Research shows that dogs tear up when reunited with their owners

Sign up for CNN’s Wonder Theory newsletter. Explore the universe with news of amazing discoveries, scientific advances and more.

CNN
–

Tail wagging, loving licking, playful leap, heart-wrenching look. You know when your dog is happy to see you.

Now, new research by Japanese scientists suggests that a dog’s eyes may well be flooded with tears of happiness when reunited with its owner after a period of absence. Tears may help strengthen the bond between humans and dogs A relationship dating back tens of thousands of years.

Like humans, dogs have tear ducts that are filled with tears to keep their eyes clean and healthy. But tears in dogs that do not tend to fall as they do when humans cry, It has not been associated with passion before.

Takefumi Kikusui, a professor in the Laboratory for Human-Animal Interaction and Reciprocity at Azabu University in Japan, decided to investigate canine tears after witnessing a standard poodle when she had puppies six years ago. Notice that her eyes watered as she breastfed her dogs.

“We found that dogs shed tears associated with positive emotions,” said Kikusui, who co-authored the research published Monday in Journal of Current Biology, sHelp with a press release.

“We’ve also come to discover oxytocin as a possible mechanism behind it,” Kikusui said, referring to the hormone sometimes called in humans the love or mother hormone.

To verify the link, Kikusui and his team measured the amount of tears among 18 dogs with a standard test known as the Schirmer tear test. He. She It included a paper tape that was placed inside the dogs’ eyelids for a minute before they were reunited with their owners five to seven hours after parting.

“Tear volume was assessed by wet part length on the STT. Baseline was approximately 22 mm, and owner reunion increased by 10%,” Kikusui explained via email.

With the help of 20 dogs, researchers compared the amount of tears before and after they were reunited Owners and people with whom the animals were familiar. Only the reunion with the owner increased the amount of tears.

To understand whether oxytocin plays a role in tear production, a solution containing the hormone was applied to the surface of 22 dogs’ eyes. The amount of tears increased significantly after the application of oxytocin, compared to the control solution.

There’s still a lot researchers don’t know about dog tears. Humans often cry in response to negative emotions, but the researchers did not test whether dogs did the same either. Nor do they know if a dog’s ability to tear up plays a social role in dogs Globalism.

Kikusui said Humans could have taken better care of the dogs that got the tears. His team showed 74 People He photographed dogs with and without artificial tears in their faces and asked them to arrange the animals. People gave more positive reactions when they saw the dogs with teary eyes.

“Dogs become partners with humans and we can form bonds,” Kikusui said in a statement.