The development of sensitivity to social traits of faces

The ability to discriminate social signals from faces is a fundamental component of human social interactions. So far, only a few studies have investigated the developmental origins of the sensitivity to these fine-grained characteristics of faces, focusing only on explicit trustworthiness judgements. In this study, a group of 5-year-old and 7-year-old children and a group of adults performed two tasks aimed to measure their implicit perceptual sensitivity to physical cues to trustworthiness (oddmanout task) and their ability to make explicit trustworthiness judgments (pairwise preference). In the oddmanout task, participants observed three simultaneously presented faces and selected the one they judged to be more different from the others. In the pairwise preference task, participants selected the face they trusted more among two simultaneously presented faces. For both tasks, the stimuli consisted of 7 variations of the same female face identity varying along a continuum of expressed trustworthiness. Preliminary results show that 5-year-old children perform significantly worse than both 7-year-olds and adults in both tasks. Nevertheless, multidimensional scaling (MDS) analyses performed on dissimilarity scores derived from the oddmanout task show that already at the age of 5 children represent faces in memory as a function of the level of trustworthiness they express, and provide explicit judgments favouring the face that display more intense physical cues to trustworthiness. This overlap between implicit and explicit judgements for younger as well as older children suggests that sensitivity to social signals from faces is already present early in the development and specializes in time.