Horses Read Emotion in People's Faces

The horse-human bond is so intense that with just a passing glance, a horse can tell how a person is feeling.

Horses understand and react to human facial expressions, suggesting that they get our moods and may even empathize with us.

A new study revealing how horses read human emotions puts horses on the very short list of known animals that understand our facial expressions. Only dogs have previously been shown to have the skill.

"It's possible that horses developed this ability during their 6,000-year co-evolution with humans, or indeed that individual horses learn it during their lifetimes," Amy Smith, who co-led the research, told Discovery News.

Photos: Horses, Humans Share Facial Expressions

"It's been shown in dogs that familiarity improves their ability to recognize emotions, which supports the idea that the ability is based, at least in part, on personal experience," added Smith, who is a doctoral student in the Mammal Vocal Communication and Cognition Research Group at the University of Sussex.

Smith, research co-leader Karen McComb and their colleagues recruited 28 horses from five riding stables in Sussex and Surrey, U.K., for the study, which appeared in Biology Letters. Each horse was shown photographs of men with different facial expressions corresponding to particular moods.

Earlier research found that horses recognize people and horses that they have only seen before in photographs, so they seem to perceive photos as we do. When first presented with photos, however, some horses examine the image from various angles, as if trying to find the rest of the individual.

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The horses' reaction to angry faces was pronounced, the researchers report. The horses viewed these images primarily with their left eye, due to the right brain hemisphere's specialization for processing threatening stimuli. (Information from the left eye is processed in the right hemisphere.)

McComb, a professor of Animal Behavior & Cognition at the University of Sussex, told Discovery News that this outcome, in particular, was very revealing.

"It gives us a real insight into how they are viewing the situation and shows clearly that they see it as negative," McComb explained. "The way in which their heart rate increases also backs this up. So being in a negative mood around horses is not something that goes unnoticed and is likely to have negative impacts on behavior and physiology."

Co-author Leanne Proops points out that prior research, conducted both by this team and others, found that horses are sensitive to the direction of human eye gazes. This latest study, however, is the first to directly assess horses' reaction to specific expressions of emotion.

It could be that many other animals understand us better than we tend to think. Smith said that despite very different facial structures, some expressions are shared among social mammals. Fear, for example, tends to be expressed through widened eyes and dilated nostrils.

Smith continued, "Social mammals may have a general drive towards understanding facial expressions, because this is such an important skill in terms of survival, and this ability may well be used to assess the emotions of other species when it would benefit them to do so."

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Empathy and "theory of mind" (the ability to fully attribute mental states to oneself and to others, even predicting the latter's future behavior) are more difficult to prove in other species, but it is looking like horses are incredibly sensitive to both our feelings, and those of other familiar horses.

"For instance, there is evidence that when a handler or rider becomes stressed, this can lead to a corresponding increase in stress levels in the horse," Proops said. "Horses will also apparently console a companion in their own herd."

Alex Thornton, who did not work on the study and is a research fellow at the University of Exeter's Center for Ecology and Conservation, says he found the results very persuasive."

He added, "Horses certainly appear capable of discriminating between the angry and happy faces of human males, though, as the authors acknowledge, it is not yet clear whether this ability results from previous experience or the extent to which it is generalizable to humans of different age, gender, etc., or indeed to other horses."

With just a passing glance, a horse can tell how a person is feeling.

Horses share some surprisingly similar facial expressions with humans, a new study finds. The study, published in the journal PLOS ONE, found that, like humans, horses use muscles underlying various facial features, including their nostrils, lips and eyes. These alter their facial expressions in a variety of situations. "Horses have rich social lives, and to me it seems likely that horses have evolved a wide range of facial expressions to help them communicate effectively with other members of their species," lead author Jennifer Wathan of the University of Sussex told Discovery News. She added, "I think what surprised me most was that we didn't expect horses to have any similarities with humans at all. They're two such distantly related species and, at first glance, have such differently shaped faces." If there is a horse version of laughing, that is not yet known. The researchers are still investigating what emotions are tied to the horse facial expressions.

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The study was built on prior research that determined cues from the face are important for horses to communicate. For this latest research, Wathan and her team analyzed video footage of a wide range of naturally occurring horse behaviors to identify all of the different movements it is possible for horses to make with their face. The researchers also carried out an anatomical investigation of the facial muscles that control these movements. As for humans, the showing of the upper and or lower sets of teeth was found to be one commonly used expression. In this case, the pony is likely showing what's known as the Flehmen response. By curling back its upper lip and exposing its front teeth, it facilitates air transfer over a scent-related organ (the vomeronasal organ) located above the roof of the mouth just behind the front teeth. Often animals will do this when they encounter a pungent odor or another member of their own species. Scientists still debate vomeronasal function in humans. It's possible, however, that some of our expressions evolved from similar needs and modes of sniffing.

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While humans have bonded with horses for centuries, horse facial expressions evolved for interaction with their own kind, the researchers believe. "There might be some elements of their communication that have been influenced by domestication, but it seems most likely that the wide repertoire of facial expressions in horses has evolved to support horse-horse communication," Wathan explained.

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This particular horse appears to be relaxed and curious. As for humans, underlying tension is revealed (or not) in the muscles between the jaw and eyes, and also just above the eyes.

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Previous research

found that horses are among the most loyal of friends to humans. They seem to never forget a kind deed, or a problem. Horses, however, appear to often forgive past conflicts, even if they do not forget them. Despite this knowledge, senior author Karen McComb of the University of Sussex said, "It was previously thought that, in terms of other species, the further away an animal was from humans, the more rudimentary their use of facial expressions would be." Horse expressions, as for humans expressions, are anything but rudimentary, however, as the new study revealed.

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Although differences clearly exist between the face structure of horses versus that of humans, there are many similar expressions in relation to movements of the lips and eyes. Wathan said, "One example is that horses and humans can both raise the skin above their eyes, which seems to happen in negative emotional situations. Another example is the retraction of the lip corners, which seems to be part of a submissive gesture in horses."

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Dogs and cats remain the most popular pets for humans. If cost, size and upkeep were not factors, though, it would be interesting to see how many people would get a horse, considering how close the emotional connection can be between horses and humans. "Dogs, horses, cats and humans are all very different animals, however, there are some similarities across the species and horses demonstrate more similarities to humans than cats or dogs do," Wathan said.

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Wathan, McComb and their colleagues Anne Burrows and Bridget Waller identified 17 discrete facial movements in horses. They refer to these as "action units." Dogs have very expressive faces, but they remarkably have fewer such discrete facial movements than horses do. Dogs have three more than chimps do, though. Humans turn out to be the most expressive of all these animals, having 27 such facial movements.

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Stoppers, the racehorse shown here, has a lot to "smile" about, since horses have extremely keen eyesight. Wathan said, "Horses are predominantly visual animals, with eyesight that's better than domestic cats and dogs." She explained that, in the wild, horses are prey animals, and visual detection for them is a life or death matter. The wolf relatives of dogs and the feline wild ancestors of cats, conversely, will scavenge or hunt down prey. This requires good eyesight too, but the visual abilities of these animals pale in comparison to that of horses. "Horses also have quite rich social lives," Wathan continued, "where they have many close range interactions with other members of their species. Visual communication and a good ability to be able to perceive visual signals seem as though they would be adaptive in this situation." "Moreover," she added, "visual communication may reduce the chances of horses being spotted by a predator compared to, say, vocal communication."

Horses Evolved 4 Million Years Ago

The researchers are now looking at how the facial expressions relate to emotional states. Studies just on the latter are also ongoing. The team is also investigating facial expressions in a range of other animals. As for why horses and humans seem to have so much in common, the researchers now have two working theories. Wathan explained that the "similarities suggest that either these facial movements are a very old form of communication that was used by our ancestors and has been preserved in some species, or they evolved in a similar way in both horses and humans in response to common evolutionary pressures." In short, facial expressions are just one example of the many things horses and humans have in common.