Shy? Outgoing? And if we had a brain signature for our level of sociability?

We all know people who are very shy and others who are extroverts, going through all intermediate profiles. Indeed, there is a huge difference in social behavior depending on the person. Do variations also exist at the heart of our brain that could explain these differences in behavior? Prof. Monica Zilbovicius, Inserm research director, and Prof. Nathalie Boddaert, head of the pediatric radiology department at Necker-Enfants Malades hospital AP-HP, Professor of Medicine at the University of Paris and director of the Image team within the Imagine Institute, have turned to magnetic resonance brain imaging (MRI) and eye-tracking to answer this question. Everything seems to lie in the ability to follow the gaze of others.

Published on 19.07.2019


  • Neurodevelopment

Why do some people go out to meet others more easily? Can we explain the fact that some people seem more comfortable in society? For several years neurosciences have explored these fields and tried to establish links between behavior and physiological data.

signature cérébrale

The team in charge of this study looked for the possible existence of a cerebral basis to these differences and if there was a way of detecting them. This team used measures of gaze behavior (eye-tracking) and magnetic resonance brain imaging (MRI). By analyzing the gaze of young adult volunteers when watching scenes from the film “Le Petit Nicolas”, the study showed, for the first time, that the way of looking at presented social interactions varies greatly, and that there is a meaning behind this: there are those who look in the characters’ eyes a lot and those who look in them very little, which reflects the social behavior of each of them. 

This way of looking at the other is unique to each individual and does not change over time. “It is a sort of individual signature of the level of sociability”, notes Ana Saitovitch.

To try to understand the brain mechanisms that underlie these different behaviors, the team then quantified resting brain activity in the same people, with an MRI and separately from the viewing of videos, by measuring cerebral blood flow.

A significant correlation was recorded between the number of times where a person looks in the eyes and the resting blood flow only in a very specific region of the brain. This is the superior temporal sulcus (STS), which is a key place in the brain for social cognition. Therefore, people who look in the eyes of others a lot are those who have a more significant resting brain activity in this region. On the other hand, those who look less in the eyes of others have a less significant activity.

This work has helped to establish different brain signatures unique to each individual, which determine the level of sociability.

These innovative results provide new ways of understanding the variability in social behavior and its neural substrates. In addition, they could contribute to a better understanding of diseases that have an impact on social behavior, such as autism spectrum disorders.