Interesting little blurb that they found a spot in a woman's brain that made her feel like someone was following her. They're suggesting that a brain problem in this area might cause paranoia and lead to people divising improbable conspiracy theories. (Ok, I made up that last part)

http://www.newscientist.com/article/mg19125704.500-activating-the-feeling-of-being-followed.html

The predictable patterns of behavior with mentally un healthy individuals denotes some physiological sources.

Which then implies also that many mentally healthy behaviors are physiological in origin.