A group of Japanese researchers found in one of their studies that dogs become teary when they meet their owners after a long time. Their eyes filled with water. The researchers said that there is a relationship between these tears and the increase in the level of ‘bonding hormone’ oxytocin. They said, the dog’s eyes filled with water with love and emotion.

Researchers claim that animals other than humans shed tears in positive emotions and oxytocin works behind these tears. In a paper published in the journal ‘Current Biology’, the researchers show how eye contact between humans and dogs makes people more caring towards dogs. Whereas a dog’s gaze can cause an oxytocin release in its owner. Dogs have also evolved the ability to wiggle their inner eyebrows. It’s a habit that scientists say motivates people to take care of them. Tears may have similar powers, Japanese researchers say. ‘From there it occurred to me that oxytocin might bring on tears’, said one researcher, ‘we had previously seen oxytocin released by both dogs and their owners during interactions. So we did a reconciliation experiment.’

In the first phase of the study, the team measured the tear volume of 18 dogs while they were in a natural home environment with their owners, using the Shimmer test method. In this process, a special strip of paper is placed on the lower eyelid of their eye and the extent of the wetness of the strip is measured. The team compared this amount to the amount of tears shed by dogs in the first 5 minutes of being reunited with their owners after more than 5 hours of separation. Dogs shed significantly more tears when reunited with their owners than when they spend the day alone at home, the researchers said. However, this increase was not seen when 20 dogs were re-introduced to a similarly familiar human who was not their owner. Another study of 22 dogs found that eye drops rich in oxytocin increased tear production—another oxytocin.

Not seen using free drops.

The team then presented 74 participants with 10 pictures of 5 dogs, each with wet eyes or dry eyes, and were asked to rate the group on a five-point scale how much they liked or avoided the animals. According to Kikusui, the results showed that dogs with teary eyes were preferred by 10-15 percent of people. According to the team, this suggests that teary-eyed essences evoke such emotions in humans. The researchers also reported that dogs have a very high-level ability to communicate with humans using their eyes. which is different from other animals.

Kikusui says that when dogs are reunited with their owners, their eyes fill with tears, but there are still questions about this. He further said, ‘We still don’t know whether dogs’ eyes fill with tears during the mating. We also don’t know how dogs use tears to communicate with each other. We need to be able to clarify the social role of seminal tears.