LANGLOIS, JUDITH H., and DowNs, A. CHRIS. Mothers, Fathers, and Peers as Socialization Agents of Sex-typed Play Behaviors in Young Children. CrHiL DEVELOPMENT, 1980, 51, 1237-1247. Differential reward and punishment of 3and 5-year-old girls' and boys' sex-typed behaviors were examined using a laboratory analog of a natural play context. In study 1, mothers' and peers' reactions to sex-appropriate and sex-inappropriate play were observed. Fathers' reactions were assessed in study 2. Mothers used more reward for their children's play than did peers, while peers used more punishment than mothers. Both mothers and peers differentially rewarded and punished girls' sex-typed play, but boys received only differential punishment from peers. Fathers were generally more rewarding to girls and to 3-year-olds and more punishing to boys and to 5-year-olds. Moreover, fathers differentially rewarded play with same-sex toys and punished play with cross-sex toys for both sons and daughters. Implications for social learning and reciprocal-role theories of sex-role development are explored and a social network perspective emphasizing the complementary roles of mothers, fathers, and peers in children's social development is discussed.