Nonshared environmental processes in social-emotional development: an observational study of identical twin differences in the preschool period

Differences in mothers' parenting behaviors toward their identical twin preschoolers were examined to identify environmental processes in social-emotional development. The study included 62 pairs of 3(1)/(2)-year-old same-nonshared sex identical twins. Indicators of each child's social-emotional development (temperament, prosocial behavior, behavior problems and noncompliance) and parenting environment (warmth and negativity, positive and negative control, responsiveness) were assessed using observers, interviewers', and parents' ratings. Mothers treated their identical twins differently, and this differential treatment covaried in expected ways with identical twin differences in social-emotional adjustment. The twin who received more supportive and less punitive forms of parenting was also higher in positive mood and prosocial behaviors and lower in negative mood and behavior problems when compared to her or his twin.