A study has shown that horses can distinguish between happy and angry human facial expressions. The study was performed by psychologists at the University of Sussex (UK) on twenty-eight horses.

When viewing angry human faces, horses look more through their left eye. This phenomenon has also been seen in dogs and other animal species, the rationale being that the right side of the brain, where left-eye information is processed, is the hemisphere activated by threatening stimuli. Angry faces also produced increased heart rates and other stress-related behavior in the horses.

The horses were recruited from livery stables in the area and had received no previous training for the experiments. They were shown photographs of unknown human male faces in both angry and happy attitudes. The experimenters recorded the horses’ responses without knowing which photographs were being shown to the horses.

Amy Smith, a doctoral student in the Mammal Vocal Communication and Cognition Research Group at the University of Sussex who co-led the research, said, “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.”

The study was published today (February 10, 2016) in Biology Letters. Journal Reference: Amy Victoria Smith, Leanne Proops, Kate Grounds, Jennifer Wathan and Karen McComb. Functionally relevant responses to human facial expressions of emotion in the domestic horse (Equus caballus). Biology Letters, 2016 DOI: 10.1098/rsbl.2015.0907

Posted February 10, 2016