Man’s best friend sheds more than just hair.
Dogs tear up with joy when they’re reunited with their owners — proof of the powerful emotional bond between humans and their canine companions, according to a new study.
Pooches have tear ducts that well up with happiness in a variety of situations, including seeing their owners for the first time after long periods of absence, according to researchers in Japan.
“We found that dogs shed tears associated with positive emotions,” said Takefumi Kikusui, of the Laboratory of Human-Animal Interaction and Reciprocity at Azabu University, said in a statement.
“We also made the discovery of oxytocin as a possible mechanism underlying it,” Kikusui said, referring to the so-called love hormone, which produces warm, fuzzy feelings.
During the study, published Monday in the journal Current Biology, Kikusui and his team placed paper strips known as a Schirmer Tear Test inside the eyelids of 22 dogs.
They then measured the amount of tears the pooches produced for one minute before and after they were reunited with their owners after being separated for five to seven hours.
After the owner returned, the tears they produced increased by an average of 10%, researchers said.
By contrast, researchers did the same thing with people who were not the canines’ owners and found that the dogs’ tears did not increase at all.
To examine the role oxytocin played, researchers placed a solution containing the hormone in the animals’ eyes and found the number of tears significantly increased after the liquid was added, according to the study.
Kikusui said he was inspired to probe the reason for Fidos’ emo eyeballs after seeing one of his poodles get teary as she nursed her puppies six years ago.
Researchers said they still don’t know if, like humans, dogs tear up from negative feelings. And they don’t know if a dog’s tears serve a social function in the canine world.
But Kikusui said the study shows, “Dogs have become a partner of humans.”