by Joseph Master

When it comes to building social networks, white matter in the brain matters. A lot. In fact, anatomical connections between the amygdala and other brain regions can predict how social we are, according to a recent study by researchers from Temple University’s Cognitive Neuroscience Laboratory.

The study, co-authored by Ingrid R. Olson, professor of psychology and director of Temple’s Brain and Cognitive Sciences area, and doctoral student William H. Hampton, is the first to show that the amygdala, historically known as the brain’s fear hub, is also the brain’s social hub — suggesting that if a person’s amygdala is well connected, then so is their social life.

Historically, neuroscientists have focused on the brain’s grey matter in trying to understand the biological basis of complex behaviors. However, this study focused on the connections between gray matter regions – networks defined by bundles of axons – and showed that specific white matter connections of the brain predict one’s social network size. The findings also suggest that the transition from adolescence to adulthood is a key period when both the brain’s structural networks and individual’s underlying friendship-building occur.

"We found that the number of friends increases across adolescence, which is quite intuitive, and prior work has shown that white matter continues to develop through adolescence,” says Olson.

It's possible that the transition from your teenage years to adulthood is a critical period for optimizing white-matter networks underlying friendship-building behaviors.

Why does white matter matter so much?

Because more high-quality white matter connections from the amygdala to other regions of the brain — including the anterior temporal lobe and the orbitofrontal cortex — predicted larger social network sizes, suggesting that individuals with better wiring in the brain are more likely to have a larger group of friends outside of the nuclear family unit, according to the study.

“There is an interesting chicken-and-egg mystery here,” Olson says. “Does your white matter control your social behavior or does your social behavior sculpt your white matter? My best guess is that it operates in both directions."

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