Thanks to this (dirty) trick of babies, whether people have a close relationship | Family

The idea of ​​having to lick the same lollipop as a stranger is likely to induce a lot of revulsion. We only exchange saliva with people we really like. Even babies know it. According to scientists at Harvard University, babies and toddlers use it as a trick to figure out who to trust.

After nine months in a safe cocoon, babies enter a whole new world that they don’t understand. Slowly but surely they learn to understand everything. Apparently, infants even have a handy method of checking which people have a close relationship. Key word: spit. When people exchange saliva—for example, by kissing, sharing an apple, or drinking from each other’s glasses—they must have a close bond.

Two actresses and a doll

Sharing food – and exchanging saliva – is an important signal to children that people are close. ©Getty Images

This is shown by an experiment by Ashley Thomas, a researcher at Harvard University and MIT (Massachusetts Institute of Technology). She let dozens of children between 8 and 19 months watch a movie. The video featured two actresses and a hand puppet. A woman ate an orange slice and then gave it to the doll. Or yes, of course she pretended. The other woman played with a ball and threw it at the doll. A little later, the doll began to cry, and babies and toddlers immediately looked at the actress who had shared the orange, as if expecting her to take care of the crying doll.

Then the crying doll was replaced by a new one, which also started crying after a while. Then suddenly there was no difference anymore: the children looked at both actresses.

Of course, it could be that the children thought one woman was just cuter than the other because she shared a treat with the doll. To rule this out, the experiment was repeated. This time, the first actress had to put her finger in the mouth and then into the doll’s mouth. The other actress just had to touch her forehead and the doll’s. The result was exactly the same: when the doll began to whimper, eyes immediately turned to the first lady.

We all really don’t like other people’s spit. The same goes for saliva. Except when it comes to your own baby, but what if your baby spits up too much? Now the parents answer.

Innate disgust

For the little ones, things like hugs or emotional support are important signs that people are close. But exchanging saliva is also one of them. And it’s important, because it’s how children know who they can count on when they’re scared or need someone. Thomas writes this in the scientific journal Science.

(Read more under the picture.)

Photo for illustration.
Photo for illustration. ©Getty Images/Westend61

The question is: how does it come about? Thomas and her colleagues think it’s a kind of innate insight, an evolutionary advantage that allows babies to distinguish which people to trust. But there could also be another explanation.

Psychologist Christine Fawcett, from Uppsala University in Sweden, has written a commentary on the study. She says people have a built-in aversion to sharing saliva. Worldwide, we find it very dirty. Only for our own child, or dear and best friends, do we make an exception and think it’s okay to kiss. And also very exceptional: sharing cutlery or a toothbrush. Babies see that and just adopt the behavior.





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