Connecting the dots from infancy to childhood: a longitudinal study connecting gaze following, language, and explicit theory of mind.

This longitudinal study tested the same children at three time points: infancy (10.5 months of age), toddlerhood (2.5 years of age), and early childhood (4.5 years of age). At 10.5 months, infants were assessed experimentally with a gaze-following paradigm. At 2.5 years, children's language skills were measured using the MacArthur-Bates Communicative Development Inventories. At 4.5 years, children's explicit theory of mind was assessed with a standard test battery. Analyses revealed that infants with higher gaze-following scores at 10.5 months produced significantly more mental-state words at 2.5 years and that children with more mental-state words at 2.5 years were more successful on the theory-of-mind battery at 4.5 years. These predictive longitudinal relationships remained significant after controlling for general language, maternal education, and nonsocial attention. The results illuminate the bridging role that language plays in connecting infants' social cognition to children's later understanding of others' mental states. The obtained specificity in the longitudinal relations informs theories concerning mechanisms of developmental change.