Dogs can differentiate between happy and angry human faces

Dogs may be able to differentiate between happy and angry expressions in people.

They may also be able tell that these expressions correlate with positive and negative meanings, respectively--a conclusion resulting from a study led by the Messerli Research Institute at the University of Veterinary Medicine Vienna in Austria.

In the research, dogs were trained to discriminate between a happy and an angry human expression from 15 pairs of photos which revealed only the upper half or lower half of the face.

Researchers then showed the dogs a mix of photos displaying different halves of familiar and unfamiliar faces, and based on the results, determined that "the dogs performed significantly above chance level" of recognizing when a face was happy or angry, even in people they didn't know.

It also appears that dogs who were rewarded for identifying happy expressions learned more quickly than when picking out angry ones, indicating previous knowledge that angry people are less likely to give a treat or other reward.

According to the study authors, this is the first study to date which convincingly shows that an animal can discriminate between expressions of another species without simply responding to local cues.

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