Maternal mind-mindedness and attachment security as predictors of theory of mind understanding.

This study investigated relations between social interaction during infancy and children's subsequent theory of mind (ToM). Infant-mother pairs (N = 57) were observed in a free-play context at 6 months. Interactions were coded for (a) mothers' use of mental state language that commented appropriately on the infants' mental states, and (b) mothers' use of mental state language that did not appropriately reflect their infants' minds. A third variable was (c) security of attachment, which was assessed using the Strange Situation procedure at 12 months. Performance on a battery of ToM tasks at 45 and 48 months was positively correlated with (a), but was not related to (b) or (c). A regression analysis showed that mothers' use of appropriate mental state comments independently predicted overall ToM performance, accounting for 11% of the variance. Children's verbal ability was the only other independent predictor of ToM performance, accounting for 16% of the variance. These findings represent the earliest known social predictor of individual differences in ToM.