Testing the stability of theory of mind: A longitudinal approach.

An explicit understanding of false belief develops around the age of four years. However, tasks based on spontaneous responses have revealed an implicit understanding of belief and other theory of mind constructs in infants in their second year of life. The few longitudinal studies that have examined conceptual continuity of theory of mind from infancy to early childhood have reported mixed findings. Here we report two longitudinal experiments to investigate the developmental relation between implicit and explicit theory of mind. No link was observed in the first experiment between false belief and intention understanding measured at 14 and 18 months with the violation of expectation paradigm and tasks measuring explicit and implicit false belief at four or five years of age. In the second experiment, infants aged 18 months were tested with a battery of tasks that measured knowledge inference and false belief. They were then tested with the theory of mind scale at five years of age. The parents completed the Children's Social Understanding Scale (CSUS) and the Social Communication Questionnaire (SCQ). As in the first experiment, there were no associations between early and later forms of theory of mind. We suggest that these findings do not support the view that there is conceptual continuity in theory of mind development.