MIT: Saliva Sharing Is Used by Babies to Determine the Level of Intimacy in Relationships

Babies carefully observe their environment, especially when two people participate in actions where sharing saliva takes place. According to MIT, this allows them to gauge the level of intimacy between people.

Mother With Baby

By nature, Humans are social animals, and knowing who we should and should not count on is crucial to the survival of our species. In fact, for babies and young children, one close indicator of how close two people are is determined by whether saliva is exchanged between them through actions like kissing, sharing food, or any other activity that involves sharing of saliva. This is the conclusion of a study done at MIT, which suggests that babies use these signals to know who in their environment is most likely to help if a need arises. “Babies don’t know in advance which relationships are close, so they need a way to find out by observing what’s going on around them,” explains Rebecca Saxe, one of the scientists who conducted the study which was published in Science.

Saliva is an indicator of social bonding for infants

The MIT researchers wanted to know whether babies can determine whether there is a strong or weak bond between two individuals. Obviously, people who are intimately close and share a strong relationship such as members of a family, a married couple or siblings, are more likely to share bodily fluids, such as saliva. The question that scientists wanted to have answered was whether this is a clue that babies use to understand their social environment? To answer this question, the researchers looked at how 16- to 18-month-old infants and babies under one-year-old interact with stuffed animals and dolls.

The researchers set up a first situation where a doll shares an orange with one of the actors and then plays ball with a second. After this initial situation, the doll was placed between the two actors that were simulating an emergency situation. The researchers expected the infants to look at the person who is most likely to help the doll. In most cases, the infants looked at the actor who shared an orange with the doll. The second situation was more focused on saliva and reversed the roles. An actor put his finger in his mouth or on his forehead before touching a doll and then simulated an emergency situation. The babies looked at the doll with which the actor had contact with the saliva.

For the MIT team, these observations suggest that saliva exchanges allow babies and children to instinctively gauge the level of intimacy in the relationship between two people.