Discontinuity from implicit to explicit theory of mind from infancy to preschool age

Recent studies have reported stability in Theory of Mind (ToM) skills from infancy to early childhood, although others have failed to report such findings. The present longitudinal study tested infants’ performance on two implicit ToM tasks at 18 months of age, assessing the false belief concept and knowledge attribution abilities. Explicit ToM was measured at 4 years of age with the Wellman and Liu (2004) Theory of Mind Scale and a parental questionnaire, the Children’s Social Understanding Scale (CSUS). None of the cross-wave correlations reached statistical significance. To increase the sample size, we then combined the data with a published experiment that tested the same constructs (N = 97) and replicated the lack of stability in the larger sample. These results challenge the conclusion that explicit false belief reasoning develops out of a precocious false belief concept.