Study says dogs shed tears when reunited with owners

A new study has found that dogs shed tears of joy when reunited with their owners due to the oxytocin hormone.

According to the study, published in Current Biology, the bi-weekly peer-reviewed scientific journal, the tears deepen the bond between dogs and their owners.

To arrive at their findings, researchers at Azabu University and Jichi Medical University in Japan sampled the reactions of 22 dogs when reunited with their owners and other people they are generally familiar with.

Using the Schirmer tear test (STT), the researchers measured the tear volume in dogs before and after reunions with owners and familiar non-owners.

They also placed a paper strip inside the eyelids of the dogs for a minute before and after they were reunited with their owners following five to seven hours of separation.

The study found that “tear volume increased significantly during the reunion with the owner, but not with a familiar non-owner.”

The researchers further applied a solution containing oxytocin — the hormone responsible for social bonding — to the dogs’ eyes to establish if such tears were related to their emotions.

“When an oxytocin solution was applied to dogs’ eyes, the tear volume also increased, suggesting that oxytocin might mediate tear secretion during owner-dog reunions,” the study added.

Dogs are generally known for shedding tears occasionally to cleanse their ducts.

Takefumi Kikusui, one of the researchers, said this makes it the first time a study would link the tears of dogs to an emotional response.