That Can't Be Right! What Causes Pragmatic Language Impairment Following Right Hemisphere Damage?

Right hemisphere damage (RHD) following unilateral stroke is often associated with impairment of pragmatic language, specifically, the ability to comprehend inferences that arise from language used in context. Three kinds of cognitive deficits have been proposed to explain the pragmatic deficits in RHD individuals, impaired Theory of Mind (TOM), weak central coherence (CC), and impaired executive function (EF). This study aims to evaluate the explanatory ability of these theories in relation to the comprehension of nonliteral (ironic) jokes versus literal lies. Twenty-one RHD patients and 21 age-matched controls were assessed on tasks tapping TOM, CC processing and general inference ability (EF) and the comprehension of irony. Second-order TOM and EF were found to play a significant role. However, neither construct, either in isolation or combined, completely explained the poor performance of RHD patients on this task compared to control participants.