Supersized Amygdalas Linked to Sprawling Social Circles

By Andrew Moseman | December 27, 2010 2:20 pm

Large amygdalas, it seems, are social amygdalas.

These paired regions, typically referred to as almond-shaped (indeed their name comes from the Greek for almond), are known to be part of the brain responsible for sociability as well as fear and other deep-seated emotions. Lisa Feldman Barrett and colleagues sought to find out whether size matters in the amygdala, and according to their study in Nature Neuroscience, there is a connection between people having big amygdalas and having big, complex social networks.

The researchers measured two social network factors in 58 adults. First, they calculated the size of a participant’s network, which is simply the total number of people that are in regular contact with the participant. Second, they measured the network’s complexity, based on how many different groups a participant’s contacts can be divided into. … Linear regression revealed a positive correlation in amygdala size with both social network size and complexity. [Ars Technica]

The team’s MRI scans found a wide variation in amygdala size, from about 2.5 cubic millimeters to more than five. But other factors like a person’s happiness didn’t match up with amygdala size. And the subjects’ hippocampus, which the scientists used as a control, showed no variation when compared to a person’s social network. Only the amygdala size showed the connection, Barrett says.

The amygdala is shared across many species, and the finding by Barrett’s team would fit with what scientists know about the brain region’s purpose in some of our primate relatives.

The findings correspond to previous research that found that primates also have a larger amygdala, relative to the overall size of their brain and body. Like humans, primates live in fairly complex social groups, suggesting that a larger amygdala has evolved to help navigate these landscapes. The amygdala has also been shown to be involved with fear, emotion and even seizures, said Paul Sanberg, director of the University of South Florida Center of Excellence for Aging and Brain Repair in Tampa. Sanberg was not involved with the new study. “It’s part of the ‘old’ section of the brain,” he explained. [U.S. News & World Report]

Supposing Barrett’s team is correct, what they’ve found is simply a correlation. The big question that surfaces as a result is: Which comes first? Do people with large amygdalas tend to seek out more social connections, or do people grow larger amygdalas because they have more social connections? Barrett leans toward the latter.

“People who have large amygdalas may have the raw material needed to maintain larger and more complex social networks,” said Barrett. “That said, the brain is a use it or lose it organ. It may be that when people interact more their amygdalas get larger. That would be my guess.” [The Guardian]

Related Content:
Not Exactly Rocket Science: Meet the Woman Without Fear
80beats: Study: Damage to Brain’s Fear Center Makes People Riskier Gamblers
DISCOVER: Conquering Your Fears, One Synapse at a Time
DISCOVER: Emotions and the Brain: Fear

Image: Wikimedia Commons

  • Brandon Keim

    The coverage this study got makes me understand why some people hate science journalism so much. There are *so many* reasons not to get carried away: there were just 58 people in the study, including only 22 women; the findings weren’t replicated; the amygdala’s involved in just about everything, so one might as well say, “people who have more friends can be more afraid”; and the regression analyses hides all sorts of variability. There are many of people in there with small amygdalas and large networks, and vice versa.

    At best, the study was an interesting preliminary finding that could suggest further avenues of research. It didn’t deserve to be covered journalistically at all. And not only was it covered, it was conflated with Facebook and online social networks — even though the study didn’t look at these. Blech.

  • Andrew Moseman

    Good point about the regression analysis. Indeed, the Facebook-dropping whenever there’s a study about social networking annoys me as well, so I try to avoid it as best I can.

    I thought the argument here was interesting despite the study problems, though it would be interesting to see how many well-publicized neuroscience studies would never have been covered at all if sample size had been a disqualifier.

  • Amos

    The lefties are already trying to use it to paint conservatives as ‘fearful’ and irrational, despite the small size of the sample etc etc. That’s what ‘science’ is now, anything they say it is for the purposes of cheap political points-scoring and tribal self-congratulation.

    Utterly pathetic. It’s like they say, the only thing dumber than a journalist is a political hack, and the Venn diagram of those two groups is a pretty much a 99% convergence.

    Did I call you pathetic yet? Well one more time; you’re pathetic

  • Albuquerque

    correlation does not imply causality. Checking this out on populations not aligned with access to facebook would be interesting. In all research you must start with one study, then move onward and outward.


Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!


80beats is DISCOVER's news aggregator, weaving together the choicest tidbits from the best articles covering the day's most compelling topics.

See More

Collapse bottom bar