Psychologists studied how 28 horses reacted to photos of positive versus negative human facial expressions, and have found that these animals can read our emotions.
According to a study published in 'Biology Letters', when the horses were shown angry faces, they seemed to look more with their left eye, a behavior associated with perceiving negative stimuli, in addition to that their heart rate increased more quickly and they showed more related behaviors with stress. The authors believe that this response indicates that they had a functionally relevant understanding of the angry faces they were seeing.
The effect of facial expressions on heart rate has not been seen before in interactions between animals and humans. "What is really interesting about this research is that it shows that horses have the ability to read emotions across the species barrier," says Amy Smith, PhD student at the Mammal Vocal Communication and Cognition Research Group. , from the University of Sussex, in the United Kingdom.
"We have long known that horses are a socially sophisticated species, but this is the first time that we have seen that they are able to distinguish between positive and negative human facial expressions," adds Smith, who co-led the research. the facial expressions of anger were particularly clear: there was a more rapid increase in their heart rate and the horses turned their heads to look at the angry faces with their left eye. "
Research shows that many species look at negative events with their left eye because of the brain's right hemisphere's specialization to process threatening stimuli. Information from the left eye is processed in the right hemisphere.
"It is interesting to note that horses had a strong reaction to negative expressions but to a lesser extent positive, which may be because it is particularly important for animals to recognize threats in their environment. In this context, face recognition Angry can act as a warning system, allowing horses to anticipate negative human behavior, such as rough handling, "continues Smith.
A possible adaptation of an ancestral capacity
Previously, a tendency to display negative human facial expressions with the left eye had been documented specifically in dogs. Professor Karen McComb, co-lead author of the research, stresses: "There are several possible explanations for our findings. Horses may have adapted an ancestral ability to read emotional signals in other horses to respond appropriately to human facial expressions during their coevolution ".
"Alternatively, individual horses may have learned to interpret human expressions during their own lives. What is interesting is that accurate assessment of a negative emotion is possible across the species barrier despite the dramatic difference in facial morphology between horses and humans ", he highlights.
He continues: "Emotional awareness is likely to be very important in highly social species like horses, and our ongoing research is examining the relationship between a range of emotional abilities and social behavior."
The horses tested were from five stables in Sussex and Surrey, UK, which were recruited for the study between April 2014 and February 2015. They were shown photographs of two happy and angry unknown male faces.
The experimental tests examined the horses' spontaneous reactions to the photos, without any prior training, and the testers could not see which photos they were showing so as not to inadvertently influence the horses.