Watching the brain think about friends.

Work from Wlodarski and Dunbar (open source) produces imaging data suggesting that maintaining friendships may be more cognitively exacting than maintaining kin relationships. The graphics of imaging showing differences in kin versus friend processing are very nice. Their introduction offers background on the cognitive underpinnings for managing different types of relationships having varying degrees of closeness. Their abstract:

The aim of this study was to examine differences in the neural processing of social information about kin and friends at different levels of closeness and social network level. Twenty-five female participants engaged in a cognitive social task involving different individuals in their social network while undergoing functional magnetic resonance imaging scanning to detect BOLD (Blood Oxygen Level Dependent) signals changes. Greater levels of activation occurred in several regions of the brain previously associated with social cognition when thinking about friends than when thinking about kin, including the posterior cingulate cortex (PCC) and the ventral medial prefrontal cortex (vMPFC). Linear parametric analyses across network layers further showed that, when it came to thinking about friends, activation increased in the vMPFC, lingual gyrus, and sensorimotor cortex as individuals thought about friends at closer layers of the network. These findings suggest that maintaining friendships may be more cognitively exacting than maintaining kin relationships.