David DeHetre via Flickr Creative Commons // CC BY-NC 2.0
David DeHetre via Flickr Creative Commons // CC BY-NC 2.0

Research Suggests Horses Can Read Human Expressions

David DeHetre via Flickr Creative Commons // CC BY-NC 2.0
David DeHetre via Flickr Creative Commons // CC BY-NC 2.0

Everybody loves a good interspecies friendship story. But do the animals in those relationships actually know how their friends are feeling? Some of them might. A new study published in Biology Letters suggests that horses can read different emotions on human faces. 

Researchers rounded up 28 horses from stables in Surrey and Sussex in the UK. The horses were shown photos of men they'd never seen before while researchers monitored their heart rates and behavior.  

Happy pictures didn’t provoke much of a response in the horses, but when the men in the pictures looked angry, the horses’ heart rates increased. They also turned their heads to view those pictures with their left eye—an action associated with increased attention. Previous studies have shown that many animals use their left eyes to look at things that are scary or alarming. This is likely because input from the left eye is sent to the brain’s right hemisphere, a region associated with processing threats. 

Dogs, too, have been shown to look at angry human faces with their left eyes; and dogs, too, have had close relationships with humans for thousands of years. Is it any wonder they learned to read us?

"It's interesting to note that the horses had a strong reaction to the negative expressions but less so to the positive,” study co-author Amy Smith said in a press 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." 

The study marks the first time human expressions have been shown to affect another animal’s heart rate. Co-author Karen McComb has a few theories on how this interaction evolved. “There are several possible explanations for our findings,” she said in the press release. “Horses may have adapted an ancestral ability for reading emotional cues in other horses to respond appropriately to human facial expressions during their co-evolution. Alternatively, individual horses may have learned to interpret human expressions during their own lifetime.”

Part of what makes this finding so unusual, McComb added, is the fact that a horse’s facial structure and expressions are so different from a human’s. Smith agreed: "What's really interesting about this research is that it shows that horses have the ability to read emotions across the species barrier. We have known for a long time that horses are a socially sophisticated species but this is the first time we have seen that they can distinguish between positive and negative human facial expressions."

nextArticle.image_alt|e
Jana Mueller
arrow
Animals
Ravens Can Figure Out When Someone Is Spying on Them
Jana Mueller
Jana Mueller

Corvids, the family of birds that includes crows and ravens, are canny beasts. They've been known to exercise self-control, count, hold grudges, and more. Now, new research suggests they possess at least a rudimentary Theory of Mind—the ability to attribute mental states to others.

A study in Nature finds that ravens can tell when someone else can see them, guarding their food when a peephole to their cache is open. While previous research suggested that birds might have an awareness of other animals' mental states, the results have been inconclusive. The Nature study is evidence that corvids can do more than just track other birds' gaze; they may understand the concept of "seeing."

Vienna-based researchers set up two rooms separated by windows that could be closed with covers. These covers had peepholes in them that could also be opened or closed. First, the 10 ravens were each allowed to cache food, while other birds were in the next room and the windows were open or closed. Then, they were trained to look through the peepholes to find food in the other room, so that they knew that the holes could be used to see through the window covers. Afterwards, each of the ravens was again presented with food with one of the two peepholes open. The adjacent observation room didn't have any birds in it, but the researchers played the sounds of another raven recorded during one of the previous trials.

When the birds heard the sounds of another raven in the next room, and the peephole was open, the birds behaved as if they knew they were being watched—they hid their cache of food quickly and didn't add more food to it as often, as if they knew that it might be compromised. However, they behaved normally when the peephole was closed.

This suggests that ravens don't just track their competitors' gaze to know when they’re being watched, but can infer from past experience when they can be seen.

nextArticle.image_alt|e
iStock
arrow
Big Questions
Why Do Dogs Crouch Forward When They’re Playing?
iStock
iStock

Whether they're tilting their heads or exposing their bellies for rubs, dogs are experts at looking adorable. But these behaviors do more than elicit squeals from delighted humans; in many cases, they serve important evolutionary functions. A prime example is the "play bow": If you've ever seen a dog crouch forward with its elbows on the ground and its rear end in the air, wagging tail and all, then you know what it is. The position is the ultimate sign of playfulness, which is important for a species that often uses playtime as practice for attacking prey.

The play bow first evolved in canids as a form of communication. When a dog sees another dog it wants to play with, it extends its front paws forward and lifts up its behind as a visual invitation to engage in a friendly play session. Dogs will "bow" in the middle of playtime to show that they're having fun and wish to continue, or when a session has paused to signal they want to pick it back up. Play bows can also be a sort of apology: When the roughhousing gets too rough, a bow says, “I’m sorry I hurt you. Can we keep playing?”

Play between canines often mimics aggression, and starting off in a submissive position is a way for all participating parties to make sure they’re on the same page. It’s easy to see why such a cue would be useful; the more puzzling matter for researchers is why the ancestors of modern dogs evolved to play in the first place. One theory is that play is crucial to the social, cognitive, and physical development of puppies [PDF]. It’s an opportunity for them to interact with their own kind and learn important behaviors, like how to moderate the strength of their bites. Play also requires the animals to react quickly to new circumstances and assess complex actions from other dogs.

Shiba inus playing outside.
Taro the Shiba Inu, Flickr // CC BY 2.0

Another evolutionary explanation is that playtime prepares puppies for the hunting they do later as adults. Watch two puppies play and you’ll see them stalking, biting, and pouncing on one another—all behaviors canines exhibit in the wild when taking down prey.

Of course, it’s also possible that dogs simply play because it’s fun. This is a strong case for why pet dogs continue to play into adulthood. “Devoting a lot of time to play may be less advantageous for a wild species who spends much of its time hunting or foraging for food, searching for mates, or avoiding predators,” Dr. Emma Grigg, an animal behaviorist and co-author of The Science Behind a Happy Dog, tells Mental Floss. “Many domestic dogs are provisioned by humans, and so have more time and energy to devote to play as adults.”

Because play is a lifelong activity for domestic dogs, owners of dogs of all ages have likely seen the play bow in person. Wild canids, like wolves, foxes, and coyotes, tend to reserve this behavior for members of their own species, but pet dogs often break out the bow for their humans—or anyone else who looks like they might be up for a play session. Grigg says, “One of my dogs regularly play bows to her favorite of our cats.”

SECTIONS

arrow
LIVE SMARTER
More from mental floss studios