It's all in the size of your amygdalae, small almond-shaped portions of the brain nestled within the temporal lobe, say scientists who conducted the study using 58 participants. They concluded that the amygdala's size can predict just how social anyone will be, regardless of age or gender.
"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," says the leader of the study, Lisa Feldman Barrett, PhD, a professor at Northwestern University,
Another one of the scientists conducting the study says its results are consistent with the "social brain hypothesis," the notion that the human brain evolved to adapt to increasingly complex social structures.