The Nurture Assumption

The Nurture Assumption is a book written by Judith Harris with the foreword by Steven Pinker. Its answer to "Why Children Turn Out the Way They Do" is that "Parents Matter Less Than You Think and Peers Matter More".

In this book, she challenges the idea that the personality of adults is determined chiefly by the way they were raised by their parents. She looks at studies which claim to show the influence of the parental environment and claims that most fail to control for genetic influences.

For example, if aggressive parents are more likely to have aggressive children, this is not necessarily evidence of parental example. It may also be that aggressiveness has been passed down through the genes. Indeed, many adopted children show little correlation with the personality of their adoptive parents, and significant correlation with the natural parents who had no part in their upbringing.

The role of genetics in personality has long been accepted in psychological research. However, even identical twins, who share the same genes, are not exactly alike, so inheritance is not all. Psychologists have tended to assume that the non-genetic factor is the parental environment, the "nurture". However, many twin studies have failed to find a strong connection between the home environment and personality. Identical twins differ to much the same extent whether they are raised together or apart. Adoptive siblings are as unalike in personality as non-related children. Birth order effects seem to be minimal.

Harris' most innovative idea was to look outside the family and to point at the peer group as an important shaper of the child's psyche. For example, children of immigrants learn the language of their home country with ease and speak with the accent of their peers rather than their parents. Children identify with their classmates and playmates rather than their parents, modify their behavior to fit with the peer group, and this ultimately helps to form the character of the individual.

Contrary to some reports, Harris did not claim that "parents don't matter". The book did not cover cases of serious abuse and neglect. Harris pointed out that parents have a role in selecting their children's peer group, especially in the early years. Parents also affect the child's behavior within the home environment and the interpersonal relationship between child and parent.

Critical reaction
The Nurture Assumption received mixed responses. Neuroscientist Robert Sapolsky of Stanford University says her book is "based on solid science." Psychologist Steven Pinker of Harvard predicts that the book "will come to be seen as a turning point in the history of psychology." Frank Farley of Temple University claims that "she's taking an extreme position based on a limited set of data. Her thesis is absurd on its face, but consider what might happen if parents believe this stuff!" Wendy Williams of Cornell University, who studies how environment affects IQ, argues that "there are many, many good studies that show parents can affect how children turn out in both cognitive abilities and behavior." Jerome Kagan of Harvard University argues that Harris "ignores some important facts, ones that are inconsistent with this book's conclusions".

Some critics of Harris' book argue that she defines "nurture" differently than it is traditionally defined by psychologists talking about "nature and nurture." These critics charge that "nurture" should include all the environmental inputs, and not just the parent/child relationship. Since contemporary American parents who send their children to conventional schools and allow them to spend hours in front of television and videogame screens have less time with their children than these other inputs do, naturally those other inputs would be likely to have a significant and perhaps larger effect than the parents.

Harris rejects the idea that her book will encourage parents to neglect or mistreat their children. She maintains that parents will continue to treat their children well "for the same reason you are nice to your friends and your partner, even though you have no hopes of molding their character. For the same reason your great-grandparents were nice to their children, even though they didn't believe in the nurture assumption".

Reviews

 * "Do Parents Matter?", Malcolm Gladwell, The New Yorker, August 17, 1998.
 * Psychpage review, Richard Niolon.
 * "The Nature of Nurture", Steve Sailer.
 * "Peer Pressure", Carol Tavris, New York Times, September 13, 1998.
 * A Parent's Influence Is Peerless Jerome Kagan, Harvard Education Letter, November/December 1998