A Piagetian analysis of social development focuses on the changes in children's social concepts and the social factors which facilitate these changes. Piaget's early analysis of children's language into a 3-stage transition from egocentrism to fully socialized speech led to more general study of social behavior. Observations of children playing at various ages facilitated the study of developmental changes in behavior with respect to rules, and changes in ideas about rules. The observed development from blind allegiance to the rule to concern for cooperative agreement was seen as the basis of the whole social-moral developmental process. Discussion of social development is constantly related to the total ongoing intellectual development, so that social interactions are interpreted in terms of their positive contributions to cognitive processes. Literature is reviewed concerning relationships between social development and preschool experience. To counteract the problems in interpreting these studies (permanence of gains, lack of adequate controls), a detailed review of research which analyzed the effects of specific social variables is presented. Focus is on studies of dominative-integrative behavior, training in independent problem solving through social reinforcement, social learning by imitation, and the use of the whole peer group to promote social development. (DP)