Harris's most famous work is "The Nurture Assumption". It was published in 1998. A revised version was published in 2009. Children often act like their parents act. Some psychologists thought this was because of the way that parents raised their children. Harris argues that (some or all of) this similarity is due to genetics. Otherwise, parents are not the most important factor in child development. This book argues that peers are more important. Harris argues that children are socialized by peers.