Individual differences in perceptual sensitivity and representation of facial signals of trustworthiness

One of the most important sources of social information is the human face, on whose appearance we easily form social judgments: Adults tend to attribute a certain personality to a stranger based on minimal facial cues, and after a short exposure time. Previous studies shed light on the cognitive and neural mechanisms underlying the ability to discriminate facial properties conveying social signals, but the underlying processes supporting individual differences remain poorly understood. In the current study, we explored whether differences in sensitivity to facial cues to trustworthiness and in representing such cues in a multidimensional space are associated with individual variability in social attitude, as measured by the extraversion/introversion dimension. Participants performed a task where they assessed the similarity between faces that varied in the level of trustworthiness, and multidimensional scaling analyses were performed to describe perceptual similarity in a multidimensional representational space. Extraversion scores impacted RTs, but not accuracy or face representation, making less extraverted individuals slower in detecting similarity of faces based on physical cues to trustworthiness. These findings are discussed from an ontogenetic perspective, where reduced social motivation might constrain perceptual attunement to social cues from faces, without affecting the structuring of the face representational space.