence on our development in adolescence. (credit: “manseok_Pixabay”/

Physical Development

As noted above, adolescence begins with puberty. While the sequence of physical changes in puberty is
predictable, the onset and pace of puberty vary widely. Several physical changes occur during puberty,
such as adrenarche and gonadarche, the maturing of the adrenal glands and sex glands, respectively.
Also during this time, primary and secondary sexual characteristics develop and mature. Primary sexual
characteristics are organs specifically needed for reproduction, like the uterus and ovaries in females
and testes in males. Secondary sexual characteristics are physical signs of sexual maturation that do not
directly involve sex organs, such as development of breasts and hips in girls, and development of facial
hair and a deepened voice in boys. Girls experience menarche, the beginning of menstrual periods, usually
around 12–13 years old, and boys experience spermarche, the first ejaculation, around 13–14 years old.

During puberty, both sexes experience a rapid increase in height (i.e., growth spurt). For girls this begins
between 8 and 13 years old, with adult height reached between 10 and 16 years old. Boys begin their
growth spurt slightly later, usually between 10 and 16 years old, and reach their adult height between 13
and 17 years old. Both nature (i.e., genes) and nurture (e.g., nutrition, medications, and medical conditions)
can influence height.

Because rates of physical development vary so widely among teenagers, puberty can be a source of
pride or embarrassment. Early maturing boys tend to be stronger, taller, and more athletic than their
later maturing peers. They are usually more popular, confident, and independent, but they are also at a
greater risk for substance abuse and early sexual activity (Flannery, Rowe, & Gulley, 1993; Kaltiala-Heino,
Rimpela, Rissanen, & Rantanen, 2001). Early maturing girls may be teased or overtly admired, which
can cause them to feel self-conscious about their developing bodies. These girls are at a higher risk for
depression, substance abuse, and eating disorders (Ge, Conger, & Elder, 2001; Graber, Lewinsohn, Seeley,
& Brooks-Gunn, 1997; Striegel-Moore & Cachelin, 1999). Late blooming boys and girls (i.e., they develop

Chapter 9 | Lifespan Development 325

more slowly than their peers) may feel self-conscious about their lack of physical development. Negative
feelings are particularly a problem for late maturing boys, who are at a higher risk for depression and
conflict with parents (Graber et al., 1997) and more likely to be bullied (Pollack & Shuster, 2000).

The adolescent brain also remains under development. Up until puberty, brain cells continue to bloom
in the frontal region. Adolescents engage in increased risk-taking behaviors and emotional outbursts
possibly because the frontal lobes of their brains are still developing (Figure 9.16). Recall that this area
is responsible for judgment, impulse control, and planning, and it is still maturing into early adulthood
(Casey, Tottenham, Liston, & Durston, 2005).

Figure 9.16 Brain growth continues into the early 20s. The development of the frontal lobe, in particular, is important
during this stage.

According to neuroscientist Jay Giedd in the Frontline video “Inside the Teenage Brain” (2013), “It’s sort of
unfair to expect [teens] to have adult levels of organizational skills or decision-making before their brains
are finished being built.” Watch this segment on “The Wiring of the Adolescent Brain”
( to find out more about the developing brain during adolescence.

Cognitive Development

More complex thinking abilities emerge during adolescence. Some researchers suggest this is due to
increases in processing speed and efficiency rather than as the result of an increase in mental capacity—in
other words, due to improvements in existing skills rather than development of new ones (Bjorkland,
1987; Case, 1985). During adolescence, teenagers move beyond concrete thinking and become capable of
abstract thought. Recall that Piaget refers to this stage as formal operational thought. Teen thinking is also
characterized by the ability to consider multiple points of view, imagine hypothetical situations, debate
ideas and opinions (e.g., politics, religion, and justice), and form new ideas (Figure 9.17). In addition, it’s
not uncommon for adolescents to question authority or challenge established societal norms.

Cognitive empathy, also known as theory-of-mind (which we discussed earlier with regard to
egocentrism), relates to the ability to take the perspective of others and feel concern for others (Shamay-
Tsoory, Tomer, & Aharon-Peretz, 2005). Cognitive empathy begins to increase in adolescence and is an
important component of social problem solving and conflict avoidance. According to one longitudinal
study, levels of cognitive empathy begin rising in girls around 13 years old, and around 15 years old in


326 Chapter 9 | Lifespan Development

This OpenStax book is available for free at

boys (Van der Graaff et al., 2013). Teens who reported having supportive fathers with whom they could
discuss their worries were found to be better able to take the perspective of others (Miklikowska, Duriez,
& Soenens, 2011).

Figure 9.17 Teenage thinking is characterized by the ability to reason logically and solve hypothetical problems such
as how to design, plan, and build a structure. (credit: U.S. Army RDECOM)

Psychosocial Development

Adolescents continue to refine their sense of self as they relate to others. Erikson referred to the task of the
adolescent as one of identity versus role confusion. Thus, in Erikson’s view, an adolescent’s main questions
are “Who am I?” and “Who do I want to be?” Some adolescents adopt the values and roles that their
parents expect for them. Other teens develop identities that are in opposition to their parents but align
with a peer group. This is common as peer relationships become a central focus in adolescents’ lives.

As adolescents work to form their identities, they pull away from their parents, and the peer group
becomes very important (Shanahan, McHale, Osgood, & Crouter, 2007). Despite spending less time with
their parents, most teens report positive feelings toward them (Moore, Guzman, Hair, Lippman, & Garret