Individual differences in facial expressivity: Social function, facial anatomy and evolutionary origins

ongoing

Communicating with others via the face is crucial for navigating our social world. Deficits in facial expression production can have debilitating effects on social interaction, characterising several clinical conditions such as autism spectrum disorder, schizophrenia and Parkinson’s disease. Despite this, we know surprisingly little about individual differences in facial expressivity in the typical population, what causes these differences and whether such differences impact on individual lives. In part, this could be due to an historical focus on the universal nature of facial expression, assigning individual difference to random ‘noise’, rather than an evolutionarily relevant characteristic. The FACEDIFF project will diverge from this classic approach and test the novel hypothesis that individual differences in facial expressivity equip individuals’ differentially to engage with their social environment: expressivity has a benefit (social engagement) but also a cost (over-exposure and thus risk of being cheated by others) and is related to the size and quality of an individual’s social network. FACEDIFF will combine psychological, anatomical and cross-species methods to provide the first thorough interdisciplinary investigation of individual differences. First, individual variation in production and perception of facial expressions will be measured via laboratory experiments and in relation to social network size and quality. Second, variation in human facial musculature will be documented through cadaveric dissection and existing MRI databases. Third, facial expressivity will be examined in a primate model to determine whether patterns are unique to humans. This project will be the first to provide a comprehensive and interdisciplinary perspective on individual differences in facial expression and will stimulate new theories on the function and evolution of individual differences in humans.