Knocking on wood is meant to be good luck because benevolent spirits were thought to live in trees and thus knocking on anything made of wood is meant to protect you from misfortune. Crossing your fingers is meant to be good luck because you make the sign of the cross and thus prevent evil spirits from harming you. However, I have no idea why a robin flying into your house is meant to be lucky - unless it's an excuse for poor housekeeping.

In ancient Egypt the goddess Bast was in the form of a female, black cat. When the Christian priests wanted to remove all traces of other religions, they asked their followers to destroy black cats. Unfortunately, those who had black cats were thought to be witches and were destroyed too. I think that proves black cats are unlucky.

Before gallows were invented, criminals were hung from the top rung of a ladder and their spirits were believed to linger underneath. That's why it's meant to be unlucky to walk under a ladder. I disagree. I think it's unlucky to climb a ladder and more than 222,000 people agree with me. That's how many people a year go to emergency rooms because of ladder accidents - and that's not counting the women who hit their heads on glass ceilings when trying to climb ladders.

A mandala is a design made with rice powder. In India the woman of the house is meant to put a mandala on the front doorstep every morning to ward off evil spirits. Today making mandalas is a dying art. It's not because the women don't have enough time for the ritual. It's because today's Indian women have moved into cities and don't have doorsteps.

Then there's the superstition about hanging a horseshoe over a door. Niels Bohr, winner of the Nobel Prize for physics in 1922 for his contribution to the understanding of atomic structure, hung a horseshoe over the door to his lab. When he was asked if he believed it would bring him luck, he said no. However, he also said he'd been told it would work whether he believed it or not.