The current longitudinal study explores associations between language and social competence. Specifically, I examine whether language variables, such as using and hearing mental state words and specific aspects of communication, are linked to social competence through the social skill of perspective-taking and the ability to understand that other people might hold a false belief. A cohort of 67 children were assessed at three time points. The initial assessment took place at ages of 24–30 months; and the first follow-up assessment occurred at ages of 41–49 months, and the outcome assessment took place when the children were aged 52–60 months. Data were collected through standardised tests of language and cognition, coded spontaneous play-based language samples, a nonverbal false-belief task and parental questionnaires that represent aspects of Cavell's (1990) social competence model.

The findings indicated that mothers' connected communication played a role in their children's social development. Mothers who more often referred to their 2-year-old child's utterances, reformulated, elaborated or answered to them in an appropriate manner described their children as socially more advanced later in development compared to mothers who were less connected in communication with their child. However, mothers' connectedness in communication with their children was no longer a significant predictor once the children's expressive and receptive language abilities were added to the regression model. Children's expressive vocabulary including words to refer to mental states at the age of two years was a predictor of their social competence at five years. Children who produced more words in general and more often used words to refer to their own and others’ mental states such as emotions, desires or cognition at two years had fewer social difficulties at five years than children who produced fewer words and made fewer references to mental states.

No relationship was found among mental-state talk, communication connectedness and false-belief understanding and between false-belief understanding and social competence.

These findings indicate that being able to express oneself and to refer to mental states helps young children to interact more effectively in the social world. Therefore, considering the impact that early language competency has on social development identification of children with language difficulties becomes even more important.