This is the first time that a positive emotion has been shown to cause tears in a non-human. So far, in dogs, the reunion with the master, it was jumps in the air, licks, fast tail beats. It took these Japanese researchers from the University of Azabu to submit 18 dogs to the Schirmer test – concretely, they place a strip under their eyelid – to note a much greater tear production when the master reappears after five hours of separation. . It is published by the journal Current Biology.
What’s interesting is that they also studied the effect it has on the master. We know that the crying of an infant causes its parents to take care of it. The dog’s tears too, obviously. They presented 74 participants with ten photos of five dogs, represented with more or less tears. They asked them to rate on a scale of one to five how much they wanted to care for the animal. Watery-eyed dogs gained 10-15% more people wanting to care for them. According to the team, the more the dog’s eyes are moist, the more it releases, in the master this time, oxytocin, which is the hormone of love and happiness. And the animal feels it. The study says it: dogs would have sociocognitive skills similar to those of humans, which would result from convergent evolution with humans.
In the same order of idea, clever, the dog: with domestication, he began to develop a very particular muscle, that of the internal eyebrow which gives him this little air of a puppy. It triggers the nurturing act of its master, according to a 2019 study. A flick of the eyebrow, and presto: double ration.
Professor Takefumi Kikusui, the co-author of the research, explained how he obtained this certainty to our colleagues from the English newspaper The Guardian. He had two poodles and when the female was pregnant six years ago he was struck by her change in face while nursing her puppies. A much more tender face with tears in her eyes. Hence the idea that oxytocin could increase tears. And as it is released both in animals and in humans, he wanted to try this experience of reunion. Note that the result is completely different if the dog finds other humans – he only cries for his master. The team now intends to study what happens when he finds his congeners.