This One Thing Helps Babies Identify Close Family Relationships, Study Says

Young children pick up on much more than we think. Our interactions help them navigate social relationships, and, as one new study is finding, maybe even learn who they can and cannot rely on to take care of them. Neuroscientists from MIT have found there may be one thing in particular that tips young kids off to whether or not two people share a strong familial relationship and will take care of each other.

Their study, published in in the journal Science, looked at babies, toddlers and young children. They found that babies expect two people who have shared saliva in a previous interaction to come to each other’s aid in times of distress.

“Babies don’t know in advance which relationships are the close and morally obligating ones, so they have to have some way of learning this by looking at what happens around them,” Rebecca Saxe, a member of MIT’s McGovern Institute for Brain Research and the Center for Brains, Minds, and Machines (CBMM) and senior author of the study, said.

To get to their findings, the researchers looked at toddlers, aged 16.5 to 18.5 months, and babies, aged 8.5 to 10 months, as they observed interactions between human actors and puppets. During one round of experiments, the children watched the puppet share an orange with one actor, and then toss a ball back and forth with another actor. Researchers noticed that, when the puppet seemed upset, the kids were more likely to look to the actor who had shared food to step in and help.

In a second round of experiments, the kids watched the actor place a finger in their mouth and then into the mouth of the puppet, or the actor place their finger on their forehead and then onto another puppet’s forehead. When the actor seemed upset, the kids were more likely to look at the puppet the actor shared saliva with.

The first round of studies was done shortly before the pandemic’s onset, and the children came into the lab with their families. Later experiments for the study were conducted via Zoom. However, researchers noticed that their findings were similar before and after the pandemic. This confirmed that pandemic-related hygiene concerns didn’t affect the outcome of their studies.

“We actually know the results would have been similar if it hadn’t been for the pandemic,” Saxe said. “You might wonder, did kids start to think very differently about sharing saliva when suddenly everybody was talking about hygiene all the time? So, for that question, it’s very useful that we had an initial data set collected before the pandemic.”

While the study’s results are interesting, it’s important to note more research needs to be done. Next, researchers hope to conduct similar studies with babies in different cultures and with different family structures.

“The general skill of learning about social relationships is very useful,” Ashley Thomas, MIT postdoc and lead author of the study, also said. “One reason why this distinction between ‘thick and thin’ [relationships] might be important for infants in particular, especially human infants, who depend on adults for longer than many other species, is that it might be a good way to figure out who else can provide the support that they depend on to survive.”