According to a new study by researchers from the University of Vienna published in the journal iScience, dogs’ brains not only distinguish between positive and negative emotions, but are also able to differentiate between various negative human facial expressions, such as fear and sadness. Although previous experiments studied dogs’ perception of human facial expressions only at a general level, the new paper confirms for the first time that four-legged pets are also capable of differentiating negative emotions within the same category.
Within the framework of the study, scientists examined the brain activity of dogs that were specially trained to stay calmly and without any restriction inside a magnetic resonance imaging (MRI) scanner. In the first experiment, the animals were shown photos of happy and neutral faces of unfamiliar people. The results showed that when happy facial expressions were shown, activity increased significantly in the areas of the dogs’ brains that control visual, social, and reward-related processes.
In the second experiment, scientists showed 12 dogs four different human facial expressions: joy, sadness, fear, and anger. Through machine learning and analysis of complete brain activity, it was determined that a dog’s brain easily distinguishes a happy face from a negative one, and scanning of brain regions showed that the animals distinguish between fear and sadness, as well as fear and anger faces (except for cases of anger and sadness, which they found difficult to tell apart).
According to the researchers, perceiving different negative emotions is important for dogs because they are associated with different types of threats, although to distinguish between anger and sadness, they may require additional cues, such as human body language. The obtained results once again highlight how the dog’s brain has changed during thousands of years of coexistence and domestication with humans, which in practice—for example, when training dogs—provides the opportunity to effectively use positive emotions.
