Processing Of Face Trustworthiness:an ERP Study

During the interpersonal interaction,faces are a particularly rich source of social information,meantime,it also has a great impact on our behavior and decisions.As the old saying goes,“men cannot be judged by their looks.” However,in daily life,this sentence is hard to follow,especially,when people have to make quick decisions to approach benefits and avoid harm.Further interaction and cooperation is based on how much trust people play onstrangers,which makes face trustworthiness evaluation prevalent.Thus understanding the nature of the processes pertaining to trustworthiness has wide ranging implications.Based on knowledge about the neural mechanism of face trustworthiness,people can get along with each other more smoothly and make better decisions.To investigate the underlying mechanism of face trustworthiness processing,this study used ERP technique.The whole study can be divided into two ERP experiments.The aim of the firstexperiment was to investigate the time course of face evaluation for trustworthiness,with facial expression evaluation as comparison.The aim of the second experiment was to investigate the mediation of spatial attention on face trustworthiness processing.Each part of the results are as follows:(1)In the first experiment,behaviorally,participants could make rapid trustworthiness judgment,nearly,as soon as facial expressions judgment.However,congruency associated with facial emotional judgment was significantly higher than trustworthiness judgment.The ERP results showed that untrustworthy faces and trustworthy faces elicited larger P1 amplitudes than neutral faces on face trustworthiness task.However,this effect did occur on facial emotional judgment task.Untrustworthy faces and trustworthy faces elicited larger N170 amplitudes than neutral faces on facial emotional judgment task,but not face trustworthiness task.For both tasks,untrustworthy faces and trustworthy faces elicited larger EPN amplitudes than neutral faces and the EPN component was enhanced for facial emotional judgment task than trustworthiness judgment task.Additionally,the LPC amplitudes of untrustworthy faces was larger than trustworthy faces and neutral faces.Overall,these results suggested that facial trustworthiness and facial expression evaluation began at early perceptual processing stages.Facial trustworthiness evaluation and facial expression evaluationwere different in structural encoding.During middle preliminary selective attention stage,compared to facial trustworthiness,facial expression attracted more attention resources.Additionally,in both early stage and middle stage,people can distinguish trustworthy and untrustworthy face from neutral face.However,it was till the later elaborative stages,people was able to distinguish untrustworthy,neutral and trustworthy faces.(2)In the second experiment,behaviorally,participants responded faster to untrustworthy and trustworthy faces than neutral faces.Moreover,thecongruency of untrustworthy faces was similar to trustworthy faces.The ERP results showed that when faces were attended,untrustworthy faces and trustworthy faces elicited larger P1 amplitudes than neutral faces.However,when faces were unattended,no such effect was found.Besides that,amplitudes of N170 component and EPN component elicited by attentional condition were not different form un-attentional condition.In addition,whenever faces were attended or not,untrustworthy faces and trustworthy faces elicited larger LPC amplitudes than neutral faces.Overall,these results suggested that attention could facilitate the quick processing of face trustworthiness during the early stage.Moreover,during the later stage,to some extent,even in the un-attentional condition,stimulus with adaptive meaning such as trustworthy faces and untrustworthy faces could also be processed.