Theory of mind after traumatic brain injury.

This study investigated whether people with severe traumatic brain injury (TBI) demonstrate a specific impairment on tasks requiring them to make inferences about others' mental states (theory of mind tasks). Participants with severe TBI were compared to a healthy group on verbal first-order and second-order theory of mind (ToM) tasks, non-verbal ToM tasks and on verbal and non-verbal tasks requiring them to make general (non-mental) inferences (NMIs). The clinical group performed more poorly than controls on both ToM and NMI tasks. This performance was not completely accounted for by the working memory or implicit language demands of the tasks. Multiple regression analyses suggested that patients with TBI have a general weakness in inference-making that, combined with linguistic and working memory limitations, impairs their performance on both non-verbal and second-order ToM tasks. However, a specific ToM impairment may underlie their poor performance on verbal first-order tasks. Implications of this finding for the possibility of a separate cognitive module of ToM are discussed, as well as for the rehabilitation of social deficits after TBI.