Siblings, Theory of Mind, and Executive Functioning in Children Aged 3–6 Years: New Longitudinal Evidence

Longitudinal data were obtained from 157 children aged 3 years 3 months to 5 years 6 months at T ime 1. At T ime 2 these children had aged an average of 12 months. Theory of mind ( ToM ) and executive functioning ( EF ) were measured at both time points. Results suggest that T ime 1 ToM scores predict Time 2 EF scores. Detailed examination of sibling influences suggests that benefits—in terms of advanced ToM development—accrue to children with siblings versus without, and to those with a larger number of child‐aged siblings. Any advance in either area ( ToM or EF ) is likely to benefit the other, and early sibling interaction appears to act as a catalyst.