FACS is anatomically based and describes minimal units of facial movement called Action Units (AUs) with detailed descriptions of the resulting changes in facial appearance 1.

While many studies measure the inferences made by observers when viewing faces, some questions are better addressed by measuring what the face itself does ( Ekman & Rosenberg, 2005). In contrast to nonhuman primate research, the investigation of many of the complexities of human facial communication has been greatly facilitated by the development of the Facial Action Coding System (FACS Ekman & Friesen, 1978 Ekman, Friesen, & Hager, 2002) this method allows for the objective and standardized measurement of facial movement based on the underlying mimetic musculature. Here we describe the development and application of ChimpFACS to examine the phylogeny of facial displays in terms of both underlying functional anatomy and related appearance changes. To fully understand species-unique characteristics of the human face, ideally the same measurement tools should be used.

Despite the literature describing facial displays in primates, including the study of both captive and wild chimpanzees ( Ladygina-Kohts, 1935/2002 Marler, 1976 Parr, Cohn, & de Waal, 2005 van Hooff, 1973 van Lawick-Goodall, 1968), our understanding of nonhuman primate facial communication has been limited by the lack of an appropriate measurement tool for recording facial behaviors and allowing meaningful cross-species comparisons ( Chevalier-Skolnikoff, 1973 Fridlund, 1994). This evolutionary perspective on the form and function of facial movements allows us to gain further insight into the pressures shaping communicative capacities in primates ( Parr, Waller, & Fugate, 2005 Schmidt & Cohn, 2001 Sherwood et al., 2005). While the underlying mimetic musculature shows minimal differences, important differences in facial morphology impact upon the identification and detection of related surface appearance changes across these two species.Įlaborate facial communication is a primate adaptation and a comparative approach has long been integral to our understanding of facial expressions ( Andrew, 1963 Chevalier-Skolnikoff, 1973 Darwin, 1872/1998 Redican, 1975 van Hooff, 1972, 1976).

Here we describe the ChimpFACS and use it to compare the repertoire of facial movement in chimpanzees and humans. We demonstrate that FACS can be applied to other species, but highlight that any modifications must be based on both underlying anatomy and detailed observational analysis of movements. FACS has been employed to identify the repertoire of human facial movements. We report the application of a common methodology, the Facial Action Coding System (FACS) to examine facial movement across two species of hominoids, namely humans and chimpanzees. However, cross-species comparisons are often difficult to draw due to methodological limitations. A comparative perspective has remained central to the study of human facial expressions since Darwin’s insightful observations on the presence and significance of cross-species continuities and species-unique phenomena.

Chimpanzee teeth pics