The impact of sign language on the cognitive development of deaf children: the case of theories of mind.

The ability to attribute false beliefs (i.e., demonstrate theory of mind) by 155 deaf children between 5 and 8 years of age was compared to that of 39 hearing children ages 4 to 6. The hypotheses under investigation were (1) that linguistic features of sign language could promote the development of theories of mind and (2) that early exposure to language would allow an easier access to these theories. Deaf children were grouped according to their communication mode and the hearing status of their parents. The results obtained in three false belief tasks supported the hypotheses: effective representational abilities were demonstrated by deaf children of deaf parents, whereas those born to hearing parents appeared delayed in that regard, with differences according to their communication mode.