WASHINGTON — Dogs can tell the difference between a happy person and an angry one, just by looking at their faces, according to a new study.
Researchers at the University of Veterinary Medicine Vienna say this is the first solid evidence that an animal other than humans can discriminate between emotional expressions in another species.
The scientists trained dogs to discriminate between images of the same person making either a happy or angry face, but only the upper or lower half of the face.
After training on 15 picture pairs, the dogs’ ability to discriminate was tested in four types of trials: the same half of the faces as in the training but of novel faces, the other half of the faces used in training, the other half of novel faces, and the left half of the faces used in training.
“We think the dogs in our study could have solved the task only by applying their knowledge of emotional expressions in humans to the unfamiliar pictures we presented to them,” says researcher Corsin Muller.
The dogs were able to choose the angry or happy face more often than would have been expected by random chance in every case, according to the study.
The findings show that not only were the dogs able to identify facial expressions, they could also transfer what they’d learn to faces they’d never seen.
“Our study demonstrates that dogs can distinguish angry and happy expressions in humans, they can tell that these two expressions have different meanings, and they can do this not only for people they know well, but even for faces they have never seen before,” says Ludwig Huber, senior author and head of the group at the university’s Messerli Research Institute.
While it is difficult to know whether the dogs understood why the human was angry or happy, the researchers report the dogs were slower to learn to associate an angry face with a reward, suggesting they already had an idea it’s best to stay away from people when they look angry.
The research, “Dogs can discriminate emotional expressions of human faces,” is published in Current Biology.
See video of the testing: