Impaired emotion and sincerity perception after severe traumatic brain injury

Background: People with a severe traumatic brain injury (TBI) show impaired Theory of Mind or mentalising abilities which affect their capacity to recognise sarcasm and lies in dyadic exchanges. This study aimed to investigate whether: i) these problems are seen in more complex scenarios with four speakers; and ii) is associated with deficits in basic emotion perception, empathy and abstract reasoning.

Methods: Thirty-one adults with severe TBI (24 males) and 25 demographically-matched Controls (20 males) participated. Purpose-designed video vignettes depicted four actors volunteering for additional duties. Limited verbal responses were used; these literally suggested a willingness to be involved but their intended meaning was tempered by the actor’s emotional demeanour. Measures included: participants’ ratings (0-100%) and rankings (1, 2, 3, 4) of actors’ sincerity; basic emotion evaluation; self-reported empathy levels; verbal and nonverbal abstract reasoning.

Results: Compared to Controls, TBI participants were worse at differentiating between sincere and insincere expressions (p<0.05), and rated insincere expressions as more sincere (p<0.05), though performed similarly in how they rated sincere expressions (p>0.10). TBI participants were also less consistent (α = 0.65) than Controls (α = 0.90) in their rankings of sincere and insincere expressions (p<0.01). Poorer abstract reasoning, emotion perception and cognitive empathy were all associated with poorer sincerity/sarcasm detection overall (all p<0.05); poorer emotional empathy and emotion perception were both associated with rating insincere expressions as sincere (p<0.05).

Conclusions: TBI-related impairments in sincerity/sarcasm detection may be due to a failure to differentiate between sincerity and insincerity. Moreover, poorer emotion perception, empathic and abstract reasoning abilities may all contribute to poorer sincerity/sarcasm detection after TBI, suggesting that both cognitive and emotional impairments are implicated in social deficits.