Sibling composition, executive function, and children's thinking about mental diversity.

Prior investigations of relations between sibling composition and theory of mind have focused almost exclusively on false belief understanding in children 6 years of age and younger. The current work expands previous research by examining whether sibling composition predicts 4- to 11-year-olds' (N=192) more advanced mental state reasoning on interpretive theory of mind tasks. Even when controlling for age and executive function, children with a greater number of older siblings or with more same-sex siblings demonstrated stronger knowledge in both their predictions and explanations that people with different past experiences can have diverse interpretations of ambiguous stimuli. These data provide some of the first documentation of sibling constellations that predict individual differences in theory of mind during middle childhood.