If it seems like your horse is sneering at you, you may be right. A new “directory” of horse facial movements shows that these animals are more expressive than we once thought.

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Humans, of course, have such dexterous musculature that we’re able to tacitly communicate our most subtle feelings using 27 different facial expressions. But scientists at the University of Sussex have discovered that the horse repertoire isn’t that far behind. Using their so-called Equine Facial Action Coding System (EquiFACS for short), the team identified 17 distinct facial movements in horses, many of them—especially in the lips and eyes—similar to humans. That’s at least three more than the number of recognizable facial expressions in chimpanzees, and one more than in dogs. This range of possibilities is much more immense than scientists could have ever predicted, considering they originally thought that the further away a species is from Homo sapiens on the family tree, the more limited the use of its facial expressions would be.

The finding shouldn’t come as too much of a surprise—horses are visual creatures; their eyesight is better than that of domestic dogs or cats. But it wasn’t until lead author Jennifer Watham and her colleagues dissected a horse’s head and photographed all aspects of its muscular design that scientists fully understood the emotional role of the eye in equine communication. Here’s Tim Radford, quoting Watham in the Guardian:

Related Jaglavak, Prince of Insects Dogs' Dazzling Sense of Smell Digging Up Panama's Past “Horses and humans can both raise the skin above their eyes, which seems to happen in negative emotional states,” said Watham. “Another example is the retraction of lip corners, which seems to be part of a submissive gesture in horses. Our paper has only identified the movements horses can make—the challenge now is to document what contexts these occur in, and then we will be able to make more informed comparisons.”

To begin correlating muscle movement with context, the researchers have recorded 15 hours of behavior in 86 horses, aged four weeks to 27 years (both male and female and across a variety of breeds). In future studies, they’ll attempt to elucidate the relationship between facial expression and different behavioral contexts. As Radford put it, “Horses are social animals: most of their behaviour must have evolved to help keep family groups together during seasonal migration in search of changing food sources, and to warn of possible predator attack.” The way equine social situations relate to the colorful palette of expression could help illuminate the effect of deeply engrained emotional communication between man and horse over thousands of years.

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