Chapter Summary 4 Child Development

Table of Contents

Child Development

Use the attachment book and do Chapter 4 Summary 

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Child Development

Choose one way to respond to the chapter from the following list. You must choose a different response type for each reading response:

A.  Outline the chapter.   I expect to see not just titles/subtitles but short descriptions to help you organize and understand the material.  Please show the big ideas, medium sized ideas, and small ideas.  Your may use Roman Numerals or bullet points.  Please see me if you have questions.  Here is what a sample outline should look like:

          I.  Understanding How And Why

               A.  The Need for Science:  to understand how and why all people change over time.       

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                1.   The Scientific Method

                2.  Begins with Curiosity

B.  Describe at least 3 concepts and the understanding that you now have based on your own childhood experiences or from your experiences as a caregiver.

C.  Choose 6 questions from the “What Have you Learned” section throughout each chapter.  Type the question and your response. 

D.  What do you value and appreciate from this chapter? What concept/idea could you personally apply as a parent or teacher?  What concept/idea is still unclear or fuzzy?

Child Development

The Developing Person

Through Childhood and Adolescence


The Developing Person

Through Childhood and Adolescence

Kathleen Stassen Berger Bronx Community College City University of New York

Vice President, Social Sciences and High School: Charles Linsmeier Director of Content and Assessment, Social Sciences: Shani Fisher Executive Program Manager: Christine Cardone Developmental Editor: Andrea Musick Page Assistant Editor: Melissa Rostek Executive Marketing Manager: Katherine Nurre Marketing Assistant: Morgan Ratner Director of Media Editorial, Social Sciences: Noel Hohnstine Senior Media Editor: Laura Burden Assistant Media Editor: Nik Toner Director, Content Management Enhancement: Tracey Kuehn Managing Editor: Lisa Kinne Senior Content Project Manager: Peter Jacoby Senior Project Manager: Andrea Stefanowicz, Lumina Datamatics, Inc. Media Producer: Joseph Tomasso Senior Workflow Supervisor: Susan Wein Photo Editor: Sheena Goldstein Photo Researcher: Candice Cheesman Director of Design, Content Management: Diana Blume Cover and Interior Design: Lumina Datamatics, Inc. Art Manager: Matthew McAdams Illustrations: Lumina Datamatics, Charles Yuen Composition: Lumina Datamatics, Inc. Cover Photograph: Images By Tang Ming Tung/DigitalVision/Getty Images

Child Development

Library of Congress Control Number: 2017936099 ISBN-13: 978-1-319-14624-5 (EPUB)

Copyright © 2018, 2015, 2012, 2009 Worth Publishers All rights reserved.

WORTH PUBLISHERS One New York Plaza Suite 4500 New York, NY 10004-1562


Kathleen Stassen Berger received her undergraduate education at Stanford University and Radcliffe College, and then she earned an MAT from Harvard University and an M.S. and Ph.D. from Yeshiva University. Her broad experience as an educator includes directing a preschool, serving as chair of philosophy at the United Nations International School, and teaching child and adolescent development at Fordham University graduate school, Montclair State University, and Quinnipiac University. She also taught social psychology to inmates at Sing Sing Prison who were earning paralegal degrees.

Currently, Berger is a professor at Bronx Community College of the City University of New York, as she has been for most of her professional career. She began there as an adjunct in English and for the past decades has been a full professor in the Social Sciences Department, which includes psychology, sociology, economics, anthropology, political science, and human services. She has taught introduction to psychology, child and adolescent development, adulthood and aging, social psychology, abnormal psychology, and human motivation. Her students—from diverse ethnic, economic, and educational backgrounds, of many ages, ambitions, and interests—honor her with the highest teaching evaluations.

Berger is also the author of Invitation to the Life Span and The Developing Person Through the Life Span. Her developmental texts are used at more than 700 colleges and universities worldwide and are available in Spanish, French, Italian, and Portuguese as well as English. Her research interests include adolescent identity, immigration, bullying, and grandparents, and she has published articles on developmental topics in the Wiley Encyclopedia of Psychology, Developmental Review, and in publications of the American Association for Higher Education and the National Education Association for Higher Education. She continues teaching and learning from her students as well as from her four daughters and three grandsons.



PART I The Beginnings CHAPTER 1 The Science of Human Development

CHAPTER 2 Theories

CHAPTER 3 The New Genetics

CHAPTER 4 Prenatal Development and Birth

PART II The First Two Years CHAPTER 5 The First Two Years: Biosocial Development

CHAPTER 6 The First Two Years: Cognitive Development

CHAPTER 7 The First Two Years: Psychosocial Development

PART III Early Childhood CHAPTER 8 Early Childhood: Biosocial Development

CHAPTER 9 Early Childhood: Cognitive Development

CHAPTER 10 Early Childhood: Psychosocial Development

PART IV Middle Childhood CHAPTER 11 Middle Childhood: Biosocial Development

CHAPTER 12 Middle Childhood: Cognitive Development

CHAPTER 13 Middle Childhood: Psychosocial Development

PART V Adolescence CHAPTER 14 Adolescence: Biosocial Development

CHAPTER 15 Adolescence: Cognitive Development

CHAPTER 16 Adolescence: Psychosocial Development

EPILOGUE Emerging Adulthood

APPENDIX More About Research Methods

Glossary References Name Index Subject Index



The Beginnings

Chapter 1 The Science of Human Development Understanding How and Why

The Scientific Method A VIEW FROM SCIENCE: Overweight Children and Adult Health The Nature–Nurture Controversy

The Life-Span Perspective Development Is Multidirectional

Development Is Multicontextual INSIDE THE BRAIN: Thinking About Marijuana Development Is Multicultural Development Is Multidisciplinary Development Is Plastic

A CASE TO STUDY: David Designing Science

Observation The Experiment The Survey Studying Development over the Life Span

Cautions and Challenges from Science Correlation and Causation Quantity and Quality Ethics

Chapter 2 Theories What Theories Do

Questions and Answers Past and Future

Grand Theories Psychoanalytic Theory: Freud and Erikson Behaviorism: Conditioning and Learning Cognitive Theory: Piaget and Information Processing INSIDE THE BRAIN: Measuring Mental Activity

Newer Theories Sociocultural Theory: Vygotsky and Beyond Evolutionary Theory OPPOSING PERSPECTIVES: Toilet Training—How and When?

What Theories Contribute

Chapter 3 The New Genetics The Genetic Code

46 to 21,000 to 3 Billion Same and Different Matching Genes and Chromosomes OPPOSING PERSPECTIVES: Too Many Boys?

New Cells, New People Cells and Identity Twins and More

From Genotype to Phenotype Many Factors Gene–Gene Interactions Nature and Nurture Practical Applications

Chromosomal and Genetic Problems Spontaneous Mutations Not Exactly 46 Gene Disorders Genetic Counseling and Testing

A CASE TO STUDY: Raising Healthy Children

Chapter 4 Prenatal Development and Birth Prenatal Development

Germinal: The First 14 Days Embryo: From the Third Week Through the Eighth Week Fetus: From the Ninth Week Until Birth INSIDE THE BRAIN: Neuronal Birth and Death

Birth The Newborn’s First Minutes Medical Assistance

Problems and Solutions Harmful Substances Applying the Research A VIEW FROM SCIENCE: What Is Safe? Prenatal Diagnosis Low Birthweight: Causes and Consequences OPPOSING PERSPECTIVES: “What Do People Live to Do?” Complications During Birth

The New Family The Newborn New Mothers

New Fathers Parental Alliance Family Bonding


The First Two Years

Chapter 5 The First Two Years: Biosocial Development Body Changes

Body Size Sleep Brain Development INSIDE THE BRAIN: Neuroscience Vocabulary Harming the Infant Body and Brain A VIEW FROM SCIENCE: Face Recognition

Perceiving and Moving The Senses Motor Skills Cultural Variations

Surviving in Good Health Better Days Ahead A CASE TO STUDY: Scientist at Work Immunization Nutrition

Chapter 6 The First Two Years: Cognitive Development Sensorimotor Intelligence

Stages One and Two: Primary Circular Reactions Stages Three and Four: Secondary Circular Reactions Stages Five and Six: Tertiary Circular Reactions A VIEW FROM SCIENCE: Object Permanence

Information Processing Affordances Memory

Language: What Develops in the First Two Years? The Universal Sequence INSIDE THE BRAIN: Understanding Speech Cultural Differences Theories of Language Learning


Chapter 7 The First Two Years: Psychosocial Development Emotional Development

Early Emotions Toddlers’ Emotions Temperament INSIDE THE BRAIN: Expressing Emotions

The Development of Social Bonds Synchrony Attachment Insecure Attachment and the Social Setting A CASE TO STUDY: Can We Bear This Commitment? Social Referencing Fathers as Social Partners

Theories of Infant Psychosocial Development Psychoanalytic Theory Behaviorism Cognitive Theory Evolutionary Theory Sociocultural Theory Conclusion


Early Childhood

Chapter 8 Early Childhood: Biosocial Development

Body Changes Growth Patterns Nutrition Brain Growth INSIDE THE BRAIN: Connected Hemispheres

Advancing Motor Skills Gross Motor Skills A VIEW FROM SCIENCE: Eliminating Lead Fine Motor Skills

Injuries and Abuse Avoidable Injury A CASE TO STUDY: “My Baby Swallowed Poison” Prevention

Child Maltreatment Definitions and Statistics Frequency of Maltreatment Consequences of Maltreatment Preventing Maltreatment

Chapter 9 Early Childhood: Cognitive Development Thinking During Early Childhood

Piaget: Preoperational Thought A CASE TO STUDY: Stones in the Belly Vygotsky: Social Learning Children’s Theories

Brain and Context Language Learning

A Sensitive Time The Vocabulary Explosion Acquiring Grammar Learning Two Languages

Early-Childhood Schooling Homes and Schools Child-Centered Programs Teacher-Directed Programs Intervention Programs Long-Term Gains from Intensive Programs

Chapter 10 Early Childhood: Psychosocial Development Emotional Development

Initiative Versus Guilt Motivation

Play Playmates Active Play Learning Emotional Regulation

Challenges for Caregivers Styles of Caregiving A VIEW FROM SCIENCE: Culture and Parenting Style Discipline

OPPOSING PERSPECTIVES: Is Spanking OK? Becoming Boys or Girls: Sex and Gender A CASE TO STUDY: The Berger Daughters What Is Best?


Middle Childhood

Chapter 11 Middle Childhood: Biosocial Development A Healthy Time

Slower Growth, Greater Strength Physical Activity Health Problems in Middle Childhood A VIEW FROM SCIENCE: What Causes Childhood Obesity?

Children with Special Brains and Bodies Measuring the Mind Special Needs in Middle Childhood Specific Learning Disorders OPPOSING PERSPECTIVES: Drug Treatment for ADHD and Other Disorders

Special Education A CASE TO STUDY: Unexpected and Odd Labels, Laws, and Learning Early Intervention Gifted and Talented

Chapter 12 Middle Childhood: Cognitive Development Building on Theory

Piaget and Concrete Thought Vygotsky and Culture A CASE TO STUDY: Is She Going to Die? Information Processing INSIDE THE BRAIN: Coordination and Capacity Memory Control Processes

Language Vocabulary Speaking Two Languages Differences in Language Learning OPPOSING PERSPECTIVES: Happiness or High Grades?

Teaching and Learning International Schooling Schooling in the United States Choices and Complications

Chapter 13 Middle Childhood: Psychosocial Development The Nature of the Child

Self-Concept OPPOSING PERSPECTIVES: Protect or Puncture Self-Esteem? Resilience and Stress

Families and Children Shared and Nonshared Environments Family Structure and Family Function A VIEW FROM SCIENCE: “I Always Dressed One in Blue Stuff . . .” Connecting Structure and Function Family Trouble

The Peer Group The Culture of Children A CASE TO STUDY: Ignorance All Around

Children’s Moral Values Moral Reasoning What Children Value



Chapter 14 Adolescence: Biosocial Development Puberty Begins

Unseen Beginnings Brain Growth When Will Puberty Begin? INSIDE THE BRAIN: Lopsided Growth A VIEW FROM SCIENCE: Stress and Puberty Too Early, Too Late

Growth and Nutrition Growing Bigger and Stronger Diet Deficiencies Eating Disorders

Sexual Maturation Sexual Characteristics Sexual Activity Sexual Problems in Adolescence

Chapter 15 Adolescence: Cognitive Development Logic and Self

Egocentrism Formal Operational Thought Two Modes of Thinking A CASE TO STUDY: Biting the Policeman INSIDE THE BRAIN: Impulses, Rewards, and Reflection

Digital Natives Technology and Cognition Sexual Abuse?

Addiction Cyber Danger

Secondary Education Definitions and Facts Middle School High School OPPOSING PERSPECTIVES: Testing Variability

Chapter 16 Adolescence: Psychosocial Development Identity

Not Yet Achieved Four Arenas of Identity Formation

Relationships with Adults A VIEW FROM SCIENCE: Teenagers, Genes, and Drug Use Parents

Peer Power Peer Pressure A CASE TO STUDY: The Naiveté of Your Author Romance Sex Education

Sadness and Anger Depression Delinquency and Defiance

Drug Use and Abuse

Variations in Drug Use OPPOSING PERSPECTIVES: E-Cigarettes: Path to Addiction or Healthy Choice?

Harm from Drugs Preventing Drug Abuse: What Works?

Epilogue Emerging Adulthood Biosocial Development

Strong and Active Bodies Taking Risks

Cognitive Development Countering Stereotypes Cognitive Growth and Higher Education

Psychosocial Development Identity Achievement Intimacy Needs Concluding Questions and Hopes

Appendix More About Research Methods Make It Personal Read the Research

Professional Journals and Books The Internet

Additional Terms and Concepts Who Participates? Research and Design Reporting Results


If human development were simple, universal, and unchanging, there would be no need for a new edition of this textbook. Nor would anyone need to learn anything about human growth. But human development is complex, varied, and never the same.

This is evident to me in small ways as well as large ones. Yesterday, I made the mistake of taking two of my grandsons, aged 6 and 7, to the grocery store, asking them what they wanted for dinner. I immediately rejected their first suggestions—doughnuts or store-made sandwiches. But we lingered over the meat counter. Asa wanted hot dogs and Caleb wanted chicken. Neither would concede.

At least one universal is apparent in this anecdote: Grandmothers seek to nourish grandchildren. But complexity and variability were evident in two stubborn cousins and one confused grandmother.

This small incident is not unlike the headlines in today’s newspaper. Indeed, other developmental questions seem more urgent now, interweaving what is universally true about humans with what is new and immediate, balancing them in order to move forward with our public and personal lives. I found a compromise for dinner—chicken hot dogs, which both boys ate, with whole wheat bread and lots of ketchup. I do not know the solutions to public dilemmas such as climate change, immigration, gun violence, and systemic racism, but I believe that a deeper and more accurate understanding of human development might help.

That is why I wrote this eleventh edition, which presents both the enduring and the current findings from the study of child and adolescent development. Some of those findings have been recognized for decades, even centuries, and some are new, as thousands of scientists study how humans grow and change with new circumstances. I hope they will help us with the public and private aspects of our lives.

What’s New in the Eleventh Edition? New Material Every year, scientists discover and explain more concepts and research. The best of these are integrated into the text, with hundreds of new references on many topics, including epigenetics at conception, prenatal protections, infant nutrition, autism spectrum disorder, attachment, high- stakes testing, drug addiction and opioid-related deaths, sex education, and diversity of all kinds —ethnic, economic, gender, and cultural. Cognizant of the interdisciplinary nature of human development, I include recent research in biology, sociology, education, anthropology, political science, and more—as well as my home discipline, psychology.

What Can You Learn? Scientists first establish what is, and then they try to change it. In one recent experiment, Deb Kelemen (shown here) established that few children under age 12 understand a central concept of evolution (natural selection). Then she showed an experimental group a picture book illustrating the idea. Success! The independent variable (the book) affected the dependent variable (the children’s ideas), which confirmed Kelemen’s hypothesis: Children can understand natural selection if instruction is tailored to their ability.

Genetics and social contexts are noted throughout. The interaction of nature and nurture is discussed in many chapters, because neuroscience relates to every aspect of life. Among the many topics described with new research are the variations, benefits, and hazards of breast- feeding, infant day care, preschool education, single parenthood, exercise, vaccination, same-sex marriage—always noting differences, deficits, and resilience.

No paragraph in this edition is exactly what it was in the tenth edition. To help professors who taught with the earlier texts, or students who have friends who took the course a few years ago, here are some highlights of the updates:

Is She Awake? This 36-year-old mother in Hong Kong put her 7-month-old baby on her back, protecting her from SIDS as the Chinese have done for centuries. However, the soft pillow and comforter are hazards. Will she carry the baby to a safe place before she falls asleep?

Updated examples illustrating replication, race and ethnicity, and cross-sequential study

(Chapter 1). New feature on childhood obesity illustrating the scientific method (Chapter 1). New feature on marijuana use and sensitive periods (Chapter 1). Expanded discussion and new examples of what theories do (Chapter 2). New example and figure on opioid-related deaths illustrating classical conditioning (Chapter 2). Descriptions of newer brain imaging techniques such as DTI (diffusion tensor imaging) (Chapter 2). Grandmother hypothesis added to the discussion of evolutionary theory (Chapter 2). New coverage on the impact of the microbiome (Chapter 3). Updated material on stem cells and the use of CRISPR (Chapter 3). New feature on genetic counseling (Chapter 3). New feature on neurogenesis in the developing fetus (Chapter 4). Updated coverage and data on cesarean sections, the utilization of midwives, and alternatives to hospital birth (Chapter 4). Added discussion of teratogens, including recent research and data on Zika virus (Chapter 4). New research and data on international trends in low birthweight (Chapter 4). Updated coverage and research examples of infant sleep, bed-sharing, and co-sleeping (Chapter 5). New feature explaining neuroscience terms and brain structures (Chapter 5). New research on newborn vision and experience of pain (Chapter 5). Added coverage of motor-skill development, including walking (Chapter 5). New research on memory in infancy (Chapter 6). New coverage of bilingualism in babies (Chapter 6). Added discussion of attachment and the work of Bowlby and Ainsworth (Chapter 7). New features on emotional expression and adoptive parents’ attachment to their children (Chapter 7). Expanded coverage and research on infant day care, including new data on international trends in paid family leave (Chapter 7). Updated research on childhood obesity and nutrition (Chapter 8). Added discussion and research on childhood allergies (Chapter 8). New research on dangers of environmental pollutants in early childhood (Chapter 8). New research examples in discussion of young children’s logic (Chapter 9). Expanded discussion and new research on STEM learning, educational software use, and bilingualism in early childhood (Chapter 9). New research on brain plasticity and emotional regulation (Chapter 10). New coverage and data on screen time (Chapter 10). New research on gender development and gender differences (Chapter 10). Added discussion of embodied cognition and the importance of physical activity for overall health (Chapter 11). Added coverage on Sternberg, Gardner, and multiple intelligences (Chapter 11).

Updated coverage of childhood psychopathology, including ADHD, autism spectrum disorder, and specific learning disorders, and special education (Chapter 11). New feature on cognition in middle childhood (Chapter 12). Added discussion of Vygotsky and the role of instruction (Chapter 12). New discussion of the U.S. Common Core standards and of Finland’s recent education reform (Chapter 12). Added discussion and research on social comparison in middle childhood (Chapter 13). New U.S. and international research on various family structures (Chapter 13). New feature and research on bullying (Chapter 13). Added discussion of the benefits of psychotherapy for emotional problems during adolescence (Chapter 14). New coverage and research on executive function (Chapter 14). New research on eating disorders and sexual activity during adolescence (Chapter 14). Added discussion and research on advances in cognition during adolescence (Chapter 15). Updated coverage of media use among adolescents (Chapter 15). New research on adolescents’ experience of middle school (Chapter 15). Updated coverage of ethnic and gender development, as well as sexual orientation (Chapter 16). Updated coverage of teenage drug use, including e-cigarettes (Chapter 16). More coverage on exercise and new data on family-planning trends worldwide (Epilogue). Updated material on college completion and debt, including a new infographic (Epilogue). Updated material and new research on dating, cohabitation, and romance in emerging adults (Epilogue).

Universal Morality Remarkable? Not really. By the end of middle childhood, many children are eager to express their moral convictions, especially with a friend. Chaim Ifrah and Shai Reef believe that welcoming refugees is part of being a patriotic Canadian and a devout Jew, so they brought a welcoming sign to the Toronto airport where Syrian refugees (mostly Muslim) will soon deplane.

New Inside the Brain Feature

Since new discoveries abound almost daily in the field of neuroscience, I have added Inside the Brain features to several chapters, exploring topics such as the intricacies of prenatal and infant brain development, brain specialization and speech development, and brain maturation and emotional development.

New and Updated Coverage of Neuroscience Inclusion of neuroscience is a familiar feature of this book. In addition to the new Inside the Brain features, I include the latest, cutting-edge research on the brain in virtually every chapter, often enhancing it with charts, figures, and photos to help students understand the brain’s inner workings. A list highlighting this material is available at

New Developing Lives Developing Lives is a robust and sophisticated interactive experience in which each student “raises” a virtual child from sperm-and-egg to teenager—fully integrated into LaunchPad. With Developing Lives, each student creates a personal profile, selects a virtual partner (or chooses to be a single parent), and marks the arrival of their newborn (represented by a unique avatar based on the parents’ characteristics). As the child grows, the student responds to events both planned and unforeseen, making important decisions (nutrition choices, doctor visits, sleeping location) and facing uncertain moments (illness, divorce, a new baby), with each choice affecting how the child grows. Throughout, Developing Lives deepens each student’s attachment and understanding of key concepts in the field with immediate, customized feedback based on child development research. It integrates more than 200 videos and animations and includes quizzes and essay questions that are easy to assign and assess.

New Integration with LaunchPad Throughout the book, the margins include LaunchPad call-outs to online videos about people in a particular context or key scientists who might become role models. For example, Susan Beal, the Australian scientist who revolutionized our understanding of SIDS (sudden infant death

syndrome) and infant sleep is shown. The video demonstrates that she is not an aloof expert, but a wife and mother, like many students and their relatives. Application to Developing Lives (described above) and Data Connections activities (described below) are also highlighted for the reader.

Renewed Emphasis on Critical Thinking and Application in the Pedagogical Program We all need to be critical thinkers. Virtually every page of this book presents questions as well as facts. A new marginal feature, Think Critically, encourages student reflection and analysis. There are no pat answers to these questions: They could be used to start a class discussion or begin a long essay.

Every chapter begins with a few What Will You Know? questions, one for each major heading. Of course, much of what readers will learn will be reflected in new attitudes and perspectives— hard to quantify. But these What Will You Know? questions are intended to be provocative and to pose issues that the students will remember for decades.

In addition, after every major section, What Have You Learned? questions appear. They are designed to help students review what they have just read, a pedagogical technique proven to help retention. Ideally, students will answer these learning objective questions in sentences, with specifics that demonstrate knowledge. Some items on the new lists are straightforward, requiring only close attention to the chapter content. Others require comparisons, implications, or evaluations.

Key terms are indicated with bold print and are defined in the margins as well as in the glossary, because expanded vocabulary aids expanded understanding. To help students become better observers, occasional Observation Quizzes accompany a photo or figure. And, since many students reading this book are preparing to be teachers, health care professionals, police officers,

or parents, every chapter contains Especially For questions that encourage students to apply important developmental concepts just as experts in the field do.

As a professor myself, I continue to seek ways to deepen knowledge. Cognitive psychology and research on pedagogy finds that vocabulary, specific applications details, and critical thinking are all part of learning. These features are designed to foster all four.

Updated Features Online Data Connections Activities Understanding how scientists use data helps students realize that the study of human development is much more than personal experience and common sense. Evidence sometimes contradicts myths and assumptions, and sometimes it confirms them. This edition continues to offer interactive activities—many of which have been updated with the latest available data—to allow students to interpret data on topics ranging from infant breast-feeding to adolescent risk- taking.

For example, students discover how U.S. poverty rates are worse for children than for adults, data that may be surprising. These interactive activities advance active thinking, deepening their understanding of the need for data. Instructors can assign these activities in the online LaunchPad that accompanies this book.

Opposing Perspectives, A View from Science, and A Case to Study Special topics and new research abound in childhood and adolescent development. This edition

of The Developing Person Through Childhood and Adolescence includes boxed features in every chapter. Opposing Perspectives focuses on controversial topics—from prenatal sex selection to e-cigarettes. Information and opinions on both sides of each issue are presented, so students can weigh evidence, assess arguments, and reach their own conclusions while appreciating that an opposite conclusion also has merit. A View from Science explains research in more detail, illustrating the benefits of the scientific method. A Case to Study focuses on particular individuals, helping students to recognize the personal implications of what they learn.

Infographics Information is sometimes better understood visually and graphically. Carefully chosen, updated photos and figures appear on almost every page, with captions that explain and increase knowledge. In addition, every chapter includes a full-page, graphical depiction.

These infographics explain key concepts, from brain development to school attendance rates, often with data that encourage students to think of other nations, other cultures, other times. My two awesome editors and I have worked closely with noted designer Charles Yuen to create these infographics, hoping they reinforce key ideas.

Child Development and Nursing Career Correlation Guides Many students taking this course will become nurses or early-childhood educators. This book and accompanying testing material are fully correlated to the NAEYC (National Association for the Education of Young Children) career preparation goals and the NCLEX (nursing) licensure exam. These two supplements are available in LaunchPad.

Ongoing Features Writing That Communicates the Excitement and Challenge of the Field Writing about the science of human development should be lively, just as people are. Each sentence conveys attitude as well as content. Chapter-opening vignettes describe real-life situations. Examples and clear explanations abound, helping students connect theory, research, and experiences.

Coverage of Diversity Cross-cultural, international, multiethnic, sexual orientation, poverty, age, family structure, gender—all these words and ideas are vital to appreciating how children develop. Research uncovers surprising similarities and notable differences: All people have much in common, yet each human is unique. From the discussion of social contexts in Chapter 1 to the coverage of cultural differences among emerging adults in the Epilogue, each chapter explains that no one is average; each of us is diverse.

New research on family structures, immigrants, bilingualism, and ethnic differences in health are among the many topics that illustrate human diversity. Respect for human differences is

evident throughout. Examples and research findings from many parts of the world are not add- ons but are integral to our understanding of child development. A list of these examples and research is available at

Learning to Button Most shirts for 4-year-olds are wide-necked without buttons, so preschoolers can put the shirts on themselves. But the skill of buttoning is best learned from a mentor, who knows how to increase motivation.

Current Research from the Field My mentors encouraged curiosity, creativity, and skepticism; as a result, I read and analyze thousands of articles and books on everything from the genetic alleles that predispose children to autism spectrum disorder to the complications of ethnic identity. The recent explosion of research in neuroscience has challenged me, once again, first to understand and then to explain many complex findings and speculative leaps. My students continue to ask questions and share their experiences, providing new perspectives and concerns.

Topical Organization Within a Chronological Framework The book’s basic organization remains unchanged. Four chapters begin the book with coverage of definitions, theories, genetics, and prenatal development. These chapters function not only as a developmental foundation but also as the structure for explaining plasticity, nature and nurture, multicultural awareness, risk analysis, gains and losses, family bonding, and many other concepts that yield insights for all of human development.

The other three parts correspond to the major periods of development. Each age is discussed in three chapters, one for the biological, one for the cognitive, and one for the social world. I believe that this topical organization within a chronological framework provides a scaffold for students’ understanding of the interplay between chronological age and specific topics.

Sisters and Brothers Gender equality has become important to both sexes, as evidenced by the thousands of men who joined the Women’s March on January 21, 2017—the day after President Trump’s inauguration. Many who attended took exception with his positions on sex and gender issues, and the result was one of the largest protest marches ever: an estimated 4 million people in more than one hundred towns and cities. This shows Washington, D.C., where more than half a million gathered.

Photographs, Tables, and Graphs That Are Integral to the Text Students learn a great deal from this book’s illustrations because Worth Publishers encourages authors to choose the photographs, tables, and graphs and to write captions that extend the content. Observation Quizzes that accompany many of them inspire readers to look more closely at certain photographs, tables, and figures. The online Data Connections further this process by presenting numerous charts and tables that contain detailed data for further study.

Media and Supplements After teaching for many years, I know personally that supplements can make or break a class, and that some publisher’s representatives are helpful in explaining how to use them while others are not. Many new quizzes, videos, and other aids are available for both students and professors. Ask your publisher’s representative how these might be used. I have taught with texts from many publishers; I expect you will find that Worth representatives are among the best, and you will be glad you asked for help.

Global Decay Thousands of children in Bangalore, India, gathered to brush their teeth together, part of an oral health campaign. Music, fast food, candy bars, and technology have been exported from the United States, and many developing nations have their own versions (Bollywood replaces Hollywood). Western diseases have also reached many nations; preventive health now follows.

Observation Quiz Beyond toothbrushes, what other health tools do most children here have that their parents did not? (see answer, p. 314)

LaunchPad with Developing Lives, LearningCurve Quizzing, and Data Connections Activities Built to solve key challenges in the course, LaunchPad gives students what they need to prepare for class and gives instructors what they need to set up a course, shape the content, craft presentations and lectures, assign and assess homework, and guide the learning of every student.

LaunchPad, which can be previewed at, includes the following:

An interactive e-Book, which integrates the text with videos that aid student learning. Developing Lives, the sophisticated interactive experience in which students “raise” their own virtual child. This fascinating simulation integrates more than 200 videos and animations and includes quizzes and essay questions that are easy to assign and assess. Data Connections, interactive activities that allow students to interpret data on topics ranging from breast-feeding to risk-taking. The LearningCurve adaptive quizzing system, which is based on the latest findings from learning and memory research. It combines adaptive question selection, immediate and valuable feedback, and a gamelike 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 can review using 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. Worth’s Video Collection for Human Development, which covers the full range of the course, from classic experiments (like the Strange Situation and Piaget’s conservation tasks) to investigations of children’s play to adolescent risk-taking. Instructors can assign these videos to students through LaunchPad or choose 1 of 50 popular video activities that combine videos with short-answer and multiple-choice questions. (For presentation purposes, our videos are also available on flash drive.) Instructor’s Resources, which has been hailed as the richest collection of instructor’s resources in developmental psychology. They include learning objectives, springboard topics for discussion and debate, handouts for student projects, course-planning suggestions, ideas for term projects, and a guide to audiovisual and online materials. Lecture Slides, which include two sets of prebuilt slides: one comprised of chapter art and illustrations, and another consisting of comprehensive, book-specific lectures. These slides

can be used as-is or customized to fit your course needs. A Test Bank containing at least 100 multiple-choice and 70 fill-in-the-blank, true-false, and essay questions per chapter. Good test questions are critical to every course, and we have gone through each and every one of these test questions with care. We have added more challenging questions, and questions are keyed to the textbook by topic, page number, and level of difficulty. Questions can be organized by NCLEX, NAEYC, and APA goals and Bloom’s taxonomy. We have also written rubrics for grading all of the essay questions in the test bank.

The Diploma computerized test bank guides instructors step by step through the process of creating a test. It also allows them to quickly add an unlimited number of questions; edit, scramble, or re-sequence items; format a test; and include pictures, equations, and media links. The accompanying gradebook enables instructors to record students’ grades throughout the course and includes the capacity to sort student records, view detailed analyses of test items, curve tests, generate reports, and add weights to grades.

Thanks I would like to thank the academic reviewers who have read this book in every edition and who have provided suggestions, criticisms, references, and encouragement. They have all made this a better book.

I want to mention especially those who have reviewed this edition:

Chris Alas, Houston Community College Adrienne Armstrong, Lone Star College William Robert Aronson, Florida International University T. M. Barratt, Arizona State University Daniel Benkendorf, The City University of New York–Baruch College Gina Brelsford, Pennsylvania State University–Harrisburg Melissa A. Bright, University of Florida Alda Cekrezi, Lone Star College Kristi Cordell-McNulty, Angelo State University Barbara Crosby, Baylor University Faith T. Edwards, Univeristy of Wisconsin—Oshkosh Naomi Ekas, Texas Christian University Michael A. Erickson, Hawaii Pacific University Diane Klieger Feibel, University of Cincinnati—Blue Ash College Lori Neal Fernald, The Citadel Military College of South Carolina Valerie C. Flores, Loyola University Chicago Stacie Foster, Arizona State University Kathryn Frazier, Northeastern University Christopher Gade, Berkeley City College Dan Grangaard, Austin Community College Jiansheng Guo, California State University—East Bay Pinar Gurkas, Clayton State University E. Allison Hagood, Arapahoe Community College

Toni Stepter Harris, Virginia State University Raquel Henry, Lone Star College—Kingwood Danelle Hodge, California State University—San Bernadino Vernell D. Larkin, Hopkinsville Community College Richard Marmer, American River College Jerry Marshall, Green River College T. Darin Matthews, The Citadel Military College of South Carolina Elizabeth McCarroll, Texas Woman’s University Alejandra Albarran Moses, California State University–Los Angeles Kelly A. Warmuth, Providence College

The editorial, production, and marketing people at Worth Publishers are dedicated to meeting the highest standards of excellence. Their devotion of time, effort, and talent to every aspect of publishing is a model for the industry, and the names of all those who helped with this edition are listed on the second page of this book. I particularly would like to thank Andrea, Chris, and Chuck.

New York July 2017

The Beginnings





In the Introduction module of Developing Lives, you will begin to customize the developmental journey of your child with information about your personality, cognitive abilities, and demographic characteristics. Next, as you progress through the Prenatal simulation module, how you decide the following will impact the biosocial, cognitive, and psychosocial development of your baby.

Biosocial Cognitive Psychosocial

Will you modify your behaviors and diet during pregnancy?

Will you find out the gender of your baby prior to delivery?

What kind of delivery will you and your partner plan for (in the hospital with medication, at home with a doula, etc.)?

Are you going to talk to your baby while he or she is in the womb?

How much does your baby understand during prenatal development?

How will your relationship with your partner change as a result of the pregnancy?

Will you begin bonding with your baby prior to birth?

he science of human development includes many beginnings. Each of the first four chapters of this text forms one corner of a solid foundation for our study.

Chapter 1introduces definitions and dimensions, explaining research strategies and methods that help us understand how people develop. The need for science, the power of culture, and the necessity of an ecological approach are all explained.

Without ideas, our study would be only a jumble of observations. Chapter 2 provides organizing guideposts: Five major theories, each leading to many other theories and hypotheses, are described.

Chapter 3 explains heredity. Genes never act alone, yet no development — whether in body or brain, at any time, in anyone — is unaffected by DNA.

Chapter 4 details the prenatal growth of each developing person from a single cell to a breathing, grasping, crying newborn. Many circumstances — from the mother’s diet to the father’s care to the culture’s values — affect development during every day of embryonic and fetal growth.

As you see, the science and the wonder of human life begin long before birth. These four chapters provide the basic ideas and concepts that enable us to understand each developing child — and all of the rest of us.

The Science of Human Development CHAPTER


✦ Understanding How and Why The Scientific Method A VIEW FROM SCIENCE: Overweight Children and Adult Health The Nature–Nurture Controversy

✦ The Life-Span Perspective Development Is Multidirectional Development Is Multicontextual INSIDE THE BRAIN: Thinking About Marijuana Development Is Multicultural Development Is Multidisciplinary Development Is Plastic A CASE TO STUDY: David

✦ Designing Science Observation The Experiment The Survey Studying Development over the Life Span

✦ Cautions and Challenges from Science Correlation and Causation Quantity and Quality Ethics

What Will You Know?1

1. Why is science especially crucial for understanding how people develop?

2. Are children always and everywhere the same, or is each child unique, changing from day to day and place to place?

3. What methods are used to study development?

4. What must scientists do to make their conclusions valid and ethical?

hen I was 4 years old, professional photographers came to our house to take pictures of my

Wmother and me, wearing matching dresses. I was bathed and dressed for the occasion,and my mother wore lipstick and perfume. Right before they came, I found a scissors andcut my hair. My mother stopped me before I could finish, but some tufts were short. She laughed, tying bows to make my hair presentable. I do not remember any of this, but my mother has told this anecdote many times. There are photographs to prove it.

What surprises you most about this memory? Is it normal for children to misbehave, or does my hair-cutting suggest something pathological — maybe defiance, or antisocial behavior? Would you have punished me if I were your child?

What about this incident reflects culture and history — maybe photographers coming to homes, mother–daughter dresses, lipstick, ribbons, scissors within a child’s reach? Why did my mother laugh and cherish the memory?

This chapter introduces the developmental perspective, which seeks to answer questions like these. Every action of each child could be natural, could be cultural, or could reflect something odd about their genes or upbringing. To really understand this incident, we need research — on other 4-year-olds, on other mothers, and on my mother and me over the years.

Perhaps my mother did not want those photographers, but, as expected of wives at the time, she may have agreed to please my father. But perhaps she resented the pressure on appearance, so she was glad that I cut my hair. Does that interpretation come from my current viewpoint, not from hers? Maybe, maybe not.

You, and everyone who was ever a child, experienced dozens of incidents like this one. Are you the product of genes, culture, context, or child rearing? This chapter suggests how to find answers.

Understanding How and Why The science of human development seeks to understand how and why people—all kinds of people, everywhere, of every age—change or remain the same over time. The goal is for the 7.6 billion people on Earth to fulfill their potential. Their development is multidirectional, multicontextual, multicultural, multidisciplinary, and plastic, five terms that will be explained soon.

science of human development The science that seeks to understand how and why people of all ages change or remain the same over time.

First, however, we need to emphasize that developmental study is a science. It depends on theories, data, analysis, critical thinking, and sound methodology, just like every other science. All scientists ask questions and seek answers in order to ascertain “how?” and “why?”

Science is especially useful when we study people: Lives depend on it. What should pregnant women eat? How much should babies cry? When should children be punished, how, and for what? Should schools be coed or single-sex, public or private? Should education encourage independence or obedience, be optional or required, through eighth grade or twelfth grade? People disagree about all this and more, sometimes vehemently.

The Scientific Method Almost everyone cares about children, yet many people respond to children without understanding them. Disputes occur often because facts are unknown, and applications spring from assumptions, not from data.

Five Crucial Steps To avoid unexamined opinions, to rein in personal biases, and to discover new truths, researchers follow the five steps of the scientific method (see Figure 1.1):

FIGURE 1.1 Process, Not Proof Built into the scientific method—in questions, hypotheses, tests, and replication—is a passion for possibilities, especially unexpected ones.

scientific method A way to answer questions using empirical research and data-based conclusions.

1. Begin with curiosity. On the basis of theory, prior research, or a personal observation, pose a question.

2. Develop a hypothesis. Shape the question into a hypothesis, a specific prediction to be examined.

3. Test the hypothesis. Design and conduct research to gather empirical evidence (data). 4. Analyze the evidence. Conclude whether the hypothesis is supported or not. 5. Report the results. Share the data, conclusions, and alternative explanations.

hypothesis A specific prediction that can be tested.

empirical evidence Evidence that is based on observation, experience, or experiment; not theoretical.

Replication As you see, developmental scientists begin with curiosity and then seek the facts, drawing conclusions after careful research. Reports are written so that other scientists can examine the procedures, analyze the data, check the conclusions, and then replicate the results.

Replication—repeating the study with different participants — is needed before conclusions are considered solid. Scientists study the reports (Step 5) of other scientists and build on what has gone before. Sometimes they try to duplicate a study exactly, using the same methods; often they follow up with related research (Stroebe & Strack, 2014). Conclusions are then revised, refined, rejected, or confirmed.

replication Repeating a study, usually using different participants, sometimes of another age, socioeconomic status (SES), or culture.

Obviously, the scientific method is not foolproof. Scientists may draw conclusions too hastily, misinterpret data, or ignore alternative perspectives. The results from one group of people may differ from the results from another group. Sometimes scientists discover outright fraud (Bouter, 2015). Ideally, results are replicated, not only by conducting the same research again but also by designing other research that will verify and extend the same hypothesis (Larzelere et al., 2015).

An effort to replicate 100 published studies in psychology found that about one-third did not produce the same results and another one-third were less conclusive than the original (Open Science Collaboration, 2015). Problems often arose from the research design (Step 3) of the original studies and the pressure to publish.

The push for replication is welcomed by scientists in many disciplines. For instance, educators reevaluated the effects of preschool education paid by state taxes in Virginia. They confirmed that children who attended preschool recognized nine more letters, on average, than children of

the same age who did not (Huang, 2017). Since replication reveals that some well-intentioned programs are not effective, it is good to know that this one was.

Asking questions and testing hypotheses are crucial for every aspect of child development. A View from Science shows this process in more detail.


Overweight Children and Adult Health2

Obesity is a serious problem. Over the life span, from infancy to age 60, rates of obesity increase, and with it, rates of diabetes, heart disease, and stroke. The connection between overweight and disease was not always known. Indeed, the opposite seemed true.

Since tiny newborns and underweight children are more likely to die, people made a logical, but false, assumption: Heavier children must be healthier (Laraway et al., 2010).

That assumption had fatal consequences. Adults were proud of their pudgy babies and overfed their children. Not until the middle of the twentieth century, in the famous Framingham Heart Study, did scientists discover that obese adults risked premature death— of heart disease, stroke, diabetes, and many other ailments.

This discovery sparked a new question (Step 1): Was childhood obesity a health risk when those children grew up? That led to a hypothesis (Step 2) that overweight in childhood impairs health in adulthood.

What Will Become of Her? This happy, beautiful girl in Sweden may become an overweight woman . . . or she may not. Research finds that if she slims down by adulthood, she is likely to be healthier than the average woman who was never overweight.

This hypothesis is now widely assumed to be true. For instance, a poll found that most Californians consider childhood obesity “very serious,” with one-third of them rating poor eating habits as a worse risk to child health than drug use or violence (Hennessy-Fiske, 2011). But is their assumption valid?

The best way to test that hypothesis (Step 3) is to examine adult health in people who had been weighed and measured in childhood. Several researchers did exactly that, using data on children’s height and weight—and their measurements as adults—from four studies. A summary of those studies (Juonala et al., 2011) found that most people (83 percent) maintained their relative weight. Thus most overweight children became overweight adults. (See Figure 1.2a.) Analysis of those data led to a strong conclusion (Step 4), which was then published (Step 5): Overweight children are likely to become obese adults.

FIGURE 1.2 Not Yet Obese You probably know that more than half of all adults in the United States are overweight, so this chart—with only 21 percent of adults obese—may seem inaccurate. However, three facts explain why the data are accurate: (1) “Obese” is much heavier than overweight; (2) the average adult in this study was 34 years old (middle-aged and older adults are more often obese); and (3) one of the studies that provided much of the longitudinal data was in Finland, where rates of obesity are lower than in the United States.

Other research finds that childhood obesity is increasing in almost every nation of the world, including those countries where, in the past, malnutrition and infectious diseases were prime causes of child death. That is no longer true: Very few children die of malnutrition, but many become overweight adults, a health hazard that can be traced to childhood. As one review states it:

The prevalence of overweight and obesity in children and adults continues to increase worldwide and, because of their association with cardiovascular disorders, diabetes, and dyslipidemia, are becoming one of the major health issues.

[Susic & Varagic, 2017, p. 139]

For instance, in those four studies, 29 percent of the adults who were overweight all their lives had high blood pressure, compared to 11 percent of those who were never overweight (Juonala et al., 2011). Hypertension is a proven risk factor for heart disease and strokes, which are becoming the most common cause of death in poor nations (Mozaffarian et al., 2016).

A new question arose (Step 1), building on those earlier findings. What about overweight children who become normal-weight adults? Have they already harmed their health? That led to another hypothesis (Step 2): Overweight children will have a higher rate of heart attacks, strokes, diabetes, and death in adulthood, even if they slim down. The research design (Step 3) was to measure indications of health in adults who had been overweight as children but who now were normal weight.

The data (Step 4)disproved the hypothesis (see Figure 1.2b): As normal-weight adults, those who had been overweight as children were not at high risk of disease, a conclusion replicated by several studies with quite different populations (Juonala et al., 2011). Scientists were happy with that conclusion— disproving a commonly believed hypothesis may be even more welcome than proving it, because science ideally uncovers false assumptions as well as confirms true ones.

Many other issues, complications, and conclusions regarding diet are discussed later in this book. For now, all you need to remember are the steps of the scientific method and that developmentalists are right: Significant “change over time” is possible.

The Nature–Nurture Controversy An easy example of the need for science concerns a great puzzle of life, the nature—nurture debate. Nature refers to the influence of the genes that people inherit. Nurture refers to influences from the environment, which is broadly interpreted to include the entire context of development. The environment begins with the health and diet of the embryo’s mother and continues lifelong, including experiences in the family, school, community, and nation.

nature In development, nature refers to the traits, capacities, and limitations that each individual inherits genetically from his or her parents at the moment of conception.

nurture In development, nurture includes all of the environmental influences that affect the individual after conception. This includes everything from the mother’s nutrition while pregnant to the cultural influences in the nation.

The nature—nurture debate has many manifestations, among them heredity-environment, maturation-learning, and sex-gender. Under whatever name, the basic question is, “How much of any characteristic, behavior, or emotion is the result of genes, and how much is the result of experience?“

Some people believe that most traits are inborn, that children are innately good (“an innocent child”) or bad (“beat the devil out of them”). Others stress nurture, crediting or blaming parents, neighborhood, drugs, or even food, when someone is good or bad, a hero or a scoundrel.

Neither belief is accurate. The question is “how much,” not “which,” because both genes and the environment affect every characteristic: Nature always affects nurture, and then nurture affects nature. Even “how much” is misleading, because it implies that nature and nurture each contribute a fixed amount. Instead, the dynamic interaction between them shapes the person (Eagly & Wood, 2013; Lock, 2013; Shulman, 2016).

A further complication is that the impact of any good or bad experience — a beating, or a beer, or a blessing—is magnified or inconsequential because of the particular genes or events. Thus, every aspect of nature and nurture depends on other aspects of nature and nurture in ways that vary for each person.

Chopin’s First Concert Frederick Chopin, at age 8, played his first public concert in 1818, before photographs. But this photo shows Piotr Pawlak, a contemporary prodigy playing Chopin’s music in the same Polish Palace where that famous composer played as a boy. How much of talent is genetic and how much is cultural—a nature-nurture question that applies to both boys, 200 years apart.

Epigenetics The science of this interaction is explored in epigenetics, the study of the many ways in which the environment alters genetic expression. Epigenetics begins with methylation at conception and continues lifelong. For example, brain formation is directed by genes inherited at conception, but those genes are not alone. Soon, nutrients and toxins affect the prenatal brain, nurture affecting nature.

epigenetics The study of how environmental factors affect genes and genetic expression—enhancing, halting, shaping, or altering the expression of genes.

Not only do biological influences shape the brain, social experiences do as well. Chronic loneliness, for example, changes brain structures (Cacioppo et al., 2014). More than that, over thousands of years, human experiences shape genes. We are affected not only by our own nature and nurture but also by the nature and nurture of our parents, grandparents, and so on (Young, 2016).

Sometimes protective factors, in either nature or nurture, outweigh our liabilities. As one review explains, “there are, indeed, individuals whose genetics indicate exceptionally high risk of disease, yet they never show any signs of the disorder” (Friend & Schadt, 2014, p. 970). Why? Epigenetics. [Developmental Link: More discussion of epigenetics occurs in Chapter 3.]

Dandelions and Orchids There is increasing evidence of differential susceptibility — that sensitivity to any particular experience differs from one person to another because of the particular genes each person has inherited, or because of events that the person experienced years earlier.

differential susceptibility The idea that people vary in how sensitive they are to particular experiences. Often such differences are genetic, which makes some people affected “for better or for worse” by life events. (Also called differential sensitivity.)

Some people are like dandelions — hardy, growing and thriving in good soil or bad, with or without ample sun and rain. Other people are like orchids — quite wonderful, but only when ideal growing conditions are met (Ellis & Boyce, 2008; Laurent, 2014).

For example, in one study, depression in pregnant women was assessed and then the emotional maturity of their children was measured. Those children who had a particular version of the serotonin transporter gene (5-HTTLPR) were likely to be emotionally immature if their mothers were depressed, but more mature than average if their mothers were not depressed (Babineau et al., 2015).

Each of us carries both joys and scars from childhood experiences that would not have affected another person. Think about your favorite teacher. What about you — either in your genes or in your experiences—made that particular teacher wonderful for you? Could that same teacher be hated, or ignored, by another student? That’s differential susceptibility.

THINK CRITICALLY:3 Should we try to assign a percent to nature and a percent to nurture so that they add up to 100 percent?

Male and Female The nature—nurture debate is not merely academic. In a tragic case, an infant’s penis was mistakenly destroyed in 1966. At that time, sex differences were thought to originate from the genitals and child rearing, not from the genes. So his parents had his testicles removed and renamed him Brenda. They raised him as a girl (Money & Ehrhardt, 1972).

But we now know that some male—female differences are genetic and hormonal— in the brain, not the body; in nature, not nurture. After a troubled childhood, Brenda chose to become David, a man, at age 15. That was too late; David killed himself at age 38 (Diamond & Sigmundson, 1997; Associated Press, 2004).

From this example, it is tempting to conclude that all male—female differences are due to nature, but that would be incorrect. For instance, it was once believed that biology made females inferior in math. Girls who wanted to be physicists or engineers were told to choose another career. But in the 1960s millions of women insisted that nurture, not nature, kept women from excelling in math.

Consequently, more girls were allowed to study calculus. Recent international tests find that math scores of the two sexes have become quite similar: In some nations (Russia, Singapore, Algeria, and Iran) girls are ahead of boys! The practical implications of that research are that college women are encouraged to become engineers, physicists, or chemists (Brown & Lent, 2016). The scientific implications are, again, that nature and nurture interact, in sex differences and in everything else.

Video Activity: The Boy Who Was a Girl examines the case of David/Brenda Reimer and what it means to be a boy or a girl.4


1. What are the five steps of the scientific method? 2. What is the difference between asking a question (Step 1) and developing a hypothesis (Step

2)? 3. Why is replication important for scientific progress? 4. What basic question is at the heart of the nature-nurture controversy? 5. When in development does nature begin to influence nurture? 6. What is the difference between genetics and epigenetics?

7. How might differential susceptibility be evident when students respond to a low exam grade?

The Life-Span Perspective The life-span perspective (Baltes, 1987; Fingerman et al., 2011; Lerner et al., 2014) began as a lens through which to view the entire human life span, particularly adult development. Insights from that perspective soon transformed our understanding of development at every age. The crucial idea is that, at every moment in life, context and culture affect each person’s past and shape their future. The life-span perspective views development as multidirectional, multicontextual, multicultural, multidisciplinary, and plastic (Baltes et al., 2006; Barrett & Montepare, 2015; Raz & Lindenberger, 2013).

life-span perspective An approach to the study of human development that takes into account all phases of life, not just childhood or adulthood.

Development Is Multidirectional Multiple changes, in every direction, characterize development. Traits appear and disappear, with increases, decreases, and zigzags (see Figure 1.3). An earlier assumption — that all development advances until about age 18, steadies, and then declines—has been soundly disproven by life- span research.

FIGURE 1.3 Patterns of Developmental Growth Many patterns of developmental growth have been discovered by careful research. Although linear (or nonlinear) progress seems most common, scientists now find that almost no aspect of human change follows the linear pattern exactly.

Patterns of Change Sometimes discontinuity is evident: Change can occur rapidly and dramatically, as when caterpillars become butterflies. Sometimes continuity is found: Growth can be gradual, as when redwoods add rings over hundreds of years. Some characteristics do not seem to change at all: The person I am now is an older version of the person I was as an infant. The same is true of you.

Children experience simple growth, radical transformation, improvement, and decline as well

as stability, stages, and continuity — day to day, year to year, and generation to generation. Not only do the pace and direction of change vary, but each characteristic follows its own trajectory.

Losses in some abilities occur simultaneously with gains in others. For example, babies lose some ability to distinguish sounds from other languages when they begin talking in whatever language they hear; school-age children become quite realistic, losing some of the magical imagination of younger children.

Critical and Sensitive Periods The timing of losses and gains, impairments or improvements, varies as well. Some changes are sudden and profound because of a critical period, which is either when something must occur to ensure normal development or the only time when an abnormality might occur. For instance, the human embryo grows arms and legs, hands and feet, fingers and toes, each over a critical period between 28 and 54 days after conception. After that, it is too late: Unlike some insects, humans never grow replacement limbs.

critical period A crucial time when a particular type of developmental growth (in body or behavior) must happen for normal development to occur, or when harm (such as a toxic substance or destructive event) can occur.

We know this fact because of a tragic episode. Between 1957 and 1961, thousands of newly pregnant women in 30 nations took thalidomide, an antinausea drug. This change in nurture (via the mother’s bloodstream) disrupted nature (the embryo’s genetic program).

If an expectant woman ingested thalidomide during the critical period for limb formation, her newborn’s arms or legs were malformed or absent (Moore et al., 2015, p. 480). Whether all four limbs, or just arms, hands, or fingers were missing depended on exactly when the drug was taken. If thalidomide was ingested only after day 54, no harm occurred.

Life has few such dramatic critical periods. Often, however, a particular development occurs more easily—but not exclusively — at a certain time. That is called a sensitive period.

sensitive period A time when a certain type of development is most likely, although it may still happen later with more difficulty. For example, early childhood is considered a sensitive period for language learning.

An example is learning language. If children do not communicate in their first language between ages 1 and 3, they might do so later (hence, these years are not critical), but their grammar is impaired (hence, these years are sensitive).

Similarly, childhood is a sensitive period for learning to speak a second or third language with native pronunciation. Adults who master new languages are asked, “Where are you from?” by those who can detect an accent, even when the speaker does not. Indeed, adults born in the United States whose first language was English reveal whether they grew up in Boston, Brooklyn, or Boise. The same is true within every other nation, as the tone, timing, and pronunciation of every language varies by region and social class.

Sometimes the multidirectional nature of development shows the influence of national culture. Childhood and adolescence are a sensitive period for attitudes about psychosocial drugs, as

evident from changes in acceptance of marijuana. This is discussed further in Inside the Brain.

I Love You, Mommy We do not know what words, in what language, her son is using, but we do know that Sobia Akbar speaks English well, a requirement for naturalized U.S. citizens. Here she obtains citizenship for her two children born in Pakistan. Chances are they will speak unaccented American English, unlike Sobia, whose accent might indicate that she learned British English as a second language.

Development Is Multicontextual The second insight from the life-span perspective is that “human development is fundamentally contextual” (Pluess, 2015, p. 138). Some of the many contexts that affect development are physical (climate, noise, population density, etc.); some relate to family (parents’ relationship, siblings’ values, income, other relatives, etc.); and some to community (urban, suburban, or rural; multiethnic or not; etc.).


Thinking About Marijuana 6

Brains are affected by drugs, for better or worse, in two ways. First, structural changes are possible in the size and activity of particular regions. Second, the links between neurons are strengthened or weakened. These findings again reveal differential susceptibility, as well as multidirectional development.

The most studied drug is alcohol, which (1) reshapes the brain during fetal development and (2) strengthens desire. As a result, (1) some newborns are brain damaged lifelong, and (2) some social drinkers suddenly find that a drink awakens neuronal links that make another drink impossible to refuse.

Now consider marijuana. Links between fear from part of the brain (the amygdala) or pleasure from other parts of the brain (especially in the basal ganglia) precede drug use. Both are multidirectional, powerfully affected by childhood. Consequently, attitudes change because of the rise and fall of fear (see Figure 1.4).

FIGURE 1.4 Double Trends Both cohort and generational trends are evident. Note that people of every age are becoming more accepting of marijuana, but the effect is most obvious for adults who never heard about “reefer madness.”

Observation Quiz Why is the line for the 1981-1997 cohort much shorter than the line for the older cohorts? (see answer, p. 14)7

In the United States in the 1930s, marijuana was declared illegal. The 1936 movie Reefer Madness was shown until about 1960, with vivid images connecting marijuana with a warped brain, suicide, and insanity. Most adolescents feared and shunned marijuana. However, marijuana was part of the jazz and popular music scene: In the 1960s, the Beatles, Bob Dylan, James Brown, and Bob Marley smoked it and sang about it.

Young adolescents listened to that music, resisted adult rules, and increasingly tried marijuana themselves. By 1980, half of all high school seniors had smoked “weed” in the previous year, according to Monitoring the Future . an annual report (Miech et al., 2016).

That worried older adults, whose emotional reactions to marijuana had been formed decades earlier. They believed it would permanently damage vulnerable teenage brains, leading to psychological disorders and drug addiction (Estroff & Gold, 1986).

President Nixon declared that drug abuse (especially marijuana, but not cigarettes or alcohol) was “Public Enemy Number One.” A decade later, Nancy Reagan (first lady from 1981 to 1989) advocated, “Just say no to drugs.” That affected the attitudes and behavior of the next cohort: By 1991, the rate of high school seniors who had ever tried marijuana (21 percent) was only one-third of what it had been.

Attitudes, politics, and behavior are multidirectional, and so another shift has occurred. The parents of current adolescents are not from the generation that most feared the drug. One result is that far fewer (30 percent) of their teenagers think regular use of marijuana is “a great risk,” compared to about 80 percent in the early 1980s. Behavior has shifted as well: In 2016, 38 percent of high school students reported smoking marijuana in the past year.

This signifies changes in the neurological links to marijuana use—irrational fears and desires. Some evidence finds that marijuana smoking alters the brain (Mandelbaum & de la Monte, 2017), but many scientists are not convinced. Some question research that finds a correlation between marijuana use and “structural abnormalities in the brains of young people,” but we lack good “scientific evidence about the effects of marijuana on the adolescent brain.” As a result, we are “gambling with the health and safety of our youth” (DuPont & Lieberman, 2014, p. 557).

It may be that pregnant women who use marijuana damage the brains of their fetus (Alpár et al., 2016; Volkow et al., 2017). On the other hand, some find that marijuana relieves pain, with fewer dangerous side effects (addiction and death) than prescribed opiates (Miller, 2016).

The best we have longitudinally may be from Australians who were regular users of marijuana from age 18 on. By midlife, they had more financial and relationship problems than those who were drug-free—but not more than those who abused alcohol (Cerdá et al., 2016). However, data on Australians who smoked an illegal drug 20 years ago may not apply to Americans now.

Unfortunately, federal laws passed decades ago impede current research: Longitudinal, unbiased studies on

brain benefits and costs of marijuana have not been published, and earlier data may confuse correlation with causation (a topic discussed at the end of this chapter).

We know that the effects of the drug on the brain vary, and that just thinking about marijuana triggers extreme brain reactions, including phobia and ecstasy. Are current attitudes (mostly positive) more rational than the mostly negative ones of our great-grandparents? More science needed.

For example, a student might decide on a whim to stop by a social gathering instead of heading straight to the library. The social context of the party (perhaps free drinks and food, lively music, many friends, ample room, and interesting strangers) is influential, affecting that student’s performance in class the next morning, and perhaps his or her future. We each encounter several contexts each day, some by choice and some not; they all could affect our later thoughts and actions.

Ecological Systems Leading developmentalist Urie Bronfenbrenner (1917–2005) emphasized the importance of considering contexts. Just as a naturalist studying an organism examines the ecology (the relationship between the organism and its environment) of a tiger, or a tree, or a trout, Bronfenbrenner recommended an ecological-systems approach (Bronfenbrenner & Morris, 2006) to study humans.

ecological-systems approach A perspective on human development that considers all of the influences from the various contexts of development. (Later renamed bioecological theory.)

Where in the World? Like every child, this boy is influenced by dozens of contexts from each of Bronfenbrenner’s systems, some quite direct and some in the macro-and exosystems. His cap (called a kopiah), diligence, all-boys school, and slanted desk each affects his learning, but those could occur in many nations—in the Americas, Europe, or Africa. In fact, this is in Asia, in Kota Bharu, Malaysia.

This approach recognizes three nested levels (see Figure 1.5). Most obvious are microsystems — each person’s immediate social contexts, such as family and peer group. Next are exosystems (local institutions such as school and church, temple, or mosque) and then macrosystems (the larger social setting, including cultural values, economic conditions, and political processes).

FIGURE 1.5 The Ecological Model According to developmental researcher Urie Bronfenbrenner, each person is significantly affected by interactions among a number of overlapping systems, which provide the context of development. Microsystems —family, peer group, classroom, neighborhood, house of worship—intimately and immediately shape human development. Surrounding and supporting the microsystems are the exosystems, which include all the external networks, such as community structures and local educational, medical, employment, and communications systems, that affect the microsystems. Influencing both of these systems is the macrosystem, which includes cultural patterns, political philosophies, economic policies, and social conditions. Mesosystems refer to interactions among systems, as when parents and teachers coordinate to educate a child. Bronfenbrenner eventually added a fifth system, the chronosystem, to emphasize the importance of historical time.

Two more systems affect these three. One is the chronosystem (literally, “time system”), which is the historical context. The other is the mesosystem, consisting of the connections among the other systems.

Toward the end of his life, Bronfenbrenner renamed his approach bioecological theory to highlight the role of a sixth set of systems, those within the body (e.g., the sexual-reproductive system, the cardiovascular system) that affect the external systems (Bronfenbrenner & Morris, 2006).

Bronfenbrenner’s perspective remains useful. For example, a puzzling fact is that children who have been sexually abused are likely to be abused again, in childhood and adulthood. Why? Fault of the family? The culture?

Perhaps all three and more. Psychologists using the bioecological approach to analyze repeated sexual victimization conclude that the micro-, macro-, and exosystems each have an impact (Pittenger et al., 2016).

History and Social Class Two contexts — the historical and the socioeconomic — are basic to understanding everyone, from conception onward. Since they are relevant to every stage, we explain them now.

People born within a few years of one another are called a cohort, a group defined by its members’ shared age. Cohorts travel through life together, affected by the values, events, technologies, and culture of the historical period as it interacts with their age at the time. From the moment of birth, when parents name their baby, historical context affects what may seem like a private and personal choice (see Table 1.1).

cohort People born within the same historical period who therefore move through life together, experiencing the same events, new technologies, and cultural shifts at the same ages. For example, the effect of the Internet varies depending on what cohort a person belongs to.


Popular First Names


2015: Emma, Olivia, Sophia, Isabella, Ava

1995: Jessica, Ashley, Emily, Samantha, Sarah

1975: Jennifer, Amy, Heather, Melissa, Angela

1955: Mary, Deborah, Linda, Debra, Susan

1935: Mary, Shirley, Barbara, Betty, Patricia


2015: Noah, Liam, Mason, Jacob, William

1995: Michael, Matthew, Christopher, Jacob, Joshua

1975: Michael, Jason, Christopher, James, David

1955: Michael, David, James, Robert, John

1935: Robert, James, John, William, Richard

Information from U.S. Social Security Administration.

If you know someone named Emma, she is probably young: Emma is the most common name for girls born in 2015 but was not in the top 100 until 1996, and not even in the top 1,000 in 1990. If you know someone named Mary, she is probably old: About 10 percent of all girls born from 1900 to 1965 were named Mary, but now Mary is unusual.

Two of my daughters, Rachel and Sarah, have names that were common when they were born.

One wishes she had a more unusual name; the other is glad she does not. That is differential susceptibility, which applies to you as well as to my daughters. Your name is influenced by history; your reaction is yours.

The second pervasive context is economic, reflected in a person’s socioeconomic status, abbreviated SES: (Sometimes SES is called tocial class, as in middle class or working class) SES reflects education, occupation, and neighborhood, as well as income.

socioeconomic status (SES) A person’s position in society as determined by income, occupation, education, and place of residence. (Sometimes called social class.)

Measuring SES is complex, especially internationally. The United Nations rates the United States and Canada as wealthy nations, but most North Americans do not consider themselves rich. (see Figure 1.6.)

FIGURE 1.6 Children of the Future The United States is an exception to a general rule: the wealthier a nation, the smaller the income gap. Since young families tend to be the least wealthy, and since education and health care are affected by neighborhood and employment, a wide gap bodes ill for children. Particularly troubling are the trend lines— unless changes occur, the United States will be worse than Mexico by 2035.

SES is not just about money. Suppose a U.S. family is comprised of an infant, an unemployed mother, and a father who earns less than $17,000 a year. Their SES would be low if they live in a violent, drug-infested neighborhood and the wage earner is a high school dropout working 45 hours a week for minimum wage (in 2016, the federal minimum wage was $7.25 an hour). But SES would be much higher if the wage earner is a postdoctoral student living on campus and teaching part time. Both of these families are below the official poverty line for a family of three ($19,790), but only one is low-SES.

SES brings advantages and disadvantages, opportunities and limitations — all affecting housing, health, nutrition, knowledge, and habits. Although low income obviously limits a child, other factors are pivotal, especially education and national policy.

Same Situation, Far Apart: Shelter Rules The homeless shelter in Paris, France (left) allows dogs, Christmas trees, and flat-screen televisions for couples in private rooms. The one in Cranston, Rhode Island (right) is only for men (no women, children, or dogs), who must leave each morning and wait in line each night for one of the 88 beds. Both places share one characteristic: Some of the homeless are turned away, as there is not room for everyone.

Answer to Observation Quiz (from p. 11) Because surveys rarely ask children their opinions, and the youngest cohort on this graph did not reach adulthood until about 2005.

For example, the nations of northern Europe seek to eliminate SES disparities as much as possible, and the health and school achievement of children from their low-income families are not far behind the richest children. By contrast, developing nations, especially in Latin America, tend to have large SES achievement gaps (Ravallion, 2014). Among advanced nations, the United States has “recently earned the distinction of being the most unequal of all developed countries” (Aizer & Currie, 2014, p. 856). Such differences by nation are a result of the macrosystem, not the microsystem.

Income differences are not only found by ethnic group but also by age. Young children with young parents are poorest, and poverty in early childhood reduces academic achievement even more than poverty during adolescence (Wagmiller 2015). The reason probably relates to the quality of education before age 5.

Development Is Multicultural In order to study “all kinds of people, everywhere, at every age,” research must include people of many cultures. For social scientists, culture is far more than food or clothes; it is a set of ideas, beliefs, and patterns of behavior.

culture A system of shared beliefs, norms, behaviors, and expectations that persist over time and prescribe social behavior and assumptions.

Creating Culture Culture is a powerful and pervasive social construction, that is, a concept created, or constructed, by a society. Social constructions affect how people think and act—what they value, ignore, and punish.

social construction An idea that arises from shared perceptions, not on objective reality. Many age-related terms (such as childhood, adolescence, yuppie, and senior citizen) are social constructions, strongly influenced by social assumptions.

Although most adults think they accept, appreciate, and understand many cultures, that may not be accurate. It is easy to overgeneralize, becoming simplistic about cultures that are not one’s own. For example, when people speak of Asian culture or Hispanic culture, they may be stereotyping, ignoring cultural differences between people from Korea and Japan, for instance, or those from Mexico and Guatemala.

Hard Floor, Hard Life These are among the thousands of unaccompanied minors who fled Latin America and arrived in Arizona and Texas in 2014. Developmentalists predict that the effects of their hazardous journey will stay with them, unless sources of resilience—such as caring family and supportive community—are quickly found. Culture and context affect everyone lifelong.

Observation Quiz How many children are sleeping here in this photograph? (see answer, p. 16)

Every generalization risks harming individuals. For example, the idea that Asian children are the “model minority” increases the pressure on children to excel, and then to be teased when they do. Further, some people in every group deliberately rebel against the expected beliefs and behaviors from their culture.

Thus, the words culture and multicultural need to be used carefully, especially when they are applied to individuals, lest one slides from awareness to stereotype.

In a diverse nation such as the United States, everyone is multicultural. Within each person, ethnic, national, school, and family cultures sometimes clash, with no one a pristine exemplar of

only one culture. One of my students, whose parents had immigrated to the United States, wrote:

My mom was outside on the porch talking to my aunt. I decided to go outside; I guess I was being nosey. While they were talking I jumped into their conversation which was very rude. When I realized what I did it was too late. My mother slapped me in my face so hard that it took a couple of seconds to feel my face again.

[C., personal communication]

Notice how my student reflects her mother’s culture; she labels herself “nosey” and “very rude.” She later wrote that she expects children to be seen, not heard. Her son makes her “very angry” when he interrupts.

In this example, she and her son both reflect U.S. culture, where talkative children are encouraged, as well as the culture of her mother’s homeland, where they are not. Do you think my student was nosey or, on the contrary, that her mother should not have slapped her? Or do you hesitate to choose either option? Your answer — or non-answer—reflects your culture.

As with my student’s mother, people tend to believe that their culture is better than others. This belief has benefits: People who endorse their culture’s attitudes and habits tend to be happy, proud, and willing to help strangers. However, that belief becomes destructive if it reduces respect for people from other groups. Thoughtlessly, differences are assumed to be inferior (Akhtar & Jaswal, 2013).

Difference and Deficit Developmentalists recognize the difference-equals-deficit error, which is the assumption that people unlike us (difference) are inferior (deficit). Sadly, when humans notice that someone else does not think or act as they do, the human tendency is to believe that such a person is to be pitied, feared, or encouraged to change. Even 3-year-olds assume that the way things are done by their parents, or in their community, is the right way (Schmidt et al., 2016).

difference-equals-deficit error The mistaken belief that a deviation from some norm is necessarily inferior to behavior or characteristics that meet the standard.

The difference-equals-deficit error is one reason that a careful multicultural approach is necessary. Never assume that another culture is wrong and inferior—or the opposite, right and superior. Assumptions can be harmful.

For example, one Japanese child, on her first day in a U.S. school, was teased for the food she brought for lunch. The next day, when she arrived at school, she dumped the contents of her lunchbox in the garbage — she would rather go hungry than be considered deficient.

Video: Research of Geoffrey Saxe further explores how difference does not equal deficit.

This example illustrates the problem with judging another culture: A Japanese lunch might, or might not, be healthier than a typical American one. The children did not know or care about

nutrition; they assumed that their usual lunch was best. Meanwhile, the Japanese child’s mother may have thought she was packing a better lunch than the standard U.S. one.

To further develop a multicultural perspective, we need to differentiate culture, ethnicity, and race . Members of an ethnic group almost always share ancestral heritage and often have the same national origin, religion, and language. That shared history affects them when they are far from their original home.

ethnic group People whose ancestors were born in the same region and who often share a language, culture, and religion.

Consequently, ethnic groups often share a culture, but this is not always true (see Figure 1.7). There are “multiple intersecting and interacting dimensions” to ethnic identity (Sanchez & Vargas, 2016 . p. 161). People may share ethnicity but differ culturally, especially if they left their original home long ago and adopted the culture of their new place, such as people of Irish descent in Ireland, Australia, and North America. The opposite is also true: People of many ethnic groups may all share a culture, as evident in all the people who identify with British, American, or Canadian culture.

FIGURE 1.7 Overlap—But How Much? Ethnicity, culture, and race are three distinct concepts, but they often—though not always—overlap.

Ethnicity is a social construction, a product of the social context, not biology. It is nurture, not nature, with specifics dependent on the other people nearby. For example, African-born people in North America typically consider themselves African, but African-born people in Africa identify with a more specific ethnic group. Awareness of ethnicity has increased in the United States, in part because the recent influx of immigrants has awakened an interest in family history among many Americans. People in the United States are more aware of ethnicity and race than people elsewhere (Verkuyten, 2016). That itself is cultural.

Answer to Observation Quiz (from p. 15) Nine—not counting the standing boy or the possible tenth one whose head is under the blanket. Rumpled blankets suggest that eight more are elsewhere at the moment. Each night hundreds of children sleep in this Border Protection Processing Facility in Brownsville, Texas. They are detained while authorities decide whether to send them back to the countries they fled or to a safe place in the United States.

Some Americans are puzzled by civil wars in distant nations (e.g., in Syria, or Sri Lanka, or Kenya), where bitter enemies may appear to be of the same ethnicity. Do not be surprised: Within every nation, people recognize ethnic differences that outsiders do not see. Social constructions are potent.

THINK CRITICALLY: To fight racism, must race be named and recognized?

Ethnic identity flourishes when co-ethnics are nearby, when ethnic distinctions are visible, and people of other groups emphasize differences (Sanchez & Vargas, 2016). For those reasons, race, thought to signify biological distinctions, may be confused with ethnicity.

race A group of people who are regarded by themselves or by others as distinct from other groups on the basis of physical appearance, typically skin color. Social scientists think race is a misleading concept, as biological differences are not signified by outward appearance.

That mistake was made in South Africa. Apartheid separated the population into four distinct groups, supposedly racial ones: White, Black, Coloured, and Asian. This simple division was one reason that the end of apartheid was called a “bloodless revolution,” with no violence between Whites and Blacks. However, there was extensive violence among Black groups, not noted at first in the press because Westerners did not expect or understand it (Thompson & Berat, 2014).

Social scientists are convinced that race is a social construction, without biological usefulness. Skin color is particularly misleading, because dark-skinned people with African ancestors have the “highest levels of genetic diversity” (Tishkoff et al., 2009, p. 1035), and because many dark- skinned people whose ancestors were not African share neither culture nor ethnicity with Africans.

Concern that the word race is inaccurate and misleading is expressed by biologists as well as social scientists. As one team writes:

We believe the use of biological concepts of race in human genetic research — so disputed and so mired in confusion—is problematic at best and harmful at worst. It is time for biologists to find a better way.

[Yudell et al., 2016, p. 564]

However, the fact that race is a social construction does not make it irrelevant. African American adolescents who are proud of their race are likely to achieve academically, resist drug addiction, and feel better about themselves (Zimmerman et al., 2013). Thousands of medical, educational, and economic conditions — from low birthweight to college graduation, from home ownership to marriage rates — reflect racial disparities.

Thus, some social scientists believe that, in order to overcome racism, race must be recognized. They say that to be “color-blind” is to be racist (Neville et al., 2016). Perhaps. In any case, remember that race is a social construction, not a biological one, and that it indicates neither culture nor ethnicity.

Fitting In The best comedians are simultaneously outsider and insider, giving them a perspective that helps people laugh at the absurdity of their lives. Trevor Noah—son of a Xhosa South African mother and a German Swiss father—grew up within, yet outside, his native culture. For instance, he was seen as “Coloured” in his homeland, but as “White” on a video, which once let him escape arrest!

Observation Quiz What four aspects of Noah’s attire signify that he belongs at this fashion gala? (see answer, p. 19)

Development Is Multidisciplinary Historically, the various specialities within universities were each called a discipline. This continues, but developmental science is increasingly multidisciplinary (Lerner et al., 2014). The reason is that every academic discipline risks becoming a silo, a storage tank for research in that discipline, isolated from other disciplines. Breaking out of silos is crucial for understanding the whole person.

Nonetheless, scientists need to burrow into specific aspects of human life in order to fully grasp the developmental process. For that reason, development is often divided into three domains—biosocial, cognitive, and psychosocial. (Figure 1.8 describes each domain.) Each domain is the focus of several academic disciplines: Biosocial includes biology, neuroscience, and medicine; cognitive includes psychology, linguistics, and education; and psychosocial includes sociology, economics, and history.

FIGURE 1.8 The Three Domains The division of human development into three domains makes it easier to study, but remember that very few factors belong exclusively to one domain or another. Development is not piecemeal but holistic: Each aspect of development is related to all three domains.

Genetics The need for multidisciplinary research is obvious when considering genetic analysis. When the human genome was first mapped in 2003, some people assumed that humans became whatever their genes destined them to be—heroes, killers, or ordinary people. Biology was thought to be destiny: For example, thousands of scientists searched for a particular gene that would make a person develop alcohol use disorder, schizophrenia, or diabetes. And those thousands failed. Multidisciplinary research shows that many influences from many domains make a person more, or less, likely to have specific traits.


Diverse Complexities

It is often repeated that “the United States is becoming more diverse,” a phrase that usually refers only to ethnic diversity and not to economic and religious diversity (which are also increasing and merit attention). From a developmental perspective, two other diversities are also important — age and region, as shown below. What are the implications for schools, colleges, employment, health care, and nursing homes in the notable differences in the ages of people of various groups? And are attitudes about immigration, or segregation, or multiracial identity affected by the ethnicity of one’s neighbors?

Yes, genes affect every aspect of behavior. But even identical twins, with identical genes, differ physically, cognitively, and socially. The reasons abound, including non-DNA influences in utero and their position in the womb, both of which affect birthweight and birth order, and dozens of other epigenetic influences throughout life (Carey, 2012t. [Developmental Link: Mapping of the human genome is discussed in Chapter 3.] The need for many disciplines to understand the effect of genes is evident in our discussion of dandelions and orchids, and of nature and nurture.

Answer to Observation Quiz (from p. 17) Tie, tiepin, handkerchief, white cuffs—all appropriate costume for this context, and all impractical for most people in their daily lives.

Overall, multidisciplinary research broadens and deepens our knowledge. People are complex. A proper grasp of all of the systems — from the workings of the microbiome in the gut to the effects of climate change in the entire world — requires scientific insights from many disciplines. Adding to this complexity, people change over time. That leads to the final theme of the life-span perspective, plasticity.

Birth of a Neuron A decade ago, neuroscientists thought that adult brains lost neurons, with age or alcohol, but never gained them. Now we know that precursors of neurons arise in the lateral ventricles (bright blue, center) to become functioning neurons in the olfactory bulb (for smell, far left) and the hippocampus (for memory, the brown structure just above the brain stem). Adult neurogenesis is much less prolific than earlier in life, but the fact that it occurs at all is astounding.

Development Is Plastic The term plasticity denotes two complementary aspects of development: (1) Human traits can be molded (as plastic can be), yet (2) people maintain a certain durability of identity (as plastic does). The concept of plasticity in development provides both hope and realism — hope because change is possible, and realism because development builds on what has come before.

plasticity The idea that abilities, personality, and other human characteristics can change over time. Plasticity is particularly evident during childhood, but even older adults are not always “set in their ways.”

Dynamic Systems

Plasticity is basic to our contemporary understanding of human development (Lerner, 2009). This is evident in the dynamic-systems approach. The idea is that human development is an ongoing, ever-changing interaction between the body and mind and between the individual and every aspect of the environment, including all of the systems described in the ecological-systems approach.

dynamic-systems approach A view of human development as an ongoing, ever-changing interaction between the physical, cognitive, and psychosocial influences. The crucial understanding is that development is never static but is always affected by, and affects, many systems of development.

Note the word dynamic: Physical contexts, emotional influences, the passage of time, each person, and every aspect of the ecosystem are always interacting, always in flux, always in motion. For instance, a new approach to developing the motor skills of children with autism spectrum disorder stresses the dynamic systems that undergird movement — the changing aspects of the physical and social contexts (Lee & Porretta, 2013). [Developmental Link: Autism spectrum disorder is discussed in Chapter 11.]

Similarly, a dynamic-systems approach to understanding the role of fathers in child development takes into account the sex and age of the child, the role of the mother, and the cultural norms of fatherhood. The result is a complex mix of complementary effects — and, dynamically, this affects the child in diverse ways as plasticity of family systems would predict (Cabrera, 2015).

The dynamic-systems approach builds on the multidirectional, multicontextual, multicultural, and multidisciplinary nature of development. With any developmental topic, stage, or problem, the dynamic-systems approach urges consideration of all the interrelated aspects, every social and cultural factor, over days and years. Plasticity and the need for a dynamic-systems approach are most evident when considering the actual lived experience of each individual. My nephew David (A Case to Study, below) is one example.

Plasticity emphasizes that people can and do change, that predictions are not always accurate. Even “brain anatomy can change noticeably as a function of learning” (Zatorre, 2013, p. 587).

The early months and years are especially plastic, “for better or for worse” (Hartman & Belsky, 2015). Parent responses, early education, nutrition, and exercise put each child on a path. With each year, it is increasingly difficult to change direction. However, plasticity means that even adults can chart a new course.

Comfortable Routine? This 37-year-old father in Stockholm, Sweden, uses his strong tattooed arm to buckle his daughter’s sandals—caregiving as millions of contemporary men do. Plasticity means that many sex differences that were thought to be innate are actually the result of culture and experience. Is this an example?



My sister-in-law contracted rubella (also called German measles) early in her third pregnancy; it was not diagnosed until David was born, blind and dying. Immediate heart surgery saved his life, but surgery to remove a cataract activated a hidden virus and destroyed that eye.

The eye doctor was horrified at the unexpected results of surgery, and he decided that the cataract on the other eye should not be removed until the virus was finally gone. But one dead eye and one thick cataract meant that David’s visual system was severely impaired for the first five years of his life. That affected all of his other systems.

For instance, he interacted with other children by pulling their hair. Fortunately, the virus that had damaged the embryo occurred after the critical period for hearing. As dynamic systems might predict, David developed extraordinary listening ability in response to his diminished sight.

The virus harmed many other aspects of fetal development— thumbs, ankles, teeth, toes, spine, and brain. David attended three special preschools—for the blind, for children with cerebral palsy, for children who were intellectually disabled. At age 6, when some sight was restored, he entered regular public school, learning academics but not social skills— partly because he was excluded from physical education and recess.

My Brother’s Children Michael, Bill, and David (left to right) are adults now, with quite different personalities, abilities, numbers of offspring (4, 2, and none), and contexts (in Massachusetts, Pennsylvania, and California). Yet despite genes, prenatal life, and contexts, I see the shared influence of Glen and Dot, my brother and sister-in-law—evident here in their similar, friendly smiles.

By age 10, David had blossomed intellectually: He had skipped a year of school and was in fifth grade, reading at the eleventh-grade level. Before age 20, he learned to speak a second and a third language. In emerging adulthood, he enrolled in college.

As development unfolded, the interplay of systems was evident. David’s family context allowed him to become a productive and happy adult. He told me, “I try to stay in a positive mood.” This was especially important when David’s father died in 2014. David accepted the death (he said, “Dad is in a better place”) and comforted his mother.

Remember, plasticity cannot erase a person’s genes, childhood, or permanent damage. The brain destruction and compensation from that critical period of prenatal development remain. David is now 50. He still lives with his widowed mother. They both need each other.

Despite David’s lifelong disabilities, his listening skills continue to be impressive. He once told me:

I am generally quite happy, but secretly a little happier lately, especially since November, because I have been consistently getting a pretty good vibrato when I am singing, not only by myself but also in congregational hymns in church. [He explained vibrato:] When a note bounces up and down within a quartertone either way of concert pitch, optimally between 5.5 and 8.2 times per second.

David works as a translator of German texts, which he enjoys because, as he says, “I like providing a service to scholars, giving them access to something they would otherwise not have.” As his aunt, I have seen him repeatedly overcome disabilities. Plasticity is dramatically evident. This case illustrates all five aspects of the life-span perspective (see Table 1.2).


Five Characteristics of Development

Characteristic Application in David’s Story

Multidirectional. Change occurs in every direction, not always in a straight line. Gains and losses, predictable growth, and unexpected transformations are evident.

David’s development seemed static (or even regressive, as when early surgery destroyed one eye), but then it accelerated each time he entered a new school or college.

Multidisciplinary. Numerous academic fields— especially psychology, biology, education, and sociology, but also neuroscience, economics, religion, anthropology, history, medicine, genetics, and many more—contribute insights.

Two disciplines were particularly critical: medicine (David would have died without advances in surgery on newborns) and education (special educators guided him and his parents many times).

Multicontextual. Human lives are embedded in many contexts, including historical conditions, economic constraints, and family patterns.

The high SES of David’s family made it possible for him to receive daily medical and educational care. His two older brothers protected him.

Multicultural. Many cultures—not just between nations but also within them—affect how people develop.

Appalachia, where David lived, is more accepting of people with disabilities.

Plasticity. Every individual, and every trait within each individual, can be altered at any point in the life span. Change is ongoing, although it is neither random nor easy.

David’s measured IQ changed from about 40 (severely intellectually disabled) to about 130 (far above average), and his physical disabilities became less crippling as he matured.


1. What aspects of development show continuity? 2. What is the difference between a critical period and a sensitive period? 3. Why is it useful to know when sensitive periods occur? 4. What did Bronfenbrenner emphasize in his ecological-systems approach? 5. What are some of the social contexts of life? 6. How does cohort differ from age group? 7. What factors comprise a person’s SES? 8. How might male-female differences be examples of the difference-equals-deficit error? 9. What is the difference between race and ethnicity?

10. What is the problem with each discipline having its own silo? 11. How is human development plastic?

Designing Science To verify or refute a hypothesis (Step 2), researchers must choose among hundreds of research designs and decide who, what, how, and when to study (Step 3) in order to gather results that will lead to valid conclusions (Step 4) that are worth publishing (Step 5). Often they use statistics to discover relationships between various aspects of the data. (See Table 1.3.)


Statistical Measures Often Used to Analyze Search Results

Measure Use

Effect size There are many kinds, but the most useful in reporting studies of development is called Cohen’s d, which can indicate the power of an intervention. An effect size of 0.2 is called small, 0.5 moderate, and 0.8 large.

Significance Indicates whether the results might have occurred by chance. If chance would produce the results only 5 times in 100, that is significant at the 0.05 level; once in 100 times is 0.01; once in 1,000 is 0.001.

Cost-benefit analysis

Calculates how much a particular independent variable costs versus how much it saves. This is useful for analyzing public spending, finding that preschool education, or preventative health measures, save money.

Odds ratio Indicates how a particular variable compares to a standard, set at 1. For example, one study found that, although less than 1 percent of all child homicides occurred at school, the odds were similar for public and private schools. The odds of it in high schools, however, were 18.47 times that of elementary or middle schools (set at 1.0) (MMWR, January 18, 2008).

Factor analysis

Hundreds of variables could affect any given behavior. In addition, many variables (such as family income and parental education) overlap. To take this into account, analysis reveals variables that can be clustered together to form a factor, which is a composite of many variables. For example, SES might become one factor, child personality another.

Meta- analysis

A “study of studies.” Researchers use statistical tools to synthesize the results of previous, separate studies. Then they analyze the accumulated results, using criteria that weigh each study fairly. This approach improves data analysis by combining studies that were too small, or too narrow, to lead to solid conclusions.

Every research design, method, and statistic has strengths as well as weaknesses. Understanding these helps people assess whether the conclusions of a particular study are solid or flimsy, believable or open to doubt. To help you evaluate what you learn, here are three basic research strategies and three ways to study change over time.

Video Activity: What’s Wrong with This Study? explores some of the major pitfalls of the process of designing a research study.

Observation Yogi Berra famously said, “You can observe a lot just by watching.” Like many of his sayings, that quote is amusing but also deep. Scientists agree with Berra.

Scientific observation requires researchers to record behavior systematically and objectively. Observations often occur in a naturalistic setting such as a public park or a home, as people go about their daily lives. Scientific observation can also be done in a laboratory, where scientists record human reactions, often with wall-mounted video cameras and the scientist in another room.

scientific observation A method of testing a hypothesis by unobtrusively watching and recording participants’ behavior in a systematic and objective manner—in a natural setting, in a laboratory, or in searches of archival data.

Observation is crucial to develop hypotheses. However, observation does not prove a hypothesis.

For example, in one study of children arriving at a preschool, several weeks after the start of the year, scientists observed how long parents stayed to hug and kiss their children before saying goodbye. When parents lingered three minutes or more, their “children spent less time involved in the preschool peer social environment,” measured by whether the child looked at or played with other children (Grady et al., 2012, p. 1690).

The authors suggest that this “has implications for not only children’s later peer interactions and peer status, but also for children’s engagement in school and, ultimately, academic achievement” (J. Grady et al., 2012, p. 1690). Perhaps, by staying, the parents made the children anxious about school.

But those implications are not proven. Perhaps parents of shy children stayed to help the children become more comfortable with school. Contrary to the researchers’ speculation, those children might become academically strong later on. Thus, the data led to two alternative hypotheses: (1) Parental anxiety impairs child social engagement, or (2) shy children are given parental support. More research is needed.

The Experiment The experiment proves what causes what. In the social sciences, experimenters typically do something to a group of participants or expose them to something and then note their reaction.

experiment A research method in which the researcher tries to determine the cause-and-effect relationship between two variables by manipulating one (called the independent variable) and then observing and recording the ensuing changes in the other (called the dependent variable).

In technical terms, the experimenters manipulate an independent variable, which is the imposed treatment or special condition (also called the experimental variable; a variable is anything that can vary). They note whether and how the independent variable affects whatever they are studying, called the dependent variable (which depends on the independent variable).

independent variable In an experiment, the variable that is introduced to see what effect it has on the dependent variable. (Also called experimental variable.)

dependent variable In an experiment, the variable that may change as a result of whatever new condition or situation the experimenter adds. In other words, the dependent variable depends on the independent variable.

Thus, the independent variable is the possible cause; the dependent variable is the result. The purpose of an experiment is to see whether the independent variable affects the dependent variable. In other words, what (independent variable) causes what (dependent variable).

What Can You Learn? Scientists first establish what is, and then they try to change it. In one recent experiment, Deb Kelemen (shown here) established that few children under age 12 understand a central concept of evolution (natural selection). Then she showed an experimental group a picture book illustrating the idea. Success! The independent variable (the book) affected the dependent variable (the children’s ideas), which confirmed Kelemen’s hypothesis: Children can understand natural selection if instruction is tailored to their ability.

In a typical experiment (as diagrammed in Figure 1.9), at least two groups of participants are studied. One group, the experimental group, receives the particular treatment or condition (the independent variable); the other group, the comparison group (also called the control group), does not.

FIGURE 1.9 How to Conduct an Experiment The basic sequence diagrammed here applies to all experiments. Many additional features, especially the statistical measures listed in Table 1.3 and various ways of reducing experimenter bias, affect whether publication occurs. (Scientific journals reject reports of experiments that were not rigorous in method and analysis.)

Especially for Nurses9 In the field of medicine, why are experiments conducted to test new drugs and treatments? (see response, p. 26)

To follow up on the observation study above, researchers could experiment. For example, they could assess the social skills (dependent variable) of hundreds of children in the first week of school and then require parents in half of the classes to linger at drop-off (independent variable, experimental group), and in the other classes, ask the parents to leave immediately or let the parents do whatever they thought best (both control or comparison groups).

Several months later, the social skills (dependent variable) of the children could be measured again. A few years later, their school achievement (another dependent variable) could be recorded. Would this experiment prove that lingering at drop-off caused later academic success?

The Survey A third research method is the survey, in which information is collected from a large number of people by interview, questionnaire, or some other means. This is a quick, direct way to obtain data. It avoids assuming that the people we know are representative of people in general.

survey A research method in which information is collected from a large number of people by interviews, written questionnaires, or some other means.

For example, perhaps you know an 8-year-old boy who is a bully, or a 16-year-old girl who is pregnant. Some people might jump to the conclusion that boys are bullies and that many teenagers have babies. But one of the lessons from science is that one case proves nothing. At best, it raises questions, or provides an example of something found in research that included

hundreds of participants.

THINK CRITICALLY: If you want to predict who will win the next U.S. presidential race, what survey question would you ask, and who would you ask?

If you surveyed several hundred people, you would discover that most boys are not bullies and that the birth rate of 15- to 19-year-old women has fallen steadily in past decades, from a peak of 96 per 1,000 in 1957 to 22 per 1,000 in 2015. Births are increasing in only one group, those over age 35. For instance, in 2015, the birth rate for women aged 35 to 39 was 52 per 1,000, more than twice that of the birth rate for women aged 15 to 19 (Martin et al., 2016).

I hese birth data come from birth certificates, which are more accurate than surveys. Indeed, although surveys are quick and direct, they are not always accurate. People sometimes lie to please the researcher, and answers are influenced by the wording and the sequence of the questions.

Survey respondents may even lie to themselves. For instance, every two years since 1991, high school students in the United States have been surveyed confidentially. The most recent survey included 15,713 students from all 50 states and from schools large and small, public and private (MMWR, June 10, 2016).

Students are asked whether they had sexual intercourse before age 13. Every year, more ninth- grade boys than eleventh-grade boys say they had sex before age 13, yet those eleventh-graders were ninth-graders a few years before (see Figure 1.10).

FIGURE 1.10 I Forgot? If these were the only data available, you might conclude that ninth-graders have suddenly become more sexually active than eleventh-graders. But we have 20 years of data— those who are ninth-graders now will answer differently by eleventh grade.

Why? Do ninth-graders lie because they want to appear sexually active? Or do eleventh- graders lie because they are embarrassed by their earlier actions? Or do some students forget, or misunderstand the question? The survey cannot tell us.

Studying Development over the Life Span In addition to conducting observations, experiments, and surveys, developmentalists must measure how people change or remain the same over time, as our definition explains. Remember that systems are dynamic, ever-changing. To capture that dynamism, developmental researchers use one of three basic research designs: cross-sectional, longitudinal, and cross-sequential.

Cross-Sectional Versus Longitudinal Research The quickest and least expensive way to study development over time is with cross-sectional research, in which groups of people of one age are compared with people of another age. Cross- sectional design seems simple. However, the people being compared may differ in more ways than just age.

cross-sectional research A research design that compares groups of people who differ in age but are similar in other important characteristics.

All Smiling, All Multiethnic, All the Same? Cross-sectional research comparing these people would find age differences, but there might be cohort differences as well. Only longitudinal research could find them.

For example, because most women now in their 50s gained an average of a pound every year throughout their adulthood, does this mean that women now age 20 who weigh 140 pounds will, on average, weigh 170 pounds at age 50? Not necessarily.

To help discover whether age itself rather than cohort causes a developmental change, scientists undertake longitudinal research. This requires collecting data repeatedly on the same individuals as they age. The current cohort of young women, aware of the risks of overweight and the need for exercise, may not gain as much weight as older generations did (Arigo et al., 2016).

longitudinal research A research design in which the same individuals are followed over time, as their development is repeatedly assessed.

For insight about the life span, the best longitudinal research follows the same individuals from infancy to old age. Long-term research requires patience and dedication from a team of

scientists, but it can pay off. As you read in A View from Science on page 6, longitudinal research was needed to reveal that one-third of overweight children become normal-weight adults.

Response for Nurses (from p. 24) Experiments are the only way to determine cause-and-effect relationships. If we want to be sure that a new drug or treatment is safe and effective, an experiment must be conducted to establish that the drug or treatment improves health.

Consider another example. A longitudinal study of 790 low-SES children in Baltimore found that only 4 percent graduated from college by age 28 (Alexander et al., 2014). Without scientific data, a person might think that the problem was not enough counselors in high school or too many teenagers making poor choices.

However, because this was a longitudinal study, the data pinpointed when those children were pushed toward, or away from, higher education. Surprisingly, it was long before adolescence. The strongest influences on college attendance were good early education and encouraging, friendly neighbors.

Good as it is, longitudinal research has a problem, something already mentioned — the historical context. Science, popular culture, and politics change over time, and each alters the experiences of a child. Data collected on children born decades ago may not be relevant today.

Seven Times of Life These photos show Sarah-Maria, born in 1980 in Switzerland, at seven periods of her life: infancy (age 1), early childhood (age 3), middle childhood (age 8), adolescence (age 15), emerging adulthood (age 19), and adulthood (ages 30 and 36).

Observation Quiz Longitudinal research best illustrates continuity and discontinuity. For Sarah- Maria, what changed over 30 years and what didn’t? (see answer, p. 28)

For instance, many recent substances that were once thought to be beneficial might be harmful, among them phthalates and bisphenol A (BPA) (chemicals used in manufacturing in plastic baby bottles), hydrofracking (a process used to get gas for fuel from rocks), e-waste (from old computers and cell phones), and more. Some nations and states ban or regulate each of these; others do not. Verified, longitudinal data are not yet possible.

Because of the outcry among parents, bisphenol A has been replaced with bisphenol S (BPS). But we do not know if BPS is better, or worse, than BPA, because we do not have data on babies who drank from both kinds of bottles and are now adults (Zimmerman & Anastas, 2015).

A new example is e-cigarettes. They are less toxic (how much less?) to the heart and lungs than combustible cigarettes. Some (how many?) smokers reduce their risk of cancer and heart disease by switching to e-cigs (Bhatnagar et al., 2014). But some teenagers (how many?) are more likely to smoke cigarettes if they start by vaping.

The best research shows that nonsmoking teenagers who use e-cigarettes are almost four times as likely to say they “will try a cigarette soon,” an ominous result. But that is a survey, not longitudinal proof (Park et al., 2016).

Until longitudinal data on addiction and death for e-cig smokers are known, 10 or 20 years from now, no one can be certain whether the harm outweighs the benefits (Dutra & Glantz, 2014; Hajek et al., 2014; Ramo et al., 2015). [Developmental Link: The major discussion of e- cigarette use is in Chapter 16.] Do we need to wait until e-cig smokers die of lung disease, or not?

Cross-Sequential Research Scientists have discovered a third strategy, a sequence of data collection that combines cross- sectional and longitudinal research. This combination is called cross-sequential research (also referred to as cohort-sequential or time-sequential research). In sequential designs, researchers study people of different ages (a cross-sectional approach), follow them for years (a longitudinal approach), and then combine the results.

cross-sequential research A hybrid research design in which researchers first study several groups of people of different ages (a cross-sectional approach) and then follow those groups over the years (a longitudinal approach). (Also called cohort-sequential research or time-sequential research.)

A cross-sequential design lets researchers compare findings for, say, 7-year-olds with findings for the same individuals at age 1 as well as with data from people who were 7 long ago, who are now ages 13, 19, or even much older (see Figure 1.11). Cross-sequential research is complicated, in recruitment and analysis, but it lets scientists disentangle age from history.

FIGURE 1.11 Which Approach Is Best? Cross-sequential research is the most time-consuming and complex, but it yields the best information. One reason that hundreds of scientists conduct research on the same topics, replicating one another’s work, is to gain some advantages of cohort-sequential research without waiting for decades.

The first well-known cross-sequential study (the Seattle Longitudinal Study) found that some intellectual abilities (vocabulary) increase even after age 60, whereas others (speed) start to decline at age 30 (Schaie, 2005/2013), confirming that development is multidirectional. This study also discovered that declines in adult math ability are more closely related to education than to age, something neither cross-sectional nor longitudinal research could reveal.

Especially for Future Researchers What is the best method for collecting data? (see response, p. 29)

The advantages of cross-sequential research are now evident. Accordingly, many researchers

combine cross-sectional and longitudinal data collected by other scientists, thus using cross- sequential analysis without needing to do all of the data collection themselves.

For example, six scientists combined data from 14 longitudinal studies. They found that adolescent optimism about the future predicted health in middle age (Kern et al., 2016). Without a cross-sequential analysis, would people know that teenagers who say “life will be better when I grow up” are likely to be in good health decades later?

Answer to Observation Quiz (from p. 26) Of course, much changed and much did not change, but evident in the photos is continuity in Sarah-Maria’s happy smile and discontinuity in her hairstyle and color, which shows dramatic age and cohort changes.


1. Why does observation NOT prove “what causes what”? 2. Why do experimenters use a control (or comparison) group as well as an experimental group? 3. What are the strengths and weaknesses of the survey method? 4. Why would a scientist conduct a cross-sectional study? 5. What are the advantages and disadvantages of longitudinal research? 6. What current substances or practices might be found to be harmful in the future? 7. Why do developmentalists use cross-sequential research?

Cautions and Challenges from Science The scientific method illuminates and illustrates human development as nothing else does. Facts, consequences, and possibilities have emerged that would not be known without science — and people of all ages are healthier, happier, and more capable because of it.

Response for Future Researchers (from p. 27) There is no best method for collecting data. The method used depends on many factors, such as the age of participants (infants can’t complete questionnaires), the question being researched, and the time frame.

For example, death of newborns, measles in children, girls not sent to school, and boys being bullied are all less prevalent today than a century ago. Science deserves credit. Even violent death — in war, from homicide, or as punishment for a crime — is less likely in recent centuries than in past ones: Inventions, discoveries, and education are reasons (Pinker, 2011).

Developmental scientists have also discovered unexpected sources of harm. Video games, cigarettes, television, shift work, asbestos, and even artificial respiration are all less benign than people first thought.

As evident in these examples, the benefits of science are many. However, there are also serious pitfalls. We now discuss three potential hazards: misinterpreting correlation, depending too heavily on numbers, and ignoring ethics.

Correlation and Causation Probably the most common mistake in interpreting research is confusing correlation with causation. That was evident in Inside the Brain on page 10. It is true that 14-year-olds who regularly smoke marijuana are less likely to graduate from high school. But marijuana may not be the cause: It may be a symptom of academic problems that predated the first use of marijuana.

A correlation exists between two variables if one variable is more (or less) likely to occur when the other does. A correlation is positive if both variables tend to increase together or decrease together, negative if one variable tends to increase while the other decreases, and zero if no connection is evident. (Try the quiz in Table 1.4.)

correlation A number between +1.0 and -1.0 that indicates the degree of relationship between two variables, expressed in terms of the likelihood that one variable will (or will not) occur when the other variable does (or does not). A correlation indicates only that two variables are somehow related, not that one variable causes the other to occur.


Quiz on Correlation

Two Variables Positive, Negative, or ZeroCorrelation? Why? (Third


1. Ice cream sales and murder rate ____________ ____________

2. Reading ability and number of baby teeth

____________ ____________

3. Sex of adult and his or her average number of offspring

____________ ____________

For each of these three pairs of variables, indicate whether the correlation between them is positive, negative, or nonexistent. Then try to think of a third variable that might determine the direction of the correlation. The correct answers are printed upside down below.


1. Positive; third variable: heat

2. Negative; third variable: age

3. Zero; each child must have a parent of each sex; no third variable

Expressed in numerical terms, correlations vary from +1.0 (the most positive) to —1.0 (the most negative). Correlations are almost never that extreme; a correlation of +0.3 or —0.3 is noteworthy; a correlation of +0.8 or —0.8 is astonishing.

Many correlations are unexpected. For instance, a positive correlation is evident in being a first-born child and having asthma, in being a teenage girl and attempting suicide, and in living in a county with few dentists and being obese. The dentist study found that surprising correlation even after taking into account community poverty and the number of medical doctors. The authors suggest that dentists provide information about nutrition, which improves health (Holzer et al., 2014).

Remember that correlation is not causation. Just because two variables are correlated does not mean that one causes the other — even if it seems logical that it does. Can you think of other possible explanations for the correlation between dentists and obesity?

Quantity and Quality A second caution concerns quantitative research (from the word quantity). Quantitative research data can be categorized, ranked, or numbered and thus can be easily translated across cultures and for diverse populations. One example of quantitative research is the use of children’s school achievement scores to compare the effectiveness of education within a school or a nation.

quantitative research Research that provides data that can be expressed with numbers, such as ranks or scales.

A Pesky Third Variable Correlation is often misleading. In this case, a third variable (the supply of fossil fuels, a crack in the window, or the profit of the corporation) may be relevant.

Since quantities can be easily summarized, compared, charted, and replicated, many scientists prefer quantitative research. Statistics require numbers. Quantitative data are easier to replicate (Creswell, 2009). However, when data are presented in categories and numbers, some nuances and individual distinctions are lost.

Many developmental researchers thus turn to qualitative research (from the word quality) — asking open-ended questions, reporting answers in narrative (not numerical) form. Qualitative researchers are interested in understanding how people interpret their experiences and how they construct their worlds (Merriam, 2009, p. 24).

qualitative research Research that considers qualities instead of quantities. Descriptions of particular conditions and participants’ expressed ideas are often part of qualitative studies.

Qualitative research reflects cultural and contextual diversity, but it is also more vulnerable to bias and harder to replicate. Both types of research, and research that combines the two, are needed (Mertens, 2014).

Ethics The most important caution for all scientists, especially for those studying humans, is to uphold ethical standards. Each academic discipline and professional society involved in the study of human development has a code of ethics (a set of moral principles).

Ethical standards and codes are increasingly stringent. Most educational and medical institutions have an Institutional Review Board (IRB), a group that permits only research that follows certain guidelines. One crucial focus is on the well-being of the participants in a study: They must understand and consent to their involvement, and the researcher must keep results confidential and must ensure that no one is harmed.

Especially for Future Researchers and Science Writers Do any ethical guidelines apply when an author writes about the experiences of family members, friends, or research participants? (see response, p. 31)

Although IRBs slow down science, some research conducted before IRBs was clearly unethical, especially when the participants were children, members of minority groups,

prisoners, or animals. Even so, some ethical dilemmas remain (Leiter & Herman, 2015). Many ethical issues arose in the 2014–2016 Ebola epidemic in West Africa (Gillon, 2015;

Rothstein, 2015t. Among them: Is it fair to use vaccines whose safety is unproven when such proof would take months? What kind of informed consent is needed to avoid both false hope and false fear? Is it best to keep relatives away from people who have Ebola, even though social isolation makes it more likely that a sick person will die?

More broadly, is justice served by a health care system that is inadequate in some countries and high-tech in others? Medicine has tended to focus on individuals, ignoring the customs and systems that make some people more vulnerable. One observer noted:

When people from the United States and Europe working in West Africa have developed Ebola, time and again the first thing they wanted to take was not an experimental drug. It was an airplane that would cart them home.

[Cohen, 2014, p. 911]

Video Activity: Eugenics and the “Feebleminded”: A Shameful History illustrates what can happen when scientists fail to follow a code of ethics.

As stressed early in this chapter, scientists, like all other humans, have strong opinions, which they expect research to confirm. They might try (sometimes without noticing it) to achieve the results they want. As one team explains:

Our job as scientists is to discover truths about the world. We generate hypotheses, collect data, and examine whether or not the data are consistent with those hypotheses …. [but we] often lose sight of this goal, yielding to pressure to do whatever is justifiable to compile a set of studies we can publish. This is not driven by a willingness to deceive but by the self-serving interpretation of ambiguity . . .

[Simmons et al., 2011, pp. 1359, 1365]

Science and Ebola Ebola was halted as much because of social science as medicine, which has not yet found an effective vaccine. Fortunately, social workers taught practices that were contrary to West African culture—no more hugging, touching, or visiting from one neighborhood to another. Psychologists advised health workers, like this one from Doctors Without Borders, to hold, reassure,

and comfort children as much as possible. This girl was not among the 5,000 Liberians who died.

Obviously, collaboration, replication, and transparency are essential f. ethical safeguards. Hundreds of questions regarding human development 5 need answers, and researchers have yet to find them. That is the most g important ethical mandate of all. For instance:

Do we know enough about prenatal drugs to protect every fetus? Do we know enough about preschool to ensure that every 6-year-old will read? Do we know enough about poverty to enable every child to be healthy? Do we know enough about transgender children, or single parenthood, or divorce, or same- sex marriages to ensure optimal development?

The answer to all of these questions is a resounding NO. Scientists and funders tend to avoid questions that might produce unwanted answers. People

have strong opinions about drugs, preschool, income, sex, and families that may conflict with what science discovers. Religion, politics, and ethics shape scientific research, sometimes stopping investigation before it begins.

For instance, in 1996, the U.S. Congress, in allocating funds for the Centers for Disease Control, passed a law stating, “None of the funds made available for injury prevention and control at the Centers for Disease Control and Prevention may be used to advocate or promote gun control.” Some believe that this prohibition is one reason that the rate of gun death in the United States is higher than in any other nation. What laws — if any — would change that? Scientists do not agree on the answer, partly because solid research with a national sample has not been done (Gostin, 2016).

THINK CRITICALLY: Can you think of an additional question that researchers should answer?

An even greater question is about the “unknown unknowns,” the topics that we assume we understand but do not, hypotheses that have not yet occurred to anyone because our thinking is limited by our cultures and contexts. This probably applies to both sides of the gun debate.

We hope that the next cohort of developmental scientists will tackle these ethical problems — building on what is known, mindful of what needs to be explored, and raising questions that no one has thought of before. Remember that the goal is to help everyone fulfill their potential. Much more needs to be learned. The next 15 chapters are only a beginning.


1. Why does correlation not prove causation? 2. What are the advantages and disadvantages of quantitative research? 3. What are the advantages and disadvantages of qualitative research? 4. What is the role of the IRB? 5. Why might a political leader avoid funding developmental research? 6. What questions about human development remain to be answered?

Response for Future Researchers and Science Writers (from p. 30) Yes. Anyone you write about must give consent and be fully informed about your intentions. They can be identified by name only if they give permission. For example, family members gave permission before anecdotes about them were included in this text. My nephew David read the first draft of his story (see pp. 20–21) and is proud to have his experiences used to teach others.


Understanding How and Why 1. The study of human development is a science that seeks to understand how people change or

remain the same over time. As a science, it begins with questions and hypotheses and then gathers empirical data.

2. Replication confirms, modifies, or refutes conclusions, which are not considered solid until they are confirmed by several studies.

3. The universality of human development and the uniqueness of each individual’s development are evident in both nature (the genes) and nurture (the environment); no person is quite like another. Nature and nurture always interact, and each human characteristic is affected by that interaction.

4. Crucial to the study of nature and nurture is the concept of differential susceptibility — that genes or experiences affect the likelihood that a person will be affected by the environment.

The Life-Span Perspective 5. The assumption that growth is linear and that progress is inevitable has been replaced by the

idea that both continuity (sameness) and discontinuity (sudden shifts) are part of every life and that gains and losses are apparent at every age.

6. Time is a crucial variable in studying human development. A critical period is a time when something must occur or when an abnormality might occur. Often a particular development can occur more easily at a particular time, called a sensitive period.

7. Urie Bronfenbrenner’s ecological-systems approach notes that each of us is situated within larger systems of family, school, community, and culture, as well as part of a historical cohort. Changes in the context affect all other aspects of the system.

8. Certain experiences or innovations shape people of each cohort because they share the experience of significant historical events. Socioeconomic status (SES) affects each child’s opportunities, health, and education.

9. Culture, ethnicity. and race are social constructions, concepts created by society. Culture includes beliefs and patterns; ethnicity refers to ancestral heritage. Race is also a social construction, not a biological one.

10. Developmentalists try to avoid the difference-equals-deficit error. Differences are alternate ways to think or act. They are not necessarily harmful.

11. Within each person, every aspect of development interacts with the others, but development can be divided into three domains — biosocial, cognitive, and psychosocial. A multidisciplinary, dynamic-systems approach is needed.

12. Throughout life, human development is plastic. Brains and behaviors may change over time. Plasticity means that change is possible, not that everything can change.

Designing Science 13. Commonly used research methods are scientific observation, the experiment, and the survey.

Each can provide insight and discoveries, yet each is limited. 14. Developmentalists study change over time, often with cross-sectional and longitudinal

research. Ideally, results from both methods are combined in cross-sequential analysis.

Cautions and Challenges from Science 15. A correlation shows that two variables are related not that one causes the other: Both may be

caused by a third variable. 16. Quantitative research provides numerical data. This makes it best for comparing contexts

and cultures via verified statistics. By contrast, more nuanced data come from qualitative research, which reports on individual lives.

17. Ethical behavior is crucial in all of the sciences. Results must be fairly gathered, reported, and interpreted. Participants must understand and consent to their involvement.

18. The most important ethical question is whether scientists are designing, conducting, analyzing, publishing, and applying the research that is most critically needed.


science of human development (p. 4) scientific method (p. 4) hypothesis (p. 4) empirical evidence (p. 4) replication (p. 4) nature (p. 6) nurture (p. 7) epigenetics (p. 7) differential susceptibility (p. 7) life-span perspective (p. 8) critical period (p. 9) sensitive period (p. 9) ecological-systems approach (p. 12) cohort (p. 13) socioeconomic status (SES) (p. 13) culture (p. 14) social construction (p. 14) difference-equals-deficit error (p. 15) ethnic group (p. 16) race (p. 16) plasticity (p. 19) dynamic-systems approach (p. 19) scientific observation (p. 22) experiment (p. 23) independent variable (p. 23) dependent variable (p. 23) survey (p. 24) cross-sectional research (p. 25) longitudinal research (p. 26) cross-sequential research (p. 27) correlation (p. 29) quantitative research (p. 30) qualitative research (p. 30)


1. It is said that culture is pervasive but that people are unaware of it. List 30 things you did today that you might have done differently in another culture. Begin with how and where you woke up.

2. How would your life be different if your parents were much higher or lower in SES than they are? Consider all three domains.

3. A longitudinal case study can be insightful but is also limited in generality. Interview one of your older relatives, and explain what aspects of his or her childhood are unique and what might be relevant for everyone.

Theories CHAPTER



✦ What Theories Do Questions and Answers Past and Future

✦ Grand Theories Psychoanalytic Theory: Freud and Erikson Behaviorism: Conditioning and Learning Cognitive Theory: Piaget and Information Processing INSIDE THE BRAIN: Measuring Mental Activity

✦ Newer Theories Sociocultural Theory: Vygotsky and Beyond Evolutionary Theory OPPOSING PERSPECTIVES: Toilet Training—How and When?

✦ What Theories Contribute

What Will You Know? 1. What is practical about a theory?

2. Do childhood experiences affect adults?

3. Would you be a different person if you grew up in another place or century?

4. Why do we need so many theories?

n a frigid November night, Larry DePrimo, a 25-year-old police officer on duty in Times Square, saw a man with “blisters the size of his palm” on his bare feet. He asked the man his shoe size (12) and then bought him all-weather boots and thermal socks. As DePrimo

bent down to help the man don his gift, a tourist from Arizona snapped his photo. Days later, the tourist wrote to the New York Police Department, who put the image on their Web site. It went viral.

Then came theories, in half a million comments on Facebook. Commentators asked: Was this real or a hoax? Was DePrimo’s act typical (“most cops are

honorable, decent people”), atypical (“truly exceptional”), or in between (“not all NYC cops are short-tempered, profiling, or xenophobic”)? Is the officer young and naive? Are his parents proud? Was his assignment (anti-terrorism patrol) neglected or boring?

These questions reflect not science but “folk theories,” which arise from pre-conceptions and everyday experience (Bazinger & Kuhberger, 2012). We all have dozens of folk theories, without realizing that they lead us to opinions that are not shared by people with other theories (Gerstenberg & Tenenbaum, 2017). This anecdote illustrates three aspects shared by every theory, scientific as well as folk: (1) Behavior can be surprising, (2) humans develop theories to explain everything, and (3) experience and culture matter.

Past experience is particularly powerful. This was apparent with the boots: An advocate for the homeless suspected that the photo was staged; the photographing tourist thought of her father (also a police officer); many commentators blamed someone, among them the mayor (for not helping the poor), the police (for harassing the homeless), journalists (for focusing on “murder and mayhem”), and the barefoot man himself (for choosing his plight).

One year later, DePrimo was promoted. His father, wanting people to understand the totality of his son, said that his service record was the reason, not the boots (Antenucci, 2013). DePrimo himself was pleasantly surprised, commenting on the new detective badge on his shirt: “I look down and it’s still unreal to me” (DePrimo, quoted in Antenucci, 2013). For him and for all of us, a badge is a symbol, infused with decades of theories.

Badge and Boots This is Larry DePrimo, a New York City police officer in Manhattan, who astonished many people when he bought boots for a barefoot man on a cold afternoon.

In this chapter, we explain five insightful theories of human development. Three of them— psychoanalytic, behaviorist, and cognitive—have been touchstones for developmentalists for decades and are thus called “grand theories.” You will read how each has evolved over the years, with newer versions of the originals set out by Freud, Pavlov, and Piaget.

The other two theories—sociocultural and evolutionary—are newer for developmentalists. Their implications and applications are still in flux, but both add intriguing perspectives.

Facts regarding what happened in a single moment are relatively easy to prove. I can do this with DePrimo and the boots. He was from my local precinct. I know his commanding officer; I

listened to his personal take on this event; it was not a hoax. Understanding why is more difficult: Each of the theories in this chapter has a different perspective.

What Theories Do Kurt Lewin (1945) once quipped, “Nothing is as practical as a good theory.” Like many other scientists, he knew that theories help analysis and move us toward a clearer understanding. Imagine trying to build a house without a design. You might have all the raw materials—bricks, wood, nails—and you might have willing workers. But without a detailed plan, you could not proceed. It is possible that you would want to add a window or move a door, but the basic plan is essential before you begin.

Similarly, all of the momentary experiences of each day are the raw material of a human life. But without a theory for how it all fits together, life would be meaningless. Revisions may occur (as you will soon see), but theories are needed to start.

Every theory explains observations via concepts and ideas that organize the confusing mass of sensations that we encounter every moment. Some theories are idiosyncratic, narrow, and useless to anyone except the people who thought of them. Others are much more elaborate and insightful, such as the five major theories described in this chapter.

Of course, theories differ; some are less adequate than others, and some reflect one culture but not another. The five in this chapter are “good” theories, because they have proven to be practical and useful for developmental scientists for many years. They are also useful for anyone who cares about children. What should an adult do when a child refuses to eat dinner, or crawls into bed with his mother, or multiplies 7 × 8 correctly? The answer depends on theory, ideally a theory that has stood the tests of time and science.

Because they are comprehensive and complex, these five theories propel science forward, inspiring thousands of scientists to experiment, explain, and dispute. Scientific theories of development lead to new insights and elicit alternate interpretations.

Theories are meant to be tested. Indeed, sometimes a theory leads to a hypothesis that turns out to be false, an outcome that is considered a benefit, not a liability, of theory.

For example, would you expect that as wives earn more money they do less housework? Some theories would predict that. But testing that hypothesis reveals gaps in those theories. The relationship between earnings and housework is surprising, with high-earning women still doing more housework than their husbands (Hook, 2017). “Various theoretical models compete” to explain these results, but none is adequate by itself (Carlson & Lynch, 2017, p. 212). More research and better theories are needed.

A developmental theory is a systematic statement of general principles that provides a framework for understanding how and why people change over time. Facts and observations connect to patterns, weaving details into a meaningful whole.

developmental theory A group of ideas, assumptions, and generalizations that interpret and illuminate the thousands of observations that have been made about human growth. A developmental theory provides a framework for explaining the patterns and problems of development.

A developmental theory is more than a hunch or a hypothesis; it is more comprehensive than a folk theory. Developmental theories provide insights that are both broad and deep, connecting the distant past and the far-off future.

Questions and Answers As you remember from Chapter 1, the first step in the science of human development is to pose a question, which often springs from theory. Among the thousands of important questions are the following, each central to one of the five theories in this chapter:

1. Do early experiences—of breast-feeding or attachment or abuse—shape adult personality? 2. Does learning depend on encouragement, punishment, and/or role models? 3. Do morals develop spontaneously in childhood so children do not need to be taught right

from wrong? 4. Does culture determine parents’ behavior, such as how to respond to an infant’s cry? 5. Is survival an inborn instinct, underlying all personal and social decisions?

The answer to each of these questions is “yes” when examined in order by the following theories: psychoanalytic, behaviorism, cognitive, sociocultural, and evolutionary. Each question is answered “no” or “not necessarily” by several others. For every answer, more questions arise: Why or why not? When and how? SO WHAT? This last question is crucial; implications and applications affect everyone’s daily life.

To be more specific about what theories do:

Theories produce hypotheses. Theories generate discoveries. Theories offer practical guidance.

Past and Future Humans spontaneously develop theories about everything they observe. Scientists have realized this for centuries. Charles Darwin wrote, “As soon as the important faculties of the imagination, wonder, and curiosity, together with some power of reasoning, had become partially developed, man would naturally crave to understand what was passing around him, and would have vaguely speculated on his own existence” (Darwin, 1871, quoted in Thomson, 2015, p. 104; Culotta, 2009, and many others).

Give My Regards to Broadway Those lyrics written by George Cohan (1878-1942) are inscribed on his bronze statue overlooking thousands of twenty-first-century tourists from every state and nation in Times Square in New York City. Like all five theories in this chapter, this scene depicts the dynamic interaction of old insights and new realities.

Quoting Darwin (a controversial figure) evokes theories about creation and evolution, including the theory that science and religion are opposing worldviews, a theory not held by most scientists. Most agree with the theologian and civil rights leader Martin Luther King Jr., who said:

Science investigates; religion interprets. Science gives man knowledge, which is power; religion gives man wisdom, which is control. Science deals mainly with facts; religion deals mainly with values. The two are not rivals.

[King, 1977, p. 4]

Backpacks or Bouquets? Children worldwide are nervous on their first day of school, but their coping reflects implicit cultural theories. Kindergartner Madelyn Ricker in Georgia shows her new backpack to her teacher, and elementary school students in Russia bring flowers to their teachers.

Theories are meant to be useful. That is why we need them. Without developmental theories, we would be reactive and bewildered, blindly following our culture and our prejudices to the detriment of anyone who wonders about their children, their childhood, their future.

Not surprisingly, given that history and culture shape perspectives (as stressed in Chapter 1), each of the major theories in this chapter became ascendant in a particular decade during the past 100 years. Of course, all five shed light on current issues—otherwise, they would not still be useful. All were developed primarily by European and North American scientists, another limitation.

But that perspective is not a reason to reject them. In fact, all of these theories echo ideas written by ancient sages, in Greece, China, India, and elsewhere, since humans always “naturally crave to understand,” and since humans everywhere and always are one species. Consider them a benchmark, useful for understanding human development. Also remember that none of them is the final theoretical word: As explained in Chapter 1, human growth is dynamic, always affected by cohort and culture.


1. What are the similarities and differences between folk theories and scientific theories? 2. What three things do theories do? 3. Why do people need theories to move forward with their lives? 4. Who develops theories—everyone or just scientists? 5. What is the focus of a developmental theory?

Grand Theories In the first half of the twentieth century, two opposing theories—psychoanalytic and behaviorism —dominated the discipline of psychology, each with extensive applications to human development. In about 1960, a third theory—cognitive— arose, and it too was widely applied to development.

These three are called “grand theories” and explained here because they are comprehensive, enduring, and far-reaching. In developmental studies, these theories continue to be useful. But be forewarned: None of them is now considered as grand as developmentalists once believed.

Psychoanalytic Theory: Freud and Erikson Inner drives, deep motives, and unconscious needs rooted in childhood— especially the first six years—are the focus of psychoanalytic theory. These unconscious forces are thought to influence every aspect of thinking and behavior, from the smallest details of daily life to the crucial choices of a lifetime.

psychoanalytic theory A grand theory of human development that holds that irrational, unconscious drives and motives, often originating in childhood, underlie human behavior.

Freud at Work In addition to being the world’s first psychoanalyst, Sigmund Freud was a prolific writer. His many papers and case histories, primarily descriptions of his patients’ symptoms and sexual urges, helped make the psychoanalytic perspective a dominant force for much of the twentieth century.

Freud’s Ideas Psychoanalytic theory originated with Sigmund Freud (1856–1939), an Austrian physician who treated patients suffering from mental illness. He listened to their remembered dreams and uncensored streams of thought. From that, he constructed an elaborate, multifaceted theory.

According to Freud, development in the first six years of life occurs in three stages, each characterized by sexual interest and pleasure arising from a particular part of the body. In

infancy, the erotic body part is the mouth (the oral stage); in early childhood, it is the anus (the anal stage); in the preschool years, it is the penis (the phallic stage), a source of pride and fear among boys and a reason for sorrow and envy among girls. Then, after a quiet period (latency), the genital stage arrives at puberty, lasting throughout adulthood. (Table 2.1 describes stages in Freud’s theory.)


Comparison of Freud’s Psychosexual and Erikson’s Psychosocial Stages

Approximate Age Freud (psychosexual) Erikson (psychosocial)

Birth to 1 year Oral Stage The lips, tongue, and gums are the focus of pleasurable sensations in the baby’s body, and sucking and feeding are the most stimulating activities.

Trust vs. Mistrust Babies either trust that others will satisfy their basic needs, including nourishment, warmth, cleanliness, and physical contact, or develop mistrust about the care of others.

1-3 years Anal Stage The anus is the focus of pleasurable sensations in the baby’s body, and toilet training is the most important activity.

Autonomy vs. Shame and Doubt Children either become self-sufficient in many activities, including toileting, feeding, walking, exploring, and talking, or doubt their own abilities.

3-6 years Phallic Stage The phallus, or penis, is the most important body part, and pleasure is derived from genital stimulation. Boys are proud of their penises; girls wonder why they don’t have them.

Initiative vs. Guilt Children either try to undertake many adultlike activities or internalize the limits and prohibitions set by parents. They feel either adventurous or guilty.

6-11 years Latency Not really a stage, latency is an interlude. Sexual needs are quiet; psychic energy flows into sports, schoolwork, and friendship.

Industry vs. Inferiority Children busily practice and then master new skills or feel inferior, unable to do anything well.

Adolescence Genital Stage The genitals are the focus of pleasurable sensations, and the young person seeks sexual stimulation and satisfaction in heterosexual relationships.

Identity vs. Role Confusion Adolescents ask themselves “Who am I?” They establish sexual, political, religious, and vocational identities or are confused about their roles.

Adulthood Freud believed that the genital stage lasts throughout adulthood. He also said that the goal of a healthy life is “to love and to work.”

Intimacy vs. Isolation Emerging adults seek companionship and love or become isolated from others, fearing rejection.

Generatility vs. Stagnation

Adults contribute to future generations through work, creative activities, and parenthood or they stagnate. Integrity vs. Despair Older adults try to make sense of their lives, either seeing life as a meaningful whole or despairing at goals never reached.

Freud maintained that sensual satisfaction (from stimulation of the mouth, anus, or penis) is linked to major developmental stages, needs, and challenges. During the oral stage, for example, sucking provides not only nourishment for the infant but also erotic joy and attachment to the mother. Kissing between lovers is a vestige of the oral stage. Next, during the anal stage, pleasures arise from selfcontrol, initially with toileting but later with wanting everything to be clean, neat, and regular (an “anal personality”).

One of Freud’s most influential ideas was that each stage includes its own struggles. Conflict occurs, for instance, when parents wean their babies (oral stage), toilet train their toddlers (anal stage), deflect the sexual curiosity and fantasies of their 5-year-olds (phallic stage), and limit the sexual interests of adolescents (genital stage). Freud thought that the experiences surrounding these conflicts determine later personality.

Freud did not believe that any new stage occurred after puberty; rather, he believed that adult personalities and habits were influenced by childhood. Unconscious conflicts rooted in early life are evident in adult behavior—for instance, cigarette smoking (oral) or meticulous housecleaning (anal) or falling in love with a much older partner (phallic).

Erikson’s Ideas Many of Freud’s followers became famous theorists themselves—Carl Jung, Alfred Adler, and Karen Horney among them. They agreed with Freud that early-childhood experiences affect everyone, often unconsciously, but they also expanded and modified his ideas. For scholars in human development, one neo-Freudian, Erik Erikson (1902–1994), is particularly insightful. He proposed a comprehensive developmental theory of the entire life span.

No Choking During the oral stage, children put everything in their mouths, as Freud recognized and as 12-month-old Harper Vasquez does here. Toy manufacturers and lawyers know this, too, which is why

many toy packages read “Choking hazard: small parts, not appropriate for children under age 3.”

Erikson described eight developmental stages, each characterized by a particular challenge, or developmental crisis. Although Erikson named two polarities at each crisis, he recognized a wide range of outcomes between those opposites. Typically, development at each stage leads to neither extreme but to something in between.

A Legendary Couple In his first 30 years, Erikson never fit into a particular local community, since he frequently changed nations, schools, and professions. Then he met Joan. In their first five decades of marriage, they raised a family and wrote several books. If Erikson had published his theory at age 73 (when this photograph was taken) instead of in his 40s, would he still have described life as a series of crises?

In the stage of initiative versus guilt, for example, 3- to 6-year-olds undertake activities that exceed the limits set by their parents and their culture. They leap into swimming pools, pull their pants on backward, make cakes according to their own recipes, and wander off alone.

Erikson thought that those preschool initiatives produce feelings of pride or failure, depending on adult reactions. Should adults pretend to like the cake that a preschooler made or, instead, punish that child for wasting food and messing up the kitchen? According to Erikson’s theory, a child will feel guilty lifelong if adults are too critical or if social norms are too strict regarding the young child’s initiatives.

As you can see from Table 2.1, Erikson’s first five stages are closely related to Freud’s stages. Like Freud, Erikson believed that unresolved childhood conflicts echo throughout life, causing problems in adulthood.

Erikson considered the first stage, trust versus mistrust, particularly crucial. For example, an adult who has difficulty establishing a secure, mutual relationship with a life partner may never have resolved that first crisis of early infancy. If you know people who are “too trusting” or “too suspicious,” Erikson would suggest that you ask them about their care when they were infants.

In his emphasis on childhood, Erikson agreed with Freud. However, in two crucial aspects, Erikson’s stages differ significantly from those of his mentor.

1. Erikson’s stages emphasized family and culture, not sexual urges. 2. Erikson recognized adult development, with three stages after adolescence.

Behaviorism: Conditioning and Learning The comprehensive theory that dominated psychology in the United States for most of the twentieth century was behaviorism. This theory began in Russia, with Pavlov, who first described conditioning.

behaviorism A grand theory of human development that studies observable behavior. Behaviorism is also called learning theory because it describes the laws and processes by which behavior is learned.

Just Like Her Grandparents She sits on London Bridge, establishing her identity via hair, shoes, and clothes. Erikson would say she is quite conventional, doing what adolescents have always done!

Classical Conditioning More than a century ago, Ivan Pavlov (1849–1936) did hundreds of experiments to examine the link between something that affected a living creature (such as a sight, a sound, a touch) and how that creature reacted. Technically, he was interested in how a stimulus affects a response.

While studying salivation in his laboratory, Pavlov noticed that his research dogs drooled (response) not only at the smell of food (stimulus) but also, eventually, at the sound of the footsteps of the people bringing food. This observation led Pavlov to perform a famous experiment: He conditioned dogs to salivate (response) when hearing a particular noise (stimulus).

Pavlov began by sounding a tone just before presenting food. After a number of repetitions of the tone-then-food sequence, dogs began salivating at the sound even when there was no food. This simple experiment demonstrated classical conditioning (also called respondent conditioning).

Especially for Teachers Your kindergartners are talkative and always moving. They almost never sit quietly and listen to you. What would Erik Erikson recommend? (see response, p. 43)

classical conditioning The learning process in which a meaningful stimulus (such as the smell of food to a hungry animal) is connected with a neutral stimulus (such as the sound of a tone) that had no special meaning before conditioning. (Also called respondent conditioning.)

In classical conditioning, a person or animal learns to associate a neutral stimulus with a meaningful one, gradually responding to the neutral stimulus in the same way as to the meaningful one. In Pavlov’s original experiment, the dog associated the tone (the neutral stimulus) with food (the meaningful stimulus) and eventually responded to the tone as if it were the food itself. The conditioned response to the tone, no longer neutral but now a conditioned stimulus, was evidence that learning had occurred.

Behaviorists see dozens of examples of classical conditioning. Infants learn to smile at their parents because they associate them with food and play; toddlers learn to fear busy streets if the noise of traffic repeatedly frightens them; students learn to enjoy—or hate—school, depending on their kindergarten experience.

One current application of this theory is to explain the sudden increase of opioid overdose deaths in the United States (see Figure 2.1). (Opioids include heroin, morphine, and many prescription painkillers.) Many such deaths may not really be caused by an excessive quantity of the drug, because the deadly dose may be far less than others consume with no ill effect. Indeed, an “overdose” might be the same quantity as what that very person had taken before.

FIGURE 2.1 A Deadly Response The epidemic of opioid deaths is most notable among white, middle-aged men. There are many explanations for this demographic, but one that arises from behaviorism is that these drug-users are not conditioned to heroin. Tolerance may be psychological as well as physical; novice substance abusers have not acquired it.

Nor is every overdose death the consequence of some hidden “extra” within the drug. Indeed, people die of legally prescribed and carefully produced pills at doses they have taken before. One

hypothesis is that the person died because of a conditioned response (Siegel, 2016). This is how the stimulus—response link might work. When people habitually take a certain

drug, they become conditioned to it—their body and mind tolerate it, protecting them from serious side effects. That explains craving: Those with substance use disorder (SUD) are conditioned to seek the drug when they feel anxious, or in pain, or lonely. They connect relief of those feelings (response) with the drug (stimulus).

However, that same dose might be too much if the circumstances have not allowed the body and mind to prepare to adjust to it. A relatively small dose in a new context might be too much. A study of 44 “overdose” victims who survived (they were hospitalized and treated immediately, usually with naloxone, a potent antidote to opioid poisoning) found that often the dose was usual but conditioning made the response extreme (Neale et al., 2017). Two examples:

Alan (23 years) . . . had been told to leave the hostel where he had been staying because he had taken drugs and was intoxicated. . . . He had then taken more heroin and was wandering around outside, but could not remember overdosing. He was found unconscious . . .

[2017, p. 171]

Thus he was tolerant of heroin taken in his hostel room, but the same dose outside made him unconscious.

James (38 years) reported . . . [that] a friend had injected him. He stated that he could not remember anything about the effects of the heroin as he had instantly “blacked out” as the needle “went in”.

[2017, p. 172]

A Contemporary of Freud Ivan Pavlov was a physiologist who received the Nobel Prize in 1904 for his

research on digestive processes. It was this line of study that led to his discovery of classical conditioning, when his research on dog saliva led to insight about learning.

Observation Quiz How is Pavlov similar to Freud in appearance, and how do both look different from the other theorists pictured?, (see answer, p. 44)

Of course, the friend did not know that James had been psychologically conditioned to instantly connect injection—even before any physiological effects in the bloodstream—with blacking out. Thus, a relatively small dose (the friend thought he was being helpful) could have killed him.

Behaviorists notice many reactions linked to stimuli that once were neutral. Think of how some people react to the buzzing of a bumble bee or the sight of a police car in the rearview mirror. Such reactions are learned. The announcement of a final exam makes some students sweat—as no young child would.

Behaviorism in the United States Pavlov’s ideas seemed to bypass most Western European developmentalists but were welcomed in the United States, because many North Americans disputed the psychoanalytic emphasis on the unconscious.

The first of three famous Americans who championed behaviorism was John B. Watson (1878–1958). He argued that if psychology was to be a true science, psychologists should examine only what they could see and measure, not invisible unconscious impulses. In his words:

Why don’t we make what we can observe the real field of psychology? Let us limit ourselves to things that can be observed, and formulate laws concerning only those things. . . . We can observe behavior—’what the organism does or says.

[Watson, 1924/1998, p. 6]

According to Watson, if the focus is on behavior, it is apparent that everything is learned. He wrote:

Give me a dozen healthy infants, well-formed, and my own specified world to bring them up in and I’ll guarantee to take any one at random and train him to become any type of specialist I might select—doctor, lawyer, artist, merchant-chief, and yes, even beggar-man and thief, regardless of his talents, penchants, tendencies, abilities, vocations, and race of his ancestors.

[Watson, 1924/1998, p. 82]

An Early Behaviorist John Watson was an early proponent of learning theory. His ideas are still influential and controversial today.

Other American psychologists agreed. They chose to study observable behavior, objectively and scientifically. For everyone at every age, behaviorists believe there are natural laws of human behavior. They experiment with mice and pigeons, as well as with people, to discover the laws that apply to all living creatures. Such laws explain how simple actions become complex competencies, because stimuli in the environment affect each action. Children are taught how to act, whether parents know it or not.

Learning in behaviorism is far more comprehensive than the narrow definition of learning, which focuses on academics, such as learning to read or multiply. Instead, for behaviorists, everything that people think, do, and feel is learned, step by step, via conditioning.

Response for Teachers (from p. 41) Erikson would note that the behavior of 5-year-olds is affected by their developmental stage and by their culture. Therefore, you might design your curriculum to accommodate active, noisy children.

For example, newborns learn to suck on a nipple; infants learn to smile at a caregiver; preschoolers learn to hold hands when crossing the street. Such learning is conditioned and can endure when no longer useful. That explains why children suck lollipops, adults smile at strangers, and I still grab my children’s hands in traffic. My children laugh and say, “Mom, I know how to avoid cars now.” Of course, I understand that they are adults, quite able to walk the city by themselves, but I have been conditioned by the years when they were children.

Operant Conditioning The most influential North American proponent of behaviorism was B. F. Skinner (1904–1990). Skinner agreed with Watson that psychology should focus on observable behavior. He did not dispute Pavlov’s classical conditioning, but, as a good scientist, he built on Pavlov’s conclusions. His most famous contribution was to recognize another type of conditioning— operant conditioning (also called instrumental conditioningl —in which animals (including people) act and then something follows that action.

operant conditioning The learning process by which a particular action is followed by something desired (which makes the person or animal more likely to repeat the action) or by something unwanted (which makes the action less likely to be repeated). (Also called instrumental conditioning.)

In other words, Skinner went beyond learning by association, in which one stimulus is paired with another stimulus (in Pavlov’s experiment, the tone with the food). He focused instead on what happens after the response. If the consequence that follows is enjoyable, the creature (any living thing—a bird, a mouse, a child) tends to repeat the behavior; if the consequence is unpleasant, the creature does not do it again.

Consequences that increase the frequency or strength of a particular action are called reinforcers; the process is called reinforcement (Skinner, 1953). According to behaviorism, almost all of our daily behavior, from saying “Good morning” to earning a paycheck, is the result of past reinforcement.

reinforcement When a behavior is followed by something desired, such as food for a hungry animal or a welcoming smile for a lonely person.

Rats, Pigeons, and People B. F. Skinner is best known for his experiments with rats and pigeons, but he also applied his knowledge to human behavior. For his daughter, he designed a glass-enclosed crib in which temperature, humidity, and perceptual stimulation could be controlled to make her time in the

crib enjoyable and educational. He encouraged her first attempts to talk by smiling and responding with words, affection, or other positive reinforcement.

Pleasant consequences are sometimes called rewards, but behaviorists do not call them that because they want to avoid the confusion of the word “reward.” What some people consider a reward may actually be a punishment, an unpleasant consequence. For instance, a teacher might reward good behavior by giving the class extra recess time, but some children hate recess. For them, recess is not a reinforcer.

The opposite is true as well: Something thought to be a punishment may actually be reinforcing. For example, parents “punish” their children by withholding dessert. But a particular child might dislike the dessert, so being deprived of it is no punishment.

Culture matters, too. Japanese parents threaten to punish their children by refusing to let them come home; American parents threaten to make the children stay home. Whether these opposite strategies are really punishments depends on the child as well as the culture (Bornstein, 2017).

The crucial question is “What works as a reinforcement or punishment for that individual?” The answer varies by age, as developmentalists have shown. For instance, adolescents find risk and excitement particularly reinforcing, and they consider punishments much less painful than adults do. That was one conclusion of a study of teenagers who were violent: For them, the thrill of breaking the law was reinforcing, outweighing the pain of getting caught (Shulman et al., 2017).

Consider a common practice in schools: Teachers send misbehaving children out of the classroom. Then principals suspend the worst violators from school.

However, if a child hates the teacher, leaving class is rewarding; and if a child hates school, suspension is a reinforcement. Indeed, research on school discipline finds that some measures, including school suspension, increase later disobedience (Osher et al., 2010). Educators have learned that, to stop misbehavior, it is often more effective to encourage good behavior, to “catch them being good” (Polirstok, 2015, p. 932).

Answer to Observation Quiz (from p. 42) Both are balding, with white beards. Note also that none of the other theorists in this chapter have beards—a cohort difference, not an ideological one.

In the United States, the chance of an African American child being suspended from school is three times higher than for a European American child. The rate is also higher than average for children designated as needing special education. Those statistics raise a troubling question: Is suspension a punishment for the child, or is it a reinforcer for the teacher? (Tajalli & Garba, 2014; Shah, 2011).

The data show that children who are suspended from school are more likely than other children to be imprisoned years later. That is a correlation; it does not prove that suspension causes later imprisonment. But behaviorists suggest that it might (Mallett, 2016). [Developmental Link: Correlation and causation are discussed in Chapter 1.]

Remember, behaviorists focus on the effect that a consequence has on future behavior, not whether it is intended to be a reward or not. Children who misbehave again and again have been reinforced, not punished, for their actions—perhaps by their parents or teachers, perhaps by their friends or themselves.

Social Learning At first, behaviorists thought all behavior arose from a chain of learned responses, the result of

(1) the association between one stimulus and another (classical conditioning) or (2) past reinforcement (operant conditioning). Thousands of experiments inspired by learning theory have demonstrated that both classical conditioning and operant conditioning occur in everyday life. We are all conditioned to react as we do.

Video Activity: Modeling: Learning by Observation features the original footage of Albert Bandura’s famous experiment.

However, people at every age are social and active, not just reactive. Instead of responding merely to their own direct experiences, “people act on the environment. They create it, preserve it, transform it, and even destroy it . . . [in] a socially embedded interplay” (Bandura, 2006, p. 167).

That social interplay is the foundation of social learning theory (see Table 2.2), which holds that humans sometimes learn without personal reinforcement. As Albert Bandura, the primary proponent of this theory, explains, this learning often occurs through modeling, when people copy what they see others do (also called observational learning) (Bandura, 1986, 1997).

social learning theory An extension of behaviorism that emphasizes the influence that other people have over a person’s behavior. Even without specific reinforcement, every individual learns many things through observation and imitation of other people. (Also called observational learning.)

modeling The central process of social learning, by which a person observes the actions of others and then copies them.


Three Types of Learning

Behaviorism is also called learning theory because it emphasizes the learning process, as shown here.

Type of Learning Learning Process Result

Classical Conditioning

Learning occurs through association.

Neutral stimulus becomes conditioned response.

Operant Conditioning

Learning occurs through reinforcement and punishment.

Weak or rare responses become strong and frequent — or, with punishment, unwanted responses become extinct.

Social Learning occurs through Observed behaviors become copied behaviors.

Learning modeling what others do.

Modeling is not simple imitation: Some people are more likely to follow or to be role models than others. Indeed, people model only some actions, of some individuals, in some contexts. Sometimes people do the opposite of what they have seen.

Generally, modeling is most likely when the observer is uncertain or inexperienced (which explains why modeling is especially powerful in childhood) and when the model is admired, powerful, nurturing, or similar to the observer. Social learning occurs not only for behavior and preferences (why do teenagers wear their hair as they do?) but also for morals, which may appear to be decided by each individual but also are affected by what people learn from others (Bandura, 2016).

THINK CRITICALLY: Is your speech, hairstyle, or choice of shoes similar to those of your peers, or of an entertainer, or a sports hero? Why?

Cognitive Theory: Piaget and Information Processing According to cognitive theory, thoughts and expectations profoundly affect attitudes, values, emotions, and actions. This may seem obvious now, but it was not always so clear. Social scientists recognize a “cognitive revolution,” which occurred around 1980. Suddenly how and what people think became important. This added to psychoanalysis (which emphasized hidden impulses) and behaviorism (which emphasized observed actions). Thoughts come between impulses and actions, and they are crucial.

cognitive theory A grand theory of human development that focuses on changes in how people think over time. According to this theory, our thoughts shape our attitudes, beliefs, and behaviors.

The cognitive revolution is ongoing: Contemporary researchers use new tools to study cognition, with neuroscience, large data, and body—mind connections (e.g., Griffiths, 2015). To understand the impact of cognitive theory on development, we begin with Piaget.

Piaget’s Stages of Development Jean Piaget (1896–1980) transformed our understanding of cognition, leading some people to consider him “the greatest developmental psychologist of all time” (Haidt, 2013, p. 6). His academic training was in biology, with a focus on shellfish—a background that taught him to look closely at small details.

Before Piaget, most scientists believed that babies could not yet think. But Piaget used scientific observation with his own three infants. He took meticulous notes, finding infants curious and thoughtful.

Later he studied hundreds of schoolchildren. From this work emerged the central thesis of cognitive theory: How children think changes with time and experience, and their thought processes affect behavior. According to cognitive theory, to understand people, one must understand their thinking.

Would You Talk to This Man? Children loved talking to Jean Piaget, and he learned by listening carefully—especially to their incorrect explanations, which no one had paid much attention to before. All his life, Piaget was absorbed with studying the way children think. He called himself a “genetic epistemologist”—one who studies how children gain knowledge about the world as they grow.

Piaget maintained that cognitive development occurs in four age-related periods, or stages: sensorimotor, preoperational, concrete operational, and formal operational (see Table 2.3). Each period fosters certain cognitive processes: Infants think via their senses; preschoolers have language but not logic; school-age children have simple logic; adolescents and adults can use formal, abstract logic (Inhelder & Piaget, 1958/2013b; Piaget, 1952/2011).


Piaget’s Periods of Cognitive Development

Name of Period

Characteristics of the Period Major Gains During the Period

Birth to 2 years

Sensorimotor Infants use senses and motor abilities to understand the world. Learning is active, without reflection.

Infants learn that objects still exist when out of sight (object permanence) and begin to think through mental actions. (The sensorimotor period is discussed further in Chapter 6.)

2-6 years Preoperational Children think symbolically, with language, yet children are egocentric, perceiving from their own perspective.

The imagination flourishes, and language becomes a significant means of self- expression and social influence. (The preoperational period is discussed further in Chapter 9.)

6-11 Concrete Children understand By applying logic, children grasp concepts of

years operational and apply logic. Thinking is limited by direct experience.

conservation, number, classification, and many other scientific ideas. (The concrete- operational period is discussed further in Chapter 12.)

12 years through adulthood

Formal operational

Adolescents and adults use abstract and hypothetical concepts. They can use analysis, not only emotion.

Ethics, politics, and social and moral issues become fascinating as adolescents and adults use abstract, theoretical reasoning. (The formal-operational period is discussed further in Chapter 15.)

Piaget found that intellectual advancement occurs because humans at every age seek cognitive equilibrium —a state of mental balance. The easiest way to achieve this balance is to interpret new experiences through the lens of preexisting ideas. For example, infants grab new objects in the same way that they grasp familiar objects; a child’s concept of God as loving or punishing depends on their experience with their own parents. That is why people of many faiths call themselves “a child of God.”

cognitive equilibrium In cognitive theory, a state of mental balance in which people are not confused because they can use their existing thought processes to understand current experiences and ideas.

At every age, people interpret other people’s behavior by assuming that everyone thinks as they themselves do. Once a child gets an idea, he or she sticks to it—even when logic or adults say it is wrong.

Cognition is easier when the mind simplifies ideas. For instance, once children grasp the concept of “dog,” they can see unfamiliar animals on the street, from Great Danes to Chihuahuas, and say “doggie.” They also expect dogs to sniff, bark, wag tails, and so on. Some children want to pet every dog they see; some fear them all—but in either case, generalities o

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