The look in your eyes: The role of pupil dilation in disguising the perception of trustworthiness

Pupil size reflects the cognitive and affective states of the beholder and thus shapes interpersonal impressions. Individuals with dilated pupils are evaluated more positively than those with constricted pupils. The present study investigated the role of pupil dilation in building interpersonal trust. We used face photographs taken by Okubo et al. (2017), in which models (N = 81) were posed as trustworthy persons for a photograph shown in an economic game. We measured the pupil diameter of each model’s photographs using image processing software. The pupils were dilated when the models expressed trustworthiness in their faces. Moreover, untrustworthy choices in an economic game predicted pupil dilation. As dilated pupils produce positive impressions, the results suggest that pupil dilation may be associated with concealing signals of trustworthiness. Untrustworthy individuals may use pupillary responses almost incapable of voluntary control to exploit others in social interactions.