Dogs cry tears of joy when reunited with pet parents – study

A Japanese study shows that not only are our dogs happy to see us, but they actually cry tears of joy when we're reunited after a long break

We all know how happy our dogs are to see us when we’ve been away for a few days, a few hours, or even a few minutes. You’ll get the jumps, the licks, the cuddles, the wagging tails, the presenting of the belly for rubs, or whichever display of barely contained excitement they prefer. But, according to a new Japanese study, they cry actual tears of joy when we return – a reaction previously thought to be unique to humans.

The study, the brainchild of Takefumi Kikusui of the School of Veterinary Medicine at Azabu University, was inspired by seeing his standard poodle, Jasmine, get teary-eyed as she nursed her pups.

“That gave me the idea that oxytocin might increase tears,” he told The Scientist. “Oxytocin, as you know, is the maternal hormone.”

The cuddle hormone

It’s also known as the ‘cuddle’ hormone, because it surges in both dogs and humans during positive interactions, and is believed to be important to the bonding between pets and pet parents. Kikusui’s hypothesis was that a reunion between the two after an extended period apart “would be [an] emotional event to dogs” that could lead to a surge in oxytocin – and some happy tears.

Kikusui’s team of researchers separated pooches form their favourite humans for several hours before reuniting them. Five to seven minutes later, they tested to see how teary the dogs’ eyes had become (dogs’ eyes don’t overflow like ours, so don’t worry if your pup isn’t sobbing when you come home).

"A dog's tears make pet parents more nurturing or protective"

They then tested the dogs’ tear production when reunited with someone they knew but who wasn’t their pet parent – and the results showed that they welled up significantly less.

To confirm that it was a positive emotional response, the team also applied a solution containing oxytocin to the dogs’ eyes to see if it would increase tear production compared to a control solution. It did, backing up Kikusui’s hypothesis.

Better bonding

It’s not all about the dogs, mind. The study found that when a dog cries tears of joy, they stimulate the secretion of oxytocin in humans, making pet parents more nurturing or protective of their pet.

"Their tears might play a role in the deepening of mutual relationships and further leading to interspecies bonding," the researchers wrote.

So, there you go. The next time you’re reunited with your furriest friend, gaze deep into their eyes. Those beautiful peepers aren’t just saying “Where’s my dinner?” – they’re an emotional cord tying the two of you together. Though obviously dinner would be nice, too.