Researchers at the University of Sussex, in the United Kingdom, have confirmed that horses can read human facial expressions. For the first time horses have been shown to be able to distinguish between angry and happy human facial expressions.

Sussex psychologists studied how 28 horses reacted to seeing photographs of positive and negative human facial expressions. When viewing angry faces, horses looked more with their left eye, a behavior associated with perceiving negative stimuli. Their heart rate also increased more quickly and they showed more stress-related behaviors when looking at negative human expressions.

The researchers said this response indicates that the horses had a functionally relevant understanding of the angry faces they were seeing. The effect of facial expressions on heart rate has not been seen before in interactions between animals and humans.

“What’s really interesting about this research is that it shows that horses have the ability to read emotions across the species barrier,” said Amy Smith, BSc (Hons.), MSc, a doctoral student in the Mammal Vocal Communication and Cognition Research Group at Sussex, who co-led the research. “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.

“The reaction to the angry facial expressions was particularly clear—there was a quicker increase in their heart rate, and the horses moved their heads to look at the angry faces with their left eye.”

Research shows that many species view nega