Scientists discover: dogs perceive human smiles as a reward

A human smile triggers a brain response in dogs similar to receiving a reward, according to a new study by researchers at the University of Vienna, reported by the BBC. It turns out that dogs don't care whether the smiling person is familiar or a complete stranger — the brain's positive response is the same either way.

It has long been known that dogs are able to recognise human emotions, a skill honed over thousands of years of living alongside humans, which has evolutionarily "tuned" them to understand us better than any other animal species on the planet. This new study went a step further, revealing exactly what happens inside a dog's brain the moment it sees a smiling or frowning human face.

How the experiment worked

The study involved 14 dogs, who were placed in a brain scanner and shown photographs of human faces. When the animals saw happy, smiling faces, the region of the brain linked to the reward system lit up — triggering the release of dopamine, the same hormone associated in humans with a good mood, tasty food, or praise.

Previous research had already shown that the same brain region activates in dogs when they anticipate a treat or when a familiar person appears nearby. "This finding suggests that happy faces — even the faces of strangers — carry positive meaning for dogs," explained one of the study's lead researchers, Laura Cuaya.

Dogs recognise positivity, but not different types of negativity

The study's authors also examined how dogs respond to other emotions — joy, anger, fear, and sadness. It turned out that the brain's "reward zone" responded exclusively to happy faces. "Dogs can distinguish positive emotions from all others, but it seems they are not able to tell different negative emotions apart from one another," said study co-author Raúl Hernández-Pérez.

According to Cuaya, from a neuroscience perspective, the brains of our beloved pets are "absolutely fascinating." "When we compare humans to other primates, we look at abilities that might have been inherited from a common ancestor. Dogs, on the other hand, have a completely different story — they followed an entirely separate evolutionary path, but through domestication they developed the social skills needed to understand us and cooperate with us," she noted.

The researcher concluded that dogs can be rewarded not only with treats but simply by showing them joy. "We should smile at dogs more often — including strangers' dogs we meet on the street," Cuaya said.

Around Prague, based on reporting by seznamzpravy.cz