Your loyal pup could be able to read your mood by looking at your face.
New research suggests dogs have the ability to distinguish between happy and angry human facial expressions, Cell Press reported. The findings represent the first solid evidence that animals other than humans can interpret the facial expressions of another species.
"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," said Corsin Müller of the University of Veterinary Medicine Vienna.
Past attempts to determine whether or not dogs can discriminate between different human facial expressions have fallen short. In this new study, researchers trained dogs to recognize the difference between images of a person making either a happy or angry face. In each image, only the upper or lower half of the subject's face was shown.
After being trained on 15 pairs of images, the dogs' abilities to discriminate between the facial expressions were tested in four different 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," the researchers reported.
The researchers found that the dogs were able to distinguish between happy and angry faces more often than random chance in every case. This suggests dogs could be trained to identify facial expressions, and could even transfer this learning into new cues.
"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," said Ludwig Huber, senior author and head of the group at the University of Veterinary Medicine Vienna's Messerli Research Institute.
The researchers noted that the dogs were slower to learn to associate an angry face with a reward, suggesting they already had prior ideas about human facial expressions. In the future, the researchers plan to look at how dogs express their own emotions and how these emotions are affected by human behavior.
"We expect to gain important insights into the extraordinary bond between humans and one of their favorite pets, and into the emotional lives of animals in general," Müller concluded.
The findings were published in a recent edition of the journal Current Biology.