Most dog owners would agree that a smile will always be matched by their pet’s friendly tail-wagging.
Sure, the dog is happy to be getting some attention. But a dog owner likes to think that Spike is happy because her owner is happy.
That may indeed be what’s happening, according to researchers at the Messerli Research Institute in Vienna, Austria, who demonstrated that dogs can tell the difference between happy and sad facial expressions.
The researchers, who recently published their findings in the science journal Current Biology, tested 11 dogs: a Golden Retriever, Fox Terrier, German Shepherd Dog, and few Border Collies and mixed-breeds.
Each dog was placed in a small booth and faced a computer screen showing two images of the same person making and angry face and a smiling face. However, the images showed only half of each face—either the top half where the eyes are visible or the bottom half where the mouth is seen.
Using treats as rewards, the researchers trained one group of dogs to pick out the happy half-face by touching the screen with their noses. The other group was trained to select the angry half-faces.
Once trained, the testing began.
The dogs were asked to pick images of the half-face they were trained to select. However, sometimes they were shown the opposite half-face they were trained to recognize (if trained to pick the upper-half of a smiling face, they were instead show the lower-half of the same face, and vice versa). In other cases, they were shown a smiling or frowning half of a different person’s face.
The researchers found that the dogs demonstrated an uncanny ability to select a happy half-face, even when it hadn’t previously seen that particular image. They noted that “the dogs performed significantly above chance level” in distinguishing between happy and angry expressions.
They also found that dogs rewarded for selecting happy faces learned the difference faster than the dogs rewarded for recognizing angry faces. The researchers suggest that this might be attributed to a dog’s learned experience—he doesn’t expect a treat from an angry person.
The researchers suggested that the dogs’ ability to recognize happy and angry expressions from images of half faces can likely be attributed to their memories of actual happy and angry people.
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