Due to their thousands of years of domestication, dogs are geared towards us humans in a very special way. As a result, they are not only highly social among each other, but have also transferred some of their social skills to dealing with us - an alien species. So they can often hear from our tone of voice, whether we are angry or in a good mood. Dogs and humans look each other in the eye, and the cuddly hormone oxytocin is released by both partners, as researchers recently discovered.
This also shows how closely human and dog are connected. However, one of the dogs' abilities has been controversial so far: the recognition of our mood based on our facial expressions. Though a recent study has shown that dogs can, after some training, distinguish a smiling from a neutral or annoying human face. "But these results could also be explained by simple association and training, " said Natalia Albuquerque of the University of Lincoln and her colleagues. Whether the dog has just learned the features of the different facial expressions or really understands which emotion is behind it, could not be proved by this attempt alone.
Therefore, the researchers have now put dogs to the test in another experiment. They each showed 17 portraits of either human or canine faces to 17 family-owned dogs of various breeds. One of these faces looked friendly and playful, the other aggressive. While the dogs saw the human faces, either a short word sounded in a friendly, neutral or aggressive tone. In the dog faces sounded the corresponding dog louder. The researchers now observed whether or not the dogs looked at the face with the appropriate face for a longer time. For if the dog understands facial expressions as the expression of an emotion, then he should recognize when the sound and the image fit together and which face has in a sense "addressed" him.
And indeed: "The dogs showed a clear preference for the appropriate face in 67 percent of the passes, " report Albuquerque and her colleagues. The dogs then looked at the dog's or human's face with the aggressive expression for an annoying sound longer. On the other hand, they looked at the happy face longer with a positive sound. When a neutral sound sounded, the four-legged subjects treated both faces the same. These reactions took place without any previous training, as the scientists emphasize. "This suggests that dogs can recognize and interpret the emotional expression of faces, " say the researchers. "They probably have at least some ability to categorize themselves emotionally." The experiment also shows that the four-legged friends can match information from two different sensory channels, an ability that has so far only been proven in apes, as Albuquerque and her colleagues explain. display
So dogs do not just react to learned key stimuli in our facial expressions, but really seem to understand that this face expresses a feeling - and which one. Surprising is the fact that this ability extends not only to the facial expressions of conspecifics, but also to an alien being - the human being. "Such heterospecific recognition of emotions is not yet known by other animals, " say the scientists. They suspect that this ability was probably developed in the dog during its domestication. The strong sensitivity among other species of the sensibilities of others transferred the dogs to their new caregiver - the human being.
- Natalia Albuquerque (University of Lincoln) et al., Biology Letters, doi: 10.1098 / rsbl.2015.0883