A curious research team from MIT recently dived into this intriguing question. If you think about it, we only share saliva with our nearest and dearest. From kissing, to sharing forks, or eating the same ice cream cones, it signifies a close bond. This could be between parents, siblings, extended family, or friends.

The study suggests as small children are always watching and absorbing, they manage to figure out social dynamics through observing this phenomenon. The way in which the team came to this conclusion was by using puppets.

In the experiment, the babies were shown a display of puppets and adults sharing saliva, followed by a video of a puppet ‘crying’. Starting at an age of eight months old, the subjects were more likely to look at an adult that had swapped saliva with this puppet than one who hadn’t.

The result, published in Science, describes how the team used other experiments similar to these. Displaying saliva sharing through orange slices and utensils, the results came to the same conclusion. Of course, scientists can’t know exactly what is going through the babies’ brains. Although, tracking their eye line is a great clue.

The study only focussed on children in the United States. Therefore, across different cultures, where different hygiene and eating practices are carried out, this cue may not be there. Although, it is still an interesting experiment to show how small children can pick up on social interactions. Other behaviors, such as hugging, are likely to also play a role in perceived intimacy, an exciting future avenue for research to go down.

Understanding how the human mind is evolutionarily programmed is a puzzle that scientists have been tackling for centuries. From the psychology of consumerist behaviors used in marketing strategies, to understanding our addictive tendencies to treat diseases such as alcoholism, we are very complex beings psychologically.

Source study: Science – Kids attend to saliva sharing to infer social relationships