Development and application of CatFACS: Are human cat adopters influenced by cat facial expressions?

Abstract

The domestic cat (Felis silvestris catus) is quickly becoming the most popular animal companion in the world. The evolutionary processes that occur during domestication are known to have wide effects on the morphology, behaviour, cognition and communicative abilities of a species. Since facial expression is central to human communication, it is possible that cat facial expression has been subject to selection during domestication. Standardised measurement techniques to study cat facial expression are, however, currently lacking. Here, as a first step to enable cat facial expression to be studied in an anatomically based and objective way, CatFACS (Cat Facial Action Coding System) was developed. Fifteen individual facial movements (Action Units), six miscellaneous movements (Action Descriptors) and seven Ear Action Descriptors were identified in the domestic cat. CatFACS was then applied to investigate the impact of cat facial expression on human preferences in an adoption shelter setting. Rehoming speed from cat shelters was used as a proxy for human selective pressure. The behaviour of 106 cats ready for adoption in three different shelters was recorded during a standardised encounter with an experimenter. This experimental setup aimed to mimic the first encounter of a cat with a potential adopter, i.e. an unfamiliar human. Each video was coded for proximity to the experimenter, body movements, tail movements and face movements. Cat facial movements were not related to rehoming speed, suggesting that cat facial expression may not have undergone significant selection. In contrast, rubbing frequency was positively related to rehoming speed. The findings suggest that humans are more influenced by overt prosocial behaviours than subtle facial expression in domestic cats.

EquiFACS: The Equine Facial Action Coding System

“…Ear actions do not feature in many primate FACS, as the auricular (ear) muscles of many the primates are gracile and vestigial. Rhesus macaques are an exception where ear action descriptors have been described [ 8 , 10 ], as they are for the domestic dog [ 12 ] and cat [ 13 ].…”

“…The original FACS was developed for use in humans [ 1 ] and this framework has since been applied to a number of different primates and domestic animals (chimpanzees ( Pan troglodytes )[ 8 ], orangutans ( Pongo pygmaeus )[ 9 ], rhesus macaques ( Macaca mulatta )[ 10 ], hylobatids (gibbons and siamangs)[ 11 ], dogs ( Canis familiaris )[ 12 ] and cats ( Felis catus )[ 13 ]. This methodology provides compatible systems that allow direct comparisons using identical techniques across species with a different facial morphology (e.g.…”

“…To modify FACS for use in non-human animals, the first step was to document and compare their facial anatomy [ 9 – 13 , 29 ]. Horses are only distantly related to primates and the other animals FACS have previously been developed for; additionally horses have a dramatically different facial morphology to these animals, including laterally placed eyes, elongated faces, and raised zygomatic arches.…”

Facial correlates of emotional behaviour in the domestic cat (Felis catus)

“…Russell, 1994); accordingly the developers of the system hold a register of qualified users for quality control purposes. Using these essential principles and knowledge of species-specific facial anatomy, open access FACS have been developed for use with other species such as chimpanzees, macaques, hylobatids, orangutans, the domestic dog, (Parr et al, 2007;Vick et al, 2007;Parr et al, 2010;Waller et al, 2012) and, most recently, the domestic cat (Caeiro et al, 2013aCaeiro et al, 2017. Figure 1 shows an example of the coding that would be associated with the mouth opening gesture illustrated in this sequence of images.…”

Horses discriminate between facial expressions of conspecifics

“…However, research investigating non-human facial expressions has been conducted predominantly with primates, and so the true ability of other species remains largely unknown311. New research systematically documenting facial muscles and expressions in non-primates (domestic horses [ Equus caballus ], dogs [ Canis familiaris ] and cats [ Felis catus ]) has demonstrated extensive capacity and a surprising amount of similarity with humans and other primates121314. A range of different facial expressions have also been documented in plains zebra ( Equus quagga ), fur seals ( Arctocephalus forsteri ), and walruses ( Odobenus rosmaru )1516.…”