Dogs shed happy tears when reuniting with owners
Japanese researchers revealed that the eyes of man’s best friend do indeed well up with tears whenever they’re flooded with positive emotion – almost regularly when dogs are reunited with their human owners. The world-first discovery that animals shed tears in joyful situations comes as a pleasant surprise.
According to Takefumi Kikusui from the School of Veterinary Medicine, Azabu University in Japan, dogs become suffused with oxytocin – widely known as the “love hormone” – when they interact with familiar faces, causing dogs’ tear volume to go up.
Kikusui first noticed this incident after one of his two standard poodles had puppies 6 years ago. When his dog was nursing the puppies, something changed in the dog’s face; there were tears. Those tears don’t fall as they often do in humans but they do get teary eyes.
“That gave me the idea that oxytocin might increase tears,” Kikusui said.
The researchers also knew from earlier observations that oxytocin is released in both dogs and their owners during interactions, and so, decided to run a reunification experiment to see if it brought dogs to tears.
First, they used a standard test to measure the canine subjects’ tear volume before and after reuniting with their owners. They found that tear volume went up when they got back together with the familiar human and not with a person they didn’t know.
When they added oxytocin to the dogs’ eyes, their tear volume also went up. That finding supports the idea that the release of oxytocin plays a role in tear production when dogs and their people get back together.
The researchers also asked people to rate pictures of dogs faces with and without artificial tears in them as part of their experiment. It turned out that people were inclined to give more positive responses when they saw dogs with teary eyes. These findings suggest that dogs’ tear production helps to forge stronger connections between people and their dogs.
“Dogs have become a partner of humans, and we can form bonds,” Kikusui said. “In this process, it is possible that the dogs that show teary eyes during interaction with the owner would be cared for by the owner more.”
In this case, it seems dogs produce tears in situations that humans would consider joyful.
However, the researchers haven’t yet tested whether dogs produce tears in response to negative emotions, too, or when they get back together with other dogs. They hope to learn if this response also has a social function in the dog world. But, for now, they say it seems to have clear implications for the dog-human bond.
