Buzz
Anyone who owns a dog knows their pet seems to understand their emotions. A recent study confirms this: Dogs can sense when people are happy or angry, and they can differentiate between the two.
"Our research proves that dogs can recognize angry and happy facial expressions in humans," said Ludwig Huber, a coauthor of the study published in Current Biology and a researcher at the University of Veterinary Medicine Vienna's Messerli Research Institute. "They can tell the distinct meanings behind these expressions, and not only for familiar faces, but also for people they've never seen before," he added in a press release.
To test if dogs could interpret facial expressions, Huber and his team trained the dogs to identify either happy or angry faces by studying pictures. The dogs observed the faces of 15 different people, but only half of each face was shown—either the eyes or the mouth—to determine if the dogs could identify emotions from these features alone. Half the dogs were rewarded for recognizing happy faces, and the other half for identifying angry ones.
The dogs then underwent four different tests: they viewed the same half of the face they had been trained to recognize, but with different individuals; they observed the other half of the faces they were trained on; they looked at the opposite half of new faces; and they saw the left side of the faces from training. Researchers instructed the dogs to choose either the happy or sad face, and the dogs made their choices by pressing their noses to a touchscreen.
The dogs correctly identified the angry and happy faces enough times to rule out chance—70 out of 100 times, the dogs chose the correct expression. Overall, they were more successful at identifying happy faces, leading researchers to believe that dogs understand the emotions behind these expressions. The study also revealed that dogs can transfer their learned knowledge to new contexts—once a dog recognized an angry expression from a familiar person, it could apply that understanding to identify an angry stranger.
"We conclude that the dogs used their memories of real emotional human faces to accomplish the discrimination task," the authors stated in the study.
The researchers also believe that dogs associate a smiling face with positive emotions and a frown with negative ones. "It seems likely to us that dogs link a smiling face with a positive meaning and an angry expression with a negative one," Huber explained.
