Siblings and theory of mind in deaf native signing children.

We report a study designed to examine the basis of "theory of mind" (ToM) reasoning in deaf children who are native signers of British Sign Language. The participants were 20 native signers (aged 4-8 years) and their siblings. The children were given a measure of the quality of sibling relations together with a referential communication test concerning physical representations of objects and people. Sibling quality as perceived by siblings predicted children's ToM scores over and above age and referential communication. We conclude that the process of ToM understanding is linked to positive sibling relations that may permit access to knowledge about the inner worlds of beliefs and other mental states.