The next time you need to schedule a potentially stressful veterinary or farriery procedure for your horse, consider setting aside a space for the appointment where other horses can’t watch.

That’s the upshot of a study from France that revealed the extent to which horses can develop positive or negative emotions by simply observing interactions between people and other horses—and how those impressions can have a lasting influence on their behavior.

For a study, conducted at the French Horse and Equitation Institute (IFCE) and National Institute for Agricultural Research Val de Loire Centre in Nouzilly, the researchers selected 47 mature Welsh Pony mares. One by one, 24 of the mares were shown two consecutive 30-second videos—one “positive” and one “negative”—projected without sound onto a large screen in a stall. In each video, the human handler maintained a neutral expression and neutral body language while an “actor” horse responded to the handler’s activity with obvious positive or negative emotions.

“In the positive video, an experimenter was grooming the actor horse in the withers area, which horses particularly enjoy,” explains doctoral student Miléna Trösch, who conducted the experiment with Léa Lansade, PhD. “The actor horse reacted by showing positive facial expressions specific to a grooming context: neck low, ears oriented backwards and their upper lips extended forward in an attempt to reciprocally groom the experimenter.”

“In the negative video, the experimenter performed unpleasant veterinary procedures: applying an ointment in the horse’s ears and using a spray towards its head,” Lansade continues. “The actor horse reacted by showing typical negative posture and facial expressions—frozen, with their head high, both ears forward and their eyes wide open —and by trying to avoid the experimenter’s contact.”

To serve as a control, the remaining 23 mares were shown the same videos, but with large ovals covering the horse and human so the nature of the interaction could not be discerned.

As the horses watched the videos, the researchers —including Lansade and Trösch—documented their reactions. “The difference of reaction between the two videos was really stunning,” says Trösch. “Just by watching these reactions we could guess which video the horse was looking at. When watching the negative video, the horses showed signs of negative emotions: They had the same specific vigilance posture as the horse in the video and their heart rate increased. On the contrary, when watching the positive video they were more relaxed, with the posture typical of positive emotions in a grooming context, and their heart rate decreased. Moreover, during the positive video, they extended their lips and attempted to reciprocate the grooming to the assistant holding them. Interestingly, the reactions of the horses watching the videos were really similar to those of the actor horse in the video, which might suggest an emotional contagion.”

Reference: “Horses feel emotions when they watch positive and negative horse-human interactions in a video and transpose what they saw to real life,” Animal Cognition, July 2020