Abstract
Background: Misappraisals in evaluating the trustworthiness of others may be one mechanism contributing to the interpersonal difficulties individuals with posttraumatic stress disorder (PTSD) face. Objective: This study used a translational experimental design to examine the behavioural and neural correlates underlying the appraisal of facial stimuli morphed on dimensions of trustworthiness across three groups: individuals with high posttraumatic stress symptoms (HPTS), low posttraumatic stress symptoms (LPTS), and healthy controls (HC). Methods: Participants (N = 70) rated how trustworthy to untrustworthy they perceived three facial morphs (trustworthy, neutral, and untrustworthy) while undergoing electroencephalography (EEG). Results: Behavioural results showed that the HPTS group rated the untrustworthy morph as more untrustworthy than the HC group (β = 0.20, SE = .07, 95% CI [0.06, 0.33], z = 2.88, p = .004). The HPTS group also showed no variation in response time across morphs ( X2 (2) = 0.92, p = 0.63), while the LPTS and HC groups did ( X2 (2) = 9.60, p = .008; X2 (2) = 23.62, p < .001). EEG data revealed significant group by morph interactions at the N170 latency and the Vertex Positive Potential (VPP): the HPTS and LPTS identified the untrustworthy morph faster than the HCs, but diverged to the degree to which they encoded each facial morph. Conclusions: Taken together our results suggest that HPTS individuals demonstrate an early attentional avoidance of faces morphed on dimensions of trustworthiness. This early, preconscious, avoidance may be one mechanism contributing to the miscalculations individuals with PTSD make in interpersonal situations.