Bilingualism and second-order theory of mind development in autistic children over time: Longitudinal relations with language, executive functions, and intelligence.

Theory of Mind has long been studied as a core weakness in autism spectrum disorder due to its relationship with social reciprocity, while bilingualism has been shown to compensate for autistic individuals' mentalizing weaknesses. However, our knowledge of the Theory of Mind developmental trajectories of bilingual and monolingual autistic children, as well as of the factors related to Theory of Mind development in autism spectrum disorder is still limited. The current study has examined first- and second-order Theory of Mind skills in 21 monolingual and 21 bilingual autistic children longitudinally across three time points, specifically at ages 6, 9, and 12, and also investigated associations between Theory of Mind trajectories and trajectories of the children's language, intelligence and executive function skills. The results reveal that bilingual autistic children outperformed their monolingual peers in second-order Theory of Mind at ages 9 and 12, and that intelligence and, especially, expressive vocabulary skills played a pivotal role in advancing bilingual autistic children's second-order Theory of Mind development. On the other hand, monolingual autistic children only managed to capitalize on their language and intelligence resources at age 12. The findings highlight the importance of investigating bilingualism effects on autistic children's advanced cognitive abilities longitudinally.