Visual attention mechanisms in happiness versus trustworthiness processing of facial expressions

Abstract

A happy facial expression makes a person look (more) trustworthy. Do perceptions of happiness and trustworthiness rely on the same face regions and visual attention processes? In an eye-tracking study, eye movements and fixations were recorded while participants judged the un/happiness or the un/trustworthiness of dynamic facial expressions in which the eyes and/or the mouth unfolded from neutral to happy or vice versa. A smiling mouth and happy eyes enhanced perceived happiness and trustworthiness similarly, with a greater contribution of the smile relative to the eyes. This comparable judgement output for happiness and trustworthiness was reached through shared as well as distinct attentional mechanisms: (a) <i>entry times</i> and (b) initial fixation <i>thresholds</i> for each face region were equivalent for both judgements, thereby revealing the same attentional <i>orienting</i> in happiness and trustworthiness processing. However, (c) greater and (d) longer <i>fixation density</i> for the mouth region in the happiness task, and for the eye region in the trustworthiness task, demonstrated different selective attentional <i>engagement</i>. Relatedly, (e) mean <i>fixation duration</i> across face regions was longer in the trustworthiness task, thus showing increased attentional intensity or processing effort.