Mothers' Mental State Talk and 3- to 5-Year-Old Children's Theory of Mind: Their Reciprocal Dynamic Impact.

The development of children's social function is influenced by the social environment, and children also play an active role in shaping and nurturing this environment. The present study investigated the potential reciprocal dynamic impact of mothers' mental state talk (MST) and the development of theory of mind (ToM) in children. Using a cross-sectional design, we explored the development of ToM in 3- to 5-year-old children using an unexpected location task, an unexpected content task, an appearance-reality task, and mothers' MST during mother-child reading. The results showed the following: (1) the mothers' MST exhibited a shift from a predilection for subjective terms (such as desires) to a preference for objective terms (such as cognitions) as their children matured; (2) the development of the children's ToM was closely related to their mothers' MST. The overall MST scores, as well as the different categories and referents used in MST, were closely associated with the children's ToM development. Notably, at the age of four, a critical period emerged where the correlation between maternal MST and ToM became significantly pronounced. These findings highlight the reciprocal nature of mother-child interactions as a two-way adaptive process.