Japanese scientists have confirmed the assumption that dog owners have long voiced: their pets miss them very much in moments of separation. Their study found that dogs' eyes filled with more tears after reuniting with absent owners than with familiar non-owners or when owners stayed at home, reports Gizmodo..

According to scientists, this behavior of dogs is influenced by an increased level of production of oxytocin, a hormone that affects the formation of attachment in both humans and dogs..

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One of its authors, Takefumi Kikusui, was inspired to conduct the study by the behavior of his dogs.. One of them, a poodle, recently gave birth. Kikusui noticed that when she was feeding the puppies, she looked even cuter than usual, and her eyes were full of tears..

The scientist knew that oxytocin is called the " Oxytocin is also released in large quantities during moments of positive emotional connection in humans, such as during sex or even just hugging, which can sometimes be expressed in tears..

Previous work by the Kikusui team has shown that dogs and humans alike produce more oxytocin when they spend a lot of time together..

“This led me to the idea that oxytocin can increase tearing. We have previously observed that oxytocin is released in both dogs and owners upon interaction.. Therefore, we conducted an experiment on reunification, ”said the scientist.

20 dogs took part in the research experiment. They went through different scenarios in which the volume of tears in the eyes of the dogs was measured.. In one of the scenarios, the owners stayed nearby and interacted as usual, in the second they left and returned after five to seven hours, and in the third, they left the dogs in a supervision group in which they communicated with both the owners and acquaintances who were not owners..

As a result, scientists found that the eyes of dogs filled with tears when they were reunited with their owners.. When the dogs saw familiar non-owners, there were no significant differences..

To further test their hypothesis, the researchers gave the dogs eye drops containing oxytocin or a placebo.. When dogs received oxytocin, they produced more tears.

Finally, the team showed volunteers photos of dogs with or without artificial tears in their eyes, asking them to rate how positive or negative they felt about dogs.. Those who had more tears were rated more positively on average, and people reported wanting to touch or care for them more..

Kikusui notes that their study is the first to investigate the relationship between emotional state and tear production in non-humans.. According to him, scientists have proven that " The hormonal trigger that causes tears is probably oxytocin.