Humans and dogs share more than 40,000 years of social interactions and life together. According to the co-domestication hypothesis, this process allowed humans and dogs to evolve special emotional signals and cognitive skills that favor mutual understanding. We know, for example, that over the millennia, dogs have evolved the ability to understand human words, iconic signs, and other gestures, and research has shown that dogs can even use tone of voice and facial expressions to recognize human emotions.
Beyond personal testimony from dog lovers, however, little attention has been paid to how well humans can understand their canine counterparts. So in a study published today in Nature Neuroscience, Max Planck Institute researchers investigated how well humans can understand the emotional displays of dogs and where that understanding comes from.
First, the team collected photographs of dogs, chimpanzees, and humans displaying happy, sad, angry, neutral, or fearful emotions as substantiated by the photographers. They then categorized their participants according to their age, the dog-positivity of their cultural context, and their personal history of dog ownership.
Each participant was presented with the photographs and asked to rate how much the individual in the picture displayed happiness, sadness, anger, or fear. The results suggested that the ability to reliably recognize dog emotions is mainly acquired through age and experience. In adults, the probability of recognizing dog emotions was higher for participants who grew up in a cultural context with a positive attitude towards dogs, regardless of whether they owned a dog themselves.
“These results are noteworthy,” says first author Federica Amici, “because they suggest that it is not necessarily direct experience with dogs that affects humans’ ability to recognize their emotions, but rather the cultural milieu in which humans develop.”
The researchers also found that regardless of age or experience with dogs, all participants were able to identify anger and happiness reliably. While these results may suggest an innate ability favored by the co-domestication hypothesis, it is also possible that humans learn to recognize these emotions quickly, even with limited exposure.
Image: Dogs use facial expressions and body language to communicate with conspecifics and humans. Image courtesy of Sylvio Tüpke.