Lucky pennies, four-leaf clovers, horseshoes—it turns out believing in them isn't totally kooky. In a study at Germany's University of Cologne, researchers asked superstitious participants to play a computer game; half got to keep their charms, half had to play without them. The participants who played with their jujus performed better than the others. The simple, non-hocus-pocus explanation: confidence. Your charm makes you believe you'll do well, and believing improves your game.