To understand human expression of emotion and its evolutionary history, it is essential to investigate emotional expressions in our closest relatives, the nonhuman primates. Given the strong association between facial movements and emotions, the aim of this project is to develop a tool to describe and classify facial expressions in gibbons and to compare them with other great apes including humans.

First, in order to create an anatomically based observational system, dissections of gibbons’ facial musculature will be conducted. Second, the specific muscles underlying each facial movement will be identified to develop GibbonFACS (Facial Action Coding System). Finally, the social function of facial expression in gibbons will be investigated based on observations of gibbon interactions in their social groups.

This project presents a collaboration with Bridget Waller, University of Portsmouth, UK and Anne Burrows, Duquesne University, US, and will contribute to a better understanding of the role of facial expressions in emotional social interaction. The cross-species approach will enable comparisons between apes and humans and demonstrate which facial expressions do those primates share and which might be unique to humans.

Publications

Liebal, K., Call, J. (2012). The origins of nonhuman primates' manual gestures. Philosophical Transactions of the Royal Society B 367 (1585). 118-128.

Burrows, A. E., Diogo, R., Waller, B.M., Bonar, C. J., Liebal, K. (2011). Evolution of the muscles of facial expression in a monogamous ape: Evaluating the relative influences of ecological and phylogenetic factors in Hylobatids. The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology 294 (4). 645–663.