Welcome to animalfacs.com, the home of all the scientific observational tools for identifying and coding facial movements in non-human species.
To date, seven systems have been adapted from the original Facial Action Coding System (FACS) used for humans, allowing the objective coding of facial movements in various species.
The development of species-specific anatomically based coding systems has facilitated within-species and cross-species comparisons of facial expression over recent years.
The investigation of human facial non-verbal communication has been greatly facilitated and standardised by the development of the Facial Action Coding System (FACS: Ekman et al., 2002; Ekman and Friesen, 1978). Prior to this, the human facial expression field was reliant on more subjective methods and did not have a systematic way to assess the muscular components of facial expression.
FACS identifies facial movements based on the underlying physiology and aims to identify individual muscle contractions, focussing not on the expression of emotions but on the production of spontaneous facial movements. For example, FACS is able to compare facial expressions objectively across individuals regardless of the inherent variability in the surface morphology of faces, e.g., bone structure, fatty deposits, skin texture, and individual muscle variations (Waller et al. 2007; Waller et al. 2008a). FACS can compare facial movements regardless of superficial individual differences in other aspects of facial anatomy, such as hair covering, facial coloration, bone structure, etc. This latter characteristic also makes FACS ideal for modification across species.
FACS uses numbers to refer to 33 facial muscle contractions (Action Units [AUs]) and 25 more general head/eye movements (Action Descriptors [ADs]). It presents each AU in terms of underlying musculature (location and direction of action), appearance changes (multiple cues for identifying AUs), reference for AUs (subtle differences between AU combinations), how to do the AU (voluntary production of AU in isolation), and intensity scoring for the AU (criteria for coding decisions).
Chimpanzee Facial Action Coding System (ChimpFACS) is an observational, scientific tool to record and analyse facial expressions in chimpanzees. It was the first system to be adapted from the original one.
Original FACS manual
Adapted FACS manuals
Examples of research using the FACS systems
Julle-Daniere, E., Micheletta, J., Whitehouse, J., Joly, M., Gass, C., Burrows, A. M., & Waller, B. M. (2015). MaqFACS (Macaque Facial Action Coding System) can be used to document facial movements in Barbary macaques (Macaca sylvanus). PeerJ, 3, e1248. https://doi.org/10.7717/peerj.1248