Magical Thinking

But that doesn't mean we're good at evaluating sources of contagion. Nemeroff found that people draw the germs of their lovers as less scary-looking than those of enemies, and they say those germs would make them less ill. She also found that undergrads base condom usage on how emotionally safe they feel with a partner more than on objective risk factors for catching STDs.

2. Anything can be cursed.

Essences are not always good. In fact, people show stronger reactions to negative taint than to positive. Mother Teresa cannot fully neutralize the evil in a sweater worn by Hitler, a fact that fits the germ theory of moral contagion: A drop of sewage does more to a bucket of clean water than a drop of clean water does to a bucket of sewage. Traditional cleaning can't erase bad vibes either. Studies by Rozin and colleagues show that people have a strong aversion to wearing laundered clothes that have been worn by a murderer or even by someone who's lost a leg in an accident.

Magical contagion can also flow in reverse. Many people wouldn't want an AIDS patient taking over a hospital bed that they had just left, and about a third of undergrads would feel uncomfortable if an enemy possessed their used hairbrush. "This rests on the assumption that there is no separation of space and time," Nemeroff says. "The hairbrush and I were in contact, we merged. At that mystical level where all is one, acting on it is acting on me."

3. Mind rules over matter.

Wishing is probably the most ubiquitous kind of magical spell around, the unreasonable expectation that your thoughts have force and energy to act on the world. Who has not resisted certain thoughts for fear of jinxing oneself? Made a wish while blowing out birthday candles? Tried to push a field goal fair mid-flight using nothing but hope and concentration?

Emily Pronin and colleagues at Princeton and Harvard convinced undergrads in a study that they had put voodoo curses on fellow subjects. While targeting their thoughts on the other students, hexers pushed pins into voodoo dolls and the "victims" feigned headaches. Some victims had been instructed to behave like jackasses during the study (the "Stupid People Shouldn't Breed" T-shirt was a nice touch), eliciting ill will from pin pushers. Those who dealt with the jerks felt much more responsible for the headaches than the control group did. If you think it, and it happens, then you did it, right? Pronin describes the results as a particular form of seeing causality in coincidence, where the "cause" is especially conspicuous because it's hard to miss what's going on in your own head.

4. Rituals bring good luck.

Whenever I fly, I place my hands on the fuselage as I step onto the plane. The habit began when I was a kid innocently in awe of flying machines, but over the years as I continued to touch the plane and continued to not die horribly, my brain decided I was keeping the apparatus aloft, and now I do it for peace of mind.

To witness the mindless repetition of actions with no proven causal effect, there's no better laboratory than the athletic field. The anthropologist George Gmelch of Union College in Schenectady has paid close attention to the elaborate dances players do during baseball games. Because performance while hitting and pitching is so unpredictable (compared to fielding), most behavioral tics occur on the mound or at the plate. Mike Hargrove was nicknamed "the human rain delay" because of his obsessive shenanigans while at bat. B.F. Skinner famously showed "superstition" in pigeons by locking them in a box, feeding them at regular intervals, and watching them associate random behaviors with food rewards, eventually building up intricate routines of behavior. When you combine kicking dirt and readjusting your helmet with strikes and home runs, you can see how the batter's box would quickly become an open-air Skinner box.

We use ritual acts most often when there is little cost to them, when an outcome is uncertain or beyond our control, and when the stakes are high—hence my communion with the fuselage. People who truly trust in their rituals exhibit a phenomenon known as "illusion of control," the belief that they have more influence over the world than they actually do. And it's not a bad delusion to have—a sense of control encourages people to work harder than they might otherwise. In fact, a fully accurate assessment of your powers, a state known as "depressive realism," haunts people with clinical depression, who in general show less magical thinking.