Individual differences in false belief understanding are stable from 3 to 6 years of age and predict children's mental state talk with school friends.

Despite a wealth of studies in the field, longitudinal assessments of both the stability and predictive utility of individual differences in preschoolers' understanding of the mind remain scarce. To address these gaps, we applied latent variable analyses to (a) experimental data gathered from a socially diverse sample (N=101, 60 boys and 41 girls) at 3 and 6 years of age and (b) transcript-based coding of children's dyadic interactions with a best friend at age 6. Our results showed significant stability between latent factors of false belief understanding at ages 3 and 6 even with effects of verbal ability and inhibitory control controlled at both time points. In addition, false belief understanding at ages 3 and 6 showed both distal and proximal links with the frequency of children's talk about mental states at age 6 even when their overall talk and their friends' mental state talk were also controlled. We conclude that preschoolers' false belief understanding both directly and indirectly supports children's growing ability to discuss thoughts and feelings in their conversations with friends.