The longitudinal relations between mental state talk and theory of mind

Background Previous investigations of associations between children's Theory of Mind (ToM) and parents' use of words relating to mental states (or mental state talk; MST) have predominantly been performed using cross-sectional designs and false belief tasks as indicators of ToM.Methods We here report a longitudinal study of 3-5 year-olds (n = 80) investigating ToM development using the ToM scale and three different parental MST types: the absolute frequency of words, the proportions of words, and the vocabulary size.Results Our results revealed significant relations between all parental MST types and later child ToM. Proportions of parental MST were most often related to the children's ToM at 4 years of age. However, the rate at which the children developed ToM from 3 to 5 years of age was associated with the other two parental MST type measures, namely, absolute frequency and vocabulary size. Additionally, our analyses revealed that parents' use of cognitive MST words (e.g., think, or know) were most frequently associated with children's ToM at 4 years of age compared to emotion and desire-related MST words.Conclusions We conclude that the parental ability to capture the thoughts, beliefs, and knowledge present in different scenarios is associated with children's ability to understand other minds. Moreover, parents' way of talking about the mental states of others is associated with their children's ability to understand and further develop ToM.