Dogs Can Distinguish Happy and Sad Human Faces

The dog has been a human's best friend since the beginning of time. And it shows the emotional intelligence to differentiate between a happy and a sad person.

In the Cell Press journal, 'Current Biology' on Thursday, a discovery shows that this is the first evidence that a non-human animal can understand the emotional expressions of another species, according to hindustantimes.com.

"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.

As dogs and humans share a "tight evolutionary bond", the researchers from the University of Vienna decided to study the special link between these two species, according to Smithsonianmag.com.

Earlier, some research tried to test whether dogs could identify between human emotions, yet none of the studies could be totally proved. In a new study, the scientists tried to distinguish between images of the same person making either a glad or an angry face. In each study, the dogs were exposed to just the upper or the lower parts of the face.

The dogs were shown 15 picture pairs, and they could identify and discriminate four types of trials, including (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, and (4) the left half of the faces used in training.

Having the ability to discriminate between the angry or happy face more frequently, the scientists noticed that not only could they locate and differentiate between facial expressions, but could also shift what they had learnt in training to newer pictures.

"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.

He added that what exactly they detected was not clear, "but it appears likely to us that the dogs associate a smiling face with a positive meaning and an angry facial expression with a negative meaning."

Müller and Huber also agreed that the dogs did not find the link between an angry face and a reward, and seemed to harbor the idea that it was better to keep away from people who harboured negative feelings.

What is the role of experience in the dogs' ability to identify emotions? It is still a subject of study. The scientists will also study how the dogs express emotions and are likely to be influenced by their owners as well as other owners.

"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.