The Nurture Assumption: Why Children Turn Out the Way They Do is a 1998 book by American author Judith Rich Harris. In her work, Harris argues modern psychology’s understanding of human development, especially in regard to socialization and personality, is being hampered by “the nurture assumption”—the widespread belief that parenting is the primary influence on children. She uses scientific evidence to deconstruct the nurture assumption, and provides an alternative theory called “group socialization theory”—in which children are more influenced by peers than parents.

This study guide refers to the 2009 Free Press second edition of this work. It includes the Foreword to the first edition and Introduction to the second edition.

Content Warning: The Nurture Assumption mentions physical and verbal abuse, postpartum depression, and concentration camps in exploring human development through traumatic experiences.

Summary

In her Introduction, Judith Rich Harris laments that most researchers and the public still accept “the nurture assumption,” which considers parenting the primary influence in child socialization and personalities. However, current research reveals the significant role genes play in human development, and she believes this will support her “group socialization theory.”

In Chapter 1, Harris argues there are many factors that inform a child’s environment other than parenting, and refutes the idea that because parents supply nature (genes) and nurture (parenting decisions), they are wholly responsible for how their children turn out. In Chapter 2, she contrasts socialization researchers interested in nurture and behavioral geneticists interested in nature. She argues socialization researchers have done a poor job of proving parenting is the most important nurture factor.

In Chapter 3, Harris cites scientific research that suggests parenting decisions do not influence child development as much as some believe, and casts doubt on birth order, family make-up, and home in creating lasting personality differences. In Chapter 4, she maintains personality is malleable, as people vary their behavior depending on social context. In Chapter 5, she explores other cultures’ approaches to parenting to show they vary. Harris argues parenting advice in America has changed over the last few centuries, with little of it based on reliable science.

In Chapter 6, Harris explains human evolution and similarities with chimpanzees. She connects the instinct to form close bonds to children’s innate desire to integrate themselves in friend groups to maximize their chance of survival. In Chapter 7, she argues humans have evolved to live in groups, and this instinct causes them to actively form groups and recognize differences. In Chapter 8, Harris focuses on child interactions through play. She argues friendships are essential to socialization and cannot be replaced with other relationships, such as the child-parental bond. In Chapter 9, she argues most children create subcultures which differ in norms and values from broader adult culture. Harris contests the notion that children are blank slates that passively receive adult influence, arguing that they socialize through play.

In Chapter 10, Harris focuses on child self-categorization based on gender, a powerful social marker. Chapter 11 addresses peer relationships at school, and how classrooms become host to different cliques. In Chapter 12, Harris considers how adolescents’ peer relationships influence them more than their parents’ strategies. In Chapter 13, she explores dysfunctional families, asserting that parenting has been overemphasized in diagnosing troubled children, while the role of genetics has been underplayed.

In Chapter 14, Harris offers advice to parents, saying their influence on their children is most relevant in home matters such as religion, politics, and household habits. She advises parents to support their children by giving them ample opportunity to establish positive peer relationships. In Chapter 15, she reiterates the main points of her group socialization theory and tries to debunk the nurture assumption. Harris urges the reader to consider the importance of peer influence and not blame parents for how children develop.