Language and theory of mind: a study of deaf children.

Theory-of-mind (ToM) abilities were studied in 176 deaf children aged 3 years 11 months to 8 years 3 months who use either American Sign Language (ASL) or oral English, with hearing parents or deaf parents. A battery of tasks tapping understanding of false belief and knowledge state and language skills, ASL or English, was given to each child. There was a significant delay on ToM tasks in deaf children of hearing parents, who typically demonstrate language delays, regardless of whether they used spoken English or ASL. In contrast, deaf children from deaf families performed identically to same-aged hearing controls (N=42). Both vocabulary and understanding syntactic complements were significant independent predictors of success on verbal and low-verbal ToM tasks.