Loneliness is processed in the same part of the brain as physical pain.

Now there’s scientific proof that words can indeed hurt you just as much as sticks and stones. In a University of California experiment, volunteers were asked to play a computer game designed to make them feel excluded, while brain scans were taken. During the virtual rejection, activity was detected in an area of the brain linked to physical pain.
The researchers wrote: "Evidence suggests that some of the same neural machinery recruited in the experience of pain may also be associated with social separation or rejection." This study seems to indicate that the average person is wired to need social acceptance.
This explains why people wear something just because everyone else does, why it stings so much to be the last person picked for a dodge ball game, and why people start knitting groups. It indicates that we have an inherent need for the company of others.
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