We should smile at our dogs - a new scientific study reveals why

Scientists have found that a dog’s brain registers a reward response when it sees a smiling human face, even if the person is a stranger. In a study conducted at the University of Vienna, 14 dogs remained still inside a brain scanner while they were shown photographs of people displaying various expressions. Images of happy, smiling faces activated a region of the canine brain associated with reward, the same circuitry that lights up when dogs anticipate a tasty snack or smell a familiar person. “It controls us having information to do things - wanting to do things,” explained Laura Cuaya, one of the study’s lead researchers. “So this finding suggests that happy faces, even those of strangers, have a positive value for dogs.” Cuaya and her co‑researcher, Raúl Hernández‑Pérez, also presented the dogs with pictures of faces showing anger, fear and sadness. The reward circuitry responded only to the happy expressions. “Dogs can distinguish between positive emotions and all the others, but they don’t appear to be able to distinguish between the different negative emotions,” Hernández‑Pérez told BBC News, noting that he is also based at the University of Vienna. The researchers, who are partners both in science and in life, have previously investigated how dogs interpret human language and behaviour. Their own border collies, Odín and Kun‑kun, took part in the experiment, and additional dogs were recruited by approaching owners in a local park and asking if their pets would be willing to help. Under a subheading titled “How humans changed dogs’ brains,” Cuaya described the canine brain as “rather fascinating” and emphasized that dogs, despite being a different species, have become adept at reading human emotions through thousands of years of domestication. “When we compare humans with other primates, we are looking at abilities that may have come from a common ancestor,” Cuaya added. “With dogs, the story is completely different. They followed a very different evolutionary path, but through domestication they developed the social abilities needed to recognize and cooperate with us.” She concluded that the findings offer a simple way to strengthen the bond between people and their pets. “We can reward our dogs with treats, but also reward them with happiness,” said Cuaya. “So we should smile at the dogs – even at random dogs in the street.” The results are published in the journal iScience (published in the journal iScience, external).