Horses use facial expressions to recognize human emotions

Horses can distinguish between friendly and angry facial expressions
Many domesticated animals are able to understand human instructions and respond to verbal commands. In addition, some species of animals can recognize our facial expressions and the underlying human emotions. According to a recent study by scientists at the University of Sussex, this also applies to horses. The researchers published their results in the journal "Biology Letters".

For the first time, horses in the study "have proved capable of distinguishing between angry and happy human facial expressions," the university reports. When looking at images with angry faces their heart rate had increased significantly and they would have preferred to view the images with the left eye, which is typical of a negative association. Comparable human facial recognition skills using facial expressions have been demonstrated in previous studies in dogs. In particular, some domesticated animals seem to have developed a fine sense for the emotional states of humans.

What does this horse feel? While horses can understand human facial expressions, most people are likely to have difficulty in interpreting the facial expression of a horse. (Image: mexitographer / fotolia.com)

Spontaneous reaction of horses analyzed
Psychologists from the University of Sussex used 28 horses to study how they respond to photos with evil and friendly human facial expressions. In the photos, unknown male faces with different facial expressions were depicted. "The experimental tests examined the spontaneous reactions of the horses to the photos, without prior training," according to the announcement from the university. An interference of the animals by the researchers was excluded because the scientists could not see during the test, which photo they just showed the horses. Accompanying the eye movements and the behavior of the horses were captured on video. The scientists also monitored the heart rate of the animals.

Strong reaction to angry facial expression
When analyzing the video footage, it became clear that the horses showed clear reactions to images with angry faces, which could be associated with a negative perception. They looked at the images with their left eye, which many animals do when threatening stimuli, the scientists report. Because such stimuli are processed in the right hemisphere and the information of the left eye are also forwarded there. Also, several stress-related behaviors were noted in the animals and their heart rate has increased, according to the University of Sussex. "The reaction to the angry expression was particularly clear - a rapid increase in heart rate and the horses moved their heads to look at the angry faces with their left eye," says graduate student Amy Smith.

Recognize emotion across species boundaries
Interestingly, the horses showed a strong reaction to the negative facial expressions, but little reaction to the friendly faces, reports Amy Smith. This may be due to the fact that the detection of environmental hazards is particularly important for the animals. In this context, the recognition of angry faces can serve as a kind of warning system. Really interesting is the realization that horses have the ability to recognize emotions across the species barrier - despite the fundamentally different face morphology. For the first time, it became clear that they can distinguish between positive and negative human facial expressions, according to Smith.

Learned or innate ability of horses?
Professor Karen McComb emphasizes that there may be several possible explanations for the horse's ability. For example, domesticated horses may have translated their age-old ability to recognize the emotional mood of their conspecifics into human facial expressions as part of their co-evolution with humans. However, it may be that the horses have learned to interpret human facial expressions only during their own life, Prof. McComb emphasizes. Further investigations are now required to more precisely determine the cross-species abilities in the interpretation of facial expressions. (Fp)