The relationship between parental mental-state language and 2.5-year-olds' performance on a nontraditional false-belief task.

A growing body of evidence suggests that children succeed in nontraditional false-belief tasks in the first years of life. However, few studies have examined individual differences in infants' and toddlers' performance on these tasks. Here we investigated whether parental use of mental-state language (i.e. think, understand), which predicts children's performance on elicited-response false-belief tasks at older ages, also predicts toddlers' performance on a nontraditional task. We tested 2.5-year-old children in a verbal nontraditional false-belief task that included two looking time measures, anticipatory looking and preferential looking, and measured parents' use of mental-state language during a picture-book task. Parents' use of mental-state language positively predicted children's performance on the anticipatory-looking measure of the nontraditional task. These results provide the first evidence that social factors relate to children's false-belief understanding prior to age 3 and that this association extends to performance on nontraditional tasks. These findings add to a growing number of studies suggesting that mental-state language supports mental-state understanding across the lifespan.