Evaluating the causes of impaired irony comprehension following traumatic brain injury

Background: Individuals with traumatic brain injury (TBI) are known to have difficulty in understanding non-literal language devices such as irony. There are at least two possible explanations for poor irony comprehension following TBI; first, deficits might be caused by a specific impairment to theory of mind (ToM) and, second, deficits could be attributed to more general impairment in executive functioning (EF). Aims: This study aimed to evaluate the role of ToM and EF in the ability to comprehend non-literal ironic jokes. Methods & Procedures: Participants were 16 individuals who had sustained a TBI and 16 age- and demographic-matched controls. The ability to make inferences about mental states was compared to inferential reasoning capacity more generally. Participants were also assessed on other aspects of EF thought to contribute to inference making (working memory, concept formation, and fluency). The extent to which scores on theses tasks were associated with participants' ability to comprehend ironic jokes was assessed using correlational and regression analyses. Outcomes & Results: Participants with TBI were significantly impaired on tasks measuring both ToM and EF. ToM was not significantly associated with irony comprehension. Instead, inferential reasoning, more broasdly defined, demonstrated the strongest association. None of the component EF tasks were associated with irony comprehension. Conclusion: The results of this study do not support the theory that a specific impairment to ToM causes poor irony comprehension in TBI. In contrast, general inferential reasoning was a strong and significant predictor.