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Interspecies friendships are heartwarming, but do animals truly understand their companions' emotions? Research indicates some might. A recent study in Biology Letters reveals that horses can discern human facial expressions.
Scientists gathered 28 horses from stables in Surrey and Sussex, UK. The horses were shown photos of unfamiliar men while their heart rates and behaviors were closely observed.
While images of happy faces elicited little reaction, angry expressions caused the horses' heart rates to spike. They also turned their heads to view these images with their left eye—a behavior linked to heightened focus. Research suggests many animals use their left eye to assess threatening stimuli, as the brain's right hemisphere, which processes such inputs, is associated with threat detection.
Dogs also exhibit a tendency to view angry human faces with their left eye, a trait shared with horses. Given their millennia-long bond with humans, it's no surprise they've developed the ability to interpret our emotions.
"It's fascinating that horses reacted strongly to negative expressions but showed less response to positive ones," noted study co-author Amy Smith in a press release. "This likely stems from the importance of identifying threats in their surroundings. Recognizing anger may serve as a warning mechanism, helping horses predict potentially harmful human actions, such as rough treatment."
This study is the first to demonstrate that human facial expressions can influence another animal's heart rate. Co-author Karen McComb proposed several theories on this evolution. "Our findings could be explained in multiple ways," she stated in the press release. "Horses might have adapted an innate ability to interpret emotional signals from other horses to respond to human expressions during their co-evolution. Alternatively, individual horses may have learned to decode human expressions through personal experience."
McComb highlighted the uniqueness of this discovery, given the stark differences between human and equine facial structures and expressions. Smith concurred, adding, "What makes this research particularly intriguing is that it demonstrates horses' capacity to recognize emotions across species. While we've long known horses are socially advanced, this is the first evidence they can differentiate between positive and negative human facial expressions."
