Theorists have speculated about the symbolic underpinnings of theory of mind (ToM), but no study has examined them across the main developmental span of ToM. Here, the onset of symbolic understandings in three domains (pretend play, language, and understanding representations) and ToM was examined. Fifty-eight children were tested on batteries of…

Relations among indices of maternal mind-mindedness (appropriate and nonattuned mind-related comments) and children's: (a) internal state vocabulary and perspectival symbolic play at 26 months ("N" = 206), and (b) theory of mind (ToM) at 51 months ("n" = 161) were investigated. Appropriate comments were positively…

A key prediction of cognitive theories of gender development concerns developmental trajectories in the relative strength or rigidity of gender typing. To examine these trajectories in early childhood, 229 children (African American, Mexican American, and Dominican American) were followed annually from age 3 to 5 years, and gender-stereotypical…

Coparenting is associated with child behavior in families with heterosexual parents, but less is known about coparenting among lesbian- and gay-parent families. Associations were studied among self-reported divisions of labor, coparenting observations, and child adjustment ("M[subscript age]" = 3 years) among 104 adoptive families headed…

In one of the first open diffusion experiments with young children, a tool-use task that afforded multiple methods to extract an enclosed reward and a child model habitually using one of these methods were introduced into different playgroups. Eighty-eight children, ranging in age from 2 years 8 months to 4 years 5 months, participated. Measures…

Although genetic influences on individual differences in activity level (AL) are well documented, few studies have considered the etiology of AL from a contextual perspective. In the present study, cross-situational and context-specific genetic effects on individual differences in AL at age 2 were examined. The AL of 312 twin pairs (144…

Imitation, vocabulary, pretend play, and socially insightful behavior were investigated in 5,206 same- and opposite-sex 2-year-old twin pairs in the United Kingdom. Individual differences in imitative ability were due to modest heritability (30%), while environmental factors shared between twins (42%) and unique to each twin (28%) also made…