Social networks in the amygdala

The size of the amygdala in the brain correlates with the size and complexity of people’s social networks, reports a study published this week in Nature Neuroscience. These findings add to previous studies which suggest that the amygdala is important for social behaviour. Lisa Feldman Barrett and colleagues asked participants to complete standard questionnaires which measured the total number of regular contacts that each participant maintained, as well the number of different social groups these contacts belonged to. These measures correspond to the size and the complexity of social networks. Participants also received a magnetic resonance imaging brain scan — which provides information about the structure of the brain — to measure the size of the amygdala. Factoring in the age of participants and the total size of the brain, the authors found significant differences in the size of the amygdala in participants with larger and more complex social networks. Feldman Barrett and colleagues found that there is no correlation between social network size and the size of another comparable brain structure, the hippocampus. These results suggest that the human amygdala may have evolved partially to deal with an increasingly complex social life.