Responses of domestic horses (Equus caballus) to human emotional signals
Student thesis: Doctoral Thesis
The communication of emotion is fundamental for social cohesion and information sharing in social species. It may be highly beneficial for domestic animals to recognise human emotional signals, as this would allow them to make informed decisions about their interactions with humans, and about events in human-dominated environments. To date, the literature in this area has largely focused on domestic dogs’ (Canis familiaris) abilities. The present thesis extends this field of research to include domestic horses (Equus caballus), which represent an appropriate alternative study species due to their close co-evolutionary history with humans, their high natural levels of sociality, and their established abilities to respond to a range of other, non-emotional social signals of humans. Previous research into horses’ abilities to read human emotions has produced mixed results, and too few studies have been conducted to draw firm conclusions. This thesis presents a series of behavioural experiments that investigate horses’ responses to human emotional expressions when presented as isolated cues: photographs showing facial expressions of anger and happiness (Article I, Part i and ii); photographs showing facial expressions of fear, happiness, and neutrality (Article II); audio files of emotional vocalisations depicting happiness and anger (Article III); and live human actors displaying body postures of dominance and submissiveness (Article IV). The results reveal that horses show aversive behavioural and physiological responses towards angry facial expressions; behavioural attractions towards fearful facial expressions (possibly due to the function of fear in appeasement); an increased vigilance towards angry vocalisations, as indicated by freeze behaviour; and preferences for approaching submissively postured humans. This thesis therefore demonstrates that horses respond appropriately to a range of human emotional signals without prior training, which may have theoretical implications for investigating the flexibility of emotion perception across species, and applied interest for horse management and welfare.