A new study found that canines may end up producing tears of genuine joy when reuniting with their owners.
Japanese researcher, Takefumi Kikusui, said the study’s findings suggest “dogs shed tears associated with positive emotions, such as reunion with the owner.” Kikusui is one of the study’s authors and is a veteran researcher at Azabu University.
If this hypothesis were true, it would mark the first time dogs’ tears were connected to feelings of emotion. However, according to The New York Times, there are doubts surrounding the conclusions derived from the experiments, with scientists dubious over the methodology involved.
The study, published in Current Biology on Monday, is based on the behavior of 22 dogs when reunited with their owners compared to people they knew.
Three hypotheses were made and tested against the empirical evidence. Firstly, dogs secrete emotional tears during reunions with owners. Secondly, tear secretion is controlled by oxytocin—a “bonding hormone”, and finally, the tears in dogs’ eyes can facilitate human caregiving behavior towards dogs.
In order to test out these hypotheses, researchers at Azabu University and Jichi University measured the difference in tear volume during normal interaction and after five-to-seven hours of separation. Strips of special paper were placed under the eyelids to soak up the tears.
Results found the tears produced had a 10 percent increase in the reunited dogs, Kikusui wrote in an email to CNN’s Katie Hunt. Tear volumes were larger when compared to reunions with a familiar non-owner.
“We had never heard of the discovery that animals shed tears in joyful situations, such as reuniting with their owners,” said Kikusi.
The second experiment revealed that dropping oxytocin into their eyes resulted in more tears produced rather than a controlled solution.
Finally, the team examined the reaction of 74 participants when judging 10 photos of dogs either with or without artificial teary eyes. In fact, the results show teary-eyed dogs were more positive, with a 10 to 15 percent increase.
“Through this process, their tears might play a role in eliciting protective behavior or nurturing behavior from their owners,” wrote the team.
Clive Wynne, a canine behavior specialist at Arizona State University, told the Times he is critical of the findings. During the first experiment, the paper may be responsible for producing more tears, as excited dogs could cause more rubbing due to excessive movement, he said.
In the second experiment, it could simply be possible that the oxytocin eye drops irritated the dog’s eyes, thus affecting the final outcome, said Lauren M Bylsma, a clinical psychologist at the University of Pittsburgh, to the Times.
