In replying to an earlier post Set referred me to the wikipedia website at http://en.wikipedia.org/wiki/Game_theory where I found the following...

"In game theory, the prisoner's dilemma is a type of non-zero-sum game in which two players can "cooperate" with or "defect" (i.e. betray) the other player. In the classic form of this game, cooperating is strictly dominated by defecting, so that the only possible equilibrium for the game is for all players to defect. In simpler terms, no matter what the other player does, one player will always gain a greater payoff by playing defect. Since in any situation playing defect is more beneficial than cooperating, all rational players will play defect."

I suppose we should all be grateful that the evidence from California is that when it comes to the crunch we behave irrationally and co-operate!
Chris