And the belief that you can feel someone staring at you from behind? Someone who sees you suddenly pivot is likely to return your stare, leading to the false conclusion that you did detect the gaze. Thanks to "confirmatory bias," people tend to remember every time a hunch like this—or like the idea that the phone rings after you think about someone—is borne out. We forget all those times it isn't.

As scientists probe deeper into the brain for what underlies superstition, they have found a surprising suspect: dopamine, which usually fuels the brain's sense of reward. In one study, two groups of people, either believers in the supernatural or skeptics, looked at quickly displayed images of faces and scrambled faces, real words and nonwords. The goal was to pick out the real ones. Skeptics called more real faces nonfaces, and real words nonwords, than did believers, who happily saw faces and words even in gibberish. But after the skeptics were given L-dopa, a drug that increases dopamine, their skeptical threshold fell, and they ID'd more faces and words as real. That suggests that dopamine inclines the brain to see patterns even in random noise. Boo!

© 2007