Researchers have questioned whether horses can recognize human signals. To date, several species of animals have been found to recognize human emotional expressions when presented with the full array of body cues or, after training to specifically match facial features associated with particular emotions. In dogs, an angry human facial expression will often elicit a left-gaze bias, with positive human facial expressions showing no gaze bias. The researchers also explored the effect that these facial expressions might have on the horse’s heart rate (HR) as HR in the horse correlates well with stress and fluctuates according to handler stress, “demonstrating a potential physiological sensitivity to human effect. The horse is also a good model for this type of research as they are able to produce complex facial expressions, they are sensitive to human facial cues, and as their eyes are placed laterally on their head, are given to lateralized behaviors.
Twenty-eight horses were recruited from stables for this study. They were shown laminated high-quality color photographs with one positive (happy) image and one negative (angry) of two human models. HR was measured and behavioral responses were recorded. Results showed that angry faces induced responses that were indicative of an understanding of the stimulus by the horse (a left gaze bias that is generally associated with stimuli perceived as negative) and a quicker increase in HR towards these angry photographs.
This study presents the first evidence of horses' abilities to spontaneously discriminate between positive (happy) and negative (angry) human facial expressions in photographs. The researchers concluded that research such as this considers the possibility of a generalized, conserved and widespread ability to read emotional cues across species.
Scientific Article: Smith, AV, Proops L, Grounds, K, Wathan J, McComb K. 2016 Functionally relevant responses to human facial expressions of emotion in the domestic horse (Equus caballus). Biol. Lett. 12:20150907.