Why is it that Tony Blair always wore the same pair of shoes when answering Prime Minister's Questions? That John McEnroe notoriously refused to step on the white lines of a tennis court between points? And that President-elect Barack Obama played a game of basketball the morning of his victory in the Iowa primary, and continued the tradition the day of every following primary? Superstitious habits are common. Do you ever cross your fingers, knock on wood, avoid walking under ladders, or step around black cats? Sentimental value often supersedes material worth. If someone offered to replace your childhood teddy bear or wedding ring with a brand new, exact replica, would you do it? How about 20 for trying on a jumper owned by Fred West? Where do such feelings come from and why do most of us have them? Humans are born with brains designed to make sense of the world and that need for an explanation can lead to beliefs that go beyond reason. To be true they would have to be supernatura