Science confirms what every dog owner has known in his heart: our canine friends can tell when we’re happy or upset. The discovery represents the first solid evidence that an animal other than humans can discriminate between emotional expressions on other species.

The experimental setup used for testing the dogs’ ability to distinguish between emotions. CREDIT: ANJULI BARBER, MESSERLI RESEARCH INSTITUTE

“We think the dogs in our study could have solved the task only by applying their knowledge of emotional expressions in humans to the unfamiliar pictures we presented to them,” says Corsin Müller of the University of Veterinary Medicine Vienna.

In this new study, the dogs distinguished between an angry face and a happy face (of the same person) – and they did so in convincing fashion. After training on 15 picture pairs, the dogs were only shown the upper or the lower half of the face. They were tested on four types of trials:

  1. the same half of the faces as in the training but of novel faces,
  2. the other half of the faces used in training
  3. the other half of novel faces
  4. the left half of the faces used in training.

The dogs weren’t able to always figure out the happy face, but they did it often enough to show that they can distinguish the emotions. The study also showed that the dogs can learn and adapt what  they’ve learned to new situations.

“Our study demonstrates that dogs can distinguish angry and happy expressions in humans, they can tell that these two expressions have different meanings, and they can do this not only for people they know well, but even for faces they have never seen before,” says Ludwig Huber, senior author and head of the group at the University of Veterinary Medicine Vienna’s Messerli Research Institute.

Müller and Huber report that the dogs were slower to learn to associate an angry face with a reward, which suggests that they already have a good idea about what they can expect when humans are happy and angry.

“We expect to gain important insights into the extraordinary bond between humans and one of their favorite pets, and into the emotional lives of animals in general,” Müller says.

Journal Reference: Current Biology, Müller et al.: “Dogs can discriminate emotional expressions of human faces”