Play behavior in the year-old infant: early sex differences.

32 boys and 32 girls, 13 months old, were observed with their mothers in a standardized free play situation. There were striking sex differences in the infant's behavior toward their mothers and in their play. Earlier observation of the mothers' behavior toward the infants at 6 months indicates that some of these sex differences were related to the mothers' behavior toward the infants. It was suggested that parents behave differently toward girls and boys, even as infants, reinforcing sex-appropriate behavior. This study emphasizes the importance of observing the freely emitted behavior of the very young child.