(SOUNDBITE OF KNOCKING ON WOOD)
SCOTT SIMON, HOST:
Knocking wood - sheer superstition, right? That doesn't mean that it doesn't work, kind of, sort of, maybe. Researchers at the University of Chicago's Booth School of Business have found that knocking wood, spilling salt, and other old medieval gestures might actually help people expel some of the fear they have that they've done or said something that could invite bad luck. Dispelling that stress might help them avoid what they dread. Or as Jane Risen, Ph.D., one of the researchers, wrote in the Journal of Experimental Psychology: General, quote, "We find that avoidant actions that exert force away from one's representation of self are especially effective for reducing the anticipated negative consequences following a jinx." Perhaps it wasn't necessary to say Ph.D. Now, one theory holds that knocking wood began in the Middle Ages when people went into the forests and knocked on trees to keep evil spirits from hearing private conversations. Of course, this is before the NSA started tapping leaves. Break a leg. Transcript provided by NPR, Copyright NPR.