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Link Between Socializing And Brain Size Discovered

December 27, 2010

Scientists from the Massachusetts General Hospital (MGH) Psychiatric Neuroimaging Research Program have discovered a link between the size of a particular part of the brain and a person’s likelihood to experience a full and active social life.

The part of the brain in question is known as the amygdala, and according to an MGH press release dated December 26, it is a small, almond shaped structure located deep inside the temporal lobe. People have one amygdala in the right side of their brain and another in the left side, and according to the study, which appears in the journal Nature Neuroscience, they are responsible for both the number of social relationships a person has and the complexity of those relationships.

As part of the study, lead researcher Dr. Lisa Feldman Barrett, a member of the MGH Psychiatric Neuroimaging Research Program and a Distinguished Professor of Psychology at Northeastern University, and colleagues polled 58 people between the ages of 19 and 83.

Each participant was asked about the size and complexity of their social networks, including the number of their contacts and the various different cliques they belonged to, and underwent an MRI scan to discern information regarding the size and structure of various parts of the brain, including the amygdala. Those who had more friends and more intricate relationships also had larger amygdala–a phenomenon that has also been observed in other primates.

“We know that primates who live in larger social groups have a larger amygdala, even when controlling for overall brain size and body size,” Barrett said in a statement Sunday. “We considered a single primate species, humans, and found that the amygdala volume positively correlated with the size and complexity of social networks in adult humans.”

“This link between amygdala size and social network size and complexity was observed for both older and younger individuals and for both men and women,” added study participant Dr. Bradford C. Dickerson, a member of the MGH Department of Neurology and an associate professor of Neurology at Harvard Medical School. “This link was specific to the amygdala, because social network size and complexity were not associated with the size of other brain structures.”

According to Guardian Science Correspondent Ian Sample, “The work builds on previous research by Robin Dunbar, director of social and cultural anthropology at Oxford University, who found a theoretical limit to the number of meaningful relationships a person can maintain. The figure is rough but considered to be about 150.”

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