Back in the early 1960s, the economist Paul Samuelson offered his colleagues a simple bet. He said he would pay $200 for a correct call of a coin toss, but added that he would collect $100 for an incorrect one.

Much laughter followed but none of Samuelson's colleagues was willing to take him up. In economic terms, they all behaved irrationally. But they were more fearful of losing $100 than happy with the thought of gaining $200.