If you expose pidgeons to intermittent random reward, you can observe the birth of supersticion: the animal will try to correlate the most disparate things to the reward. I long thought this was the kind of mechanism underlying human supersticions, but now it seems more likely that it can also be a self counterfactual mugging: if I open an umbrella in the house, I'm inviting death inside (I don't know if this belief exists outside Italy). Inviting death has such a bigger disutility that even in the tiny probability that the supersticion is real you're better not opening an umbrella in your house.