develop How Children

Robert Siegler Judy DeLoache Nancy Eisenberg Jenny Saffran

F o u r t h E d i t i o n

This is an exciting time in the field of child development. The past decade has brought new theories, new ways of thinking, new areas of research, and innumerable new findings to the field. We originally wrote How Children Develop to describe this ever improving body of knowledge of children and their development and to convey our excitement about the progress that is being made in understanding the developmental process. We are pleased to continue this endeavor with the publication of the Fourth Edition of How Children Develop. —From the Preface

As new research expands the field’s understanding of child and adolescent development, the authors of How Chil- dren Develop continue their commitment to bringing the story of today’s developmental science to the classroom in a clear and memorable way. Joined in this Fourth Edition by Jenny Saffran of the University of Wisconsin–Madison, they maintain their signature emphasis on the “Seven Classic Themes” of development, which facilitates students’ understanding by highlighting the fundamental questions posed by investigators past and present. The new and ex- panded coverage in the Fourth Edition spans a wide range of topics—from broad areas like the epigenetic aspects of development, the links between brain function and behavior, and the pervasive influence of culture to specific subjects such as the mechanisms of infants’ learning, the effects of math anxiety, and the rapidly growing influence of social media in children’s and adolescents’ lives. This edition also features the highly anticipated debut of Launch- Pad, an online learning system that features Worth Publishers’ celebrated video collection; the full e-Book of How Children Develop; and the LearningCurve quizzing system, which offers students instant feedback on their learning.

Learn more about and request access at

Order How Children Develop, Fourth Edition, with LaunchPad at no additional cost by using ISBN 10: 1-4641-8284-1 / ISBN-13: 978-1-4641-8284-6.

Coverage of contemporary developmental science is very important to me. I prefer a text that describes the relevant research and is updated regularly. I find How Children Develop to be very good in this area, as all of the authors are primarily researchers.

—Jeffery Gagne, University of Texas at Arlington

I highly recommend this textbook. The main strengths are up-to-date research with clear descriptions of study methods and findings as well as excellent real-world examples that get students interested in a topic so that they are excited enough to read about the research and evidence that support real-world developmental phenomenon. I do not think the text has a major weakness.

—Katherine O’Doherty, Bowdoin College

Since its inception, I think that How Children Develop is the best child development textbook available. I would not hesitate to use it again in my classes.

—Richard Lanthier, George Washington University

Cover art: Football, Bentota, Sri Lanka, 1998 (oil on canvas) ©Andrew Macara / Private Collection / The Bridgeman Art Library

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F o u r t h E d i t i o n

Siegler DeLoache Eisenberg




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develop How Children



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develop How Children

F o u r t h E d i t i o n

Robert Siegler Carnegie Mellon University

Judy DeLoache University of Virginia

Nancy Eisenberg Arizona State University

Jenny Saffran University of Wisconsin–Madison

And Campbell Leaper, University of California–Santa Cruz, reviser of Chapter 15: Gender Development



This is dedicated to the ones we love

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about the authors: Robert Siegler is the Teresa Heinz Professor of Cognitive Psychology at Carnegie Mellon University. He is author of the cognitive development textbook Children’s Thinking and has written or edited several additional books on child development. His books have been translated into Japanese, Chinese, Korean, Spanish, French, Greek, Hebrew, and Portuguese. In the past few years, he has presented keynote addresses at the conventions of the Cognitive Development Society, the International Society for the Study of Behavioral Development, the Japanese Psychological Association, the Eastern Psychological Association, the American Psychological Society, and the Conference on Human Development. He also has served as Associate Editor of the journal Developmental Psychology, co-edited the cognitive development volume of the 2006 Handbook of Child Psychology, and served on the National Mathematics Advisory Panel from 2006 to 2008. Dr. Siegler received the American Psychological Association’s Distinguished Scientific Contribution Award in 2005, was elected to the National Academy of Education in 2010, and was named Director of the Siegler Center for Innovative Learning at Beijing Normal University in 2012.

Judy DeLoache is the William R. Kenan Jr. Professor of Psychology at the University of Virginia. She has published extensively on aspects of cognitive development in infants and young children. Dr. DeLoache has served as President of the Developmental Division of the American Psychological Association, as President of the Cognitive Development Society, and as a member of the executive board of the International Society for the Study of Infancy. She has presented major invited addresses at professional meetings, including the Association for Psychological Science and the Society for Research in Child Development. Dr. DeLoache is the holder of a Scientific MERIT Award from the National Institutes of Health, and her research is also funded by the National Science Foundation. She has been a visiting fellow at the Center for Advanced Study in the Behavioral Sciences in Palo Alto, California, and at the Rockefeller Foundation Study Center in Bellagio, Italy. She is a Fellow of the National Academy of Arts and Sciences. In 2013, she received the Distinguished Research Contributions Award from the Society for Research in Child Development and the William James Award for Distinguished Contributions to Research from the Association for Psychological Science.

Nancy Eisenberg is Regents’ Professor of Psychology at Arizona State University. Her research interests include social, emotional, and moral development, as well as so- cialization influences, especially in the areas of self-regulation and adjustment. She has published numerous empirical studies, as well as books and chapters on these topics. She has also been editor of Psychological Bulletin and the Handbook of Child Psychology and was the founding editor of the Society for Research in Child Development journal Child Development Perspectives. Dr. Eisenberg has been a recipient of Research Scientist Development Awards and a Research Scientist Award from the National Institutes of Health (NICHD and NIMH). She has served as President of the Western Psychological Association and of Division 7 of the American Psychological Association and is president- elect of the Association for Psychological Science. She is the 2007 recipient of the Ernest R. Hilgard Award for a Career Contribution to General Psychology, Division 1, American Psychological Association; the 2008 recipient of the International Society for the Study of Behavioral Development Distinguished Scientific Contribution Award; the 2009 re- cipient of the G. Stanley Hall Award for Distinguished Contribution to Developmental Psychology, Division 7, American Psychological Association; and the 2011 William James




Fellow Award for Career Contributions in the Basic Science of Psychology from the Association for Psychological Science.

Jenny R. Saffran is the College of Letters & Science Distinguished Professor of Psychology at the University of Wisconsin–Madison, and an investigator at the Waisman Center. Her research is focused on learning in infancy and early childhood, with a particular focus on language. Dr. Saffran currently holds a MERIT award from the Eunice Kennedy Shriver National Institute of Child Health and Human Development. She has been the recipient of numerous awards for her scientific research, including the Boyd McCandless Award from the American Psychological Association for early career contributions to developmental psychology, and the Presidential Early Career Award for Scientists and Engineers from the National Science Foundation.




Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xx

1 An Introduction to Child Development . . . . . . . . . . . . . . . . . . 1

2 Prenatal Development and the Newborn Period . . . . . . . . . . . 39

3 Biology and Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . 85

4 Theories of Cognitive Development . . . . . . . . . . . . . . . . . 129

5 Seeing, Thinking, and Doing in Infancy . . . . . . . . . . . . . . . . 171

6 Development of Language and Symbol Use . . . . . . . . . . . . . 215

7 Conceptual Development . . . . . . . . . . . . . . . . . . . . . . . 259

8 Intelligence and Academic Achievement . . . . . . . . . . . . . . . 297

9 Theories of Social Development . . . . . . . . . . . . . . . . . . . 339

10 Emotional Development . . . . . . . . . . . . . . . . . . . . . . . . 383

11 Attachment to Others and Development of Self . . . . . . . . . . 425

12 The Family . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467

13 Peer Relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . . 509

14 Moral Development . . . . . . . . . . . . . . . . . . . . . . . . . . . 553

15 Gender Development . . . . . . . . . . . . . . . . . . . . . . . . . . 593

16 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 637

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G-1

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . R-1

Name Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . NI-1

Subject Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SI-1

brief contents:




Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xx

Chapter 1 An Introduction to Child Development . . . . . . 1

Reasons to Learn About Child Development . . . . . . . . . . . . . . . . 3 Raising Children 3 Choosing Social Policies 4 Understanding Human Nature 6 Review 7

Historical Foundations of the Study of Child Development . . . . . . . . 7 Early Philosophers’ Views of Children’s Development 8 Social Reform Movements 9 Darwin’s Theory of Evolution 9 The Beginnings of Research-Based Theories of Child Development 10 Review 10

Enduring Themes in Child Development . . . . . . . . . . . . . . . . . . . 10 1 . Nature and Nurture: How Do Nature and Nurture Together Shape

Development? 10 2 . The Active Child: How Do Children Shape Their Own

Development? 12 3 . Continuity/Discontinuity: In What Ways Is Development Continuous,

and in What Ways Is It Discontinuous? 13 4 . Mechanisms of Development: How Does Change Occur? 16 5 . The Sociocultural Context: How Does the Sociocultural Context

Influence Development? 17 6 . Individual Differences: How Do Children Become So Different

from One Another? 20 7 . Research and Children’s Welfare: How Can Research Promote

Children’s Well-Being? 21 Review 22

Methods for Studying Child Development . . . . . . . . . . . . . . . . . 22 The Scientific Method 23 Contexts for Gathering Data About Children 25 Correlation and Causation 28 Designs for Examining Development 32 Ethical Issues in Child-Development Research 35 Review 36





Chapter 2 Prenatal Development and the Newborn Period . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Prenatal Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Box 2.1: A Closer look Beng Beginnings 41

Conception 42 Box 2.2: Individual differences The First—and Last—Sex Differences 44

Developmental Processes 45 Box 2.3: A Closer look Phylogenetic Continuity 46

Early Development 47 An Illustrated Summary of Prenatal Development 48 Fetal Behavior 51 Fetal Experience 52 Fetal Learning 54 Hazards to Prenatal Development 56

Box 2.4: Applications Face Up to Wake Up 61

Review 66

The Birth Experience . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 Diversity of Childbirth Practices 68 Review 69

The Newborn Infant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 State of Arousal 70 Negative Outcomes at Birth 74

Box 2.5: Applications Parenting a Low-Birth-Weight Baby 78

Review 81

Chapter 3 Biology and Behavior . . . . . . . . . . . . . . . . . 85

Nature and Nurture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 Genetic and Environmental Forces 88

Box 3.1: Applications Genetic Transmission of Disorders 94

Behavior Genetics 99 Box 3.2: Individual differences Identical Twins Reared Apart 101

Review 105

Brain Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 Structures of the Brain 106 Developmental Processes 109

Box 3.3: A Closer look Mapping the Mind 110

The Importance of Experience 114 Brain Damage and Recovery 117 Review 118

The Body: Physical Growth and Development . . . . . . . . . . . . . . . 119 Growth and Maturation 119




Nutritional Behavior 121 Review 126

Chapter 4 Theories of Cognitive Development . . . . . . . 129

Piaget’s Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 View of Children’s Nature 132 Central Developmental Issues 133 The Sensorimotor Stage (Birth to Age 2 Years) 135 The Preoperational Stage (Ages 2 to 7) 138 The Concrete Operational Stage (Ages 7 to 12) 141 The Formal Operational Stage (Age 12 and Beyond) 141 Piaget’s Legacy 142

Box 4.1: Applications Educational Applications of Piaget’s Theory 143

Review 144

Information-Processing Theories . . . . . . . . . . . . . . . . . . . . . . 145 View of Children’s Nature 146 Central Developmental Issues 147

Box 4.2: Applications Educational Applications of Information-Processing Theories 154

Review 155

Sociocultural Theories . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 View of Children’s Nature 156 Central Developmental Issues 158 Review 160

Box 4.3: Applications Educational Applications of Sociocultural Theories 161

Dynamic-Systems Theories . . . . . . . . . . . . . . . . . . . . . . . . . 161 View of Children’s Nature 163 Central Development Issues 165

Box 4.4: Applications Educational Applications of Dynamic-Systems Theories 166

Review 167

Chapter 5 Seeing, Thinking, and Doing in Infancy . . . . . 171

Perception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173 Vision 173

Box 5.1: A Closer look Infants’ Face Perception 176

Box 5.2: A Closer look Picture Perception 183

Auditory Perception 182 Taste and Smell 186 Touch 186 Intermodal Perception 186 Review 188




Motor Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188 Reflexes 189 Motor Milestones 190 Current Views of Motor Development 191

Box 5.3: A Closer look “The Case of the Disappearing Reflex” 192

The Expanding World of the Infant 192 Box 5.4: Applications A Recent Secular Change in Motor Development 195

Box 5.5: A Closer look “Gangway—I’m Coming Down” 196

Review 198

Learning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198 Habituation 199 Perceptual Learning 199 Statistical Learning 200 Classical Conditioning 201 Instrumental Conditioning 201 Observational Learning/Imitation 202 Rational Learning 204 Review 205

Cognition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 Object Knowledge 206 Physical Knowledge 207 Social Knowledge 208 Looking Ahead 211 Review 211

Chapter 6 Development of Language and Symbol Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215

Language Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 The Components of Language 217 What Is Required for Language? 218

Box 6.1: Applications Two Languages Are Better Than One 222

The Process of Language Acquisition 224 Box 6.2: Individual differences The Role of Family and School Context in Early Language Development 235

Box 6.3: Applications: iBabies: Technology and Language Learning 240

Theoretical Issues in Language Development 246 Box 6.4: A Closer look: “I Just Can’t Talk Without My Hands” What Gestures Tell Us About Language 248

Box 6.5: Individual differences Developmental Language Disorders 251

Review 252

Nonlinguistic Symbols and Development . . . . . . . . . . . . . . . . . 252 Using Symbols as Information 253 Drawing 254 Review 256




Chapter 7 Conceptual Development . . . . . . . . . . . . . 259

Understanding Who or What . . . . . . . . . . . . . . . . . . . . . . . . 261 Dividing Objects into Categories 261 Knowledge of Other People and Oneself 266

Box 7.1: Individual differences Children with Autism Spectrum Disorders (ASD) 270

Box 7.2: Individual differences Imaginary Companions 273

Knowledge of Living Things 273 Review 278

Understanding Why, Where, When, and How Many . . . . . . . . . . . 278 Causality 279

Box 7.3: A Closer look Magical Thinking and Fantasy 282

Space 283 Time 286 Number 288 Relations Among Understanding of Space, Time, and Number 292 Review 293

Chapter 8 Intelligence and Academic Achievement . . . 297

What Is Intelligence? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299 Intelligence as a Single Trait 299 Intelligence as a Few Basic Abilities 299 Intelligence as Numerous Processes 300 A Proposed Resolution 300 Review 301

Measuring Intelligence . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301 The Contents of Intelligence Tests 302 The Intelligence Quotient (IQ) 304 Continuity of IQ Scores 305

Box 8.1: Individual differences Gifted Children 306

Review 306

IQ Scores as Predictors of Important Outcomes . . . . . . . . . . . . . 307 Review 308

Genes, Environment, and the Development of Intelligence . . . . . . . 308 Qualities of the Child 309 Influence of the Immediate Environment 310 Influence of Society 313

Box 8.2: Applications: A Highly Successful Early Intervention: The Carolina Abecedarian Project 318

Review 320

Alternative Perspectives on Intelligence . . . . . . . . . . . . . . . . . . 320 Review 322




Acquisition of Academic Skills: Reading, Writing, and Mathematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322

Reading 322 Box 8.3: Individual differences Dyslexia 326

Writing 328 Mathematics 330 Mathematics Anxiety 334

Box 8.4: Applications Mathematics Disabilities 335

Review 335

Chapter 9 Theories of Social Development . . . . . . . . . 339

Psychoanalytic Theories . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 View of Children’s Nature 342 Central Developmental Issues 342 Freud’s Theory of Psychosexual Development 342 Erikson’s Theory of Psychosocial Development 345 Current Perspectives 347 Review 348

Learning Theories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348 View of Children’s Nature 349 Central Developmental Issues 349 Watson’s Behaviorism 349 Skinner’s Operant Conditioning 350 Social Learning Theory 352

Box 9.1: A Closer look Bandura and Bobo 352

Current Perspectives 355 Review 356

Theories of Social Cognition . . . . . . . . . . . . . . . . . . . . . . . . . 356 View of Children’s Nature 356 Central Developmental Issues 356 Selman’s Stage Theory of Role Taking 357 Dodge’s Information-Processing Theory of Social Problem Solving 357 Dweck’s Theory of Self-Attributions and Achievement Motivation 359 Current Perspectives 361 Review 361

Ecological Theories of Development . . . . . . . . . . . . . . . . . . . . 362 View of Children’s Nature 362 Central Developmental Issues 362 Ethological and Evolutionary Theories 362 The Bioecological Model 366

Box 9.2: Individual differences Attention-Deficit Hyperactivity Disorder 370

Box 9.3: Applications Preventing Child Abuse 373

Current Perspectives 378 Review 379




Chapter 10 Emotional Development . . . . . . . . . . . . . 383

The Development of Emotions in Childhood . . . . . . . . . . . . . . . 385 Theories on the Nature and Emergence of Emotion 386 The Emergence of Emotion in the Early Years and Childhood 387

Box 10.1: Individual differences Gender Differences in Adolescent Depression 396

Review 398

Regulation of Emotion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 398 The Development of Emotional Regulation 399 The Relation of Emotional Self-Regulation to Social Competence and Adjustment 401 Review 402

Individual Differences in Emotion and Its Regulation . . . . . . . . . . . 402 Temperament 403

Box 10.2: A Closer look Measurement of Temperament 406

Review 410

Children’s Emotional Development in the Family . . . . . . . . . . . . . 410 Quality of the Child’s Relationships with Parents 410 Parental Socialization of Children’s Emotional Responding 411 Review 414

Culture and Children’s Emotional Development . . . . . . . . . . . . . . 414 Review 416

Children’s Understanding of Emotion . . . . . . . . . . . . . . . . . . . . 416 Identifying the Emotions of Others 416 Understanding the Causes and Dynamics of Emotion 418 Children’s Understanding of Real and False Emotions 419 Review 421

Chapter 11 Attachment to Others and Development of Self . . . . . . . . . . . . . . . . . . . . . . . . . . 425

The Caregiver–Child Attachment Relationship . . . . . . . . . . . . . . 427 Attachment Theory 428 Measurement of Attachment Security in Infancy 430

Box 11.1: Individual differences Parental Attachment Status 432

Cultural Variations in Attachment 434 Factors Associated with the Security of Children’s Attachment 435

Box 11.2: Applications Interventions and Attachment 436

Does Security of Attachment Have Long-Term Effects? 437 Review 439

Conceptions of the Self . . . . . . . . . . . . . . . . . . . . . . . . . . . 439 The Development of Conceptions of Self 440




Identity in Adolescence 446 Review 449

Ethnic Identity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 449 Ethnic Identity in Childhood 450 Ethnic Identity in Adolescence 451 Review 453

Sexual Identity or Orientation . . . . . . . . . . . . . . . . . . . . . . . . 453 The Origins of Youths’ Sexual Identity 453 Sexual Identity in Sexual-Minority Youth 454 Review 458

Self-Esteem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458 Sources of Self-Esteem 459 Self-Esteem in Minority Children 462 Culture and Self-Esteem 463 Review 464

Chapter 12 The Family . . . . . . . . . . . . . . . . . . . . . . . 467

Family Dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 470 Box 12.1: A Closer look Parent–Child Relationships in Adolescence 471

Review 472

The Role of Parental Socialization . . . . . . . . . . . . . . . . . . . . . . 472 Parenting Styles and Practices 472 The Child as an Influence on Parenting 477 Socioeconomic Influences on Parenting 479

Box 12.2: A Closer look Homelessness 481

Review 482

Mothers, Fathers, and Siblings . . . . . . . . . . . . . . . . . . . . . . . . 482 Differences in Mothers’ and Fathers’ Interactions with Their Children 482 Sibling Relationships 483 Review 485

Changes in Families in the United States . . . . . . . . . . . . . . . . . . 485 Box 12.3: Individual differences Adolescents as Parents 486

Older Parents 488 Divorce 489 Stepparenting 494 Lesbian and Gay Parents 496 Review 497

Maternal Employment and Child Care . . . . . . . . . . . . . . . . . . . 498 The Effects of Maternal Employment 498 The Effects of Child Care 500 Review 506




Chapter 13 Peer Relationships . . . . . . . . . . . . . . . . . . 509

What Is Special About Peer Relationships? . . . . . . . . . . . . . . . . 512

Friendships . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 513 Early Peer Interactions and Friendships 513 Developmental Changes in Friendship 515 The Functions of Friendships 517 Effects of Friendships on Psychological Functioning and Behavior over Time 520

Box 13.1: Individual differences Culture and Children’s Peer Experience 522

Children’s Choice of Friends 523 Review 525

Peers in Groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 525 The Nature of Young Children’s Groups 525 Cliques and Social Networks in Middle Childhood and Early Adolescence 526 Cliques and Social Networks in Adolescence 526 Negative Influences of Cliques and Social Networks 528

Box 13.2: A Closer look Cyberspace and Children’s Peer Experience 529

Romantic Relationships with Peers 531 Review 532

Status in the Peer Group . . . . . . . . . . . . . . . . . . . . . . . . . . . 532 Measurement of Peer Status 533 Characteristics Associated with Sociometric Status 533

Box 13.3: Applications Fostering Children’s Peer Acceptance 538

Stability of Sociometric Status 539 Cross-Cultural Similarities and Differences in Factors Related to Peer Status 539 Peer Status as a Predictor of Risk 540 Review 543

The Role of Parents in Children’s Peer Relationships . . . . . . . . . . . 544 Relations Between Attachment and Competence with Peers 544 Quality of Ongoing Parent–Child Interactions and Peer Relationships 545 Parental Beliefs 546 Gatekeeping and Coaching 546 Family Stress and Children’s Social Competence 548 Review 548

Chapter 14 Moral Development . . . . . . . . . . . . . . . . 553

Moral Judgment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555 Piaget’s Theory of Moral Judgment 555 Kohlberg’s Theory of Moral Judgment 558




Prosocial Moral Judgment 562 Domains of Social Judgment 563 Review 566

The Early Development of Conscience . . . . . . . . . . . . . . . . . . . 566 Factors Affecting the Development of Conscience 567 Review 568

Prosocial Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 568 The Development of Prosocial Behavior 569 The Origins of Individual Differences in Prosocial Behavior 571

Box 14.1: A Closer look Cultural Contributions to Children’s Prosocial and Antisocial Tendencies 573

Box 14.2: Applications School-Based Interventions for Promoting Prosocial Behavior 576

Review 577

Antisocial Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 577 The Development of Aggression and Other Antisocial Behaviors 577 Consistency of Aggressive and Antisocial Behavior 579

Box 14.3: A Closer look Oppositional Defiant Disorder and Conduct Disorder 580

Characteristics of Aggressive-Antisocial Children and Adolescents 581 The Origins of Aggression 582 Biology and Socialization: Their Joint Influence on Children’s Antisocial Behavior 587

Box 14.4: Applications The Fast Track Intervention 588

Review 589

Chapter 15 Gender Development . . . . . . . . . . . . . . . 593

Theoretical Approaches to Gender Development . . . . . . . . . . . . 595 Biological Influences 596

Box 15.1: A Closer look: Gender Identity: More than Socialization? 598

Cognitive and Motivational Influences 599 Box 15.2: A Closer look Gender Typing at Home 604

Box 15.3: Applications Where Are SpongeSally SquarePants and Curious Jane? 605

Cultural Influences 606 Review 607

Milestones in Gender Development . . . . . . . . . . . . . . . . . . . . 607 Infancy and Toddlerhood 608 Preschool Years 608 Middle Childhood 610 Adolescence 612

Box 15.4: A Closer look Gender Flexibility and Asymmetry 613

Review 614




Comparing Girls and Boys . . . . . . . . . . . . . . . . . . . . . . . . . . 614 Physical Growth: Prenatal Development Through Adolescence 617 Cognitive Abilities and Academic Achievement 619 Personality Traits 625 Interpersonal Goals and Communication 626

Box 15.5: A Closer look Gender and Children’s Communication Styles 627

Aggressive Behavior 628 Box 15.6: Applications Sexual Harassment and Dating Violence 631

Review 633

Chapter 16 Conclusions . . . . . . . . . . . . . . . . . . . . . . . 637

Theme 1: Nature and Nurture: All Interactions, All the Time . . . . . . . 638 Nature and Nurture Begin Interacting Before Birth 638 Infants’ Nature Elicits Nurture 639 Timing Matters 639 Nature Does Not Reveal Itself All at Once 640 Everything Influences Everything 641

Theme 2: Children Play Active Roles in Their Own Development . . . . 641 Self-Initiated Activity 642 Active Interpretation of Experience 643 Self-Regulation 643 Eliciting Reactions from Other People 644

Theme 3: Development Is Both Continuous and Discontinuous . . . . . 645 Continuity/Discontinuity of Individual Differences 645 Continuity/Discontinuity of Overall Development: The Question of Stages 646

Theme 4: Mechanisms of Developmental Change . . . . . . . . . . . . 648 Biological Change Mechanisms 648 Behavioral Change Mechanisms 649 Cognitive Change Mechanisms 651 Change Mechanisms Work Together 653

Theme 5: The Sociocultural Context Shapes Development . . . . . . . 653 Growing Up in Societies with Different Practices and Values 653 Growing Up in Different Times and Places 655 Growing Up in Different Circumstances Within a Society 655

Theme 6: Individual Differences . . . . . . . . . . . . . . . . . . . . . . . 656 Breadth of Individual Differences at a Given Time 657 Stability Over Time 658 Predicting Future Individual Differences on Other Dimensions 658 Determinants of Individual Differences 659

Theme 7: Child-Development Research Can Improve Children’s Lives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 660




Implications for Parenting 660 Implications for Education 662 Implications for Helping Children at Risk 662 Improving Social Policy 664

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G-1

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . R-1

Name Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . NI-1

Subject Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SI-1




This is an exciting time in the field of child development. The past decade has brought new theories, new ways of thinking, new areas of research, and innumera- ble new findings to the field. We originally wrote How Children Develop to describe this ever-improving body of knowledge of children and their development and to convey our excitement about the progress that is being made in understanding the developmental process. We are pleased to continue this endeavor with the publica- tion of the fourth edition of How Children Develop.

As teachers of child development courses, we appreciate the challenge that in- structors face in trying to present these advances and discoveries—as well as the major older ideas and findings—in a one-semester course. Therefore, rather than aim at encyclopedic coverage, we have focused on identifying the most important developmental phenomena and describing them in sufficient depth to make them meaningful and memorable to students. In short, our goal has been to write a text- book that makes the child development course coherent and enjoyable for students and teachers alike.

Classic Themes The basic premise of the book is that all areas of child development are unified by a small set of enduring themes. These themes can be stated in the form of questions that child development research tries to answer:

1. How do nature and nurture together shape development?

2. How do children shape their own development?

3. In what ways is development continuous and in what ways is it discontinuous?

4. How does change occur?

5. How does the sociocultural context influence development?

6. How do children become so different from one another?

7. How can research promote children’s well-being?

These seven themes provide the core structure of the book. They are introduced and illustrated in Chapter 1, highlighted repeatedly, where relevant, in the subse- quent fourteen content chapters, and utilized in the final chapter as a framework for integrating findings relevant to each theme from all areas of development. The continuing coverage of these themes allows us to tell a story that has a beginning (the introduction of the themes), a middle (discussion of specific findings relevant to them), and an ending (the overview of what students have learned about the themes). We believe that this thematic emphasis and structure will not only help students to understand enduring questions about child development but will also leave them with a greater sense of satisfaction and completion at the end of the course.





Contemporary Perspective The goal of providing a thoroughly contemporary perspective on how children develop has influenced the organization of our book as well as its contents. Whole new areas and perspectives have emerged that barely existed when most of today’s child development textbooks were originally written. The organization of How Children Develop is designed to present these new topics and approaches in the context of the field as it currently stands, rather than trying to shoehorn them into organizations that once fit the field but no longer do.

Consider the case of Piaget’s theory and current research relevant to it. Piaget’s theory often is presented in its own chapter, most of which describes the theory in full detail and the rest of which offers contemporary research that demonstrates problems with the theory. This approach often leaves students wondering why so much time was spent on Piaget’s theory if modern research shows it to be wrong in so many ways.

The fact is that the line of research that began over 40 years ago as an effort to challenge Piaget’s theory has emerged since then as a vital area in its own right— the area of conceptual development. Research in conceptual development provides extensive information on such fascinating topics as children’s understanding of human beings, plants and animals, and the physical universe. As with other re- search areas, most studies in this field are aimed primarily at uncovering evidence relevant to current claims, not those of Piaget.

We adapted to this changing intellectual landscape in two ways. First, our chap- ter “Theories of Cognitive Development” (Chapter 4) describes the fundamental aspects of Piaget’s theory in depth and honors his legacy by focusing on the aspects of his work that have proven to be the most enduring. Second, a first-of-its-kind chapter called “Conceptual Development” (Chapter 7) addresses the types of issues that inspired Piaget’s theory but concentrates on modern perspectives and findings regarding those issues. This approach allows us to tell students about the numerous intriguing proposals and observations that are being made in this field, without the artificiality of classifying the findings as “pro-Piagetian” or “anti-Piagetian.”

The opportunity to create a textbook based on current understanding also led us to assign prominent positions to such rapidly emerging areas as epigenetics, behavioral genetics, brain development, prenatal learning, infant cognition, acquisi- tion of academic skills, emotional development, prosocial behavior, and friendship patterns. All these areas have seen major breakthroughs in recent years, and their growing prominence has led to even greater emphasis on them in this edition.

Getting Right to the Point Our desire to offer a contemporary, streamlined approach led to other departures from the traditional organization. It is our experience that today’s students take child development courses for a variety of practical reasons and are eager to learn about children. Traditionally, however, they have had to wait two or three or even four chapters—on the history of the field, on major theories, on research methods, on genetics—before actually getting to the study of children. We wanted to build on their initial motivation from the start.

Rather than beginning the book, then, with an extensive examination of the his- tory of the field, we include in Chapter 1 a brief overview of the social and intel- lectual context in which the scientific study of children arose and provide historical




background wherever it is pertinent in subsequent chapters. Rather than have an early “blockbuster” theories chapter that covers all the major cognitive and social theories at once (at a point far removed from the content chapters to which the theories apply), we present a chapter on cognitive developmental theories just before the chapters that focus on specific aspects of cognitive development, and we simi- larly present a chapter on social developmental theories just before the chapters that focus on specific aspects of social development. Rather than have a separate chapter on genetics, we include basic aspects of genetics as part of Chapter 3, “Biology and Behavior,” and then discuss the contributions of genetics to some of the differences among individuals throughout the book. When we originally chose this organization, we hoped that it would allow us, from the first weeks of the course, to kindle students’ enthusiasm for finding out how children develop. Judging by the overwhelmingly positive response we have received from students and instructors alike, it has.

Features The most important feature of this book is the exposition, which we have tried to make as clear, compelling, and interesting as possible. As in previous editions, we have given extra attention to making it accessible to a broad range of students.

To further enhance the appeal and accessibility of the text, we have re- tained three types of discussion boxes that explore topics of special interest. “Applications” boxes focus on how child development research can be used to promote children’s well-being. Among the applications that are summed up in these boxes are board-game procedures for improving preschoolers’ understand- ing of numbers; the Carolina Abecedarian Project; interventions to reduce child abuse; programs, such as PATHS, for helping rejected children gain acceptance from their peers; and Fast Track interventions, which help aggressive children learn how to manage their anger and antisocial behavior. “Individual Differences” boxes focus on populations that differ from the norm with regard to the specific topic under consideration, or on variations among children in the general popu- lation. Some of these boxes highlight developmental problems such as autism, ADHD, dyslexia, specific language impairment, and conduct disorder, while oth- ers focus on differences in the development of children that center on attachment status, gender, and cultural differences. “A Closer Look” boxes examine important and interesting research in greater depth than would otherwise be possible: the areas examined range from brain imaging techniques to discrepant gender iden- tity to the developmental impact of homelessness.

We have also retained a number of other features intended to improve students’ learning. These features include boldfacing key terms and supplying definitions both within the immediate text and in marginal glossaries; providing summaries at the end of each major section, as well as summaries for the overall chapter; and, at the end of each chapter, posing critical thinking questions intended to promote deeper consideration of essential topics.

New to the Fourth Edition We have expanded our coverage of a number of research areas that have become increasingly important in recent years for both the students of child development and the instructors who teach it. In the following paragraphs, we outline some of




the highlights of the fourth edition. Thank you for taking the time to look through this new edition of How Children Develop. We hope that you find it to be useful and appealing.

New and Expanded Coverage In selecting what to cover from among the many new discoveries about child de- velopment, we have emphasized the studies that strike us as the most interesting and important. While retaining and thoroughly updating its essential coverage, the fourth edition of How Children Develop continues to explore a number of fascinat- ing areas in which there has been great progress in the past few years. Following is a very brief sampling of the many areas of new and expanded coverage: n Epigenetics n Gene–environment relations, including methylation n The role of specific gene variants in certain behaviors n Differential susceptibility to the environment n Brain development and functioning n Mechanisms of infants’ learning n Infants’ understanding of other people n Executive functioning n Cultural influences on development n Relations among understanding of time, space, and number n Mathematics anxiety n Applications of research to education n The growing role and impact of social media in children’s and adolescents’ lives n Interventions to foster children’s social adjustment

Supplements How Children Develop, Fourth Edition, features a wide array of multimedia tools designed for the individual needs of students and teachers. For more information about any of the items below, visit Worth Publishers’ online catalog at www. worth

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LaunchPad combines Worth Publishers’ awarding-winning media with an in- novative platform for easy navigation. For students, it is the ultimate online study guide with rich interactive tutorials, videos, e-Book, and the LearningCurve adaptive quizzing system. For instructors, LaunchPad is a full course space where class documents can be posted, quizzes are easily assigned and graded, and students’ progress can be assessed and recorded. Whether you are looking for the most effec- tive study tools or a robust platform for an online course, LaunchPad is a powerful way to enhance your class.




LaunchPad for How Children Develop, Fourth Edition, can be previewed and purchased at http:// www How Children Develop, Fourth Edition, and LaunchPad can be ordered together with ISBN 10: 1-4641-8284-1 / ISBN-13: 978-1-4641-8284-6.

LaunchPad for How Children Develop, Fourth Edition, includes the following resources: n The LearningCurve quizzing system was designed

based on the latest findings from learning and memory research. It combines adaptive question selection, immediate and valuable feedback, and a game-like interface to engage students in a learning experience that is unique to them. Each LearningCurve quiz is fully integrated with other resources in LaunchPad through the Personalized Study Plan, so students will be able to review with Worth’s extensive library of videos and activities. And state-of-the-art question analysis reports allow instructors to track the progress of individual students as well as their class as a whole.

n An interactive e-Book allows students to highlight, bookmark, and make their own notes, just as they would with a printed textbook. Digital enhancements include full-text search and in-text glossary definitions.

n Student Video Activities include more than 100 engaging video modules that instructors can easily assign for student assessment. Videos cover classic experiments, current news footage, and cutting-edge research, all of

which are sure to spark discussion and encourage critical thinking. n The Scientific American Newsfeed delivers weekly articles, podcasts, and news

briefs on the very latest developments in psychology from the first name in popular science journalism.

Additional Student Supplements CourseSmart e-Book The CourseSmart e-Book offers the complete text of How Children Develop, Fourth Edition, in an easy-to-use, flexible format. Students can choose to view the CourseSmart e-Book online or download it to a personal computer or a por- table media player, such as a smart phone or iPad. The CourseSmart e-Book for How Children Develop, Fourth Edition, can be previewed and purchased at www

Scientific American Reader to Accompany How Children Develop The authors have compiled fifteen Scientif ic American articles relevant to key top- ics in the text. The selections range from classics such as Harry Harlow’s “Love in Infant Monkeys” and Eleanor Gibson and Richard Walk’s “The ‘Visual Cliff ’” to




contemporary articles on such topics as the interaction of games and environment in the development of intelligence (Robert Plomin and John DeFries), the effects of child abuse on the developing brain (Martin Teicher), balancing work and family (Robert Pleck), and moral development (William Damon). These articles should enrich students’ learning and help them to appreciate the process by which devel- opmental scientists gain new understanding. This premium item can be packaged with the text at no additional cost.

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Presentation and Faculty Support Presentation Slides Presentation slides are available in three formats that can be used as they are or can be customized. One set includes all the textbook’s illustrations and tables. The second set consists of lecture slides that focus on key themes and terms in the book and include text illustrations and tables. A third set of PowerPoint slides provides an easy way to integrate the supplementary video clips into classroom lectures. All these prebuilt PowerPoint presentations are available through http://www.worth

Presentation Videos Worth’s video clips for development psychology span the full range of topics for the child development course. With hundreds of clips to choose from, this pre- mium collection includes research and news footage on topics ranging from pre- natal development to the experience of child soldiers to empathy in adolescence. These clips are made available to instructors for lecturing in the classroom and also through LaunchPad.

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Test Bank on CD-ROM The Diploma Test Bank CD-ROM, on a dual platform for Windows and Macintosh, guides instructors through the process of creating a test and allows them to add, edit, and scramble questions; to change formats; and to include pictures, equa- tions, and media links. The CD-ROM is also the access point for Diploma Online Testing, which allows creating and administering examinations on paper, over a network, or over the Internet.

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Acknowledgments So many people have contributed (directly and indirectly) to this textbook that it is impossible to know where to start or where to stop in thanking them. All of us have been given exceptional support by our spouses and significant oth-




ers—Jerry Clore, Jerry Harris, Xiaodong Lin, and Seth Pollak—and by our chil- dren—Benjamin Clore; Michael Harris; Todd, Beth, and Aaron Siegler; Avianna McGhee; and Eli and Nell Pollak—as well as by our parents, relatives, friends, and other loved ones. Our advisors in college and graduate school, Richard Aslin, Ann Brown, Les Cohen, Harry Hake, Robert Liebert, Jim Morgan, Paul Mussen, Ellisa Newport, and Jim Pate, helped to launch our careers and taught us how to recog- nize and appreciate good research. We also have all benefited from collaborators who shared our quest for understanding child development and from a great many exceptionally helpful and generous colleagues, including Karen Adolph, Martha Alibali, Renee Baillargeon, Sharon Carver, Zhe Chen, Richard Fabes, Cindy Fisher, Melanie Jones, David Klahr, Patrick Lemaire, Angeline Lillard, John Opfer, Kristin Shutts, Tracy Spinrad, David Uttal, and Carlos Valiente. We owe special thanks to our assistants, Sheri Towe and Theresa Treasure, who helped in innumerable ways in preparing the book.

We would also like to thank the many reviewers who contributed to this and previous editions: Daisuke Akiba, Queens College, City University of New York; Kimberly Alkins, Queens College, City University of New York; Lynne Baker- Ward, North Carolina State University; Hilary Barth, Wesleyan University; Christopher Beevers, Texas University; Martha Bell, Virginia Tech; Cynthia Berg, University of Utah; Rebecca Bigler, Texas University; Margaret Borkowski, Saginaw Valley State University; Eric Buhs, University of Nebraska–Lincoln; G. Leonard Burns, Washington State University; Wendy Carlson, Shenandoah University; Kristi Cordell-McNulty, Angelo State University; Myra Cox, Harold Washington College; Emily Davidson, Texas A&M University–Main Campus; Ed de St. Aubin, Marquette University; Marissa Diener, University of Utah; Sharon Eaves, Shawnee State University; Urminda Firlan, Grand Rapids Community College; Dorothy Fragaszy, University of Georgia; Jeffery Gagne, University of Texas–Austin; Jennifer Ganger, University of Pittsburgh; Alice Ganzel, Cornell College; Janet Gebelt, Westfield State University; Melissa Ghera, St. John Fisher College; Susan Graham, University of Calgary; Andrea Greenhoot, University of Kansas; Frederick Grote, Western Washington University; John Gruszkos, Reynolds University; Hanna Gustafsson, University of North Carolina; Alma Guyse, Midland College; Lauren Harris, Michigan State University; Karen Hartlep, California State University–Bakersfield; Patricia Hawley, University of Kansas–Main; Susan Hespos, Northwestern University; Doris Hiatt, Monmouth University; Susan Holt, Central Connecticut State University; Lisa Huffman, Ball State University; Kathryn Kipp, University of Georgia; Rosemary Krawczyk, Minnesota State University; Raymond Krukovsky, Union County College; Tara Kuther, Western Connecticut State University; Richard Lanthier, George Washington University; Elida Laski, Boston College; Kathryn Lemery, Arizona State University; Barbara Licht, Florida State University; Angeline Lillard, University of Virginia; Wayne McMillin, Northwestern State University; Martha Mendez-Baldwin, Manhattan College; Scott Miller, University of Florida; Keith Nelson, Pennsylvania State University–Main Campus; Paul Nicodemus, Austin Peay State University; Katherine O’Doherty, Vanderbilt University; John Opfer, The Ohio State University; Ann Repp, Texas University; Leigh Shaw, Weber State University; Jennifer Simonds, Westminster College; Rebekah Smith, University of Texas–San Antonio; Mark Strauss, University of Pittsburgh–Main; Spencer Thompson, University of Texas–Permian Basin; Lisa Travis, University of Illinois Urbana–Champaign; Roger Webb, University of Arkansas–Little Rock; Keri Weed, University of South Carolina–Aiken; Sherri Widen, Boston College.




We would especially like to thank Campbell Leaper, University of California– Santa Cruz, for his major contributions to the revision of our chapter on gender development (Chapter 15). We are indebted to Campbell for bringing to the fourth edition his expertise and keen insight in this important area.

Thanks are particularly due to our friends and collaborators at Worth Publishers. As acquisitions editor and publisher, respectively, Daniel DeBonis and Kevin Feyen provided exceptional support and any number of excellent suggestions. We would also like to thank Marge Byers, who nurtured our first edition from its incep- tion and helped us to realize our vision. Peter Deane, our development editor, is in a class by himself in both skill and dedication. Peter’s creative thinking and firm understanding of the field enhanced the content of the book in innumerable ways. We are deeply grateful to him. Our thanks go also to assistant editor Nadina Persaud, senior project editor Vivien Weiss, director of development (print and digital) Tracey Kuehn, art director Barbara Reingold, cover and text designer Kevin Kall, photo editor Bianca Moscatelli, photo researcher Elyse Rieder, production manager Sarah Segal, and compositor Northeastern Graphic for their excellent work. They have helped to create a book that we hope you will find a pleasure to look at as well as to read. Marketing manager Katherine Nurre provided outstand- ing promotional materials to inform professors about the book. Anthony Casciano and Stacey Alexander managed the superb package of ancillary material.

Finally, we want to thank our “book team” of sales representatives and man- agers. Tom Kling, Julie Hirshman, Kari Ewalt, Greg David, Tom Scotty, Cindy Rabinowitz, Glenn Russell, and Matt Dunning provided a sales perspective, valu- able suggestions, and unflagging enthusiasm throughout this project.



develop How Children









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DOROTHEA SHARP (1874-1955), Young Explorers (oil on canvas)




An Introduction to Child Development n Reasons to Learn About Child Development

Raising Children Choosing Social Policies Understanding Human Nature Review

n Historical Foundations of the Study of Child Development Early Philosophers’ Views of Children’s Development Social Reform Movements Darwin’s Theory of Evolution The Beginnings of Research-Based Theories of Child Development Review

n Enduring Themes in Child Development 1. Nature and Nurture: How Do Nature and Nurture Together Shape Development? 2. The Active Child: How Do Children Shape Their Own Development?

3. Continuity/Discontinuity: In What Ways Is Development Continuous, and in What Ways Is It Discontinuous? 4. Mechanisms of Development: How Does Change Occur? 5. The Sociocultural Context: How Does the Sociocultural Context Influence Development? 6. Individual Differences: How Do Children Become So Different from One Another? 7. Research and Children’s Welfare: How Can Research Promote Children’s Well-Being? Review

n Methods for Studying Child Development The Scientific Method Contexts for Gathering Data About Children Correlation and Causation Designs for Examining Development Ethical Issues in Child-Development Research Review

n Chapter Summary

chapter 1:




In 1955, a group of child-development researchers began a unique study. Their goal, like that of many developmental researchers, was to find out how bio-logical and environmental factors influence children’s intellectual, social, and emotional growth. What made their study unique was that they examined these diverse aspects of development for all 698 children born that year on the Hawaiian island of Kauai and continued studying the children’s development for more than 30 years.

With the parents’ consent, the research team, headed by Emmy Werner, col- lected many types of data about the children. To learn about possible complica- tions during the prenatal period and birth, they examined physicians’ records. To learn about family interactions and the children’s behavior at home, they arranged for nurses and social workers to observe the families and to interview the children’s mothers when the children were 1 year old and again when they were 10 years old. The researchers also interviewed teachers about the children’s academic perfor- mance and classroom behavior during the elementary school years and examined police, family court, and social service records that involved the children, either as victims or perpetrators. Finally, the researchers administered standardized intelli- gence and personality tests to the participants when they were 10 and 18 years old and interviewed them at age 18 and again in their early 30s to find out how they saw their own development.

Results from this study illustrated some of the many ways in which biological and environmental factors combine to produce child development. For example, children who experienced prenatal or birth complications were more likely than others to develop physical handicaps, mental illness, and learning difficulties. But whether they developed such problems—and if so, to what degree—depended a great deal on their home environment. Parents’ income, education, and mental health, together with the quality of the relationship between the parents, especially influenced children’s development. By age 2, toddlers who had experienced severe prenatal or birth problems but who lived in harmonious middle-income families were nearly as advanced in language and motor skills as were children who had not experienced such problems. By the time the children were 10-year-olds, prenatal and birth problems were consistently related to psychological difficulties only if the children also grew up in poor rearing conditions.

What of children who faced both biological and environmental challenges— prenatal or birth complications and adverse family circumstances? The majority of these children developed serious learning or behavior problems by age 10. By age 18, most had acquired a police record, had experienced mental health problems, or had become an unmarried parent. However, one-third of such at-risk children showed impressive resilience, growing up into young adults who, in the words of Werner (1989, p. 108D), “loved well, worked well, and played well.”

Michael was one such resilient child. Born prematurely, with low birth weight, to teenage parents, he spent the first 3 weeks of his life in a hospital, separated from his mother. By his 8th birthday, Michael’s parents were divorced, his mother had deserted the family, and he and his three brothers and sisters were being raised by their father, with the help of their elderly grandparents. Yet by age 18, Michael was successful in school, had high self-esteem, was popular with his peers, and was a caring young man with a positive attitude toward life. The fact that there are many children like Michael—children who show great resilience in the face of adversity—is among the most heartening findings of research on

Themes n Nature and Nurture

n The Active Child

n Continuity/Discontinuity

n Mechanisms of Change

n The Sociocultural Context

n Individual Differences

n Research and Children’s Welfare




child development. Learning about the Michaels of the world inspires child de- velopment researchers to conduct further investigations aimed at answering such questions as why individual children differ so much in their response to similar environments, and how to apply research findings to help more children overcome the challenges they face.

Reading this chapter will increase your understanding of these and other basic questions about child development. It also will introduce you to some historical perspectives on these fundamental questions and to the perspectives and methods that modern researchers use to address them. But first, we would like you to con- sider perhaps the most basic question of all: Why study child development?

Reasons to Learn About Child Development For us, as both parents and researchers, the sheer enjoyment of watching children and trying to understand them is reason enough for studying child development. What could be more fascinating than the development of a child? But there are also practical and intellectual reasons for studying child development. Understand- ing how children develop can improve child-rearing, promote the adoption of wiser social policies regard- ing children’s welfare, and answer intriguing questions about human nature. We examine each of these reasons in the following sections.

Raising Children Being a good parent is not easy. Among its many chal- lenges are the endless questions it raises over the years. Is it okay to take my infant outside in the cold weather? Should my baby stay at home, or would going to day care be better for his social development? If my daughter starts walking and talking early, should I consider plac- ing her in a school for gifted children? Should I try to teach my 3-year-old to read early? My son seems so lonely at preschool; how can I help him make friends? How can I help my kindergartner deal with her anger?

Child-development research can help answer such questions. For example, one problem that confronts almost all parents is how to help their children control their anger and other negative emotions. One tempting, and frequent, reaction is to spank children who express anger in inappropriate ways, such as fighting, name-calling, and talking back. In a study involving a representative U.S. sam- ple, 80% of parents of kindergarten children reported having spanked their child on occasion, and 27% reported having spanked their child the previous week ( Gershoff et al., 2012). In fact, spanking made the problem worse. The more often parents spanked their kindergartners, the more often the same children argued, fought, and acted inappropriately at school when they were 3rd-graders. This relation held true for Blacks, Whites, Hispanics, and Asians alike, and it held true above and beyond the effects of other relevant factors, such as parents’ income and education.

Fortunately, research suggests several effective alternatives to spanking (Denham, 1998, 2006). One is expressing sympathy: when parents respond to their

Will these children be resilient enough to overcome their disadvantaged environment? The answer will depend in large part on how many risk factors they face and on their per- sonal characteristics.







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children’s distress with sympathy, the children are better able to cope with the situation causing the distress. Another ef- fective approach is helping angry children find positive alter- natives to expressing anger. For example, encouraging them to do something they enjoy helps them cope with the hostile feelings.

These strategies and similar ones, such as time-outs, can also be used effectively by others who contribute to raising children, such as day-care personnel and teachers. One dem- onstration of this was provided by a special curriculum that was devised for helping preschoolers (3- and 4-year-olds) who were angry and out of control (Denham & Burton, 1996). With this curriculum, preschool teachers helped children rec- ognize their own and other children’s emotions, taught them techniques for controlling their anger, and guided them in resolving conflicts with other children. One approach that children were taught for coping with anger was the “turtle technique.” When children felt themselves becoming angry, they were to move away from other children and retreat into

their “turtle shell,” where they could think through the situation until they were ready to emerge from the shell. Posters were placed around the classroom to remind children of what to do when they became angry.

The curriculum was quite successful. Children who participated in it became more skillful in recognizing and regulating anger when they experienced it and were generally less negative. For example, one boy, who had regularly gotten into fights when angry, told the teacher after a dispute with another child, “See, I used my words, not my hands” (Denham, 1998, p. 219). The benefits of this program can be long-term. In one test conducted with children in special education classrooms, positive effects were still evident 2 years after children completed the curricu- lum (Greenberg & Kusché, 2006). As this example suggests, knowledge of child- development research can be helpful to everyone involved in the care of children.

Choosing Social Policies Another reason to learn about child development is to be able to make informed de- cisions not just about one’s own children but also about a wide variety of social-policy questions that affect children in general. For example, how much trust should judges and juries place in preschoolers’ testimony in child-abuse cases? Should children who do poorly in school be held back, or should they be promoted to the next grade so that they can be with children of the same age? How effective are health- education courses aimed at reducing teenage smoking, drinking, and pregnancy? Child-development research can inform discussion of all of these policy decisions and many others.

Consider the issue of how much trust to put in preschoolers’ courtroom tes- timony. At present, more than 100,000 children testify in legal cases each year (Bruck, Ceci, & Principe, 2006). Many of these children are very young: more than 40% of children who testify in sexual-abuse trials, for example, are younger than 5 years, and almost 40% of substantiated sexual-abuse cases involve children younger than age 7 (Bruck et al., 2006; Gray, 1993). The stakes are extremely high in such cases. If juries believe children who falsely testify that they were abused, innocent people may spend years in jail. If juries do not believe children who accurately

posters like this are used in the turtle tech- nique to remind children of ways to control anger.




report abuse, the perpetrators will go free and probably abuse other children. So what can be done to promote reliable testimony from young children and to avoid leading them to report experiences that never occurred?

Psychological research has helped answer such questions. In one experiment, re- searchers tested whether biased questioning affects the accuracy of young children’s memory for events involving touching one’s own and other people’s bodies. The re- searchers began by having 3- to 6-year-olds play a game, similar to “Simon Says,” in which the children were told to touch various parts of their body and those of other children. A month later, the researchers had a social worker interview the children about their experiences during the game (Ceci & Bruck, 1998). Before the social worker conducted the interviews, she was given a description of each child’s experiences. Unknown to her, the description included inaccurate as well as accurate information. For example, she might have been told that a particular child had touched her own stomach and another child’s nose, when in fact the child had touched her own stomach and the other child’s foot. After receiving the descrip- tion, the social worker was given instructions much like those in a court case: “Find out what the child remembers.”

As it turned out, the version of events that the social worker had heard often in- fluenced her questions. If, for example, a child’s account of an event was contrary to what the social worker believed to be the case, she tended to question the child repeatedly about the event (“Are you sure you touched his foot? Is it possible you touched some other part of his body?”). Faced with such repeated questioning, children fairly often changed their responses, with 34% of 3- and 4-year-olds eventually corroborating at least one of the social worker’s incorrect beliefs. Children were led to “remember” not only plau- sible events that never happened but also unlikely ones that the social worker had been told about. For example, some children “recalled” their knee being licked and a marble being inserted in their ear.

Studies such as this have yielded a number of con- clusions regarding children’s testimony in legal pro- ceedings. One important finding is that when 3- to 5-year-olds are not asked leading questions, their testi- mony is usually accurate, as far as it goes (Bruck et al., 2006; Howe & Courage, 1997). However, when prompted by leading questions, young children’s testimony is often inaccurate, especially when the leading ques- tions are asked repeatedly. The younger children are, the more susceptible they are to being led, and the more their recall reflects the biases of the interviewer’s ques- tions. In addition, realistic props, such as anatomically correct dolls and drawings, that are often used in judicial cases in the hopes of improving recall of sexual abuse, do not improve recall of events that occurred; they actually increase the number of inaccurate claims, perhaps by blurring the line between fantasy play and reality (Lamb et al., 2008; Poole, Bruck, & Pipe, 2011). Research on child eyewitness tes- timony has had a large practical impact, leading many judicial and police agencies to revise their procedures for interviewing child witnesses to incorporate the les- sons of this research (e.g., State of Michigan, Governor’s Task Force, 2005). In ad- dition to helping courts obtain more accurate testimony from young children, such research-based conclusions illustrate how, at a broader level, knowledge of child development can inform social policies.

In courtrooms such as this one, asking ques- tions that will help children to testify accu- rately is of the utmost importance.

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Understanding Human Nature A third reason to study child development is to better understand human nature. Many of the most intriguing questions regarding human nature concern children. For example, does learning start only after children are born, or can it occur in the womb? Can later upbringing in a loving home overcome the detrimental effects of early rearing in a loveless institutional setting? Do children vary in personality and intellect from the day they are born, or are they similar at birth, with differences arising only because they have different experiences? Until recently, people could only speculate about the answers to such questions. Now, however, developmental

scientists have methods that enable them to observe, describe, and explain the process of development.

A particularly poignant illustration of the way in which scien- tific research can increase understanding of human nature comes from studies of how children’s ability to overcome the effects of early maltreatment is affected by its timing, that is, the age at which the maltreatment occurs. One such research program has examined children whose early life was spent in horribly inadequate orphan- ages in Romania in the late 1980s and early 1990s (McCall et al., 2011; Nelson et al., 2007; Rutter et al., 2004). Children in these orphanages had almost no contact with any caregiver. For reasons that remain unknown, the brutal Communist dictatorship of that era instructed staff workers not to interact with the children, even when giving them their bottles. Staff members provided the infants with so little physical contact that the crown of many infants’ heads became flattened from the babies’ lying on their backs for 18 to 20 hours per day.

Shortly after the collapse of Communist rule in Romania, a number of these children were adopted by families in Great Britain. When these children arrived in Britain, most were severely malnourished, with more than half being in the low- est 3% of children their age in terms of height, weight, and head circumference. Most also showed varying degrees of mental retardation and were socially imma- ture. The parents who adopted them knew of their deprived backgrounds and were highly motivated to provide loving homes that would help the children overcome the damaging effects of their early mistreatment.

To evaluate the long-term effects of their early deprivation, the physical, intel- lectual, and social development of about 150 of the Romanian-born children was examined at age 6 years. To provide a basis of comparison, the researchers also fol- lowed the development of a group of British-born children who had been adopted into British families before they were 6 months of age. Simply put, the question was whether human nature is sufficiently flexible that the Romanian-born children could overcome the extreme deprivation of their early experience, and if so, would that flexibility decrease with the children’s age and the length of the deprivation.

By age 6, the physical development of the Romanian-born children had im- proved considerably, both in absolute terms and in relation to the British-born comparison group. However, the Romanian children’s early experience of depriva- tion continued to influence their development, with the extent of negative effects depending on how long the children had been institutionalized. Romanian-born children who were adopted by British families before age 6 months, and who had therefore spent the smallest portion of their early lives in the orphanages, weighed about the same as British-born children when both were 6-year-olds. Romanian- born children adopted between the ages of 6 and 24 months, and who therefore had

This infant is one of the children adopted from a romanian orphanage in the 1990s. how successfully he develops will depend not only on the quality of caregiving he receives in his adoptive home but also on the amount of time he spent in the orphanage and the age at which he was adopted.





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spent more of their early lives in the orphanages, weighed less; and those adopted between the ages of 24 and 42 months weighed even less (Rutter et al., 2004).

Intellectual development at age 6 years showed a similar pattern. The Romanian- born children who had been adopted before age 6 months demonstrated levels of in- tellectual competence comparable with those of the British-born group. Those who had been adopted between ages 6 and 24 months did somewhat less well, and those adopted between ages 24 and 42 months did even more poorly (Rutter et al., 2004). The intellectual deficits of the Romanian children adopted after age 6 months were just as great when the children were retested at age 11, indicating that the negative effects of the early deprivation persisted over time (Beckett et al., 2006; Kreppner et al., 2007).

The early experience in the orphanages had similar damaging effects on the children’s social development (Kreppner et al., 2007; O’Connor, Rutter, & English and Romanian Adoptees Study Team, 2000). Almost 20% of the Romanian-born children who were adopted after age 6 months showed extremely abnormal social behavior at age 6 years, not looking at their parents in anxiety-provoking situations and willingly going off with strangers (versus 3% of the British-born comparison group who did so). This atypical social development was accompanied by abnormal brain activity. Brain scans obtained when the children were 8 years old showed that those adopted after living for a substantial period in the orphanages had unusu- ally low levels of neural activity in the amygdala, a brain area involved in emotional reactions (Chugani et al., 2001). Subsequent studies have identified similar brain abnormalities among children who spent their early lives in poor-quality orphan- ages in Russia and East Asia as well (Nelson et al., 2011; Tottenham et al., 2010).

These findings reflect a basic principle of child development that is relevant to many aspects of human nature: The timing of experiences influences their effects. In the present case, children were sufficiently flexible to overcome the effects of living in the loveless, unstimulating institutions if the deprivation ended relatively early; living in the institutions until older ages, however, had effects that were rarely overcome, even when children spent subsequent years in loving and stimulating environments. The adoptive families clearly made a huge positive difference in their children’s lives, but the later the age of adoption, the greater the long-term effects of early deprivation.

review: There are at least three good reasons to learn about child development: to improve one’s own child-rearing, to help society promote the well-being of children in general, and to better un- derstand human nature.

Historical Foundations of the Study of Child Development From ancient Greece to the early years of the twentieth century, a number of pro- found thinkers observed and wrote about children. Their goals were like those of contemporary researchers: to help people become better parents, to improve children’s well-being, and to understand human nature. Unlike contemporary researchers, they usually based their conclusions on general philosophical beliefs and informal observations of a few children. Still, the issues they raised are suf- ficiently important, and their insights sufficiently deep, that their views continue to be of interest.




Early Philosophers’ Views of Children’s Development Some of the earliest recorded ideas about children’s development were those of Plato and Aristotle. These classic Greek philosophers, who lived in the fourth cen- tury b.c.e., were particularly interested in how children’s development is influenced by their nature and by the nurture they receive.

Both Plato and Aristotle believed that the long-term welfare of society de- pended on the proper raising of children. Careful upbringing was essential because children’s basic nature would otherwise lead to their becoming rebellious and un- ruly. Plato viewed the rearing of boys as a particularly demanding challenge for parents and teachers:

Now of all wild things, a boy is the most difficult to handle. Just because he more than any other has a fount of intelligence in him which has not yet “run clear,” he is the craftiest, most mischievous, and unruliest of brutes.

(Laws, bk. 7, p. 808)

Consistent with this view, Plato emphasized self-control and discipline as the most important goals of education (Borstelmann, 1983).

Aristotle agreed with Plato that discipline was necessary, but he was more concerned with fitting child-rearing to the needs of the individual child. In his words:

It would seem . . . that a study of individual character is the best way of making edu- cation perfect, for then each [child] has a better chance of receiving the treatment that suits him.

(Nicomachean Ethics, bk. 10, chap. 9, p. 1180)

Plato and Aristotle differed more profoundly in their views of how children acquire knowledge. Plato believed that children have innate knowledge. For example, he believed that children are born with a concept of “animal” that, from birth onward, automatically allows them to recognize that the dogs, cats, and other creatures they encounter are animals. In contrast, Aristotle believed that all knowledge comes from experience and that the mind of an infant is like a blackboard on which noth- ing has yet been written.

Roughly 2000 years later, the English philosopher John Locke (1632–1704) and the French philosopher Jean-Jacques Rousseau (1712–1778) refocused attention on the question of how parents and society in general can best promote children’s development. Locke, like Aristotle, viewed the child as a tabula rasa, or blank slate, whose development largely reflects the nurture provided by the child’s parents and the broader society. He believed that the most important goal of child-rearing is the growth of character. To build children’s character, parents need to set good ex- amples of honesty, stability, and gentleness. They also need to avoid indulging the child, especially early in life. However, once discipline and reason have been in- stilled, Locke believed,

authority should be relaxed as fast as their age, discretion, and good behavior could allow it. . . . The sooner you treat him as a man, the sooner he will begin to be one.

(Cited in Borstelmann, 1983, p. 20)

In contrast to Locke’s advocating discipline before freedom, Rousseau believed that parents and society should give children maximum freedom from the begin- ning. Rousseau claimed that children learn primarily from their own spontaneous interactions with objects and other people, rather than through instruction by par- ents or teachers. He even argued that children should not receive any formal edu- cation until about age 12, when they reach “the age of reason” and can judge for




themselves the worth of what they are told. Before then, they should be allowed the freedom to explore whatever interests them.

Although formulated long ago, these and other philosophical positions continue to underlie many contemporary debates, including whether children should receive direct instruction in desired skills and knowledge or be given maximum freedom to discover the skills and knowledge for themselves, and whether parents should build their children’s character through explicit instruction or through the implicit guidance provided by the parents’ own behavior.

Social Reform Movements Another precursor of the contemporary field of child psychology was early social reform movements that were devoted to improving children’s lives by changing the conditions in which they lived. During the Industrial Revolution of the eighteenth and nineteenth centuries, a great many children in Europe and the United States worked as poorly paid laborers with no legal protections. Some were as young as 5 and 6 years; many worked up to 12 hours a day in factories or mines, often in ex- tremely hazardous circumstances. These harsh conditions worried a number of so- cial reformers, who began to study how such circumstances affected the children’s development. For example, in a speech before the British House of Commons in 1843, the Earl of Shaftesbury noted that the narrow tunnels where children dug out coal had

very insufficient drainage [and] are so low that only little boys can work in them, which they do naked, and often in mud and water, dragging sledge-tubs by the girdle and chain. . . . Children of amiable temper and conduct, at 7 years of age, often return next season from the collieries greatly corrupted . . . with most hellish dispositions.

(Quoted in Kessen, 1965, pp. 46–50)

The Earl of Shaftesbury’s effort at social reform brought partial success—a law forbidding employment of girls and of boys younger than 10. In addition to bring- ing about the first child labor laws, this and other early social reform movements established a legacy of research conducted for the benefit of children and provided some of the earliest recorded descriptions of the adverse effects that harsh environments can have on children.

Darwin’s Theory of Evolution Later in the nineteenth century, Charles Darwin’s work on evolution inspired a number of scientists to propose that intensive study of children’s development might lead to important insights into human nature. Darwin himself was in- terested in child development and in 1877 published an article entitled “A Bio- graphical Sketch of an Infant,” which presented his careful observations of the motor, sensory, and emotional growth of his infant son, William. Darwin’s “baby biography”—a systematic description of William’s day-to-day development— represented one of the first methods for studying children.

Such intensive studies of individual children’s growth continue to be a distinc- tive feature of the modern field of child development. Darwin’s evolutionary theory also continues to influence the thinking of modern developmentalists on a wide

During the eighteenth, nineteenth, and early twentieth centuries, many young children worked in coal mines and factories. Their hours were long, and the work was often unhealthy and dangerous. concern over the well-being of such children led to some of the earliest research on child development.

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range of topics: infants’ attachment to their mothers (Bowlby, 1969), innate fear of natural dangers such as spiders and snakes (Rakison & Derringer, 2008), sex differ- ences (Geary, 2009), aggression and altruism (Tooby & Cosmides, 2005), and the mechanisms underlying learning (Siegler, 1996).

The Beginnings of Research-Based Theories of Child Development At the end of the nineteenth century and the beginning of the twentieth, the first theories of child development that incorporated research findings were formulated. One prominent theory, that of the Austrian psychiatrist Sigmund Freud, was based in large part on his patients’ recollections of their dreams and childhood experi- ences. Freud’s psychoanalytic theory proposed that biological drives, especially sexual ones, are a crucial influence on development.

Another prominent theory of the same era, that of American psychologist John Watson, was based primarily on the results of experiments that examined learning in animals and children. Watson’s behaviorist theory argued that children’s develop- ment is determined by environmental factors, especially the rewards and punish- ments that follow the children’s actions.

By current standards, the research methods on which these theories were based were crude. Nonetheless, these early scientific theories were better grounded in re- search evidence than were their predecessors, and, as you will see later in the chap- ter, they inspired more sophisticated ideas about the processes of development and more rigorous research methods for studying how development occurs.

review: Philosophers such as Plato, Aristotle, Locke, and Rousseau, as well as early scientific theorists such as Darwin, Freud, and Watson, raised many of the deepest issues about child develop- ment. These issues included how nature and nurture influence development, how best to raise children, and how knowledge of children’s development can be used to advance their welfare.

Enduring Themes in Child Development The modern study of child development begins with a set of fundamental ques- tions. Everything else—theories, concepts, research methods, data, and so on—is part of the effort to answer these questions. Although experts in the field might choose different particular questions as the most important, there is widespread agreement that the seven questions in Table 1.1 are among the most important. These questions form a set of themes that we will highlight throughout the book as we examine specific aspects of child development. In this section, we introduce and briefly discuss each question and the theme that corresponds to it.

1 Nature and Nurture: How Do Nature and Nurture Together Shape Development? The most basic question about child development is how nature and nurture in- teract to shape the developmental process. Nature refers to our biological endow- ment, in particular, the genes we receive from our parents. This genetic inheritance


Basic Questions about child Development

1. How do nature and nurture together shape development? (Nature and nurture)

2. How do children shape their own development? (The active child)

3. In what ways is development continuous, and in what ways is it discontinuous? (Continuity/discontinuity)

4. How does change occur? (Mechanisms of development)

5. How does the sociocultural context influence development? (The sociocultural context)

6. How do children become so different from one another? (Individual differences)

7. How can research promote children’s well-being? (Research and children’s welfare)

nature n our biological endowment; the genes we receive from our parents




influences every aspect of our make-up, from broad characteristics such as physical appearance, personality, intellect, and mental health to specific preferences, such as political attitudes and propensity for thrill-seeking (Plomin, 2004; Rothbart & Bates, 2006). Nurture refers to the wide range of environments, both physical and social, that influence our development, including the womb in which we spend the prenatal period, the homes in which we grow up, the schools that we attend, the broader communities in which we live, and the many people with whom we interact.

Popular depictions often present the nature–nurture question as an either/or proposition: “What determines how a person develops, heredity or environment?” However, this either/or phrasing is deeply misleading. All human characteristics— our intellect, our personality, our physical appearance, our emotions—are created through the joint workings of nature and nurture, that is, through the constant interaction of our genes and our environment. Accordingly, rather than asking whether nature or nurture is more important, developmentalists ask how nature and nurture work together to shape development.

That this is the right question to ask is vividly illustrated by findings on the development of schizophrenia. Schizophrenia is a serious mental illness, often characterized by hallucinations, delusions, confusion, and irrational behavior. There is obviously a genetic component to this disease. Children who have a schizophrenic parent have a much higher probability than other children of de- veloping the illness later in life, even when they are adopted as infants and there- fore are not exposed to their parents’ schizophrenic behavior (Kety et al., 1994). Among identical twins—that is, twins whose genes are identical—if one twin has schizophrenia, the other has a roughly 50% chance of also having schizophrenia, as opposed to the roughly 1% probability for the general population (Gottesman, 1991; Cardno & Gottesman, 2000; see Figure 1.1). At the same time, the envi- ronment is also clearly influential, since roughly 50% of children who have an identical twin with schizophrenia do not become schizophrenic themselves, and children who grow up in troubled homes are more likely to become schizophrenic than are children raised in a normal household. Most important, however, is the interaction of genes and environment. A study of adopted children, some of whose biological parents were schizophrenic, indicated that the only children who had any substantial likelihood of becoming schizophrenic were those who had a schizophrenic parent and who also were adopted into a troubled family (Tienari, Wahlberg, & Wynne, 2006).

A remarkable recent series of studies has revealed some of the biological mechanisms through which na- ture and nurture interact. These studies show that just as the genome—each person’s complete set of hered- itary information—influences behaviors and experi- ences, behaviors and experiences influence the genome (Cole, 2009; Meaney, 2010). This might seem im- possible, given the well-known fact that each person’s DNA is constant throughout life. However, the ge- nome includes not only DNA but also proteins that regulate gene expression by turning gene activity on and off. These proteins change in response to experi- ence and, without structurally altering DNA, can re- sult in enduring changes in cognition, emotion, and behavior. This discovery has given rise to a new field called epigenetics, the study of stable changes in gene








could appropriate nurture have allowed the Three Stooges to become upper-class gentlemen?

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FIGURE 1.1 Genetic relatedness and schizophrenia The closer the biological relation, the stronger the probability that relatives of a person with schizophrenia will have the same mental illness. (after Gottes man, 1991)

nurture n the environments, both physical and social, that influence our development

genome n each person’s complete set of hereditary information

epigenetics n the study of stable changes in gene expression that are medi- ated by the environment




expression that are mediated by the environment. Stated simply, epigenetics exam- ines how experience gets under the skin.

Evidence for the enduring epigenetic impact of early experiences and behav- iors comes from research on methylation, a biochemical process that reduces ex- pression of a variety of genes and that is involved in regulating reactions to stress (Champagne & Curley, 2009; Meaney, 2001). One recent study showed that the amount of stress that mothers reported experiencing during their children’s infancy was related to the amount of methylation in the children’s genomes 15 years later (Essex et al., 2013). Other studies showed increased methylation in the cord-blood DNA of newborns of depressed mothers (Oberlander et al., 2008) and in adults who were abused as children (McGowan et al., 2009), leading researchers to speculate that such children are at heightened risk for depression as adults (Rutten & Mill, 2009).

As these examples illustrate, developmental outcomes emerge from the constant bidirectional interaction of nature and nurture. To say that one is more important than the other, or even that the two are equally important, drastically oversimplifies the developmental process.

2 The Active Child: How Do Children Shape Their Own Development? With all the attention that is paid to heredity and environment, many people over- look the ways in which children’s own actions contribute to their development. Even in infancy and early childhood, this contribution can be seen in a multitude of areas, including attention, language use, and play.

Children first begin to shape their own development through their selection of what to pay attention to. Even newborns prefer to look at things that move and make sounds. This preference helps them learn about important parts of the world, such as people, other animals, and inanimate moving objects. When looking at peo- ple, infants’ attention is particularly drawn to faces, especially their mother’s face: Given a choice of looking at a stranger’s face or their mother’s, even 1-month-olds choose to look at Mom (Bartrip, Morton, & de Schonen, 2001). At first, infants’ attention to their mother’s face is not accompanied by any visible emotion, but by the end of the 2nd month, infants smile and coo more when focusing intently on their mother’s face than at other times. This smiling and cooing by the infant elic- its smiling and talking by the mother, which elicits further cooing and smiling by the infant, and so on (Lavelli & Fogel, 2005). In this way, infants’ preference for attending to their mother’s face leads to social interactions that can strengthen the mother–infant bond.

Once children begin to speak, usually between 9 and 15 months of age, their contribution to their own development becomes more evident. For example, tod- dlers (1- and 2-year-olds) often talk when they are alone in a room. Only if chil- dren were internally motivated to learn language would they practice talking when no one was present to react to what they are saying. Many parents are startled when they hear this “crib speech” and wonder if something is wrong with a baby who would engage in such odd-seeming behavior. However, the activity is entirely nor- mal, and the practice probably helps toddlers improve their speech.

Young children’s play provides many other examples of how their internally mo- tivated activity contributes to their development. Children play by themselves for the sheer joy of doing so, but they also learn a great deal in the process. Anyone who has seen a baby bang a spoon against the tray of a high chair or intentionally drop food on the floor would agree that, for the baby, the activity is its own reward.

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One of the earliest ways children shape their own development is through their choice of where to look. From the first month of life, seeing Mom is a high priority.




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play contributes to children’s development in many ways, including the spatial under- standing and attention to detail required to complete puzzles.

methylation n A biochemical process that influences behavior by suppressing gene activity and expression




At the same time, the baby is learning about the noises made by colliding objects, about the speed at which objects fall, and about the limits of his or her parents’ patience.

Young children’s fantasy play seems to make an especially large contribution to their knowledge of themselves and other people. Starting at around age 2 years, children sometimes pretend to be dif- ferent people in make-believe dramas. For ex- ample, they may pretend to be superheroes doing battle with monsters or play the role of parents taking care of babies. In addition to being inher- ently enjoyable, such play appears to teach chil- dren valuable lessons, including how to cope with fears and how to interact with others (Howes & Matheson, 1992; Smith, 2003). Older children’s play, which typically is more organized and rule- bound, teaches them additional valuable lessons, such as the self-control needed for turn-taking, adhering to rules, and controlling one’s emotions in the face of setbacks (Hirsch-Pasek et al., 2008). As we discuss later in the chapter, children’s contributions to their own development strengthen and broaden as they grow older and become increasingly able to choose and shape their environments.

3 Continuity/Discontinuity: In What Ways Is Development Continuous, and in What Ways Is It Discontinuous? Some scientists envision children’s development as a continuous process of small changes, like that of a pine tree growing taller and taller. Others see the process as a series of sudden, discontinuous changes, like the transition from caterpillar to cocoon to butterfly (Figure 1.2). The debate over which of these views is more ac- curate has continued for decades.






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adolescents who participate in sports and other extracurricular activities are more likely to complete high school, and less likely to get into trouble, than peers who are not engaged in these activities. This is another example of how children contribute to their own development.

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Pine tree: Developmental continuity Butterfly: Developmental discontinuity

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FIGURE 1.2 continuous and discon- tinuous development Some researchers see development as a continuous, gradual process, akin to a tree’s growing taller with each passing year. Others see it as a discon- tinuous process, involving sudden dramatic changes, such as the transition from cater- pillar to cocoon to butterfly. each view fits some aspects of child development.

continuous development n the idea that changes with age occur gradually, in small increments, like that of a pine tree growing taller and taller

discontinuous development n the idea that changes with age include occa- sional large shifts, like the transition from caterpillar to cocoon to butterfly




Researchers who view development as discontinuous start from a common ob- servation: children of different ages seem qualitatively different. A 4-year-old and a 6-year-old, for example, seem to differ not only in how much they know but in the whole way they think about the world. To appreciate these differences, consider two conversations between Beth, the daughter of one of the authors, and Beth’s mother. The first conversation took place when Beth was 4 years old, the second, when she was 6. Both conversations occurred after Beth had watched her mother pour all the water from a typical drinking glass into a taller, narrower glass. Here is the conversation that occurred when Beth was 4:

Mother: Is there still the same amount of water? Beth: No. Mother: Was there more water before, or is there more now? Beth: There’s more now. Mother: What makes you think so? Beth: The water is higher; you can see it’s more. Mother: Now I’ll pour the water back into the regular glass. Is there the same

amount of water as when the water was in the same glass before? Beth: Yes. Mother: Now I’ll pour all the water again into the tall thin glass. Does the

amount of water stay the same? Beth: No, I already told you, there’s more water when it’s in the tall glass.

Two years later, Beth responded to the same problem quite differently:

Mother: Is there still the same amount of water? Beth: Of course!

What accounts for this change in Beth’s thinking? Her everyday observations of liquids being poured cannot have been the reason for it; Beth had seen liquids poured on a great number of occasions before she was 4, yet failed to develop the understanding that the volume remains constant. Experience with the specific task could not explain the change either, because Beth had no further exposure to the task between the first and second conversation. Then why, as a 4-year-old, would Beth be so confident that pouring the water into the taller, narrower glass increased the amount and, as a 6-year-old, be so confident that it did not?

This conservation-of-liquid-quantity problem is actually a classic technique de- signed to test children’s level of thinking. It has been used with thousands of chil- dren around the world, and virtually all the children studied, no matter what their culture, have shown the same type of change in reasoning as Beth did (though usually at somewhat older ages). Furthermore, such age-related differences in


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children’s behavior on piaget’s conser- vation-of-liquid-quanity problem is often used to exemplify the idea that develop- ment is discontinuous. The child first sees equal amounts of liquid in similarly shaped glasses and an empty, differently shaped glass. Then, the child sees the liquid from one glass poured into the differently shaped glass. Finally, the child is asked whether the amount of liquid remains the same or whether one glass has more. Young children, like this girl, are unshakable in their belief that the glass with the taller liquid column has more liquid. a year or two later, they are equally unshakable in their belief that the amount of liquid in each glass is the same.




understanding pervade children’s thinking. Consider two letters to Mr. Rogers, one sent by a 4-year-old and one by a 5-year-old (Rogers, 1996, pp. 10–11):

Dear Mr. Rogers, I would like to know how you get in the TV.

(Robby, age 4)

Dear Mr. Rogers, I wish you accidentally stepped out of the TV into my house so I could play with you.

( Josiah, age 5)

Clearly, these are not ideas that an older child would entertain. As with Beth’s case, we have to ask, “What is it about 4- and 5-year-olds that leads them to form such improbable beliefs, and what changes occur that makes such notions laugh- able to 6- and 7-year-olds?”

One common approach to answering these questions comes from stage theories, which propose that development occurs in a progression of distinct age- related stages, much like the butterfly example in Figure 1.2b. According to these theories, a child’s entry into a new stage involves relatively sudden, qualitative changes that affect the child’s thinking or behavior in broadly unified ways and move the child from one coherent way of experiencing the world to a different co- herent way of experiencing it.

Among the best-known stage theories is Jean Piaget’s theory of cognitive development, the development of thinking and reasoning. This theory holds that between birth and adolescence, children go through four stages of cognitive growth, each characterized by distinct intellectual abilities and ways of understanding the world. For example, according to Piaget’s theory, 2- to 5-year-olds are in a stage of development in which they can focus on only one aspect of an event, or one type of information, at a time. By age 7, children enter a different stage, in which they can simultaneously focus on and coordinate two or more aspects of an event and can do so on many different tasks. According to this view, when confronted with a problem like the one that Beth’s mother presented to her, most 4- and 5-year-olds focus on the single dimension of height, and therefore perceive the taller, narrower glass as having more water. In contrast, most 7- and 8-year-olds consider both rel- evant dimensions of the problem simultaneously. This allows them to realize that although the column of water in the taller glass is higher, the column also is nar- rower, and the two differences offset each other.

In the course of reading this book, you will encounter a number of other stage theories, including Sigmund Freud’s theory of psychosexual development, Erik Erikson’s theory of psychosocial development, and Lawrence Kohlberg’s theory of moral development. Each of these stage theories proposes that children of a given age show broad similarities across many situations and that children of different ages tend to behave very differently.

Such stage theories have been very influential. In the past 20 years, however, many researchers have concluded that most developmental changes are gradual rather than sudden, and that development occurs skill by skill, task by task, rather than in a broadly unified way (Courage & Howe, 2002; Elman et al., 1996; Thelen & Smith, 2006). This view of development is less dramatic than that of stage theo- ries, but a great deal of evidence supports it. One such piece of evidence is the fact that a child often will behave in accord with one proposed stage on some tasks but in accord with a different proposed stage on other tasks (Fischer & Bidell, 2006). This variable level of reasoning makes it difficult to view the child as being “in” either stage.

stage theories n approaches that pro- pose that development involves a series of discontinuous, age-related phases

cognitive development n the develop- ment of thinking and reasoning




Much of the difficulty in deciding whether de- velopment is continuous or discontinuous is that the same facts can look very different, depending on one’s perspective. Consider the seemingly simple question of whether children’s height increases continuously or discontinuously. Figure 1.3a shows a boy’s height, measured yearly from birth to age 18 (Tanner, 1961). When one looks at the boy’s height at each age, devel- opment seems smooth and continuous, with growth occurring rapidly early in life and then slowing down.

However, when you look at Figure 1.3b, a different picture emerges. This graph illustrates the same boy’s growth, but it depicts the amount of growth from one year to the next. The boy grew every year, but he grew most during two periods: from birth to age 2½, and from ages 13 to 15. These are the kinds of data that lead people to talk about discontinuous growth and about a separate stage of adolescence that includes a physical growth spurt.

So, is development fundamentally continuous or fundamentally discontinuous? The most reasonable answer seems to be, “It depends on how you look at it and how often you look.” Imagine the difference be- tween the perspective of an uncle who sees his niece every 2 or 3 years and that of the niece’s parents, who see her every day. The uncle will almost always be struck with the huge changes in his niece since he last saw her. The niece will be so different that it will seem that she has progressed to a higher stage of develop- ment. In contrast, the parents will most often be struck

by the continuity of her development; to them, she usually will just seem to grow up a bit each day. Throughout this book, we will be considering the changes, large and small, sudden and gradual, that have led some researchers to emphasize the conti- nuities in development and others to emphasize the discontinuities.

4 Mechanisms of Development: How Does Change Occur? Perhaps the deepest mystery about children’s development is expressed by the ques- tion “How does change occur?” In other words, what are the mechanisms that produce the remarkable changes that children undergo with age and experience? A very general answer was implicit in the earlier discussion of the theme of nature and nurture. The interaction of genome and environment determines both what changes occur and when those changes occur. The challenge comes in specifying more precisely how any given change occurs.

One particularly interesting analysis of the mechanisms of developmental change involves the roles of brain activity, genes, and learning experiences in the development of effortful attention (e.g., Rothbart, Sheese, & Posner, 2007). Effortful attention in- volves voluntary control of one’s emotions and thoughts. It includes processes such as inhibiting impulses (e.g., obeying requests to put all of one’s toys away, as opposed to putting some away but then getting distracted and playing with the remaining ones);






2 B 2

Age (years)

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gh t

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( cm

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4 6 8 10 12 14 16 18







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Age (years)

H ei

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FIGURE 1.3 continuous and discon- tinuous growth Depending on how it is viewed, changes in height can be viewed as either continuous or discontinuous. (a) examining a boy’s height in absolute terms from birth to 18 years makes the growth look gradual and continuous (from Tanner, 1961). (b) examining the increases in the same boy’s height from one year to the next over the same period shows rapid growth during the first 2½ years, then slower growth, then a growth spurt in adolescence, then a rapid decrease in growth; viewed this way, growth seems discontinuous.




controlling emotions (e.g., not crying when failing to get one’s way); and focus- ing attention (e.g., concentrating on one’s homework despite the inviting sounds of other children playing outside). Difficulty in exerting effortful attention is associated with behavioral problems, weak math and reading skills, and mental illness (Blair & Razza, 2007; Diamond & Lee, 2011; Rothbart & Bates, 2006).

Studies of the brain activity of people performing tasks that require control of thoughts and emotions show that connections are especially active between the anterior cingulate, a brain structure involved in setting and attending to goals, and the limbic area, a part of the brain that plays a large role in emotional reactions (Etkin et al., 2006). Connections between brain areas such as the anterior cingulate and the limbic area develop considerably during childhood, and their development appears to be one mechanism that underlies improving effortful attention during childhood (Rothbart et al., 2007).

What role do genes and learning experiences play in influencing this mech- anism of effortful attention? Specific genes influence the production of key neuro transmitters—chemicals involved in communication among brain cells. Variations among children in these genes are associated with variations in the quality of performance on tasks that require effortful attention (Canli et al., 2005; Diamond et al., 2004; Rueda et al., 2005). These genetic influences do not occur in a vacuum, however. As noted in the discussion of epigenetics, the environment plays a crucial role in the expression of genes. Infants with a particular form of one of the genes in question show differences in effortful attention related to the quality of parenting they receive, with lower-quality parenting being associated with lower ability to regulate attention (Sheese et al., 2007). Among children who do not have that form of the gene, quality of parenting has less effect on ef- fortful attention.

Children’s experiences also can change the wiring of the brain system that pro- duces effortful attention. Rueda and colleagues (2005) presented 6-year-olds with a 5-day training program that used computerized exercises to improve capacity for effortful attention. Examination of electrical activity in the anterior cingulate indicated that those 6-year-olds who had completed the computerized exercises showed improved effortful attention. These children also showed improved perfor- mance on intelligence tests, which makes sense given the sustained effortful atten- tion required by such tests. Thus, the experiences that children encounter influence their brain processes and gene expression, just as brain processes and genes influ- ence children’s reactions to experiences. More generally, a full understanding of the mechanisms that produce developmental change requires specifying how genes, brain structures and processes, and experiences interact.

5 The Sociocultural Context: How Does the Sociocultural Context Influence Development? Children grow up in a particular set of physical and social environments, in a par- ticular culture, under particular economic circumstances, at a particular time in history. Together, these physical, social, cultural, economic, and historical circum- stances interact to constitute the sociocultural context of a child’s life. This socio- cultural context influences every aspect of children’s development.

A classic depiction of the components of the sociocultural context is Urie Bronfenbrenner’s (1979) bioecological model (discussed in depth in Chapter 9). The most obviously important component of children’s sociocultural contexts is the people with whom they interact—parents, grandparents, brothers, sisters, day-care

neurotransmitters n chemicals involved in communication among brain cells

sociocultural context n the physical, social, cultural, economic, and historical circumstances that make up any child’s environment




providers, teachers, friends, classmates, and so on—and the physical environment in which they live—their house, day-care center, school, neighborhood, and so on. Another important but less tangible component of the sociocultural context is the institutions that influence children’s lives: educational systems, religious institu- tions, sports leagues, social organizations (such as boys’ and girls’ clubs), and so on.

Yet another important set of influences are the general characteristics of the child’s society: its economic and technological advancement; its values, attitudes, beliefs, and traditions; its laws and political structure; and so on. For example, the simple fact that most toddlers and preschoolers growing up in the United States today go to child care outside their homes reflects a number of these less tangible sociocultural factors, including: 1. The historical era (50 years ago, far fewer children in the United States

attended child-care centers) 2. The economic structure (there are far more opportunities today for women

with young children to work outside the home) 3. Cultural beliefs (for example, that receiving child care outside the home does

not harm children) 4. Cultural values (for example, the value that mothers of young children should

be able to work outside the home if they wish). Attendance at child-care centers, in turn, partly determines the people children meet and the activities in which they engage.

One method that developmentalists use to understand the influence of the so- ciocultural context is to compare the lives of children who grow up in different cultures. Such cross-cultural comparisons often reveal that practices that are rare or nonexistent in one’s own culture are common in other cultures. The following com- parison of young children’s sleeping arrangements in different societies illustrates the value of such cross-cultural research.

In most families in the United States, newborn infants sleep in their parents’ bedroom, either in a crib or in the same bed. However, when infants are 2 to 6 months old, parents usually move them to another bedroom where they sleep alone (Greenfield, Suzuki, & Rothstein-Fisch, 2006). This seems natural to most people raised in the United States, because it is how we and others whom we know were

raised. From a worldwide perspective, however, such sleep- ing arrangements are highly unusual. In most other societies, including economically advanced nations such as Italy, Japan, and South Korea, babies almost always sleep in the same bed as their mother for the first few years, and somewhat older chil- dren also sleep in the same room as their mother, sometimes in the same bed (e.g., Nelson, Schiefenhoevel, & Haimerl, 2000; Whiting & Edwards, 1988). Where does this leave the fa- ther? In some cultures, the father sleeps in the same bed with mother and baby; in others, he sleeps in a separate bed or in a different room.

How do these differences in sleeping arrangements af- fect children? To find out, researchers interviewed mothers in middle-class U.S. families in Salt Lake City, Utah, and in rural Mayan families in Guatemala (Morelli et al., 1992). These in- terviews revealed that by age 6 months, the large majority of the U.S. children had begun sleeping in their own bedroom. As the children grew out of infancy, the nightly separation of child OW




EN /




In many countries, including Denmark, the country in which this mother and child live, mothers and children sleep together for the first several years of the child’s life. This sociocultural pattern is in sharp con- trast to the U.S. practice of having infants sleep separately from their parents soon after birth.




and parents became a complex ritual, surrounded by activities intended to comfort the child, such as telling stories, reading children’s books, singing songs, and so on. About half the children were reported as taking a comfort object, such as a blanket or teddy bear, to bed with them.

In contrast, interviews with the Mayan mothers indicated that their children typically slept in the same bed with them until the age of 2 or 3 years and continued to sleep in the same room with them for years thereafter. The children usually went to sleep at the same time as their parents. None of the Mayan parents reported bed- time rituals, and almost none reported their children taking comfort objects, such as dolls or stuffed animals, to bed with them.

Why do sleeping arrangements differ across cultures? Interviews with the Mayan and U.S. parents indicated that the crucial consideration for them in determining sleeping arrangements was cultural values. Mayan culture prizes interdependence among people. The Mayan parents expressed the belief that having a young child sleep with the mother is important for developing a good parent–child relationship, for avoiding the child’s becoming distressed at being alone, and for helping parents spot any problems the child is having. They often expressed shock and pity when told that infants in the United States typically sleep separately from their parents (Greenfield et al., 2006). In contrast, U.S. culture prizes independence and self- reliance, and the U.S. mothers expressed the belief that having babies and young children sleep alone promotes these values, as well as allowing intimacy between husbands and wives (Morelli et al., 1992). These differences illustrate both how practices that strike us as natural may differ greatly across cultures and how the simple conventions of everyday life often reflect deeper values.

Contexts of development differ not just between cultures but also within them. In modern multicultural societies, many contextual differences are related to eth- nicity, race, and socioeconomic status (SES)—a measure of social class that is based on income and education. Virtually all aspects of children’s lives—from the food they eat to the parental discipline they receive to the games they play—vary with ethnicity, race, and SES.

The socioeconomic context exerts a particularly large influence on children’s lives. In economically advanced societies, including the United States, most chil- dren grow up in comfortable circumstances, but millions of other children do not. In 2011, about 19% of U.S. families with children had incomes below the poverty line (in that year, $18,530 for a family of three with one adult and two children). In absolute numbers, that translates into about 16 million children growing up in pov- erty (U.S. Census Bureau, 2012). As shown in Table 1.2, poverty rates are especially high in Black and Hispanic families and in families of all races that are headed by single mothers. Poverty rates are also very high among the roughly 25% of children in the United States who are either immigrants or the children of immigrants— roughly twice as high as among children of native-born parents (Hernandez, Denton, & Macartney, 2008; Smeeding, 2008).

Children from poor families tend to do less well than other children in many ways (G. W. Evans et al., 2005; Morales & Guerra, 2006). In infancy, they are more likely to have serious health problems. In childhood, they are more likely to have social/ emotional and behavioral problems. Throughout childhood and adolescence, they tend to have smaller vocabularies, lower IQs, and lower math and reading scores on standardized achievement tests. In adolescence, they are more likely to have a baby or drop out of school (G. W. Evans et al., 2005; Luthar, 1999; McLoyd, 1998).

These negative outcomes are not surprising when we consider the huge array of disadvantages that poor children face. Compared with children who grow up in


percentages of U.S. Families with children Younger than 18 Living Below poverty Line in 2011

Group % in Poverty

Overall U.S. Population 19

White, non-Hispanic 12

Black 33

Hispanic 29

Asian 12

Married Couples 9

White, non-Hispanic 5

Black 12

Hispanic 20

Asian 9

Single Parent: Female Head of Household


White, non-Hispanic 33

Black 47

Hispanic 49

Asian 26

Source: U.S. Census Bureau, 2012

socioeconomic status (SES) n a mea- sure of social class based on income and education




more affluent circumstances, they are more likely to live in dangerous neighbor- hoods, to attend inferior day-care centers and schools, and to be exposed to high levels of air and water pollution (Dilworth-Bart & Moore, 2006; G. W. Evans, 2004). In addition, their parents read to them less, talk to them less, provide fewer books in the home, and are less involved in their schooling. Poor children also are more likely than affluent children to grow up in single-parent homes or to be raised by neither biological parent. The accumulation of these disadvantages, rather than any single one of them, seems to be the greatest obstacle to poor children’s success- ful development (Luthar, 2006; Morales & Guerra, 2006).

And yet as we saw in Werner’s study of the children of Kauai, described at the beginning of the chapter, many children do overcome the obstacles that poverty presents. Such resilient children tend to have three characteristics: (1) positive per- sonal qualities, such as high intelligence, an easygoing personality, and an optimis- tic outlook on the future; (2) a close relationship with at least one parent; and (3) a close relationship with at least one adult other than their parents, such as a grand- parent, teacher, coach, or family friend (Chen & Miller, 2012; Masten, 2007). Thus, although poverty poses serious obstacles to successful development, many children do surmount the challenges—usually with the help of adults in their lives.

6 Individual Differences: How Do Children Become So Different from One Another? Anyone who has experience with children is struck by their uniqueness—their dif- ferences not only in physical appearance but in everything from activity level and temperament to intelligence, persistence, and emotionality. These differences among children emerge quickly. Some infants in their first year are shy, others outgoing. Some infants play with or look at objects for prolonged periods; others rapidly shift from activity to activity. Even children in the same family often differ substantially, as you probably already know if you have siblings.

Scarr (1992) identified four factors that can lead children from a single family (as well as children from different families) to turn out very different from one another: 1. Genetic differences 2. Differences in treatment by parents and others 3. Differences in reactions to similar experiences 4. Different choices of environments

The most obvious reason for differences among children is that, except for identical twins, every individual is genetically unique. All other siblings (includ-

ing fraternal twins) share 50% of their genes and differ in the other 50%.

A second major source of variation among children is dif- ferences in the treatment they receive from parents and other people. This differential treatment is often associated with preexisting differences in the children’s characteristics. For example, parents tend to provide more sensitive care to easy- going infants than to difficult ones; by the second year, parents of difficult children are often angry with them even when the children have done nothing wrong in the immediate situation (van den Boom & Hoeksma, 1994). Teachers, likewise, tend to provide positive attention and encouragement to pupils who are learning well and are well behaved, but with pupils FOT






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Different children, even ones within the same family, often react to the same experi- ence in completely different ways.




who are doing poorly and are disruptive, they tend to be openly critical and to deny the pupils’ requests for special help (Good & Brophy, 1996).

In addition to being shaped by objective differences in the treatment they re- ceive, children also are influenced by their subjective interpretations of the treat- ment. A classic example occurs when each of a pair of siblings feels that their parents favor the other. Siblings also often react differently to events that affect the whole family. In one study, 69% of negative events, such as parents’ being laid off or fired, elicited fundamentally different reactions from siblings (Beardsall & Dunn, 1992). Some children were very concerned at a parent’s loss of a job; others were sure that everything would be okay.

A fourth major source of differences among children relates to the previously discussed theme of the active child: As children grow older, they increasingly choose activities and friends for themselves and thus influence their own subsequent de- velopment. They may also accept or choose niches for themselves: within a family, one child may become “the smart one,” another “the popular one,” another “the bad one,” and so on (Scarr & McCartney, 1983). A child labeled by family members as “the smart one” may strive to live up to the label; so, unfortunately, may a child labeled “the troublemaker.”

As discussed in the section on nature and nurture and in the section on mech- anisms of development, differences in biology and experience interact in com- plex ways to create the infinite diversity of human beings. Thus, a study of 11- to 17-year-olds found that the grades of children who were highly engaged with school changed in more positive directions than would have been predicted by their genetic background or family environments alone ( Johnson, McGue, & Iacono, 2006). The same study revealed that children of high intelligence were less nega- tively affected by adverse family environments than were other children. Thus, children’s genes, their treatment by other people, their subjective reactions to their experiences, and their choice of environments interact in ways that contribute to differences among children, even ones in the same family.

7 Research and Children’s Welfare: How Can Research Promote Children’s Well-Being? Improved understanding of child development often leads to practical benefits. Several examples have already been described, including the program for helping children deal with their anger and the recommendations for fostering valid eyewit- ness testimony from young children.

Another type of practical benefit arising from child-development research in- volves educational innovations. One fascinating example comes from studies of how children’s beliefs about intelligence influence their learning. Carol Dweck and her colleagues (Dweck, 2006; Dweck & Leggett, 1988) have found that some chil- dren (and adults) believe that intelligence is a fixed entity. They see each person as having a certain amount of intelligence that is set at birth and cannot be changed by experience. Other children (and adults) believe that intelligence is a changeable characteristic that increases with learning and that the time and effort people put into learning is the key determinant of their intelligence.

People who believe that intelligence increases with learning tend to react to failure in more effective ways (Dweck, 2006). When they fail to solve a problem, they more often persist on the task and try harder. Such persistence in the face of failure is an important quality. As the great British Prime Minister Winston Churchill once said, “Success is the ability to go from one failure to another with




no loss of enthusiasm.” In contrast, people who be- lieve that intelligence is a fixed entity tend to give up when they fail, because they think the problem is too hard for them.

Building on this research regarding the relation between beliefs about intelligence and persistence in the face of difficulty, Blackwell, Trzesniewski, and Dweck (2007) devised an effective educational program for middle school students from low- income backgrounds. They presented randomly se- lected students with research findings about how learning alters the brain in ways that improve sub- sequent learning and thus “makes you smarter.”

Other randomly selected students from the same classrooms were presented with research findings about how memory works. The investigators predicted that the students who were told about the effects that learning has on the brain would change their beliefs about intelligence in ways that would help them persevere in the face of failure. In particular, the changed beliefs were expected to improve stu- dents’ learning of mathematics, an area in which children often experience initial failure.

This prediction was borne out. Children who were presented information about how learning changes the brain and enhances intelligence subsequently improved their math grades, whereas the other children did not. Children who initially be- lieved that intelligence was an inborn, unchanging quality but who came to believe that intelligence reflected learning showed especially large improvements. Perhaps most striking, when the children’s teachers, who did not know which type of in- formation each child had received, were asked if any of their students had shown unusual improvement in motivation or performance, the teachers cited more than three times as many students who had been given information about how learning builds intelligence.

In subsequent chapters, we review many additional examples of how child de- velopment research is being used to promote children’s welfare.

review: The modern field of child development is in large part an attempt to answer a small set of fundamental questions about children. These include:

1. How do nature and nurture jointly contribute to development? 2. How do children contribute to their own development? 3. Is development best viewed as continuous or discontinuous? 4. What mechanisms produce development? 5. How does the sociocultural context influence development? 6. Why are children so different from one another? 7. How can we use research to improve children’s welfare?

Methods for Studying Child Development As illustrated in the preceding section, modern scientific research has advanced the understanding of fundamental questions about child development well beyond that of the historical figures who first raised the questions. This progress reflects the









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Screenshot from Brainology, a commer- cially available educational program based on the findings of Blackwell, Trzesniewski, and Dweck (2007). The software, like the research study, emphasizes that learning makes children smarter by building new connections within the brain.




successful application of the scientific method to the study of child development. In this section, we describe the scientific method and examine how its use has ad- vanced understanding of child development.

The Scientific Method The basic assumption of the scientific method is that all beliefs, no matter how probable they seem and no matter how many people share them, may be wrong. Therefore, until beliefs have been tested, they must be viewed as hypotheses, that is, as educated guesses, rather than as truth. If a hypothesis is tested, and the evi- dence repeatedly does not support it, the hypothesis must be abandoned no matter how reasonable it seems.

Use of the scientific method involves four basic steps: 1. Choosing a question to be answered 2. Formulating a hypothesis regarding the question 3. Developing a method for testing the hypothesis 4. Using the data yielded by the method to draw a conclusion regarding the

hypothesis To illustrate these steps, let’s make the question to be answered “What abilities

predict which children will become good readers?” A reasonable hypothesis might be “Kindergartners who can identify the separate sounds within words will become better readers than those who cannot.” A straightforward method for testing this hypothesis would be to select a group of preschoolers, test their ability to identify the separate sounds within words, and then, several years later, test the reading skills of the same children. Research has, in fact, shown that kindergartners who are aware of the component sounds within words later tend to read more skillfully than their peers who lacked this ability as kindergartners. This pattern holds true regard- less of whether the children live in the United States, Australia, Norway, or Sweden (Furnes & Samuelsson, 2011). These results support the conclusion that kindergart- ners’ ability to identify sounds within words predicts their later reading skill.

The first, second, and fourth of these steps are not unique to the scientific method. As we have seen, great thinkers of the past also asked questions, formu- lated hypotheses, and drew conclusions that were reasonable given the evidence available to them. What distinguishes scientific research from nonscientific ap- proaches is the third step: the methods used to test the hypotheses. When rigor- ously employed, these research methods yield high-quality evidence that allows investigators to progress beyond their initial hypotheses to draw firmly grounded conclusions.

The Importance of Appropriate Measurement For the scientific method to work, researchers must use measures that are directly relevant to the hypotheses being tested. Even measures that initially seem reason- able sometimes turn out to be less informative than originally thought. For ex- ample, a researcher who hypothesized that a supplemental food program would help children suffering from malnutrition might evaluate the program on the basis of weight gain from just before the program to just after it. However, weight is an inadequate measure of nutrition: Providing unlimited supplies of Cheetos would probably produce weight gain but not improve nutrition, and many people are obese yet malnourished (Sawaya et al., 1995). Better measures of nutrition would

scientific method n an approach to testing beliefs that involves choosing a question, formulating a hypothesis, testing the hypothesis, and drawing a conclusion

hypotheses n educated guesses




include whether more adequate levels of essential nutrients were present in the children’s bloodstreams at the end of the study (Shetty, 2006).

Regardless of the particular measure used, many of the same criteria determine whether a measure is a good one. One key criterion has already been noted—the measure must be directly relevant to the hypothesis. Two other qualities that good measures must possess are reliability and validity.

reliability The degree to which independent measurements of a behavior under study are consistent is referred to as reliability. One important type of consistency, interrater reliability, indicates how much agreement there is in the observations of different raters who witness the same behavior. Sometimes the observations are qualitative, as when raters classify a baby’s attachment to her mother as “secure” or “insecure.” Other times the observations are quantitative, as when raters score on a scale of 1 to 10 how upset babies become when they are presented with an un- familiar noisy toy or a boisterous stranger. In both cases, interrater reliability is at- tained when the raters’ observations are in close agreement—as when, for example, Baby A in a group being observed for a particular behavior gets a 6 or 7 from all the raters, Baby B gets a 3 or 4, Baby C gets an 8 or 9, and so on. Without such close agreement, one cannot have confidence in the research findings, because there is no way to tell which (if any) rating was accurate.

A second important type of consistency is test–retest reliability. This type of reliability is attained when measures of a child’s performance on the same test, administered under the same conditions, are similar on two or more occasions. Suppose, for example, that researchers presented a vocabulary test to a group of children on two occasions one week apart. If the test is reliable, those children who scored highest on the first testing should also score highest on the second, because none of the children’s vocabularies would have changed much over such a short period. As in the example of interrater reliability, a lack of test–retest reliability would make it impossible to know which result (if either) accurately reflected each child’s status.

Validity The validity of a test or experiment refers to the degree to which it mea- sures what it is intended to measure. Researchers strive for two types of validity: internal and external. Internal validity refers to whether effects observed within experiments can be attributed with confidence to the factor that the researcher is testing. For example, suppose that a researcher tests the effectiveness of a type of psychotherapy for depression by administering it to a number of depressed adoles- cents. If three months later many of the adolescents are no longer depressed, can it be concluded that this type of psychotherapy caused the improvement? No, because the students’ recovery may have been due to the mere passage of time. Moods fluc- tuate, and many adolescents who are depressed at any given time will be happier at a later date even without psychotherapy. In this example, the passage of time is a source of internal invalidity, because the factor believed to cause the improvement (the psychotherapy) may have had no effect.

External validity, in contrast, refers to the ability to generalize research findings beyond the particulars of the research in question. Studies of child development are almost never intended to apply only to the particular children and research meth- ods involved in a given study. Rather, the goal is to draw conclusions that apply to children more generally. Thus, the findings of a single experiment are only the first step in determining the external validity of the results. Additional studies with participants from different backgrounds and with different research methods are

reliability n the degree to which inde- pendent measurements of a given behavior are consistent

interrater reliability n the amount of agreement in the observations of different raters who witness the same behavior

test–retest reliability n the degree of similarity of a child’s performance on two or more occasions

validity n the degree to which a test measures what it is intended to measure

internal validity n the degree to which effects observed within experiments can be attributed to the factor that the researcher is testing

external validity n the degree to which results can be generalized beyond the particulars of the research




invariably needed to establish the external validity of the findings. (Table 1.3 sum- marizes the key properties of behavioral measures.)

Contexts for Gathering Data About Children Researchers obtain data about children in three main contexts: interviews, natu- ralistic observation, and structured observation. In the following sections, we con- sider how gathering data in each context can help answer different questions about children.

Interviews The most obvious way to collect data about children is to go straight to the source and ask the children themselves about their lives. One type of interview, the struc­ tured interview, is especially useful when the goal is to collect self-reports on the same topics from everyone being studied. For example, Valeski and Stipek (2001) asked kindergartners and 1st-graders questions regarding their feelings about school (How much does your teacher care about you? How do you feel when you’re at school?) and also questions about their beliefs about their academic competence (How much do you know about numbers? How good are you at reading?). The children’s general attitude toward school and their feelings about their relationship with their teacher proved to be positively related to their beliefs about their com- petence in math and reading. Asking large num- bers of children identical questions about their feelings and beliefs provides a quick and straight- forward way for researchers to learn about chil- dren’s beliefs and attitudes.

A second type of interview, the clinical inter­ view, is especially useful for obtaining in-depth information about an individual child. In this ap- proach, the interviewer begins with a set of pre- pared questions, but if the child says something intriguing, the interviewer can depart from the script to follow up on the child’s lead.


Key properties of Behavioral Measures

Property Question of Interest

Relevance to hypotheses Do the hypotheses predict in a straightforward way what should happen on these measures?

Interrater reliability Do different raters who observe the same behavior classify or score it the same way?

Test–retest reliability Do children who score higher on a measure at one time also score higher on the measure at other times?

Internal validity Can effects within the experiment be attributed to the variables that the researcher intentionally manipulated?

External validity How widely can the findings be generalized to different children in different places at different times?


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One-on-one clinical interviews like this one can elicit unique in-depth information about a child.

structured interview n a research pro- cedure in which all participants are asked to answer the same questions

clinical interview n a procedure in which questions are adjusted in accord with the answers the interviewee provides




The usefulness of clinical interviews can be seen in the case of Bobby, a 10-year- old child who was assessed for symptoms of depression (Schwartz & Johnson, 1985). When the interviewer asked him about school, Bobby said that he did not like it because the other children disliked him and he was bad at sports. As he put it, “I’m not really very good at anything” (p. 214). To explore the source of this sad self-description, the interviewer asked Bobby what he would wish for if three wishes could be granted. Bobby replied, “I would wish that I was the type of boy my mother and father want, I would wish that I could have friends, and I would wish that I wouldn’t feel sad so much” (p. 214). Such heartrending comments provide a sense of the painful subjective experience of this depressed child, one that would be impossible to obtain from methods that were not tailored to the individual.

As with all contexts for collecting data, interviews have both strengths and weak- nesses. On the positive side, they yield a great deal of data quickly and can provide in-depth information about individual children. On the negative side, answers to interview questions often are biased. Children (like adults) often avoid disclosing facts that show them in a bad light, distort the way that events happened, and fail to understand their own motivations (Wilson & Dunn, 2004). These limitations have led many researchers to use observational methods that allow them to witness the behavior of interest for themselves.

Naturalistic Observation When the primary research goal is to describe how children behave in their usual environments—homes, schools, playgrounds, and so on—naturalistic observation is the method of choice for gathering data. In this approach, observers try to remain unobtrusively in the background in the chosen setting, allowing them to see the relevant behaviors while minimizing the chances that their presence will influence those behaviors.

A classic example of naturalistic observation is Gerald Patterson’s (1982) com- parative study of family dynamics in “troubled” and “typical” families. The troubled families were defined by the presence of at least one child who had been labeled “out of control” and referred for treatment by a school, court, or mental health pro- fessional. The typical families were defined by the fact that none of the children in them showed signs of serious behavioral difficulties. Income levels and children’s ages were the same for the troubled and typical families.

To observe the frequency with which children and parents engaged in nega- tive behaviors—teasing, yelling, whining, criticizing, and so on—research assis-

tants repeatedly observed dinnertime interactions in both troubled and typical homes. To accustom family mem- bers to his or her presence, the research assistant for each family made several home visits before beginning to col- lect data.

The researchers found that the behaviors and attitudes of both parents and children in the troubled families dif- fered strikingly from those of their counterparts in the typical families. Parents in the troubled families were more self-absorbed and less responsive to their children than were parents in the typical households. Children in the troubled families responded to parental punishment by becoming more aggressive, whereas children in the typical households responded to punishment by becoming MO





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psychologists sometimes observe family interactions around the dinner table, because mealtime comments can evoke strong emotions.

naturalistic observation n examina- tion of ongoing behavior in an environ- ment not controlled by the researcher




less aggressive. In the troubled families, interactions often fell into a vicious cycle in which: n The child acted in a hostile or aggressive manner, for example, by defying a

parent’s request to clean up his or her room. n The parent reacted angrily, for example, by shouting at the child to obey. n The child escalated the level of hostility, for example, by yelling back. n The parent ratcheted up the aggression even further, perhaps by spanking the

child. As Patterson’s study suggests, naturalistic observations are particularly useful for illuminating everyday social interactions, such as those between children and parents.

Although naturalistic observation can yield detailed information about certain aspects of children’s everyday lives, it also has important limitations. One is that naturally occurring contexts vary on many dimensions, so it is often hard to know which ones influenced the behavior of interest. For example, it was clear in the Patterson study that the interactions of troubled families differed from those of the more harmonious families, but the interactions and family histories differed in so many ways that it was impossible to specify their contributions to the current situ- ation. A second limitation of naturalistic studies is that many behaviors of interest occur only occasionally in the everyday environment, which reduces researchers’ opportunities to learn about them. A means for overcoming both limitations is the method known as structured observation.

Structured Observation When using structured observation, researchers design a situation that will elicit behavior that is relevant to a hypothesis and then observe how different children behave in that situation. The researchers then relate the observed behaviors to char- acteristics of the child, such as age, sex, or personality, and to the child’s behavior in other situations that are also observed.

In one such study, Kochanska, Coy, and Murray (2001) investigated the links between 2- and 3-year-olds’ compliance with their mother’s requests to forego ap- pealing activities and their compliance with her requests that they participate in unappealing ones. Mothers brought their toddlers to a laboratory room that had a number of especially attractive toys sitting on a shelf and a great many less at- tractive toys scattered around the room. The experimenter asked each mother to tell her child that he or she could play with any of the toys except the ones on the shelf. Raters observed the children through a one-way mirror over the next few minutes and classified them as complying with their mother’s request wholeheart- edly, grudgingly, or not at all. Then the experimenter asked the mother to leave the room and observed whether the child played with the “forbidden” toys in the mother’s absence.

The researchers found that children who had complied wholeheartedly in the first instance tended to avoid playing with the forbidden toys for a longer time in the second. Moreover, these children were also more likely to comply with their mother’s request that they put away the many toys on the floor after she left the room. When retested near their 4th birthday, most children showed the same type of compliance as they had as toddlers. Overall, the results indicated that the quality of young children’s compliance with their mother’s requests is a somewhat stable, general property of the mother–child relationship.

structured observation n a method that involves presenting an identical situ- ation to each child and recording the child’s behavior














Temptation is everywhere, but children who are generally compliant with their moth- er’s requests when she is present are also more likely to resist temptation when she is absent (like this boy, the nephew of one of the authors, whose reach, despite appear- ances, stopped just short of the cake).




This type of structured observation offers an important advantage over natural- istic observation: it ensures that all the children being studied encounter identical situations. This allows direct comparisons of different children’s behavior in a given situation and, as in the research just discussed, also makes it possible to establish the generality of each child’s behavior across different tasks. On the other hand, structured observation does not provide as extensive information about individual children’s subjective experience as do interviews, nor can it provide the open-ended, everyday kind of data that naturalistic observation can yield.

As these examples suggest, which data-gathering approach is best depends on the goals of the research. (Table 1.4 summarizes the advantages and disadvantages of interviews, naturalistic observation, and structured observation as contexts for gathering data.)

Correlation and Causation People differ along an infinite number of variables, that is, attributes that vary across individuals and situations, such as age, sex, activity level, socioeconomic sta- tus, particular experiences, and so on. A major goal of child-development research is to determine how these and other major variables are related to one another, both in terms of associations and in terms of cause–effect relations. In the follow- ing sections, we consider the research designs that are used to examine each type of relation.

Correlational Designs The primary goal of studies that use correlational designs is to determine whether children who differ in one variable also differ in predictable ways in other variables. For example, a researcher might examine whether toddlers’ aggressiveness is related to the number of hours they spend in day care or whether adolescents’ popularity is related to their self-control.


advantages and Disadvantages of Three contexts for Gathering Data

Data-Gathering Situation

Features Advantages Disadvantages

Interview Children answer questions asked either in person or on a questionnaire.

Can reveal children’s subjective experience.

Structured interviews are inexpensive means for collecting in-depth data about individuals.

Clinical interviews allow flexibility for following up unexpected comments.

Reports are often biased to reflect favorably on interviewee.

Memories of interviewees are often inaccurate and incomplete.

Prediction of future behaviors often is inaccurate.

Naturalistic observation

Activities of children in everyday settings are observed.

Useful for describing behavior in everyday settings.

Helps illuminate social interaction processes.

Difficult to know which aspects of situation are most influential.

Limited value for studying infrequent behaviors.

Structured observation

Children are brought to laboratory and presented prearranged tasks.

Insures that all children’s behaviors are observed in same context.

Allows controlled comparison of children’s behavior in different situations.

Context is less natural than in naturalistic observation.

Reveals less about subjective experience than interviews.

variables n attributes that vary across individuals and situations, such as age, sex, and popularity

correlational designs n studies intended to indicate how two variables are related to each other




The association between two variables is known as their correlation. When variables are strongly correlated, knowing a child’s score on either variable allows accurate prediction of the child’s score on the other. For example, the fact that the number of hours per week that children spend reading correlates highly with their reading-test scores (Guthrie et al., 1999) means that a child’s reading-test score can be accurately predicted if one knows how much time the child spends reading. It also means that the number of hours the child spends reading can be predicted if one knows the child’s reading-test score.

Correlations range from 1.00, the strongest positive correlation, to 21.00, the strongest negative correlation. The direction is positive when high values of one variable are associated with high values of the other and low values of one are as- sociated with low values of the other; the direction is negative when high values of one are associated with low values of the other. Thus, the correlation between time spent reading and reading-test scores is positive, because children who spend high amounts of time reading also have high reading-test scores; the correlation between obesity and running speed is negative, because the more obese the child, the slower his or her running speed. (For a more in-depth discussion of how correlations work, see the Appendix.)

Correlation Does Not Equal Causation When two variables are strongly correlated and there is a plausible cause–effect relation between them, it often is tempting to infer that one causes the other. However, this inference is not justified, for two reasons. The first is the direction­ of­causation problem: a correlation does not indicate which variable is the cause and which variable is the effect. In the above example of the correlation between time spent reading and reading achievement, greater time spent reading might cause increased reading achievement. On the other hand, the cause–effect relation could run in the opposite direction: greater reading skill might cause children to spend more time reading, because reading faster and with greater comprehension makes reading more enjoyable.

The second reason that correlation does not imply causation is the third­ variable problem: the correlation between two variables may actually be the result of some third, unspecified variable. In the reading example, for instance, rather than greater reading achievement being caused by greater reading time, or vice versa, both of these aspects of reading could be caused by growing up in a family that val- ues knowledge and intelligence.

Recognizing that correlation does not imply causation is crucial for interpret- ing accounts of research. Even findings published in prestigious research journals can easily be misinterpreted. For example, based on a correlation between children younger than 2 years sleeping with a night-light and their later becoming near- sighted, an article in the prestigious journal Nature concluded that the light was harmful to visual development (Quinn et al., 1999). Not surprisingly, the claim received considerable publicity in the popular media (e.g., Torassa, 2000). Sub- sequent research, however, showed that the inference about causation was wrong. What actually seems to have happened is that the nearsighted infants generally had nearsighted parents, and the nearsighted parents, for unknown reasons, more often placed nightlights in their infants’ rooms (Gwiazda et al., 2000; Zadnik et al., 2000). As the example illustrates, even seemingly straightforward inferences of causation, based on correlational evidence, frequently prove to be wrong.

correlation n the association between two variables

direction-of-causation problem n the concept that a correlation between two variables does not indicate which, if either, variable is the cause of the other

third-variable problem n the concept that a correlation between two variables may stem from both being influenced by some third variable




If correlation does not imply causation, why do researchers often use correla- tional designs? One major reason is that the influence of many variables of great interest—age, sex, race, and social class among them—cannot be studied experi- mentally (see the next section) because researchers cannot manipulate them; that is, they cannot assign participants to one sex or another, to one SES or another, and so on. Consequently, these variables can only be studied through correlational methods. Correlational designs are also of great use when the goal is to describe re- lations among variables rather than to identify cause–effect relations among them. If, for example, the research goal is to discover how moral reasoning, empathy, anxi- ety, and popularity are related to one another, correlational designs would almost certainly be employed.

Experimental Designs If correlational designs are insufficient to indicate cause–effect relations, what type of approach is sufficient? The answer is experimental designs. The logic of ex- perimental designs can be summarized quite simply: If children in one group are exposed to a particular experience and subsequently behave differently from a com- parable group of children who were not exposed to the experience or were exposed to a different experience, then the subsequent differences in behavior must have resulted from the differences in experience.

Two techniques are crucial to experimental designs: random assignment of par- ticipants to groups, and experimental control. Random assignment involves assign- ing the participants to one experimental group or another according to chance so that the groups are comparable at the outset. This comparability is crucial for being able to infer that it was the varying experiences to which the groups were exposed in the experiment that caused the later differences between them. Otherwise, those differences might have arisen from some preexisting difference between the people in the groups.

Say, for example, that researchers wanted to compare the effectiveness of two interventions for helping depressed mothers improve their relationship with their infant—providing the mothers with home visits from trained therapists versus providing them with supportive phone calls from such therapists. If the research- ers provided the home visits to families in one neighborhood and the supportive phone calls to families in another neighborhood, it would be unclear whether any

differences in mother–infant relationships following the experiment were caused by differences between the effectiveness of the two types of support or by differences between the families in the two areas. Depressed mothers in one neighborhood might suffer from less severe forms of depression than mothers in the other, or they might have greater access to other support, such as close families, mental health centers, or parenting programs.

In contrast, when groups are created through random assignment and include a reasonably large number of participants (typically 20 or more per group), initial differences between the groups tend to be minimal. For example, if 40 families with mothers who suffer from depression are di- vided randomly into two experimental groups, each group is likely to have roughly equal numbers of families from each neighborhood. Similarly, each group is likely to include a few mothers who are extremely depressed, a few with mild forms of depression, and many in between, as well as a few in- fants who have been severely affected by their mother’s depression, a few RO




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Depressed mothers often have difficulty pro- viding sensitive parenting; home visits from trained therapists can help alleviate this problem.

experimental designs n a group of approaches that allow inferences about causes and effects to be drawn

random assignment n a procedure in which each child has an equal chance of being assigned to each group within an experiment




who have been minimally affected, and many in be- tween. The logic implies that groups created through random assignment should be comparable on all vari- ables except the different treatment that people in the experimental groups encounter during the experi- ment. Such an experiment was in fact conducted, and it showed that home visits helped depressed mothers more than supportive phone calls did (Van Doesum et al., 2008).

The second essential characteristic of an experi- mental design, experimental control, refers to the ability of the researcher to determine the specific ex- periences that children in each group encounter dur- ing the study. In the simplest experimental design, one with two conditions, the groups are often referred to as the “experimental group” and the “control group.” Children in the experimental group are presented with the experience of interest; children in the control group are treated identically except that they are not presented with the experience of interest or are pre- sented with a different experience that is expected to have less effect on the variables being tested.

The experience that children in the experimental group receive, and that children in the control group do not receive, is referred to as the independent variable. The behavior that is hypothesized to be affected by ex- posure to the independent variable is referred to as the dependent variable. Thus, if a researcher hypothesized that showing schoolchildren an anti-bullying film would reduce school bullying, the researcher might randomly assign some children in a school to view the film and other children in the same school to view a film about a different topic. In this case, the anti-bullying film would be the independent vari- able, and the amount of bullying after the children watched it would be the depen- dent variable. If the independent variable had the predicted effect, children who saw the anti-bullying film would show less bullying after watching it than children who saw the other film.

One illustration of how experimental designs allow researchers to draw con- clusions about causes and effects is a study that tested the hypothesis that televi- sion shows running in the background lower the quality of infants’ and toddlers’ play (Schmidt et al., 2008). The independent variable was whether or not a televi- sion program was on in the room where the participants were playing; the depen- dent variables were a variety of measures of children’s attention to the television program and of the quality of their play. The television program that was playing was Jeopardy!, which presumably would have been of little interest to the 1- and 2-year-olds in the study; indeed, they looked at it an average of only once per minute and only for a few seconds at a time. Nonetheless, the television show disrupted the children’s play, reducing the length of play episodes and the chil- dren’s focus on their play. These findings indicate that there is a causal, and nega- tive, relation between background exposure to television shows and the quality of young children’s play.

Experimental designs are the method of choice for establishing causal rela- tions, a central goal of scientific research. However, as noted earlier, experimental






The quality of infants’ and toddlers’ play is adversely affected by a television being on in the same room. This is true for even the most precocious children, such as this 1-year-old, the grandson of one of the authors.

experimental control n the ability of researchers to determine the specific experiences that children have during the course of an experiment

experimental group n a group of chil- dren in an experimental design who are presented the experience of interest

control group n the group of children in an experimental design who are not presented the experience of interest but in other ways are treated similarly

independent variable n the experience that children in the experimental group receive and that children in the control group do not receive

dependent variable n a behavior that is measured to determine whether it is affected by exposure to the independent variable




designs cannot be applied to all issues of interest. For example, hypotheses about why boys tend to be more physically aggressive than girls cannot be tested experi- mentally because gender cannot be randomly assigned to children. In addition, many experimental studies are conducted in laboratory settings; this improves experimental control but can raise doubts about the external validity of the find- ings, that is, whether the findings from the lab apply to the outside world. (The advantages and disadvantages of correlational and experimental designs are sum- marized in Table 1.5.)

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