You know the joke/true story (?) : A friend of Niels Bohr notices a horseshoe nailed on his door. When Niels opens up his friend asks : - you, one of the great

You know the joke/true story (?) : A friend of Niels Bohr notices a horseshoe nailed on his door. When Niels opens up his friend asks : - you, one of the greatest scientist of this century how could you believe in such things. - Well I've been told that superstition works even if you don't believe in it ! Incidentally a recent study seems to demonstrate that the placebo effect works even when you know it's placebo...