Consider the last example for a moment. Expensive commercial courses have long been promoted to teach people to walk barefoot on hot coals. (Why anyone would want to do this is itself an interesting question.) Firewalkers supposedly protect their feet with a technique called “neurolinguistic programming.” Many people have paid good money to learn the technique, and most do manage a quickwalk on the coals. But is the technique necessary? And is anything remarkable happening? We need a comparison group.