Theory of mind predicts conversational success in early right hemisphere stroke recovery
Those living with right hemisphere damage (RHD) often struggle with engaging in aspects of conversation that require understanding what a speaker means. There is growing evidence that conversation relies on deducing the speaker's perspective, an ability known as theory of mind (ToM). However, whether individual differences in conversation after RHD relate to ToM deficits is unknown. Here, we related individual differences in conversational success to ToM in 33 speakers during the early stages of RHD (median 5 days post-stroke) in comparison to 16 age- and education-matched controls. We measured conversational success as the number of differences identified between two images while participants conversed with study coordinators. A non-verbal false belief task measured ToM abilities. Baseline cognitive tasks assessed visual inattention, inhibitory control/visual selective attention and working memory. Linear mixed-effects modeling revealed that the ToM ability to explicitly infer others' perspectives while managing conflict with one's own reliably predicted conversational success ({beta} = 0.40, p = .035; {beta}'s = .36 - .52 across sensitivity models). Adding false belief ToM substantially increased model fit ({Delta}R2 = .108, Cohen's f2 = .14), independent of baseline cognitive abilities and demographic factors. These findings provide the first empirical evidence in unilateral RHD that the ability to reason about a partner's knowledge and manage conflict with one's privileged perspective is critical for successful conversation. Results support theoretical models of ToM as a cognitive basis for everyday conversation. The clinical implications underscore the importance of socio-cognitive screening and ToM-based interventions to enhance communication outcomes in stroke rehabilitation.