Abstract
Recently, von Dawans et al. (2012) showed that stress exposure increases facial trustworthiness judgements. Given the relation between trustworthiness and the presence/absence of subtle visual features related to happiness and anger (Oosterhof & Todorov, 2008), we verified if social stress modulates the visual perception of facial expressions. Twenty-nine men were submitted to a social stress (i.e. Trier Social Stress Test for Groups) or a control condition (i.e. identical setting save for the socio-evaluative threat component) in a counterbalanced order. Facial expression recognition was then measured using a homemade version of the ‘facial expression megamix’ (Young et al.,1997) in which each of the six basic facial expressions plus neutrality were morphed with each other at seven different percentages (from 14/86 in intervals of 12%). The task was to decide which expression the image most resembled. Recognition accuracy for each facial expression when it was dominant in the morph (i.e. over 50%) was first computed. We found that social stress modulates accuracy scores only for disgust (Mstress= 81%; Mcontrol=89%; t(28)=-3.20, p=0.028; bonferroni corrected). We also verified if the emotion signal necessary to detect each facial expression when they were part of the morph was modulated by stress. For each facial expression, we calculated, separately for each percentage level, the proportion of times that it was correctly identified as being part of the morph. This produced a curve on which we fitted a cumulated gaussian to find at what percentage level an expression was detected 50% of the time. Our results show that stress decreased the sensitivity to disgust (t(28)=3.55, p=0.007; bonferroni corrected). These results indicate that an acute social stress alters the perception of facial expressions, more specifically it decreases the sensitivity to the disgust expression.
Meeting abstract presented at VSS 2015