What a nice feeling it is when you come home and the dog rushes towards you, tail wagging with joy and would like to lick your whole face, he is so happy?

Some may shed a tear of emotion - and the same could happen to the dog, as Japanese researchers now want to have found out.

Dogs crying with happiness: That would be tantamount to a scientific sensation, because so far the law has been that only humans cry because of emotions.

Johanna Kuroczik

Editor in the "Science" department of the Frankfurter Allgemeine Sunday newspaper.

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The team led by Takefumi Kikusui, veterinarian and expert on animal behavior at Azabu University in the Japanese city of Sagamihara, reports in the renowned journal "Current Biology" that dogs produce more tears when they meet their master - and so do they too Crying is an expression of strong emotions.

Schirmer tear test

A few years ago, Kikusui reports that he noticed that his poodle lady had particularly wet eyes when she looked at her offspring.

"That gave me the idea that the hormone oxytocin might increase tears," says Kikusui.

The so-called cuddle hormone promotes social bonds in people and plays an important role in the mother-child relationship.

In dogs, for example, it increased in experiments when they met their master.

For the current study, Kikusui's team measured the tear volume of 18 dogs when they were reunited with their master after a few hours of separation.

They compared these values ​​with the amount of fluid in the dogs' eyes when the dogs met another person they knew.

To do this, the researchers used the Schirmer tear test, which is used in medicine to determine tear secretion disorders – a strip of litmus paper is held to the eye.

Moved to tears?

"Tear volume increased significantly when the animals were reunited with their owners, but not when they encountered other humans," says Kikusui.

And: "We also discovered oxytocin as a possible underlying mechanism." The scientists dripped a solution containing oxytocin into the eyes of the dog test subjects and found that the animals then produced more tears in the emotional situation than when they were given a control liquid was administered.

So do dogs get moved to tears by their emotions too?

So far, emotional crying has been considered a purely human trait.

Some experts are therefore critical of the research work.

The beloved "dog look"

"If we accept the evidence from the study, it would be one of the most amazing discoveries ever made about animal expression of emotion," Arizona State University canine behavior specialist Clive Wynne told the New York Times.

It would take a lot to convince him of that.

Another aspect that Kikusui and his team researched seems logical – people rated dogs as cuter in photos if their eyes appeared wetter.

The "crying" could have served to strengthen the relationship between dog and human evolutionarily.

For example, the inner eyebrow muscles in dogs were strengthened over time, which enable the "dog look" so loved by people.

It's conceivable, says Kikusui, that the dogs would be better cared for when their eyes were watering.

Whether the very small study is actually the first hint that dogs cry with happiness, future research will show.