Thanks to this (dirty) trick, children know if people have a close relationship | family

The thought of having to lick the same lollipop as a stranger probably disgusts many. We only exchange saliva with people we really like. Even children know that. According to scientists at Harvard University, infants and young children use it as a trick to find out who they can trust.

After nine months in a secure cocoon, babies enter a whole new world they don’t understand. Slowly but surely they learn to understand everything. Apparently, infants have an easy way of checking up on people they have a close relationship with. Key word: saliva. When people exchange spit—by kissing, sharing an apple, or drinking from each other’s cups, for example—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 proven by an experiment conducted by Ashley Thomas, a researcher at Harvard University and the Massachusetts Institute of Technology (MIT). She allowed dozens of children between the ages of 8 and 19 months to 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 I pretended. The other woman played the ball and threw it at the doll. A little later, the doll began to cry, and the little children immediately looked at the actress who shared the orange, as if they were expecting her to take care of the crying doll.

Then I replaced the crying doll with a new one, which started crying after a while. Then suddenly there was no difference: the children looked at the two actresses.

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

We all really don’t like other people’s saliva. The same goes for spitting. Except when it comes to your baby, but what if your baby spits up a lot? Parents now answer.

Congenital disgust

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

(Read more below the photo.)

The picture is for illustration.
The picture is for illustration. © Getty Images / Westend61

The question is: how so? Thomas and her colleagues think it’s a kind of innate insight, an evolutionary feature so babies can discern people they trust. But there could be another explanation.

Psychologist Christine Fawcett, of Uppsala University in Sweden, wrote a commentary on the study. She says people have an inner aversion to sharing spit. All over the world we find that very dirty. Only for our children, or our loved ones and close friends, do we make an exception and think it’s OK to kiss. And also very exceptional: sharing cutlery or toothbrushes. Children see this and adopt the behavior.

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