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

Leyhausen's (1979) work on cat behaviour and facial expressions associated with offensive and defensive behaviour is widely embraced as the standard for interpretation of agonistic behaviour in this species. However, it is a largely anecdotal description that can be easily misunderstood. Recently a facial action coding system has been developed for cats (CatFACS), similar to that used for objectively coding human facial expressions. This study reports on the use of this system to describe the relationship between behaviour and facial expressions of cats in confinement contexts without and with human interaction, in order to generate hypotheses about the relationship between these expressions and underlying emotional state. Video recordings taken of 29 cats resident in a Canadian animal shelter were analysed using 1-0 sampling of 275 4-s video clips. Observations under the two conditions were analysed descriptively using hierarchical cluster analysis for binomial data and indicated that in both situations, about half of the data clustered into three groups. An argument is presented that these largely reflect states based on varying degrees of relaxed engagement, fear and frustration. Facial actions associated with fear included blinking and half-blinking and a left head and gaze bias at lower intensities. Facial actions consistently associated with frustration included hissing, nose-licking, dropping of the jaw, the raising of the upper lip, nose wrinkling, lower lip depression, parting of the lips, mouth stretching, vocalisation and showing of the tongue. Relaxed engagement appeared to be associated with a right gaze and head turn bias. The results also indicate potential qualitative changes associated with differences in intensity in emotional expression following human intervention. The results were also compared to the classic description of "offensive and defensive moods" in cats (Leyhausen, 1979) and previous work by Gourkow et al. (2014a) on behavioural styles in cats in order to assess if these observations had replicable features noted by others. This revealed evidence of convergent validity between the methods However, the use of CatFACS revealed elements relating to vocalisation and response lateralisation, not previously reported in this literature.