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 animal species can also recognize our facial expressions and the human emotions behind them. According to a recent study by scientists from the University of Sussex, this also applies to horses. The researchers published their results in the specialist journal "Biology Letters".
For the first time, horses in the study "proved able to distinguish between angry and happy human facial expressions," reports the university. When looking at pictures with evil faces, their heart rate had increased significantly and they had preferably viewed the pictures with the left eye, which is typical of a negative association. Comparable skills in recognizing human emotions based on facial expressions have been demonstrated in earlier studies in dogs. Some domesticated animal species in particular seem to have developed a keen sense of the emotional state of the people here.
Spontaneous reaction of the horses analyzed
The University of Sussex psychologists used 28 horses to examine how they react to photos with malicious and friendly human facial expressions. In the photos they were shown unknown male faces with the different facial expressions. "The experimental tests examined the spontaneous reactions of the horses to the photos without prior training," the university said. The researchers were unable to influence the animals because the scientists could not see which photo they were showing to the horses during the test. At the same time the eye movements and the behavior of the horses were recorded on video. The scientists also observed the animals' heart rate.
Strong reaction to angry facial expression
When analyzing the video recordings, it became clear that the horses show clear reactions to pictures with angry faces, which can be linked to a negative perception. They looked at the pictures with their left eyes, what many animal species do with threatening stimuli, the scientists report. Such stimuli are processed in the right hemisphere and the information from the left eye is also forwarded there. There were also several stress-related behaviors in the animals and their heart rate increased, according to the University of Sussex. "The reaction to the angry facial 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 eyes," summarized doctoral student Amy Smith.
Recognize emotion across species borders
Interestingly, the horses showed a strong response to the negative facial expressions, but little response to the friendly faces, reports Amy Smith. This may be due to the fact that the detection of dangers in the environment is particularly important for the animals. In this context, recognizing angry faces could serve as a kind of warning system. The fact that horses have the ability to recognize emotions across species boundaries is really interesting - despite the fundamentally different facial morphology. It became clear for the first time that they can differentiate between positive and negative human facial expressions, said Smith.
Horses learned or innate ability?
Professor Karen McComb stressed that there could be several possible explanations for the horse's ability. Domesticated horses may have transferred their age-old ability to recognize the emotional mood of their peers in the course of co-evolution with humans to human facial expressions. Perhaps the horses only learned to interpret human facial expressions in their own lives, emphasizes Prof. McComb. Further investigations are now required to determine more precisely the cross-species skills in interpreting the facial expressions. (fp)