Horses are able to distinguish between at least some human facial expressions, suggests a new study by researchers at the U.K.’s University of Sussex.
In the study, published in the February edition of Biology Letters, researchers examined the reactions of 28 horses, from five different stables, to large photos that showed a man either smiling or making an angry expression.
"We found that when we presented the photograph to the horses, they really paid attention and engaged with the facial expression images, partly because this is quite a novel situation for them," lead researcher Amy Smith told The Huffington Post in an email. "Responses to real-life humans are likely to be more subtle, because they are more accustomed to these interactions."
When the horses viewed the angry images, their heart rates sped up more quickly, researchers found. Horses were also more likely to turn and look at the angry faces with their left eye -- a reaction that the researchers wrote is “generally associated with stimulus perceived as negative.” The theory behind this "left gaze bias" is that the brain's right hemisphere is specially equipped to help process negative emotions.
"It's interesting to note that the horses had a strong reaction to the negative expressions but less so to the positive,” Smith said in a news release. “This may be because it is particularly important for animals to recognize threats in their environment. In this context, recognizing angry faces may act as a warning system, allowing horses to anticipate negative human behavior such as rough handling."
However, the horses were also being shown photos of strangers, and researchers noted in the paper that the animals may have had stronger responses to the happy faces if they were familiar with the people pictured. Dogs, for instance, have better human facial expression recognition when viewing their owners, or people of the same gender as their owners, the paper notes.
The new study builds on previous work by some of the same researchers, who published a paper last year documenting how horses communicate their own emotions through facial expressions.
"Emotional awareness is likely to be very important in highly social species like horses -- and ongoing research in our lab is examining the relationship between a range of emotional skills and social behavior," Smith told HuffPost.
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