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It’s been said that eyes are a window to the soul, but new research has found that an adolescent’s brain response to a face might open a window to their social future.

A new study at the University of California, Davis Center for Mind and Brain found that high activity in the amygdala when an adolescent looks at a face showing emotions predicts their social health two years later. The increased amygdala activity for girls predicted more involvement with their peers, but predicted less involvement for boys.

The amygdala is best known for the fight-or-flight response and controls strong emotional reactions, especially fear. It is also one of the core brain regions that process information from faces.

“Faces contain a lot of social information, and perceptually or cognitively humans process that information really, really quickly,” said , lead author and postdoctoral fellow working with Professor Amanda E. Guyer, a co-author who directs the . “That makes it great for neuroscience, because as soon as you show a face to a person it doesn't take long for their brain to respond.”

The paper was recently published in the journal with 51�ԹϺ��� Davis co-authors Johnna R. Swartz and Jeffrey R. Fine.

The social brain and future social health

The “” is an idea from neuroscience that specific key brain regions are behind nearly every aspect of our social behavior. These brain regions help us recognize people we know, and they guide us in understanding the thoughts of others as well as our own. These regions’ development during adolescence plays an important role in peer relationships later on, but it’s been unclear exactly how.

This study tested the social brain’s impact on future social health with data from 5,832 participants in the . Participants were between 8 and 11 years old between 2017 and 2018 when shown images of either faces or places while their brain activity was observed with fMRI imaging showing blood flow in the brain. Data on their social health was collected two years later.

The team compared brain activity when participants viewed faces, which contain a high amount of social information, versus places, which have none. They also compared brain activity when participants viewed faces showing positive or negative emotions and faces showing no emotion. 

In addition to finding that high amygdala activation predicted boys and girls moving in opposite directions socially two years later, the analysis showed that the amygdala was the only brain region that predicted a participant’s future social health. 

Building on teen social health research

In a prior study, the team identified social health profiles that grouped teens by a mix of factors that included their number of friends, who was in their friend group and how much conflict they had with peers. Activation in the amygdala when seeing faces showing emotion predicted which of those profiles the participants would fall into two years later.

Arrington said that this study provides a valuable insight into how the brain develops during adolescence, a period when different parts of the brain develop at different rates. The results suggest that these differences in development between boys and girls may play a role in social health later on.

“For adolescents in particular, there’s a lot of development happening in this age range in the amygdala specifically, but it doesn't look the same for everyone,” said Arrington.

The work was supported by the National Institutes of Health.