Eye contact helped dogs become our friends

The secret to puppy love is in the eyes, researchers said Thursday after studying how that locking gaze boosts the love hormone, oxytocin, in both dogs and people.

The study by Japanese researchers in the US journal Science suggests that humans and dogs co-evolved to become close over the centuries via the mutual eye contact and the higher levels of oxytocin, which fosters trust and emotional connection, that it builds.

Previous research has shown that when mothers look into the eyes of their babies, this leads to production of oxytocin and with it, an outflow of loving, protective and close feelings.

The reason dogs evolved from wild wolves to become domestic pets and friends is because of this same mechanism, researchers said.

"Dogs are more skillful than wolves and chimpanzees, the closest respective relatives of dogs and humans, at using human social communicative behaviors," said the study, led by Takefumi Kikusui of the Department of Animal Science and Biotechnology at Azabu University in Japan.

They studied dogs and their owners, documenting every interaction including talking, touching, and gazing, for 30 minutes.

When they measured oxytocin levels in the dogs' and owners' urine afterward, they found that "increased eye contact between dogs and their owners had driven up levels of oxytocin in the brains of both species," said the study.

The same experiment using wolves did not produce the results seen in dogs, suggesting that as dogs evolved from wolves many centuries ago, those that became domesticated were able to master the power of the gaze, a key part of human social communication.

Researchers then decided to try another experiment, in which they sprayed oxytocin directly into the noses of dogs and placed them in a room with their owners and some strangers.

"Female dogs responded to the treatment by increasing the amount of time they gazed at their owners," said the study.

It was unclear why the same effect was not seen in male dogs.

"After 30 minutes, oxytocin levels had increased in the owners of the treated dogs... providing further evidence for the oxytocin-mediated feedback loop between owner and canine."

It is already well-known that dogs are man's best friend. But the study sheds light on more than that, Greger Larson, an evolutionary biologist at the University of Oxford in Britain, told the journal Science.

"The more that we know about the process of how dogs became associated with people, the more we learn about the origins of civilization," he said.