Book excerpt: Most studies of social development in children have relied on the assumption that adults' instructions to children pass on knowledge of the rules of behavior which govern and preserve society. In this volume, James Youniss argues that the child's relations with his or her friends and peers make a distinctive and critically important contribution to social development. While the child's relations with parents and other adults provide a sense of order and authority, peer relations are a source of sensitivity, self-understanding, and interpersonal cooperation. Following a discussion of the views of Harry Stack Sullivan and Jean Piaget, whose theories are synthesized in Youniss's perspective, Youniss presents a wealth of empirical data from studies in which children describe their own views of their two social worlds.