The present study examined children's co-construction of shared meanings and internal state language during play with their sibling and friend from early to middle childhood. Sixty-five 4-year-old children (T1) and 46 7-year-old children (T2) were observed in the home during two free play sessions with a sibling and with a friend at both time…

This study investigated relations among children's Theory-of-Mind (ToM) development, early sibling interactions, and parental discipline strategies during the transition to siblinghood. Using a sample of firstborn children and their parents (N = 208), we assessed children's ToM before the birth of a sibling and 12 months after the birth, and…

Evidence exists for two competing theories about the effects of having an older sibling on development. Previous research has found that having an older sibling has both advantages and disadvantages for younger siblings' development. This study examined whether and how older siblings influenced the onset of their own younger siblings' motor…