CHAPTER 2Section 2.2 The Neuron

CHAPTER 2Section 2.2 The Neuron

Psychology: The Human Puzzle

Guy R. Lefrançois University of Alberta



Guy R. Lefrançois Psychology: The Human Puzzle

Associate Vice President, Editor in Chief: Erik Evans

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ISBN-10: 1-9359662-4-3

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GRANT OF PERMISSION TO PRINT: Bridgepoint Education Inc., the copyright owner of this material, hereby grants the holder of this publication the right to print these materials for personal use. The holder of this material may print the materials herein for personal use only. Any print, reprint, reproduction, or distribution of these materials for commercial use without the express written consent of the copyright owner constitutes a violation of the U.S. Copyright Act, 17 U.S.C. §§ 101-810, as amended.



To Elizabeth, Liam, Zachary, Nathan, and Michael, who are still finding new pieces of the puzzle for me.




Brief Contents

Chapter 1: The Science of Psychology . . . . . . . . . . . . . . . . . . . .1

Chapter 2: The Brain and Consciousness . . . . . . . . . . . . . . . .31

Chapter 3: Sensation and Perception . . . . . . . . . . . . . . . . . . . .65

Chapter 4: Learning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .103

Chapter 5: Memory and Intelligence . . . . . . . . . . . . . . . . . . .135

Chapter 6: Motivation and Emotion . . . . . . . . . . . . . . . . . . . .169

Chapter 7: Human Development . . . . . . . . . . . . . . . . . . . . . .207

Chapter 8: Personality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .247

Chapter 9: Psychological Disorders and Therapies . . . . . . .279

Chapter 10: Social Psychology . . . . . . . . . . . . . . . . . . . . . . . .315

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .349

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .373

Photo Credits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .409





About the Author xix Preface xxi Acknowledgments xxiii

chapter 1 The Science of Psychology 1

1.1 What Is Psychology? 3 What Psychologists Do 3

Clinical Psychologists 4 Counseling Psychologists 4 Industrial/Organizational Psychologists 4 School Psychologists 4 Educational Psychologists 5 Developmental Psychologists 5 Experimental Psychologists 5 Other Divisions 5

1.2 The Beginnings of Psychology 6 Recent Origins of Psychology 7

Structuralism 8 Functionalism 8 Behaviorism 8 Psychodynamic Theory 9 Cognitivism 9 Humanism 9 Other Orientations 10

1.3 Principles of Science 10 The Scientific Method 11




1.4 Sources of Psychological Information 12 Descriptive Research 12

Naturalistic and Nonnaturalistic Observation 12 Case Studies 13 Surveys 14 Correlational Research 15

Experiments 17 Experimental and Control Groups 17

Ex Post Facto Studies 19 1.5 Cautions in Interpreting Psychological Research 20

Experimenter Bias 20 Subject Bias 22 Sampling Bias 22 Other Problems of Psychological Research 24

Research Ethics 24 Avoiding the Pitfalls 25

1.6 Philosophical Issues and Psychological Controversy 25

1.7 Psychology’s Relevance 26

1.8 This Book 27

Main Points 28 Study Terms 29

chapter 2 The Brain and Consciousness 31

2.1 Evolution 33 Early Homo Sapiens 33

Brains, Language, and Thinking 35 Evolution and the Nervous System 36

2.2 The Neuron 38 Neural Transmission 39

Dopamine 41 Norepinephrine 41 Acetylcholine 42 Serotonin 42

2.3 Organization of the Nervous System 42 The Endocrine System 44

2.4 The Brain 44 Studying Brain Functions 44

Brain Ablations 45 Brain Stimulation 45 Brain Imaging 46




Structures of the Brain 46 Hindbrain 48 The Midbrain 49 The Forebrain 49 The Hemispheres 50

2.5 Biology and Behavior 51 Consciousness 53

2.6 Sleep 54 Circadian Rhythms 54 Stages of Sleep 54 Why We Sleep 56 Dreams 58

Why We Dream 58 2.7 Hypnosis 59

Some Facts 60 Is Hypnosis a Different State of Consciousness? 60 Applications of Hypnosis 61

2.8 Drugs and Consciousness 61

Main Points 62 Study Terms 63

chapter 3 Sensation and Perception 65

3.1 Sensation and Perception 67 Functions of the Senses 67

3.2 Vision 69 Structure of the Eye 69 Eye and Brain 71 Light Waves and Vision 72

Wavelength 73 Amplitude 74 Complexity and Color Purity 74

Color Vision 74 Trichromatic Theory: Young-Helmholtz 75 Opponent Process Theory: Hering 76

Vision in Low Light 76 Characteristics of Visual Perception 78

The Visual Constancies 78 Perception of Depth and Distance 81 Perception of Movement 84

Illusions 84




3.3 Attention and Perception 86

3.4 Hearing 88 Three Functions of the Auditory System 88 Perception of Sound Waves 89

Pitch 89 Loudness 90 Timbre 91

The Auditory Apparatus 92 How the Ear Works 93

3.5 The Body Senses 94 The Vestibular Sense 94 The Skin Senses 94 The Kinesthetic Senses 96

3.6 The Chemical Senses 96 Olfaction 96

The Olfactory Organ 97 Taste 99

3.7 Adding Pieces of the Puzzle 99

Main Points 100 Study Terms 101

chapter 4 Learning 103

4.1 What Is Learning? 105 Approaches to Learning 105

4.2 Behavioristic Approaches 107 Classical Conditioning 107

Pavlov’s Experiments 107 Acquisition 109 Generalization and Discrimination 111 Extinction and Recovery 111 Contiguity 112 Blocking 112 Consequences 114

Operant Conditioning 114 The Skinner Box 114 The Basic Operant Conditioning Model 115 Shaping 116

Schedules of Reinforcement 117 Effects of Different Schedules 117 Types of Reinforcement 119




Punishment 121 The Ethics of Punishment 121 Operant Conditioning and Human Behavior 122

4.3 A Transition to Cognitivism 123 Problems for Traditional Behaviorism 123 Insight 124

4.4 Cognitive Approaches 126 The Main Beliefs of Cognitive Psychology 127

Learning Involves Mental Representation 127 Learners Are Not Identical 127 New Learning Builds on Previous Learning 127

Bandura’s Social Cognitive Theory 127 Models 128 Reciprocal Determinism 128 Effects of Imitation 130 Humans as Agents of Their Own Behaviors 130

4.5 Practical Applications of Learning Principles 131 Applications of Behaviorism 131 Applications of Cognitivism 132

Main Points 133 Study Terms 133

chapter 5 Memory and Intelligence 135

5.1 What Is Memory? 137 The Filing-Cabinet Analogy 138

5.2 Stages of Memory 138 Sensory Memory 139 Short-Term Memory 140

Studying Short-Term Memory 140 Characteristics of Short-Term Recall 140 What Happens in Short-Term Memory: Baddeley’s Model 141

Long-Term Memory 142 Long-Term Memory Is Relatively Stable 143 Long-Term Memory Is Constructive 144 Understanding and Emotion Influence Memory 144 Rehearsal and Intention Influence Long-Term Memory 145 Two Kinds of Long-Term Memory: Explicit and Implicit 145 Two Kinds of Explicit Memory: Semantic and Autobiographical 146

Physiology of Memory 147 Neuroscience 148

Processes in Long-Term Memory 149




5.3 Forgetting 150 Fading Theory 150 Repression 150 Distortion Theory 151 Interference Theory 151 Retrieval-Cue Failure 152

5.4 Improving Memory 153 Mnemonic Aids 153

Rhymes and Sayings 154 The Link System 154 The Loci System 155 The Phonetic System 155

5.5 What Is Intelligence? 156 Myths about IQ 156

Myth 1 156 Myth 2 156 Myth 3 156 Myth 4 157 Not a Myth 157

Views of Intelligence 158 Successful Intelligence: Sternberg 158 Multiple Intelligences: Gardner 159

5.6 Measuring Intelligence 161 The IQ 161 IQ Tests 161 Misuses and Abuses of Tests 162

5.7 Influences on Intelligence 164 Heredity and Environment 164

The Rubber-Band Hypothesis 165 Main Points 166

Study Terms 167

chapter 6 Motivation and Emotion 169

6.1 What Is Motivation? 171 A Definition 171

6.2 Physiological and Behavioristic Approaches 171 Instincts 171 Psychological Hedonism 173 Needs and Drives 173




Physiological Needs 173 Psychological Needs 174

6.3 Maslow’s Hierarchy 176

6.4 Cognitive Views 176 Cognitive Dissonance Theory 178 Achievement Motivation 180 Attribution Theory 181

Locus of Control 181 Attributions and Need for Achievement 182

Self-Efficacy 183 Sources of Self-Efficacy Judgments 184 Efficacy and Expectancy-Value Theory 185

6.5 Emotions 187 Arousal 187

The Yerkes-Dodson Law 187 Need for Stimulation 188 Arousal Theory 189 Sources of Arousal 190

What Is an Emotion? 190 Emotional Expression 191

Theories of Emotion 192 The James-Lange Theory 192 The Cannon-Bard Theory 192 Schachter’s Two-Factor Theory 193 Recent Theories 194 The Dual-Pathway Model for Fear 196

Emotional Control 196 The Brain and Emotions 197 Cognitive Control of Emotions 198

6.6 Hunger and Sex Drive 199 Hunger Stimuli 199

Stomach Contractions 199 The Role of the Brain 200 Taste and Smell 200 Metabolic Factors 201

Obesity 201 Anorexia, Bulimia, and Binge Eating Disorder 202

Causes 203 Sexual Motivation 203

Hormonal Factors 204 Cultural and Other Factors 204

Main Points 204 Study Terms 205




chapter 7 Human Development 207

7.1 The Beginning: Genetics and Prenatal Development 209 Chromosomes and Genes 210

Male or Female 211 The Genetic Code 211 Dominance and Recessiveness 213

Genetic Defects 216 Sex-Linked Defects 216 Non-Sex-Linked Defects 216 Chromosomal Disorders 216 Modifying Genetic Defects 217

Heredity and Environment 218 Prenatal Development 218

7.2 Infants 219 Physical and Motor Development in Infancy 219 Perception in the Newborn 220 Cognitive Development in Infancy 221

Cognition and Language Development 222 Social-Emotional Development in Infancy 223

Erikson’s Stages 223 Infant States 224 Infant-Caregiver Interaction 225 Infant Temperament 225

7.3 Children 227 Cognitive Development in Childhood: Piaget’s Theory 228

Mechanisms of Adaptation 228 Schemas 228 The Stage Theory 229 Evaluation of Piaget’s Theory 234

Children’s Social-Emotional Development 234 Initiative Versus Guilt 234 Industry Versus Inferiority 235 Play 235

7.4 Adolescents 237 Physical and Sexual Changes 237

Early and Late Maturation 238 Adolescent Egocentrism 238

The Imaginary Audience and the Personal Fable 239 Identity Formation 239

Identity Diffusion 240 Foreclosure 240 Moratorium 240 Identity Achieved 240




7.5 Adults 241 Erikson’s Stages of Adulthood 241

Intimacy Versus Isolation 242 Generativity Versus Self-Absorption 243 Integrity Versus Despair 243

Main Points 243 Study Terms 244

chapter 8 Personality 247

8.1 Personality 249 Personality and Self 249

The Real Person 250 8.2 The Common-Sense Approach 250

8.3 The Trait-Type Approach 252 Early Trait-Type Approaches 254 The Big Five 255

Extraversion 256 Openness 256 Neuroticism 256 Conscientiousness 256 Agreeableness 256

Stability of Personality 257 8.4 Biological Approaches 258

Sheldon’s Body Types 259 Research on Somatotypes 259

Eysenck’s Biological Theory 261 Research Evidence 261 Eysenck’s Organization of Personality 262

8.5 A Psychodynamic Approach: Freud 263 Freud’s Basic Ideas 263

Three Components of Personality 263 Psychosexual Stages 264 Normal and Abnormal Personality 266 Defense Mechanisms 267 Review of Freudian Theory 268

8.6 Learning-Based Approaches 268 Behaviorism 268 Bandura’s Social Cognitive Theory 269

Observational Learning 269 Reciprocal Determinism 270




Personal Agency 270 Relevance of Bandura’s Theory 270

Rotter’s Cognitive Approach 271 Externality-Internality 271

8.7 Humanistic Approaches 272 Abraham Maslow’s Self-Actualized Person 272 Rogers’s Phenomenology 273

8.8 Measuring Personality Variables 274 Projective Measures 274

The Rorschach 274 The Thematic Apperception Test 275

Nonprojective Measures 276 The NEO-PI-R 276 The MMPI-2 276

Some Cautions 277 Main Points 277

Study Terms 278

chapter 9 Psychological Disorders and Therapies 279

9.1 Historical and Current Views of Mental Disorders 281 Historical Views of the Causes of Mental Disorders 282 Current Definitions and Models 282

The Statistical Model 283 Medical/Biological Models 284 Behavioral Models 284 Cognitive Models 284 Psychodynamic Models 285 Which Model? 285 A Definition 286

Classifications of Disorders 286 The Most Common Disorders 289

9.2 Anxiety Disorders 290 Panic Attacks 290 Generalized Anxiety Disorder 291 Phobic Disorders 291

Agoraphobia 291 Social Phobias 292 Specific Phobias 293

Obsessive-Compulsive Disorders 293 Posttraumatic Stress Disorder 293




9.3 Impulse-Control Disorders Usually First Diagnosed in Children 294 Aggression-Based Impulse-Control Disorders 294 Conduct Disorder 294 Attention Deficit Hyperactivity Disorder 295 Other Impulse-Control Disorders 295

9.4 Mood Disorders 296 Major Depressive Disorder 296 Bipolar Disorder 296 Dysthymic Disorder 297

9.5 Substance-Related Disorders 297 Substance Use Disorders 297

Prevalence and Types of Drug Use 298 9.6 Other Axis I Disorders 300

Dissociative Disorders 300 Dissociative Amnesia 300 Dissociative Fugue 300 Dissociative Identity Disorder 301 Depersonalization Disorder 302

Psychotic Disorders 302 Schizophrenia 302 Causes 303

Sexual and Gender Identity Disorders 303 Gender Identity Disorders 303 Paraphilias 304 Sexual Dysfunctions 304

Somatoform Disorders 304 9.7 Axis II Personality Disorders 305

9.8 Therapies 306 Medical Therapy 306

Drug Therapy 307 Psychosurgery 307

Insight Therapy 307 Learning-Based and Cognitive Therapy 308

Behavior Modification 309 Positive Reinforcement 309 Rational Emotive Behavior Therapy 309

The Effectiveness of Therapies 311 Main Points 311

Study Terms 313




chapter 10 Social Psychology 315

10.1 Social Psychology 317 What Is Social Psychology? 317

10.2 Attitudes and Attitude Change 317 Compliance and Conformity 319 Social Pressure and Compliance 319 Obedience 321

The Milgram Studies 322 The Prison Experiment 324

Persuasion 325 Importance of Message Characteristics 325 Importance of Message Source 325 Importance of Audience Characteristics 326

Cognitive Dissonance 326 Attribution and Attitude Change 327

Overjustification 327 10.3 Antisocial Behaviors 328

Aggression and Violence 328 Theories of Aggression 328 Violence in Society 333

Bystander Apathy 334 The Bystander Effect 335 An Explanation 336 How Common Is the Bystander Effect? 337

10.4 Prosocial Behaviors 338 Altruism 338

10.5 Interpersonal Relationships 339 The Rules of Attraction 340

Propinquity 340 Similarity 340 Physical Attractiveness 341

Liking and Loving 342 A Model of Love 343 A Last Word to the Poets 346

Main Points 346 Study Terms 347

Glossary 349 References 373 Photo Credits 409



About the Author

Guy R . Lefrançois makes few claims to anything notable . “I’m an obscure French Canadian from a long line of obscure ancestors,” he insists . “Like me,” he says, “most are better remem- bered not for the things they did but for those they never accomplished . Some of the things I haven’t done yet are truly amazing!” He cur- rently holds an appointment at the University of Alberta, where he also received his PhD and where he first started teaching in 1966 . Since then, he has written numerous books in psy- chology, many of which have been translated into other languages, including Chinese, Russian, Italian, Spanish, French, and German (he does not speak all these other languages) . He has been happily married to Marie for more years that he can easily count and loves to fish, watch birds, pick berries, read other people’s words, and go on extended bicycle tours . He has 3 children (Laurier, Claire, and Rémi), and 5 grandchildren, to whom this book is dedicated .





Dear Reader,

The purpose of Psychology: The Human Puzzle is to explore psychology’s view of one of the most captivating and puzzling of all topics: ourselves . Its content is the story of the search for pieces of this puzzle and an account of how the pieces have begun to fit together . Its purpose is to teach .

But good teaching is more than just telling a story . It isn’t enough simply to gather and organize pieces of the puzzle and squeeze them into a text . Good teaching also requires motivating, illustrating, explaining, relating, evaluating, reviewing, maybe even inspir- ing . Good teachers sometimes have to do awesome somersaults and leap over burning buildings and juggle burning brands while balancing on tall ladders . Really .

Psychology: The Human Puzzle tries to be a good teacher . It illustrates and explains; it evalu- ates and reviews; it tries to inspire . Sometimes it pauses to tell stories about the heart- warming generosity of strangers, to shock with accounts of the misbehavior of violent adolescents, to intrigue with descriptions of mental disorders in other cultures, to amaze with tales of astonishing memories, to move with an analysis of the thing we call love . At least once that I can think of, it nearly does a somersault and even juggles a few things that, from far away, almost look like burning brands .

Characteristics of Psychology: The Human Puzzle

Psychology: The Human Puzzle has a number of characteristics intended to make it as useful a teaching-learning tool as it can be .

The graphic layout and format are designed with the student in mind . Pages are unclut- tered; text material flows with little interruption . All the important stuff is right in the text; there are no boxed inserts, sidebars, marginal notes, or other little gizmos to grab your eye and make you wonder where to go next . All the graphics and photographs are relevant, and definitions of important terms are gathered in the glossary . A brief summary and a list of important study terms follow each chapter .



Although it assembles all the important and essential pieces of the puzzle, this book is deliberately shorter than most other comparable textbooks, so that it can comfortably be covered in a single course .

I hope you enjoy and learn . I suspect that each is necessary for the other .


Guy R . Lefrançois




Dear People Involved with the Making of this Book,

Most of you know who you are . Sadly, I don’t know many of you . But I deeply appreci- ate everything you have done . The reviews were remarkably intelligent, and I am truly grateful to the instructors who shared their thoughts on the manuscript . I owe a debt of gratitude, as well, to Steve Wainwright, Sponsoring Editor, who initiated the project and guided its first steps, and to Dan Moneypenny, Development Editor, who developed the project astonishingly smoothly and rapidly . Thank you as well to Kim Purcell, Media Edi- tor, the copy editor, Susan Zorn, who cleaned up my mess so effortlessly, and to Shawn Vazinski of Lachina Publishing Services, and Illustrator Maury Aaseng . Finally, thank you to my amazing family, who nurture my work and my leisure, and to the University of Alberta for providing such a rich environment in which to look for pieces of the puzzle .


Guy R . Lefrançois






The Science of Psychology

Focus Questions

By the end of the chapter, you should be able to answer the following questions: • How is psychology defined? • What are the principal responsibilities of members of the main divisions in psychology? • What were the key beliefs and contributions of some of the early contributors to

the development of psychology? • What are the identifying characteristics of the scientific method? • What are some key types of descriptive research? • How does descriptive research differ from experiments and ex post facto studies? • What is the correlation fallacy? • What are some of the main sources of error in interpreting the results of psycho-

logical investigations?

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CHAPTER 1The Science of Psychology

1. Boldfaced terms are defined in the glossary.

The purpose of psychology is

to give us a completely different idea of the things we

know best. ­—Paul­Valéry,­Tel Quel,­1943

Chapter Outline

1.1 What Is Psychology? What Psychologists Do

1.2 The Beginnings of Psychology Recent Origins of Psychology

1.3 Principles of Science The Scientific Method

1.4 Sources of Psychological Information Descriptive Research Experiments Ex Post Facto Studies

1.5 Cautions in Interpreting Psychological Research

Experimenter Bias Subject Bias Sampling Bias Other Problems of Psychological Research

1.6 Philosophical Issues and Psychological Controversy

1.7 Psychology’s Relevance

1.8 This Book

My grandmother was convinced she knew best. “Not true,” she would declare when I tried to tell her what I was learning as a novice psychology student. And then, her knitting needles clacking, she would go on to inform me that boys who mature early are always messed up later. She also believed that people use only 10 percent of their brain because that is what she had read somewhere. And she knew that those suffering from mental disorders are like night and day from her and other sane people. Nor did she trust psychologists: “They have sneaky ways of looking into people’s minds,” she informed me. “Except people who have ESP powers.”

“And mark my word,” she said one time; “most geniuses are crazy.” “But you don’t have to worry,” she added.

These and a wide range of similar beliefs make up what is sometimes called bubba psychology1 (bubba or bubbe—or sometimes bubbie—means “grandmother” in some Eastern European lan- guages). Bubba psychology is also labeled naïve psychology or folk psychology.

Psychological research has not been kind to many of my grandmother’s beliefs—which is not to say that all our folk wisdom is untrue or that psychology’s beliefs are always correct. In fact, much of our folk wisdom is correct; and psychology, like most sciences, does occasionally change its mind.

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CHAPTER 1Section 1.1 What Is Psychology?

1.1 What Is Psychology?

My grandmother’s belief that psychologists have devious ways of peering into one’s mind is one reason why it is important to have a clear understanding of what psy- chology is and is not. While it’s true that its goal is to solve the puzzles of human thought and behavior, it is a science and not a collection of special powers.

In its simplest sense, psychology is the science that studies behavior and mental processes. Unfortunately, this definition does little justice to the tremendous variety of activities and interests that make up the field. In fact, members of the American Psychological Asso- ciation divide themselves into 54 different divisions (APA, 2010). These divisions reflect different interests and specializations, such as the study of aging or the application of psychological knowledge and principles in clinical settings.

What Psychologists Do

As Figure 1.1 shows, the vast majority of psychologists are involved in the practical appli- cation of psychological knowledge.

Clinical 52%


Others 19%

Social 2%

Main Specialties in Psychology

Industrial/Organizational 4%

Experimental 1% Educational 2%

Developmental 3%


Health 2%

School 4%

Figure 1.1

Main specialties in psychology. Based on a survey of the American Psychological Association’s 90,221 members in 2005. Data from APA Directory Survey 2005, compiled by APA Research Office. Retrieved July 13, 2010, from table-3.pdf.

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CHAPTER 1Section 1.1 What Is Psychology?

Clinical Psychologists About half of all psychologists are clinical psychol- ogists. These are typically psychologists working in a hospital or clinical setting. They specialize in helping people with psychological problems such as anxiety, depression, addiction, or relationship problems.

Although psychiatrists and clinical psychologists often treat similar sorts of problems, their training and expertise are quite different. Psychiatrists are medical doctors with specialized training in iden- tifying and treating mental and emotional disor- ders. In addition to the various other interventions they might use, they can prescribe drugs, which are now commonly used to treat many disorders ranging from mild anxiety to severe deviations from normality. In most jurisdictions, clinical psy- chologists cannot write prescriptions.

Counseling Psychologists A significant number of psychologists are coun- seling psychologists. They, too, treat problems related to emotional and mental disorders. In addition, they also deal with issues such as those having to do with vocational choices, learning problems, relationships, and related concerns. Whereas clinical psychologists often work in clinical settings or in private practices, counseling psychologists work mainly in private practices.

Industrial/Organizational Psychologists Roughly 4 percent of psychologists are classified as industrial/organizational psychologists. They are concerned mainly with work-related issues, such as determining how to hire the right person for a job, improving job satisfaction, increasing motivation in the workplace, reducing stress, and managing goals.

School Psychologists School psychologists deal with behavioral and learning problems that affect schoolchil- dren. They are often called upon to administer tests, to diagnose learning and behav- ior problems, and to suggest treatment for these problems. As a result, they are usually

Psychology, like most sciences, occa- sionally changes its mind. We’re no longer certain that the bumps and lumps on our skulls are roadmaps to our personalities.

Psychology hasn’t yet discovered some devious way of peering into our persons and ferreting out all the dark secrets therein.

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CHAPTER 1Section 1.1 What Is Psychology?

trained in both psychology and education and are often required to apply the principles of clinical and counseling psychology, as well as those of educational psychology.

Educational Psychologists Psychologists concerned specifically with improv- ing teaching and learning are educational psychol- ogists. Unlike school psychologists, they are less concerned with individual behavioral and learn- ing problems than with broader questions relating to how people learn in educational settings. Educa- tional psychology applies psychological principles to classroom management, special needs educa- tion, instructional design, and lesson planning.

Developmental Psychologists Developmental psychologists study systematic changes that occur between conception and death. Some specialize in the study of child develop- ment; others are more concerned with adolescent or adult development, or with aging and dying. The findings of developmental psychology are especially important for school and educational psychologists as well as for clinical and counseling psychology.

Experimental Psychologists Much of the content of psychology—and therefore of this text—is based on the work of experimental psychologists. They specialize in the use of experimental methods to inves- tigate the puzzles of psychology. Experimental research requires that the investigator control significant aspects of a situation in an attempt to uncover cause-and-effect rela- tionships. (There is more about experiments shortly.)

Other Divisions There are many other specializations in psychology: Health psychologists look at how psy- chological factors influence health and illness and often work in clinical settings or hospi- tals to promote wellness; social psychologists are concerned with how people relate to and influence each other; sports psychologists use psychological research to improve athletic performance; forensic psychologists are usually experts in criminal law as well as in psy- chology and might be called upon to assist in jury selection or as expert witnesses for assessing the state of mind of the accused at the time of the offense or the defendant’s competency to stand trial; and environmental psychologists look at the relationship between humans and their surroundings, and specifically at the effects of the environment on our well-being (Table 1.1).

About half of all psychologists are clinical psychologists specialized in helping people with psychological problems. Unlike psychiatrists, they’re not usually medical doctors.

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CHAPTER 1Section 1.2 The Beginnings of Psychology

Table 1.1 What Psychologists Do

Some Major Divisions Main Concerns and Activities

Clinical Diagnosis and treatment of emotional illnesses and disorders, frequently in a hospital or clinical setting

Counseling Evaluation of and assistance with behavioral, emotional, and other problems not serious enough to require hospital, clinical, or psychiatric treatment; assistance with important decisions such as those having to do with careers, relationships, adjustment, and stress

Industrial/organizational Applying psychology in business and industry; developing and adminis- tering tests to evaluate aptitudes; dealing with motivational, manage- ment, and interpersonal issues in the workplace

School Identifying individual aptitudes and skills among learners in a school setting; developing and administering tests pertinent to school-related abilities; diagnosing and remediating behavioral and learning problems

Educational Researching the application of psychological principles for improving teaching and learning

Developmental Studying changes that define growth, learning, and maturation from birth to death; applying findings in educational programs and in child guidance and counseling

Experimental Using experimental methods to investigate the puzzles of psychology

Regardless of their specialization, many psychologists write books, teach, do research, conduct private practices, work in business and industry, or are employed in a variety of different professions where knowledge of psychology is useful and sometimes even essential. Many are engaged in combinations of these activities.

All that affects human behavior, thought, and emotion falls within the domain of psychol- ogy. This text, with its 10 chapters and many sections, represents the most common divi- sions and interests in psychology: It is a 120,000-word definition of psychology.

1.2 The Beginnings of Psychology

That definition begins with the history of psychology—a history that goes back at least as far as ancient Greece, when the discipline of philosophy embraced almost all other disci- plines, including what is now psychology. In fact, the term psychology has its roots in the Greek language, where the word psyche means “soul” and logos means “the study or discussion of.”

More recently in psychology’s history, discoveries in medicine had a dramatic influence on our conception of the human being. When William Harvey discovered that the heart pumped blood into tubes throughout the body, many thinkers became convinced that people were nothing more than elaborate pumping machines. Many suspected that the ability to think originates in the blood. Aristotle didn’t merely suspect this—he knew it. If a person’s blood were entirely removed, he argued, no evidence of thinking would remain!

Early physics, too, contributed to the development of psychology. The psychological importance of Sir Isaac Newton’s observation that apples invariably fall earthward lies

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CHAPTER 1Section 1.2 The Beginnings of Psychology

in the fact that it illustrates a different way of looking at natural phenomena. The ancient Greek philosophers undoubtedly knew that apples fall earthward. And had they wanted to know why apples fall, they might have thought long and hard about the problem and held learned discourses with colleagues. But their approach would have made little use of the methods of science as we now know them. Newton, however, felt compelled to demonstrate and verify the phenomena he observed and to investigate them by means of controlled experimentation. We are products of Newton’s generation: Psychology, anthro- pology, sociology, and other related fields are seldom referred to as the social studies; they are the social sciences (Figure 1.2).

Recent Origins of Psychology

Scientific psychology is not much more than a century old. Its founder is generally con- sidered to be Wilhelm Wundt, who founded the first psychological laboratory in Leipzig,

Aristotle Newton Pavlov

Figure 1.2

Contemplation of their own experiences guided the ancient Greeks in learning about people. The result: the theory that the ability to think originates in the blood. Centuries later, Newton used scientific observation and experimentation to test theories about the physical world. By the 20th century, psychologists were applying scientific methods to animals and people to learn about behavior. The result: psychology as it exists today.

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CHAPTER 1Section 1.2 The Beginnings of Psychology

Germany, in 1879. Many of Wundt’s students later established laboratories of their own throughout Europe and North America. Very soon after that, psychology departments opened at all major universities. Typically these began as branches of departments of phi- losophy, but in time the discipline became totally separate. Departments of psychology now claim far more students than do departments of philosophy.

Structuralism The early history of psychology is marked by the rise—and fall—of a number of different “schools” of thought. The first dates back to Wilhelm Wundt and his followers, whose search for pieces of the puzzle relied on introspection. Introspection involves looking inside oneself, examining one’s own thoughts, feelings, and motives and generalizing the resulting insights to understand the thoughts and feelings of others. Stop, for a moment, and think about the words you are now reading. How does a physical stimulus such as a word on a page affect you? As you carefully analyze your current thoughts and feelings, you are introspecting.

The goal of introspection as practiced by Wundt and his followers was to understand the structure of thoughts, emotions, and motives. They reasoned that the conscious mind, like any other natural object, must comprise identifiable elements. In the same way as water is made up of two atoms of hydrogen and one of oxygen, so too must sensations and feel- ings be structured of basic mental elements. One of his followers, Titchener, called this approach structuralism.

Functionalism William James, widely credited with being the founder of American psychology, thought it a waste of time to try to explain the mind by looking at its structure. Heavily influenced by Charles Darwin’s new theories, James argued that it would be far better to try to deter- mine the purposes that drive behavior—that is, its functions; hence the label functionalism. James’s 1,000-page book, The Principles of Psychology (1890), did a great deal to establish what psychology would become. It is James, for example, who first wrote of the “stream of con- sciousness” and of the baby’s world as “one great blooming, buzzing confusion.” Among the topics in his book are will, interest, emotions, sensation, the brain, and, of course, the stream of consciousness. He asks questions such as “How can people strengthen habits?” “How does intention motivate action?” “What is memory, and how does it work?”

Behaviorism James’s functionalism profoundly influenced the subsequent development of psychology. But by the early 1900s, many psychologists, especially in the United States, had begun to reject difficult and subjective topics such as mind and thinking. Led by the psycholo- gist John Broadus Watson, they chose to concentrate on the objective, observable aspects of behavior; hence the label behaviorism. Behaviorism “emphasized publicly observable stimuli (s) and responses (r) and spurned supposedly unobservable, centrally initiated processes like consciousness” (Moore, 2010, p. 143).

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CHAPTER 1Section 1.2 The Beginnings of Psychology

Among the most important behaviorists are Wat- son and Skinner. Behaviorists tend to study reflex- ive behavior and the consequences of behavior. As we see in Chapter 4, many scientific experi- ments can be carried out to investigate these mat- ters. As a result, with the advent of behaviorism, psychology became progressively more scientific. But because of its emphasis on discovering how behavior is controlled by stimuli and by its conse- quences, behaviorism is sometimes interpreted as denying the existence of free will.

Psychodynamic Theory At about the same time that the behaviorists were first popular in American psychology, the Aus- trian neurologist Sigmund Freud was developing startling new ideas about the mind. As explained in Chapter 8, Freud believed that the mind is a little like an iceberg: We see only the very tip, which represents the conscious mind; the bulk of it is hidden, unconscious. Much of our behavior

is driven by unconscious forces: They lie beneath the visible iceberg, beyond our con- scious awareness. Freud believed that many of our emotional disorders stem from these unconscious psychodynamic forces. There are methods of analysis, of psychoanalysis, explained Freud, that can uncover these hidden motives and forces and that can lead to the alleviation of mental disorders.

Cognitivism Other psychologists rejected the narrow emphases of a behaviorism that limited itself to observable events, but relatively few embraced Freud’s psychoanalysis. Many can be described as belonging to the school labeled cognitivism. These are psychologists whose main concerns are with intellectual (cognitive) events such as problem solving, thinking, information processing, and imagining. Cognitivism provides explanations for behavior based on our ability to symbolize, to uncover cause-and-effect relationships, to determine what goes with what, and to anticipate the consequences of our actions.

Humanism Some psychologists object to what they see as the overly limited, mechanistic, and dehumanizing emphases of behavioristic approaches to psychology. They also reject the Freudian notion that we’re driven by dark, unconscious forces over which we have little control. These approaches, they argue, pay too little attention to the positive and healthy aspects of human nature. Humanistic psychology, as we see in Chapter 8, is concerned with the uniqueness, the individuality, the humanity of each person. It

Psychoanalysts are psychiatrists who, like Freud, believe that mental disor- ders result from deep-seated psycho- dynamic conflicts. The purpose of the couch is to allow the patient to relax so as to facilitate uncovering these con- flicts—often through free association or dream analysis.

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CHAPTER 1Section 1.3 Principles of Science

emphasizes the development of the “self” and is represented by psychologists such as Abraham Maslow and Carl Rogers.

Humanism arose primarily as a reaction against behavioristic and psychodynamic theo- ries, which Maslow (1998) described as the two great forces in psychology; he labeled the humanistic movement third force psychology. His hope was that this third force would become as powerful as the first two and that it might counter the dehumanizing influence of a rigorous scientific approach to the study of psychology.

Other Orientations There are a number of other important orientations in the study of psychology. Evolution- ary psychology emphasizes biology and genetics as a source of explanations for human learning and behavior. Evolutionary psychologists look at the evolution of human behav- ior and try to explain human characteristics in terms of historical pressures of adaptation.

Neuroscience is another important and highly current, biologically based orientation. Using powerful new brain-imaging techniques, neuroscientists look to the nervous sys- tem, especially the brain, for explanations of consciousness and of mental processes like thinking, imagining, problem solving, and remembering.

Both evolutionary psychologists and neuroscientists make extensive use of genomics, the study of genes and how they relate to human behaviors and characteristics.

1.3 Principles of Science Psychology is a science. What does that mean?

In one sense, science can mean a collection of information in a field of study. For example, the science of physics is a collection of information about the nature of matter and energy and how they interact. And the science of psychology is a collection of information about human thought and behavior and how they interact.

In another very important sense, science is a way of dealing with information. As such, it is both an attitude and a set of guidelines. It is an attitude that insists on objectivity, preci- sion, and consistency. And it is a set of guidelines meant to ensure that this is the case. As a result, science stands in sharp contrast to those ways of knowing that are based princi- pally on subjective analysis or introspection.

Attempts to explain and organize the observations of science take the form of theories. Theories are collections of related statements that clarify observations and permit predic- tions (hypotheses).

In spite of science’s preoccupation with the objective, many topics of interest to psychol- ogy cannot be observed and measured directly, but can only be inferred from behavior or from highly subjective self-reports. Emotions and thoughts, for example, are subjec- tive rather than objective. And even though these might lead to behavior from which

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CHAPTER 1Section 1.3 Principles of Science

an observer might guess the underlying emotion or thought, this is not always so. For example, I might be very angry or very sad because I now know for sure that my dog does not much like me; but you would not necessarily know my emotion from my behavior because I can easily pretend I don’t care.

One of psychology’s tasks is to devise ways of examining nonobjective events and states as objectively and scientifically as possible.

The Scientific Method

Studying phenomena objectively and scientifically means using what is often labeled the scientific method—an approach designed to ensure that observations are as accurate and valid as possible, that they can be replicated by other investigators. The sciences have now been using the scientific method for more than a hundred years to find and assemble pieces of the human puzzle. It can be described in terms of five systematic steps:

1. Ask the question. (For example: Would after-school detention be effective in stop- ping a group of boys from stealing iPods, MP3 players, and smartphones?)

2. Develop a hypothesis. On the basis of observation and a careful examination of relevant investigations and theory, make a prediction—a hypothesis. By definition, a scientific hypothesis is unproven and can be falsified (proven incorrect). Hence the outcome of a scientific investigation can lead to the rejection of the hypothesis. (Hypothesis: After-school detention will be effective in curtailing thefts of elec- tronic devices.)

3. Collect relevant observations. As we see in the next section, science suggests many different ways of collecting observations. The nature of the question being asked, as well as constraints related to money, time, instrumentation, and the availability of suitable participants, usually determines which method is best. (Method: Detain the group of thieves after school; monitor subsequent thefts.)

4. Test the hypothesis. Do your observations indicate that the hypothesis should be rejected? And even if they do not, might they be due to chance? Science is very concerned that observations might be just chance happenings—in which case, they don’t mean very much at all. For this reason, investigators often use special sta- tistical procedures to determine whether observations are statistically significant. These procedures allow investigators to

Although psychology probes and mea- sures things not as easily analyzed and quantified as matter in test tubes, it strives for the same precision, objectiv- ity, and replicability—though perhaps with somewhat more restraint than this mad scientist.

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CHAPTER 1Section 1.4 Sources of Psychological Information

determine the likelihood that observations are due to factors other than chance. (How many devices disappeared before the detention? How many disappeared after?)

5. Reach and share a conclusion. If science is to progress, the hypothesis has to be rejected or not rejected. If it is not rejected, it may be accepted as tentatively valid (we can seldom be absolutely certain). (For example: As many electronic devices disappeared after as before detention. Tentative conclusion: Detention is not an effective deterrent in this case.) The conclusions of the research then need to be shared. This means communicating the findings to others so they can apply them and so continue the research and learning process.

1.4 Sources of Psychological Information

The ways psychologists gather observations vary greatly depending on the topic being researched and sometimes on the psychologist’s preferences. What is invariably true, however, is that observation is the source of all psychological knowledge, just as it is the source of knowledge in other sciences. Psychological studies and experiments vary according to who is being observed, when, how, and under what conditions.

Descriptive Research

Descriptive research describes the characteristics of an individual or of a group. It answers the questions who, what, where, when, and how. What is the average age of a group? How common is bipolar disorder? What is current life expectancy in North America?

Descriptive research is often based on the results of archival research—research that depends on secondary sources such as census data, birth certificates, or other forms of past records. It may also be based on the results of observation, which can be naturalistic or nonnaturalistic.

Naturalistic and Nonnaturalistic Observation Naturalistic observation is observation that occurs in natural settings rather than in labora- tories, hospitals, and other surroundings. Naturalistic observation is well illustrated by the research of Jane Goodall, who, since 1960, has lived among chimpanzees in the Gombe Stream Research Centre in Tanzania, simply observing chimpanzees without disturbing them. The assumption of naturalistic observation is that if the investigator does interfere, the behavior under examination may be affected. For example, chimpanzees that would be playful and bold in their natural state might become anxious and furtive when observed too closely.

Naturalistic observation takes place in surroundings that are not altered by the observer or by the requirements of the observation; nonnaturalistic observation occurs in more contrived surroundings such as laboratories. Both are important in psychological investigation. Natu- ralistic and nonnaturalistic approaches to gathering psychological information can be classi- fied in terms of who is observed and how and when the observations are made. Thus, there are case studies (discussed in next section), where single individuals (or single units such as

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CHAPTER 1Section 1.4 Sources of Psychological Information

a family) are observed, and surveys (discussed after case studies), where large groups of individuals (or larger groups of units such as a number of families) are studied.

Studies may be longitudinal or cross-sectional, depending on when observations are made. When the goal of psychological investigation is to identify changes that occur within individuals or within a group of individuals over time, longitudinal stud- ies may be used. A longitudinal study examines the same individual(s) at different times and makes direct comparisons between the individual at this point in time and the same individual at an earlier time. In contrast, cross-sectional studies examine two or more groups of subjects at the same time.

Cross-sectional studies are much less time-consuming and consequently much less expen- sive, but they are not always appropriate for answering questions about changes that occur within individuals over time.

Torrance’s study of creativity, in which subjects were followed from childhood beginning in 1958 through a period of 50 years, provides one of the better-known examples of longi- tudinal research in psychology (Millar, 2001, 2010). Investigators kept track of all creative accomplishments of each individual in the group: books written, art exhibitions, software programs, inventions, invited lectures, leadership positions, and so on. This investiga- tion found that highly creative children tend to become highly creative adults. The most highly gifted grew up to be college presidents, inventors, doctors, diplomats, and lawyers. Strikingly, their scores on measures of creativity were far more predictive of their eventual accomplishments than were their scores on intelligence tests (Plucker, 1999).

Case Studies Descriptive research, as we noted, can be based on case studies. A classic example of a case study is that of a young Russian, known to us only as S, who presented himself to a psy- chologist one day. S was confused and poorly adjusted. He hoped that the psychologist, the very well-known and highly respected Alexandr Romanovich Luria, would help him. His problem was that he had difficulty following ordinary conversations, that his mind was such a jumble of sights and sounds that he was often absolutely overwhelmed and bewildered. From this initial meeting there developed a long relationship between the two, during which Luria conducted intensive and detailed investigations of S’s memory. Luria soon discovered that S could remember with incredible and uncanny accuracy. Nor did he remember as you or I might remember, painfully retrieving some isolated bit of information that we have suc- ceeded in storing and protecting from the ravages of time. He could remember in infinite detail, retrieving from his memory not only the item requested of him, but a host of other associations that most people would never have noticed initially, let alone remembered.

As an example, one day Luria presented S with a table of 50 single-digit numbers. S spent three minutes examining the array. He then reproduced the entire table in 40 seconds and could read off any number it contained in horizontal, vertical, or diagonal arrangements.

Naturalistic observation involves as little interference with ongoing activi- ties as possible and occurs in “natural” environments such as schools or, as shown here, playgrounds.

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CHAPTER 1Section 1.4 Sources of Psychological Information

Perhaps even more amazing, when S was asked to reproduce the same table several months later (the table had not once been presented in the interim), he could do so unerr- ingly and just as rapidly. The only difference was that the second time he required a brief period to “re-imagine” the situation in which he had first memorized the table.

As a result of this intensive and prolonged case study, Luria discovered that S didn’t simply hear sounds but sensed them as vivid and colorful images; that he could remem- ber the clothing he and Luria had been wearing on a given day years before; that he fre- quently remembered by “seeing” objects, events, or numbers in mental images of places where he had stored them. Sometimes he would imagine he was walking along a very familiar street in his hometown, and he would mentally place different numbers on vari- ous fences, trees, and houses along this street. Later, when called upon to remember these numbers, he would simply imagine the street and read off the numbers as he saw them. On one occasion when he couldn’t recall a number he had memorized in this fashion, it eventually occurred to him that he had “placed” the number in question on a dark, heav- ily shaded piece of broken board and that he simply could not “see” it!

S presents a classic case of what is termed synesthesia, a condition where one sensation evokes another related to a different sense. For example, a person with synesthesia might hear a color or see a taste or an odor. It seems that S’s synesthesia provided him with an extraordinarily vivid assortment of visual images that later became keys to his memory.

Luria’s investigation of S’s memory and his subsequent reports of the results of this inves- tigation provide us with a striking example of a case study. Numerous other examples can be found in psychological literature, especially in studies of abnormal behavior. When- ever a psychologist requires extensive and in-depth information about a single individual, a case-study approach is likely to be used.

Surveys Descriptive studies are often based on surveys. Whereas a case study involves a single individual (or a single unit), surveys involve groups of individuals or groups of units. Case studies are often inappropriate when the intent is to describe a group of people. A psychologist who wanted to find out what the average person in the street thinks of a polit- ical event could not easily accomplish this by walking up to and questioning an “average” person. In the first place, there is no average individual: he or she is an invention. When a researcher refers to the average person, it is never a single person being referred to; it is, instead, the nonexistent, idealized “averaged” result of investigating many individuals.

A survey is a research technique that attempts to discover the qualities of the average per- son by examining the characteristics of a number of real individuals. What is especially important in doing a survey is that those being surveyed be representative of the entire group to which investigators want to generalize. When researchers wanted to discover the sexual beliefs and behaviors of the average British 16- to 44-year-old, they surveyed 11,161 individuals by means of interviews and computer-based questionnaires (Gerressu, Mer- cer, Graham, Wellings, & Johnson, 2008). They were then able to state that 73 percent of men and 37 percent of women had masturbated at least once in the preceding four weeks. Had they conducted two case studies instead, one male and one female, and generalized in the same manner, they would have had to state that all men or all women between the

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CHAPTER 1Section 1.4 Sources of Psychological Information

ages of 16 and 44 have masturbated at least once, or that none of them have. Either con- clusion would have been highly misleading. (See Figure 1.3 for a comparison of surveys, longitudinal research, and cross-sectional research.)

Correlational Research A great deal of psychological research is intended to find out whether there is a relation- ship between two variables. Often psychological research tries to answer questions such as: Is hyperactivity related to parental upbringing? Does anxiety contribute to poor test performance? Are attractive people more likely to be successful in business?

Surveys reveal information about groups of individuals at a specific time. But a single survey provides no information about change over time and it gives only a composite picture of an idealized “average” individual.

Longitudinal studies provide information about one or more individuals over a period of time. But they are expensive and time consuming. Many cannot be completed in the lifetime of a single investor.

Cross-sectional studies can provide information about different groups at the same time. But, like surveys, they provide statistical averages and may not take all variables into account. For instance, did the 70-year-olds grow up with the same develop- mental stimulation as 35-year-olds, or 5-year-olds?

What is the average American IQ?

How stable is an individual’s IQ?

Does IQ peak at different ages?

A d

a m

’s I Q

Adam’s age (years)






0 5 10 15 20 80…


60 80 100 120 …


N u

m b

er o

f in

d iv

id u

al s


60 80 100 120 140 …N u

m b

er o

f in

d iv

id u

al s




Figure 1.3

Surveys, longitudinal studies, and cross-sectional studies are examples of descriptive research designed to answer different questions.

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CHAPTER 1Section 1.4 Sources of Psychological Information

Research designed to answer questions such as these typically results in a measure of correlation and is therefore called correlational research. A positive correlation exists between two variables when a change in one of these variables is reflected in a similar change in the other; a negative correlation is observed when a change in one variable is accompanied by an opposite change in the other. Numerically, correlation is expressed as –1.00 for a perfect negative correlation, +1.00 for a perfect positive correlation, and 0 for lack of correlation (Figure 1.4).

C: Low correlation

B: High negative correlationA: High positive correlation








S co

re s

o n

t es

t 2

S co

re s

o n

t es

t 3

Scores on test 1Scores on test 1

Scores on test 1

S co

re s

o n

t es

t 4

Test 1







Test 2







Test 3







Test 4







0 10 20 30 40 50







0 10 20 30 40 50







0 10 20 30 40 50







Figure 1.4

Graphic representations of correlation. In A (high positive correlation), those who scored well on test 1 tended to score well on test 2. In B (high negative correlation), those who did well on test 1 tended to do correspondingly poorly on test 3. And in C, there is little relationship between scores on test 1 and scores on test 4.

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CHAPTER 1Section 1.4 Sources of Psychological Information

It would seem logical to assume that if there is a high positive correlation between two variables, one must cause the other—and that may sometimes be the case. In fact, if a vari- able does cause another, there will be a correlation between the two. Put another way, cor- relation is essential evidence of causation—but it isn’t sufficient evidence. The assumption that correlation proves causation is known as the correlation fallacy.

For example, there is a high positive correlation between children’s shoe sizes and their ability to read. But it would be a correlation fallacy to conclude that having big feet helps children read. Having big feet, like being able to read, simply reflects the child’s continued development and growth. (The correlation fallacy is explained more fully in a later section.)


An experiment is a research procedure where investigators control one or more of the variables in a situation and observe the effects this has on other variables. The experiment is a very powerful tool in science’s quest for knowledge because controlling variables makes it possible to observe and measure causes and effects.

A variable may be a measurement, an outcome, or some other way of describing or classify- ing things such as people, events, or objects. Intelligence test scores, environmental factors, physical characteristics, medications, and so on are all examples of variables. Variables the experimenter controls and whose effects are being investigated are independent variables; variables that may be affected by changes in the independent variables are dependent variables. Independent variables are assumed to have an effect on dependent variables. Dependent variables are ordinarily measured at the end of an experimental procedure.

As a simple illustration, an experiment can easily be designed to determine whether a new approach to teaching is better than the current approach. The experiment would require that subjects be assigned to one or the other of the teaching methods, that the methods be put into practice, and that subsequent performance be measured and compared. In this case, teaching method is an independent variable; performance, a dependent variable. If teaching method affects performance, it (the independent variable) may be used to predict learning (a dependent variable) (see Figure 1.5).

Note that most experiments can be reworded in terms of an “if-then” statement. What the investigator is saying is “if such and such, then such and such.” The if-then statement is the hypothesis (prediction) that the experiment is designed to investigate. The “if” part of the statement usually defines the independent variable; the “then” part of the statement is the dependent variable. For example, the hypothesis “rewarding learners will have a positive effect on their learning” can be reworded to “if learners are rewarded, then they will learn more effectively.”

Experimental and Control Groups The most common experiment is that which makes use of an experimental group and one or more control groups (sometimes called comparison groups). When the manufacturer of

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CHAPTER 1Section 1.4 Sources of Psychological Information

some exotic toothpaste assures us that it leads to 40 percent fewer cavities, we are some- times told that one group brushed regularly with the new product while a second group brushed with their regular toothpaste. Comparison of teeth between these two groups then enabled investigators to determine the extent to which the new product prevents cavities. Cavities are a dependent variable in this experiment; toothpaste employed is an independent variable. Similarly, the group to which something is done (in this case the group given the new toothpaste) is an experimental group; the group that is used for com- parison is a control group. Without the control group for comparison, we would never know whether simply brushing with any toothpaste decreases the incidence of cavities.

Any experimental design that does not employ comparison groups similar in as many relevant ways as possible to the experimental groups cannot be relied upon, since we


Experimental group (Students are taught using new method A.)

Hypothesis: New teaching method A is more

effective than conventional method B for teaching Introductory Psychology.

Grades obtained by members of the experimental group are compared with those of the

control group.

Control group (Students are taught with the

conventional method B.)

Students are randomly assigned to one of two groups.

Independent variable

Dependent variable

Figure 1.5

A simple experiment designed to test a hypothesis. Note that hypotheses can generally be worded as “if-then” statements. The “if” part of the statement is the independent variable (in this case, the change in teaching method); the “then” part is the dependent variable (in this case, the grades obtained by members of the experimental group).

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CHAPTER 1Section 1.4 Sources of Psychological Information

have no way of determining whether outcomes might have been identical without any experimental treatment.

Note that if the results of an experiment are to be applied to a large population, it is essential that the groups involved (the sample) be representative of the larger group from which they are drawn (the population). As we see later, one way of ensuring representa- tiveness is to sample randomly from the general population.

Ex Post Facto Studies

There is an important distinction between a true experiment and what is termed an ex post facto study. In a true experiment, the investigator assigns subjects to experimental conditions, controls independent variables, and controls as many other related variables as possible. But there are many situations in which the experimenter does not have control over independent variables. For example, an experiment designed to uncover the contri- butions of smoking to lung cancer would require that the experimenter randomly assign participants to an experimental group who would be required to inhale cigarette smoke in a prescribed manner and over a specified period of time. Other participants, comparable to the experimental group in all relevant ways, would be required not to smoke. Clearly, there are ethical reasons why this experiment cannot be conducted.

In cases such as this, investigators often conduct ex post facto studies—literally, after the fact studies. These are studies in which participants are selected on the basis of differences that already exist among them, in terms of either dependent or independent variables. For example, instead of assigning participants to smoking or no-smoking groups, people who have a history of smoking or not smoking are selected and compared with respect to the dependent variable, cancer or no cancer. Alternatively, the investigator might begin by looking not at independent variables (smoking or not smoking), but at the dependent variable (cancer or no cancer) and then ask, “How many of those with cancer were smok- ers and how many were nonsmokers?” They might also ask, “How many without cancer were smokers or nonsmokers?”

Ex post facto studies are highly common in psychology, simply because investigators usu- ally don’t have control over many important independent variables such as social class, family composition, mother-infant interaction, where people live, whether they have pets in the home, and so on.

There is one important caution in interpreting the results of ex post facto research. Although these studies can establish the presence of relationships, they don’t provide evi- dence that one variable causes another. An ex post facto study might establish that there is a relationship between father absence in early childhood and delinquent behavior in ado- lescence, but it cannot prove that father absence causes delinquency because any number of other uncontrolled variables (for example, poverty, mother absence, family size, and so on) might be causally related. Only a carefully controlled experiment can provide suf- ficient evidence of causation.

For a comparison of research methods that differ in terms of who is observed, when, and how, see Table 1.2.

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CHAPTER 1Section 1.5 Cautions in Interpreting Psychological Research

Table 1.2 Common Types of Psychological Investigations

Who Case Survey, Experiment

A single individual is observed. More than one individual is observed.

When Longitudinal Cross-Sectional

The same individuals are observed at different times.

Different groups of individuals are observed at the same time.


Experimental Ex Post Facto

The experimenter controls relevant independent variables and assigns subjects to groups.

The experimenter selects subjects, but nei- ther assigns them to groups nor exercises control over independent variables.


Descriptive Experimental

Main goal is to describe the characteristics of what is being studied. May be archival (based on existing records), or can be based on surveys, interviews, case studies, longitudinal or cross- sectional research, or correlational studies.

Main goal is to look for causal links between independent and dependent variables.

1.5 Cautions in Interpreting Psychological Research

To what extent can we rely on an experiment such as the toothpaste study described earlier, assuming, of course, that the results were reported accurately? Should we all run and purchase armloads of the new toothpaste?

Would the results be affected, for example, if the control group had been selected from a small rural area where the drinking water is obtained from a questionably clean river whereas the experimental group all reside in an urban area where fluoride is added to the water? Would the results be affected if the dentists who examined the subjects were share- holders in the company that manufactures the new toothpaste and if they knew who was a member of the experimental group and who belonged to the control group? Is it impor- tant to know the number of cavities in the histories of members of each of these groups? These questions touch on various potential weaknesses of psychological research, includ- ing experimenter bias, sampling bias, and subject bias.

Experimenter Bias

An assortment of rats was divided among two groups of psychology students (Rosenthal & Fode, 1963). The students knew that psychologists had been successful in breeding strains of rats highly different in their ability to learn how to run through mazes—so- called maze-bright and maze-dull rats. In this experiment, one group of students was told that they had been given rats of the maze-bright variety; the second group had to be content with less intelligent rats. In point of fact, however, both groups received randomly assigned rats of presumably equal intelligence.

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CHAPTER 1Section 1.5 Cautions in Interpreting Psychological Research

Students were asked to work with these rats over a period of time and to train them in maze tasks. Amazingly, students who had been led to believe that they had bright rats reported considerably more success in training their rats. In addition, they thought the rats more cooperative, gentler, and generally more pleasant to work with than did stu- dents whose rats were labeled dull (see Figure 1.6).

This experiment was among the first of many that have illustrated what is termed experi- menter bias. It appears that the expectations of experimenters exert subtle and sometimes remarkable influences on their actual observations.

A similar investigation conducted with elementary school children also illustrates experi- menter bias (Rosenthal & Jacobsen, 1968). It involved telling teachers that some of their students had been identified as potential “bloomers.” “Bloomers” were described as stu- dents of average or below average achievement whose potential indicated they could



Scores reported by researchers who were told they had “maze-bright” rats

Scores reported by researchers who were told they had “maze-dull” rats

Figure 1.6

How great a role does experimenter bias play in the results of experiments? The smaller rat represents lower scores reported by researchers who were told they had maze-dull rats. Those who thought they had been given the more gifted rats reported significantly higher scores.

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CHAPTER 1Section 1.5 Cautions in Interpreting Psychological Research

easily achieve at a much higher level. The experimenters led the teachers to believe that they had developed a test that enabled them to identify these students and casually let them see a list of these “bloomers.” Astonishingly, although the “bloomers” had been ran- domly selected, they performed better than other equally intelligent students.

There have been many replications of this investigation since 1968. Some have not supported the original findings (Wineburg, 1987), but many have, although not always with results quite so dramatic (Jacobs & Harvey, 2010; Rubie-Davies, 2010). It seems clear that on occa- sion the expectations of teachers can affect not only the achievement of their students, but also their performance on objective measures of intelligence as well as their general behavior.

One of the most effective and most common means of guarding against the influence of experimenter expectations is to ensure that those responsible for gathering crucial experi- mental data not know which subjects are members of experimental groups and which are not. In the toothpaste experiment described earlier, if the dentists examining the children didn’t know which children had brushed with the new toothpaste and which were mem- bers of the control group, experimenter expectations would not likely affect the conclu- sions of the experiment. Studies where neither the examiners nor the subjects are aware of who is in the experimental group are termed double-blind procedures. In a single-blind procedure either the subject or the examiner is unaware (“blind”).

Subject Bias

Several decades ago in the Hawthorne plant of the Western Electric Company in Chi- cago, two psychologists (Roethlisberger & Dickson, 1939) experimented with different ways of increasing productivity among a group of women workers. In successive experi- ments the women were asked to work for longer periods of time, for shorter periods of time, for long periods with short rest breaks, for short periods with long rest breaks, with bright illumination, with low lighting, with lights turned almost off, with bonuses, with- out bonuses, and so on. Strangely, it didn’t matter what the experimenters did: Production always seemed to increase.

More recent research has shown that this so-called Hawthorne effect is not always appar- ent or very significant (Chiesa & Hobbs, 2008). Nevertheless, the possibility that the out- come of an experiment may be affected by the fact that subjects know they are subjects still exists and must be guarded against. Participants are often anxious to please investigators; consequently, their responses may sometimes be misleading. To guard against this pos- sibility, subjects are often not told whether or not they are members of an experimental group (a single-blind procedure).

Sampling Bias

One of the most common weaknesses of many experiments has to do with inappropriate or biased sampling. There are two crucial criteria that should be met when selecting members of experimental and control groups. First, the subjects must represent the group to which the experimenters wish to generalize. Second, the experimental and control groups must be as similar as possible on all relevant variables at the beginning of the experiment.

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CHAPTER 1Section 1.5 Cautions in Interpreting Psychological Research

If the experimental group is significantly differ- ent from other groups, then the experiment will not provide information that can be generalized to other groups. Consider, for example, an experi- ment designed to compare the effectiveness of two teaching methods. If the experimenter intends to determine the relative effectiveness of these meth- ods for all students in a given school system, it is important that experimental and control groups be as similar as possible to all students in the sys- tem in terms of intelligence, achievement, motiva- tion, and other relevant variables. If subjects are selected from a school where students have higher intelligence test scores, the results of the experi- ment might not be valid for other students.

Problems regarding the representativeness of samples are most evident in large-scale surveys where the intention is to generalize to a major segment of the population. Political fore- casts would be highly unreliable if only one segment of the population were sampled. For example, it would be difficult to predict how a nation would vote if forecasts were based only on surveys of academic populations or truck drivers.

To ensure that the results of such a survey apply to the entire population, investigators might select their sample so that it matches the population in terms of as many relevant characteristics as possible—a process called stratified sampling. If 52 percent of the popu- lation is female, close to 52 percent of the sample should also be female; if 23 percent have college degrees, then about 23 percent of the sample should also have college degrees. Similarly, in an ideal situation, the sample must match the general population in terms of age, religion, socioeconomic background, geographical location, and so on.

Another way of ensuring that experimental groups are representative of a larger popu- lation is to use random sampling. Random sampling requires that all members of the population have an equal chance of being selected. Given this condition, if enough repre- sentatives are drawn from the population, there is a high probability that the experimen- tal group’s characteristics will be very similar to those of the entire population. In other words, if 23 percent of a population is male and 77 percent female, a large enough sample drawn randomly from this population should be close to 23 percent male and 77 percent female. By the same token, the sample should resemble the entire population in terms of average intelligence, racial background, and other variables that might be important. In most cases, experimenters can make sure that this is the case by comparing the sample to the population on important variables.

Unfortunately, random and stratified sampling are only possible when investigators have access to the entire population to which they want to generalize. In many cases, circumstances dictate that samples will be samples of convenience. For example, those who do research on aging seldom have access to a random or stratified sample of the entire aging population, but are instead limited to groups such as those made up of members of clubs, religious groups, or residents of care facilities. Generalizing from these conve- nient samples requires caution. The need for comparability of experimental and control

No matter how large the sample, if its characteristics are very different from those of the population, resulting con- clusions will not have general validity. This soccer crowd, for example, might be very different from the mass of humanity who stayed home.

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CHAPTER 1Section 1.5 Cautions in Interpreting Psychological Research

groups, and for representativeness of samples, is obvious in the toothpaste experiment. Suppose, for example, that the control group averaged 30 percent more cavities than the experimental group at the beginning of the experiment: Regardless of the effects of the new toothpaste, it would be reasonable to expect that the rate at which the children developed cavities would be higher among those who initially had more cavities. Simi- larly, if all children in the study were selected from a single area where dental care was exceptionally good—or exceptionally bad—the sample might be totally unrepresentative of a more general population. Deliberately or accidentally biased sampling can easily ensure that the results of an experiment will be totally invalid.

Other Problems of Psychological Research

Among other problems that face researchers, as well as those of us who look for truth among their conclusions, are those of honesty, memory distortion, and inadvertent con- ceptual distortion. Studies of drug use, for example, have often provided inconclusive and contradictory results, probably largely because admitting to drug use is like confessing to a crime. In studies such as this, the dishonesty of participants is a crucial factor that can do much to invalidate the results of research.

A related problem is that of having to rely on imperfect memories. Child development psychologists have had some difficulty establishing conclusively the average age at which children learn to walk, a problem related directly to the memories of their moth- ers. Unless the researcher is present whenever significant developmental events occur, or unless these events can be objectively recorded, reliance must be placed on the partici- pant’s memory or on that of someone else who observed the event in question. In either case, it is often wise to question the accuracy of results that are not obtained through direct observation.

And, as we saw earlier, another pitfall in psychological research relates to the correlation fallacy—the belief that if two variables are correlated, one must cause the other. There are at least two reasons why correlation cannot be used to justify cause-and-effect conclu- sions. One is that a correlation between A and B does not, by itself, provide evidence of the direction of causality. That is, even if the correlation reflected causation, we might not know whether A causes B or B causes A.

The second reason why correlation is not proof of causation is that a correlation between A and B does not answer the question of whether the reason for the correlation might be a third variable, C. For example, an investigation of people ranging in age from 2 to 22 might reveal a very high correlation between finger length and the ability to understand concepts in advanced calculus. That, of course, would not prove that having long fingers helps people understand calculus—nor that understanding calculus leads to an increase in finger length. Rather, it likely reflects the effects of a third group of variables related to changes that occur over time.

Research Ethics The use of both human and animal participants in psychological research is an emo- tional and controversial topic. It raises some important ethical issues relating to how

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CHAPTER 1Section 1.6 Philosophical Issues and Psychological Controversy

participants in experiments are treated. Many of the procedures used in earlier investigations— where, for example, animals were euthanized or human participants were deceived, coerced, or otherwise made to do things they would not ordi- narily do—are no longer acceptable. Some believe that there are no circumstances under which ani- mals should be harmed in the interests of science (Knight, 2008); others argue that when the poten- tial benefits are sufficiently important, animals might need to be sacrificed (Brody, 2001).

The American Psychological Association provides guidelines for the ethical treatment of animal and human participants in research (Ethical principles . . . , 2011; and Guidelines for Ethical Conduct . . . , 2011). With respect to animal research, these guide- lines stipulate that the research must have a clear, scientific purpose with positive potential benefits, that animal care must comply with strict regula- tions, and that every effort must be made to mini- mize animal pain and suffering.

With respect to research with human participants, guidelines require that the ethical acceptability of the research be reviewed; that all participants be made fully aware of all aspects of the research that might affect their willingness to participate; that they be completely free not to take part; and that participants be protected from physical and mental danger or discomfort.

Avoiding the Pitfalls Have you by now developed an image of psycho- logical researchers stumbling blindly among the

numerous pitfalls of scientific research, never knowing for certain what to believe? That image would be misleading: Well-trained researchers are usually acutely aware of poten- tial pitfalls; they can guard against falling into traps that might deceive the less wary.

1.6 Philosophical Issues and Psychological Controversy

The search for explanations of human behavior is based on a number of assumptions that direct that search and that—in a very real sense—validate many of the beliefs resulting from the search. The most basic of these assumptions are philosophical in origin, have been subjects of controversy and debate that continue unresolved to this date, and cannot be tested or examined completely objectively. If they could, they would not be

Because 100 percent of divorces begin with marriage, there is a high correla- tion between number of weddings and number of divorces. But it would be meaningless to say that weddings are an important cause of divorces—or vice versa. Such reasoning illustrates the correlation fallacy.

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CHAPTER 1Section 1.7 Psychology’s Relevance

assumptions (which are, by definition, unproven) but would be laws or principles (beliefs more firmly grounded in objective observation).

Most important among these assumptions are those that deal with human nature and with the causes of behavior: Is behavior a function of free will, or is it determined by other forces? Are mind and body separate? Is behavior determined by underlying characteris- tics in the person (termed dispositions), or is it determined by the immediate situation?

Depending on the assumptions they make, some psychologists believe we exercise delib- erate control over our behavior; others are primarily deterministic: They believe behavior is an inevitable consequence of identifiable causes. Some look for the causes of behavior among genetic factors; others attribute a greater role to environmental forces. And the end result of the different assumptions psychologists make is that psychology is characterized by a number of different theories.

Psychology is a science that is sometimes gray rather than always black or white. Not all the pieces of the puzzle have yet been discovered or assembled.

1.7 Psychology’s Relevance

What do you want out of psychology? The question is not as simple as it might be in other fields. A bookkeeping course might teach you how to keep books; a course in dentistry, how to be a dentist; and a course in mathematics, how to do mathematics. But a course in psychology is not likely to teach you how to do psychology. Besides, what is involved in “doing” psychology is not at all clear. Clinical psychologists “do” psychology in one sense: They attempt to apply what they have learned or discovered to alleviate mental and emotional problems. Experimental psychologists also “do” psychology, but the thing they do is clearly different from the things done by clinical psychologists. A col- lege professor “does” psychology; but that too is different. In any case, you will probably not do any of these things as a result of this single course.

What then? Is psychology going to reveal the grand mysteries of the human psyche, expanding your understanding of yourself and of humanity? Will it enable you to func- tion better as a human being, directing you along paths of growth and happiness?

To some extent, yes. After all, psychology has enormous applications in a tremendous variety of areas. Psychology’s insights can make you a better parent, a more memorable teacher, a startlingly effective salesperson. Psychology can help you understand why you feel and act as you do, how your friends and family affect your behavior, and why you are moved to do certain things and do your utmost to avoid others. Advances in our knowledge of brain structures and functions suggest new approaches for treating addic- tions; increased understanding of how our sensory systems work has led to more effective treatments for sensory problems. Psychology gives us insights into how memory can be improved and maintained as we age. And it suggests highly effective ways of dealing with mental and emotional disorders.

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CHAPTER 1Section 1.8 This Book

1.8 This Book

In a very real sense, the remaining chapters of this book are a definition of psychology. That definition takes the form of a division of psychological topics into chapters, each dealing with a different facet of human behavior, and each attempting to summarize and interpret what is known about that aspect of behavior.

Following this introduction, we move to a consideration of our biological aspects: brain structure and functioning (Chapter 2) and sensory systems and perception (Chapter 3). Chapter 4 looks at how we learn, and Chapter 5 examines memory and thinking as well as intelligence. Chapter 6 is concerned with motivation and emotion: Why do we do certain things and not others? What moves us? In Chapter 7, we look at the forces underlying the changes that occur between birth and maturity. Chapter 8 looks at human personality—the qualities that make each of us absolutely unique—and Chapter 9 looks at mental disorders and the therapies psychology provides for righting these disorders. Finally, the 10th chap- ter looks at social psychology: how we relate to each other, how and why we fight and love.

The breadth and substance of psychology are evident in this arrangement of topics; and its definition, too, is implicit in them. That definition can be reduced to a single outline, as in Table 1.3, or can be reduced even further to a single statement that bears repeating: Psychology is the science that studies behavior and mental processes.

Table 1.3 An Outline of This Text as a Definition of Psychology

Chapter Outline Definition

1. The Science of Psychology Psychology is the science that studies behavior and mental processes.

2. The Brain and Consciousness Looks at the physiological basis of behavior and at our differ- ent states of consciousness.

3. Sensation and Perception Examines our sensory and perceptual systems, which are our sources of contact with the external and internal world.

4. Learning Asks how we learn.

5. Memory and Intelligence Investigates how we remember and studies the intellectual processes that our intelligence makes possible.

6. Motivation and Emotion Looks at the reasons for our behavior—at our motives and emotions.

7. Human Development Is concerned with the significant changes that transpire between birth and death, and with the forces that drive these changes.

8. Personality Examines human individuality and tries to understand how each of us is different and unique—and at the same time, how we share certain characteristics that define our humanity.

9. Psychological Disorders and Therapies Tries to understand mental and emotional disorders and searches for therapies to alleviate them.

10. Social Psychology Looks at relationships among individuals and at the enormous power of social influences.

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CHAPTER 1Main Points

It is important to note that even though our con- sideration of human behavior and thinking—the subject of psychology—is divided into separate topics, in the end, it is less the individual topics in which we are interested than the whole: We should not lose sight of the fact that the puzzle psychol- ogy is gnawing at involves the entire person.

Main Points 1. What Is Psychology? Psychology is

concerned with all that affects human behavior, thought, and emotion: It is the science that studies behavior and mental processes. About half of all psychologists are clinical psychologists; other divisions include counseling, industrial/organiza- tional, school, educational, developmental, experimental, and many others.

2. The Beginnings of Psychology: Psychol- ogy had its origins in Greek philosophy (psyche is Greek for “soul”; logos, for “study”), was profoundly affected by medi- cal discoveries, and borrowed its scientific methodology from Newtonian phys- ics. Its more recent origins date to Wundt’s psychological laboratory (1879) and his followers who established the structuralist school, William James’s functional- ism, Watson and Skinner’s behaviorism, Freud’s psychodynamics, and the influences of cognitivism and humanism.

3. Principles of Science: Science is an attitude that insists on precision and repli- cability, as well as a collection of methods to maximize the validity of conclu- sions. The five steps of the scientific method are (1) ask the question; (2) develop a hypothesis; (3) collect observations; (4) test the hypothesis; and (5) reach and share a conclusion.

4. Sources of Psychological Information: Observation is the source of knowledge in all sciences. Psychological investigations can be descriptive (describe charac- teristics of individuals or groups) or more experimental. Longitudinal studies look at the same individual(s) at different times; cross-sectional studies look at different groups at the same point in time. Descriptive research can be based on observation that occurs in natural surroundings (naturalistic) or in more con- trived environments such as laboratories. It can be based on observations of a single individual or unit (a case study) or of larger groups (a survey). Correlational studies try to discover relationships between variables but cannot prove causa- tion (the correlation fallacy). Experiments allow investigators to control independent variables to determine their effects on dependent variables. In an ex post facto study, investigators don’t assign participants to groups and don’t manipulate indepen- dent variables.

5. Cautions in Interpreting Psychological Research: Single-blind and double- blind procedures (where the examiners, the subjects, or both don’t know who

It’s a complex puzzle psychology is working on. These researchers are mistaken if they think it involves only the head.

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CHAPTER 1Main Points

members of the experimental group are) are used to safeguard against experi- menter and subject bias. To be able to generalize findings, the experimenter must study a sample representative of the population to which generalizations are to be made (often randomly selected for that reason). Psychological research can also be affected by problems of subject dishonesty, memory distortions, conceptual confusion, and the tendency to assume that if two events are correlated, one must have caused the other.

6. Philosophical Issues and Psychological Controversy: Psychological research is based on a number of sometimes controversial assumptions (nature vs. nurture, determinism vs. free will). The end result is a number of different theories and beliefs about human behavior.

7. Psychology’s Relevance: Psychology’s primary goals are to explain human behavior, to make increasingly accurate predictions, and to achieve a greater degree of effectiveness in alleviating human distress and in enhancing the joy- ful aspects of living. Not all the pieces of the puzzle have yet been discovered or assembled.

Study Terms

archival research




bubba psychology

case studies

clinical psychologists


control groups


correlation fallacy

correlational research

counseling psychologists


cross-sectional studies

dependent variables

descriptive research


developmental psychologists

double-blind procedures

educational psychologists

evolutionary psychology

ex post facto study


experimental group

experimental psychologists

experimenter bias




Hawthorne effect


humanistic psychology


independent variables

industrial/organizational psychologists


longitudinal studies

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CHAPTER 1Main Points

naturalistic observation


nonnaturalistic observation







random sampling


school psychologists


scientific method


single-blind procedure

statistical procedures


stratified sampling





third force psychology


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The Brain and Consciousness

Focus Questions

By the end of the chapter, you should be able to answer the following questions: • What are the principal biological advantages

and disadvantages of humans relative to other species? • What are the main components and functions of nerve cells? • How do the most important neurotransmitters relate to behavior? • How is the human nervous system organized? • What are the key brain structures and their functions? • How are biology and behavior related? • What is the nature and purpose of sleep? • What functions might dreams serve? • Is hypnosis a distinct state of consciousness?

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CHAPTER 2The Brain and Consciousness

Drinking without being thirsty and

making love at any time, Madame,

are the only things that distinguish us

from other animals. ­—Pierre-Augustin­Caron­de­

Beaumarchais,­The Marriage of Figaro, Act­2,­Scene­21,­1784

Chapter Outline

2.1 Evolution Early Homo Sapiens

2.2 The Neuron Neural Transmission

2.3 Organization of the Nervous System The Endocrine System

2.4 The Brain Studying Brain Functions Structures of the Brain

2.5 Biology and Behavior Consciousness

2.6 Sleep Circadian Rhythms Stages of Sleep Why We Sleep Dreams

2.7 Hypnosis Some Facts Is Hypnosis a Different State of Consciousness? Applications of Hypnosis

2.8 Drugs and Consciousness

No, Monsieur de Beaumarchais, these are not the only things that distinguish us from other ani- mals. And perhaps we are not, in all ways, the superior animal we flatter ourselves on being?

Take a bat, for instance: Many people think bats are blind, which they really are not. But their vision is not very good: It does not have to be. Spallanzani, an Italian priest, was fascinated by how bats seemed to be able to fly hectically about at what must be, for a bat, breakneck speed. Yet they never seem to break their necks on houses or trees even when they fly in the dark. When Spallanzani released blinded bats in a room crisscrossed with tiny silk threads, the bats zipped around the room without ever running into the threads. But when he plugged their ears, they smacked into every- thing in their way (Dijkgraaf, 1960).

We now know that as they fly, bats emit a series of high-pitched squeals that bounce predictably off the objects they encounter. Since sound travels at a relatively constant speed, it is a small trick for the bat to compute how far the sound has traveled to an object and back again. A small trick, but one that we humans find exceedingly difficult. Our echolocation capabilities are pretty limited compared with those of the bat.

The bat is not the only animal that is, in at least one sense, superior to us: Bears and dogs and even penguins can detect odors that we cannot; a golden eagle can, on a clear day, spot a green frog swimming in green water six inches below a murky green surface; the grizzly bear is physically stronger than we are; the antelope, faster; the dolphin, a more graceful swimmer.

The point is that we, and all other animals, behave as we do largely because of our different physi- ologies and our different nervous systems. Some of the pieces of the human puzzle are to be found in our “wiring” and its functioning.

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CHAPTER 2Section 2.1 Evolution

2.1 Evolution

We are Homo sapiens, the self-named wise one—a seemingly appropriate label given our well-developed “new” brains, our opposable thumbs, the fact that we walk upright, and our ability to communicate through the use of arbitrary symbols.

But we don’t have clever thumbs just because we decided they would be an advantage; we did not invent our brains; we made no conscious decision to shift from a four-legged to a two-legged form of locomotion, thereby making our front legs obsolete and even- tually changing their names to arms; nor did we, in council one day, decide that a lan- guage would be superior to the grunts and gestures we might previously have been using. Most scientists believe these revolutionary happenings resulted from evolution, although some believe they were the products of an inventive Supreme Being (creationism). Others think both explanations are valid—that evolution describes the progression of the species whereas creationism describes its origins. The issue cannot be resolved here, although we will wander briefly back into the murky depths of evolutionary history.

Evolution, the adaptive progression of species from their origins, might at first glance seem an inappropriate topic for a study of human behavior. We are, after all, concerned with understanding our current behavior. But perhaps something in evolution might help our understanding. Certainly, much in our behavior is related to biology; and much of our biology seems to be the product of evolutionary processes.

Early Homo Sapiens

Much of the evidence upon which the early details of evolutionary theory are based is drawn painfully from the few records nature has haphazardly provided: a fossil here, a bone there, a fragment of skull, a petrified dinosaur dropping. More recently, the study of change at the level of genes—termed molecular genetics—provides another rich source of information.

Those who peer back into the dimness of geological time, and those who study changes in genetic material over time, inform us that very primitive tool-making humans made their inconspicuous appearance on this planet approximately 2 million years ago. Widely accepted speculation has it that three species of humans evolved over the next million or so years: Homo habilis followed by Homo erectus, then Homo sapiens (Spoor et al., 2007). We, Homo sapiens, are thought to have appeared less than 200,000 years ago, give or take a hundred thousand years (Elert, 1997). We are now the only remaining species of humans in a world comprising approximately 1.5 million other species (Osborn, 2010). We belong to the primate order, of which there are over 300 living species (Primate Gallery, 2010). Our class is mammal, which belongs to the chordate phylum in the animal kingdom (Figure 2.1).

Not only did Homo sapiens survive, but the species thrived, although numbers grew very slowly at first, requiring more than 100,000 years to reach the first billion. This happened around 1800, but the second billion was reached in only around 100 years, and the next 100 years saw an increase of nearly 5 billion (U.S. Census Bureau, 2010a) (Figure 2.2).

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CHAPTER 2Section 2.1 Evolution

In some ways, it is astonishing that our species of humans survived, as defenseless as we were against the fangs and claws of the large carnivo- rous predators of those prehistoric times. We are a relatively slow species, endowed with unexcep- tional hearing and with a laughable sense of smell compared with that of many other species. Also, we are inadequately protected against both heat and cold, awkward at climbing trees or digging holes, clumsy in the water relative to dolphins, and incapable of flight without artificial means.

But we are more intelligent! If we could not out- fight or outrun a prehistoric enemy, we might yet outwit the beast. We could also stand upright. And while this did not make us as fast as most four-legged animals, it freed our arms and hands for purposes other than locomotion. We became an animal that could walk quite nicely on just two of its legs, freeing our arms for making tools, striking enemies while in full flight, gesticulat- ing, and blowing the nose, an undertaking that was not at all hampered by the fine opposable thumb that we now take so much for granted.

Useful though they may be for a vari- ety of purposes, our fine opposable thumbs aren’t our biggest evolutionary advantage: Our enormously complex brains are.

General Classification








Human Classification

Homo sapiens







Fr o

m m

o st

g en

er al

to m

o st

s p

ec ifi


Figure 2.1

Biological classification of humans. We are the only species left of the genus Homo. But there are more than 300 known living primate species in the world.

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CHAPTER 2Section 2.1 Evolution

Although many other primates also have opposable thumbs, no other animal can boast the manual dexterity that we have at our fingertips. And no other animal possesses as large and complex a brain as we have.

Brains, Language, and Thinking Eventually brains led to primitive tools, to agricultural and hunting implements, to the wheel, the rocket, the computer. But perhaps more important than all this, brains led to the development of language and of culture—and to the possibility of sharing informa- tion and even of transmitting it across generations. (Language learning among infants is discussed in Chapter 7.)

Thinking and language are very closely related. In fact, a school of thought that was widely popular among anthropologists a few decades ago maintained that language is essential for and determines thought—a belief labeled the Sapir-Whorf hypothesis. In its strong form, this hypothesis maintains that different languages lead people to see the world dif- ferently and to think and behave differently. For example, some early research suggested that the Inuit, who seemed to have many different words for snow, could actually per- ceive types of snow of which others were unaware. Similarly, cultures that had a different

World population in billions

P o

p u

la ti

o n

in b

ill io

n s

Year (AD)

1200 1400 1600 1800 2000










Figure 2.2

Approximate population growth for Homo sapiens on earth. The part of the graph to the left that is not shown would extend about 1 mile if it reached back to the time when humans first appeared. Based on World Population Prospects: The 2008 Revision Population Database, United Nations Population Division. Retrieved July 20, 2010, from; U.S. Census Bureau, International Data Base, June 2010 update. Retrieved June 20, 2010, from http://

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CHAPTER 2Section 2.1 Evolution

vocabulary for colors were thought to see colors differently. These beliefs have now been discredited (Pullum, 1991). Experimental research has not supported the strong form of the Sapir-Whorf hypothesis (Koerner, 2000). It seems that language is not essential for thinking. For example, there is evidence of thinking among preverbal infants (Gleitman & Papafragou, 2005). And it is also true that adults sometimes think in terms of images or other symbols rather than with language.

Still, a weaker form of the Sapir-Whorf hypothesis is widely accepted. It argues that while lan- guage does not entirely determine thinking, it greatly influences how we think and accounts for some differences in the thought and perception of different cultures (Boroditsky, 2003).

As Newell (1990) explains, a symbolic representational system such as language is essen- tial for systematic reasoning and for sharing knowledge. Language is a fundamental force in defining human cultures and in shaping our lives. There is little doubt that language is one of the most important accomplishments of the brain.

Evolution and the Nervous System The brain is part of our nervous system. In a simple sense, our nervous system is the elec- trical and chemical communication system within our bodies. It is because of our nervous system that our right hand knows what our left hand is doing, that our legs alternate rather than compete when we walk, that we are sensitive to our environments. In fact, it is because of our nervous system that we can even think about such matters; hence its tremendous importance in psychology.

In an evolutionary sense, our nervous system is among the most complex and highly developed of all animals. It stands in sharp contrast to that of more primitive creatures. At the lowest level, for example, there are single-celled organisms whose responsiveness is highly limited. There are also simple multicelled organisms such as sponges whose various nervous systems are not in communication with one another. Parts of the sponge contain specialized cells for reproduction or secretion, each of these functions being car- ried out independently of what might be happening elsewhere in the sponge.

The nervous systems of insects also provide an interesting evolutionary contrast to those of humans. In some insects, primitive clusterings of nerve cells coordinate simple functions, such as its brain telling a cockroach when and where to run (Bender, Pollack, & Ritzmann, 2010). But in many insects, there is no single “command area”—no brain to oversee all func- tions or to be aware of what is going on in all parts of the body. Cut off the head of a wasp and it will continue eating even though it has lost its abdomen and there’s nowhere for the food to go. In much the same way, the male praying mantis will continue to copulate even as the female systematically devours him from the head down (Prokop & Vaclav, 2008).

The more advanced nervous systems of fishes, reptiles, and mammals differ from these more primitive nervous systems. Not only is their functioning more complex, but their activity is coordinated by an increasingly large brain. Furthermore, brains in more advanced animals have become highly specialized: A large portion of the bat brain is devoted to hearing; the olfactory (smell) area of dog brains is far more developed than

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CHAPTER 2Section 2.1 Evolution

that of human brains; those parts of the brain that control rapid movement are more pre- dominant in bird brains; and in humans, the area of the brain devoted to thinking is larger, proportional to the remainder of the brain, than in any other living creature (Figure 2.3). It is this brain, the command center of our nervous system, that is largely responsible for what we are and for our behavior.

Figure 2.3

Homo sapiens may not see, hear, or smell as well as many other species, but greater relative brain size and the greater relative size of the “thinking” part—the association areas of the human brain—have given us an evolutionary advantage. Copyright Hungry Coyote Limited. Used by permission.

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CHAPTER 2Section 2.2 The Neuron

2.2 The Neuron

The human nervous system is a communication system; its function is to transmit mes-sages (impulses). Many of the messages it transmits go from sensory receptors (such as the skin, eyes, nose, tongue, ears, muscles, joints, and tendons) to the command center (the brain). Impulses also go from the brain to what are termed effectors (such as muscu- lar and glandular systems).

The cells that make up the nervous system, and whose specialized function is to transmit impulses, are called neurons (or nerve cells). Estimates vary widely, but scientists believe there are approximately 86 billion neurons in the human brain alone, with the bulk of these—some 69 billion—being in the part of the brain called the cerebellum (Azevedo et



sensory nerve fiber


motor nerve






Figure 2.4

Schematic conception of the components of the sensorimotor arc. Receptors (1) in eyes, tactile organs, nose, ears, taste buds, and kinesthetic senses send signals (2) to connectors (3) in the spinal cord, brain, and other neural pathways. Signals are then sent (4) to effectors (5) in mus- cles and glands.

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CHAPTER 2Section 2.2 The Neuron

al., 2009). The spinal cord contains at least a billion more, and several billion more are concentrated in sensory receptors and in muscular and glandular effector systems. Other neurons are connectors: They serve as links between receptor and effector systems (Figure 2.4). Most of the connectors are located in the brain.

Like all other living cells, neurons consist of a nucleus and surrounding matter. This mat- ter is made up of the cell body, axons, and dendrites. Neurons are surrounded by a pro- tective coating, called a myelin sheath (made up of glial cells). The axon is the elongated part of a neuron: It may be microscopically short or as long as 2 or 3 feet, as is the case for some neurons located in the spinal cord. Dendrites are hairlike extensions emanat- ing from the cell body of the neuron. The space between the ends of one cell’s axon and another cell’s dendrites is a synapse. Enlargements found at the terminating ends of some axons are synaptic knobs. Bundles of neurons make up nerves. The typical configuration of a neuron is shown in Figure 2.5.

Neural Transmission

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