Judith Rich Harris - The Nurture Assumption

Harris's most famous work, The Nurture Assumption, was first published in 1998, with a revised version published in 2009.

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. Harris also argues against the effects of birth order. The book looks outside the family and points at the peer group as an important shaper of the child's psyche. Harris argues that 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.