Abstract
Forty-two children participated in a longitudinal study that investigated the relationship between their joint engagement experience when toddlers and their development of theory of mind when preschoolers. Controlling for language comprehension at 30 months, higher preschool false belief scores were associated with more time in coordinated joint engagement earlier (18-21 mo, beta= .34) and in symbol-infused joint engagement later (27-30 mo, beta= .35) in toddlerhood. Findings suggest that the early foundation of theory of mind development is laid as toddlers attend to both social-emotional and symbolic aspects of shared events.