Cognitive factors underpinning poor expressive communication skills after traumatic brain injury: theory of mind or executive function?

Objective: The ability to see things from another’s perspective, that is, have a theory of mind (ToM), is essential to effective communication. So too is the ability to regulate verbal output, that is, to exercise executive control. People with traumatic brain injuries (TBIs) have impaired communication abilities, but the extent to which this reflects ToM versus executive dysfunction is unclear. This study explored the relative contributions of executive abilities, specifically flexibility and inhibition and ToM abilities in language production post-TBI. Method: Twenty-five adults (18 males: mean age of 48.2 years, SD = 12.0 years) with moderate to severe TBI (posttraumatic amnesia = 69.2, SD = 54.6 days) and 28 noninjured adults (19 males: mean age 49.0, SD = 12.2 years) completed three sets of communication tasks with low executive demands, high flexibility, and high inhibition demands. Within each, parallel versions had low or high ToM requirements. Results: For low executive and high flexibility tasks, scores on the high ToM versions were predicted by scores on the low ToM versions, suggesting that poor performance was explained by the executive demands the parallel tasks had in common. The exception was the high inhibition task. In this case, speakers with TBI had differential difficulty with the high ToM version, that is, they had specific difficulty inhibiting self-referential thoughts in order to cater for another’s perspective. Conclusion: We found problems with inhibiting the self-perspective accords with descriptive accounts of the egocentric nature of some communication patterns following TBI, which points to potential targets for remediation.