An anonymous reader writes "People's brains are more responsive to friends than to strangers, even if the stranger has more in common, according to a study in the Oct. 13 issue of The Journal of Neuroscience. Researchers examined a brain region known to be involved in processing social information, and the results suggest that social alliances outweigh shared interests. In a study led by graduate student Fenna Krienen and senior author Randy Buckner, PhD, of Harvard University, researchers investigated how the medial prefrontal cortex and associated brain regions signal someone's value in a social situation. Previous work has shown that perceptions of others' beliefs guide social interactions. Krienen and her colleagues wondered whether these brain regions respond more to those we know, or to those with whom we share similar interests."