Babies may use saliva sharing to figure out relationships

 Sharing morsels of food or kissing may encourage young toddlers to form tight ties.

According to a study, children as young as 8 months old keep track of who shares saliva and use it as a criterion for who is in a close connection and who isn't.  TUAN TRAN/MOMENT/GETTY IMAGES PLUS TUAN TRAN/MOMENT/GETTY IMAGES PLUS
According to a study, children as young as 8 months old keep track of who shares saliva and use it as a criterion for who is in a close connection and who isn't. 

Young youngsters are always on the lookout. A study reveals that when adults swap spit through activities like sharing food, it helps the tots figure out who is in close relationships with whom.

People are more inclined to share things that can lead to saliva interaction, such as kisses or an ice cream cone, with family members or close friends than with strangers or coworkers. As a result, according to Ashley Thomas, a developmental psychologist at MIT, intimate behaviors that share saliva might be indicators of a "thick relationship," or people who have enduring bonds to each other, such as parents, siblings, extended relatives, or best friends.

Social cues from the individuals around them are commonly picked up on by young children (SN: 1/30/14). So Thomas and colleagues went to puppet tests to see if children, even babies, and toddlers, might use saliva sharing as a cue for intimate ties.

Children as young as 8 months old were more inclined to look at an adult who had previously shared saliva with the puppet — either directly or by sharing food — rather than another adult who hadn't, according to a study published in Science on Jan. 21.

Of course, researchers have no way of knowing what babies are thinking. However, keeping track of where they gaze is one way to gain a clue. According to Thomas, the aim is that young children will not expect an adult to comfort the puppet. Instead, the researchers predicted that when the puppet exhibits distress, the young children would look to the person who they expect to move first, which would be the person who has a closer bond with the toy, she says.

The researchers showed footage of a woman sharing an orange slice with a puppet to 8- to 10-month-old babies and 16- to 18-month-old toddlers in some of the studies. Another video showed a woman and the puppet having fun with a ball. The toddlers' attention was pulled to the woman who had shared the orange slice during the last film, which showed the puppet seemingly crying while sitting between the two women - a clue the tots were expecting her to react.

When one lady engaged with two puppets, the scientists noticed comparable findings. The woman put her finger in her mouth and then into the mouth of one of the puppets to share her saliva. She just touched her own forehead and then the puppet's forehead for the other. After the woman displayed distress, the infants and toddlers spent more time looking at the puppet that had shared saliva.

Saliva sharing was also picked up on by older youngsters, ages 5 to 7, as a sign of intimate relationships. People sharing utensils or bites of food could be family, while those sharing toys or dividing up food could be friends or family, according to the kids in that age bracket.

It's unclear how the findings apply to young children's daily lives. To better understand the impact saliva may play on how infants and toddlers differentiate different forms of connections, future trials might replace the actresses in the study with family members or teachers. Other signs, such as hugging, could also play a part, according to Thomas.

The study also solely looked at youngsters in the United States and did not compare children from different cultures. Nonetheless, Darby Saxbe, a clinical developmental psychologist and co-director of the University of Southern California Center for the Changing Family in Los Angeles, says the findings are exciting. It would be interesting to see if children from other ethnic groups behave differently in the same settings, she says.

A.J. Thomas et al. Early concepts of intimacy: Young humans use saliva sharing to infer close relationships. Science. Vol. 375, January 21, 2022, p. 311. DOI: 10.1126/science.abn5157.


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