Recent evidence has begun to demonstrate that information regarding socially relevant traits is available from the static, neutral human face. In the current thesis, we replicated and extended previous research, showing that signals of personality and health were received by unfamiliar others. Further, these signals remained when information was limited to internal facial features, providing initial evidence of the location of these signals and the differing contributions of external and internal facial characteristics.By investigating the signal content of hemifaces, split vertically down the midline, we found asymmetries in the information signalled by the two sides of the face. While previous research has highlighted the role of the left hemiface in transitory signals of expression, we found that the right hemiface signalled more information regarding temporally stable personality traits.Given the similarities between humans and chimpanzees in facial morphology, face processing, and personality structure, we hypothesised an evolved system for signalling personality information that both species share. We provided the first evidence that personality information, in particular relating to dominance and extraversion, was indeed present in the chimpanzee face and could be accurately perceived by human observers. Our results support the idea that humans and chimpanzees share a system for signalling socially-relevant information from the face that dates back to our last common ancestor around six million years ago.