Those slimy bites, their wet kisses, sharing food or putting our fingers in our mouths are simple gestures of our babies that hide behind much more than meets the eye. It has to do with how they establish their close emotional bonds with other people.

Neuroscientists at the Massachusetts Institute of Technology (MIT) have identified a specific signal that infants and young children use to determine whether two people have a strong relationship and an obligation to help each other: whether those two people kiss, share food, or have other interactions that involve sharing saliva .

Sharing food, kissing, sucking or any approach with the adult in which they share saliva implies establishing a close bond .

Saliva and close emotional ties

Children pick up on social cues and can associate that there is an emotional bond between two people who kiss, and it is not uncommon for them to do the same.

People share eating utensils, kiss each other or interact in other ways that involve sharing saliva, according to the study’s authors, from Harvard University and MIT in the United States.

“We have found that infants, toddlers, and older children infer that those who share saliva (and not those who have other positive interactions such as playing with the same toy) have a special relationship ,” they say.

The researchers showed in the study published in Science that babies expect people who share saliva to help each other when one person is in distress, much more so than when people share toys or interact in other ways that don’t involve saliva sharing.

The findings suggest that babies may use these cues to try to figure out who around them is most likely to offer them help , the researchers say.

“Infants don’t know in advance which relationships are the closest and most morally binding, so they must have some way of learning this by observing what’s going on around them,” says Rebecca Saxe, lead author of the new study.

Others point out that saliva may not be the only clue, as bed-sharing and intimate physical contact likely play a role as well.

drool and confidence

To conduct the study, the researchers used experiments of people interacting with dolls and observed how infants (8.5 to 10 months) and toddlers (16.5 to 18.5 months) reacted.

They were shown scenes in which people interacted with the dolls by sharing food, toys, and performing actions such as putting a finger in and then into a doll’s mouth.

The MIT team found that infants were more likely to look at someone who had shared food with the puppet, rather than someone who had shared a toy, when the puppet was in distress.

The findings suggest that sharing saliva is likely an important signal that helps babies learn about their own social relationships and those of the people around them , the researchers say.