This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Imagine you're an infant. Just a few months in the world, trying to gather your faculties, testing gravity—you're pretty helpless and fully reliant on the people around you.
As a result, one of your primary tasks as a new person—even before hand-eye coordination and responding to your own name—is to figure out how the people you've just met are connected to each other. "Children are born into a very social world," said Brandon Woo, a researcher in UC Santa Barbara's Department of Psychological & Brain Sciences. "Because it's so important for children to work with others and collaborate with others, they need to map out these social networks." One key piece of evidence, according to Woo and collaborators from Harvard University and MIT: saliva.
The researchers' findings are published in the journal Evolution and Human Behavior. A developmental psychologist by training, Woo is broadly interested in life from the baby's point of view, namely how they make sense of others' actions, minds and relationships, all in service of understanding human sociality. "We were inspired by studies that found that across cultures, people in close relationships are often more comfortable sharing saliva with each other," he said.
"So imagine seeing two people licking the same ice cream cone—could you guess how they might know each other?" In previous work, Woo and collaborators found that older babies and toddlers could reliably infer how close—or "thick"—a relationship is based on intimate saliva-sharing, such as kissing or sharing foods and utensils. "Our past work found that by the time infants are around 8 months of age, when they view people sharing saliva, they are making inferences that those individuals will respond to each other's distress," he said. For this work, the question wasn't just whether babies could infer relationship thickness; the researchers were curious about how soon they could do it.
Compared with older children, infants at 4 to 6 months of age would have had less opportunity to observe such behaviors. They are also less likely to look at faces and ingest foods that are typically not shared with others. Working with groups of babies at 4 to 6 months of age, the researchers conducted two experiments.
In the first, a human protagonist put an orange slice in their mouth, took it out and inserted the food in an actor puppet's mouth, representing a scenario of shared saliva. This was contrasted with another human protagonist taking a ball and passing it to the puppet, representing sharing without saliva; the puppet would then express distress. The researchers watched the baby viewing the interaction to see who the infant looked at longer—the person who gave the puppet an orange slice or the person who gave the ball.
Extract — continue reading at the source.
