The Prisoners dilemma

The Prisoners dilemma game is conceptualised as a non-cooperative game where all players have complete information. There is no communication.

It encapsulates the 'tragedy of the commons' assumption that people are self-interested.

"Therein is the tragedy. Each man is locked into a system that compels him to increase his herd without limit - in a world that is limited. Ruin is the destination toward which all men rush, each pursuing his own best interest in a society that believes in the freedom of the commons." (Hardin 1968)

So the players in the game are herders using a common grazing meadow. There is a maximum limit to the number of animals that can be grazed on the meadow and be well fed. This is 'x'.

In a two-person game, the cooperate strategy would be to equally share the land with an equal number of cattle grazing. This would be x/2 animals for each herder.

The defect strategy would be for each herder to graze as many animals as possible that could then be sold at profit. This number would be > x/2

Our herders are Sam and Joe.

The game part plays out as follows:

Sam	Joe	Outcome
defect	defect	nil profit
defect	cooperate	Sam gets 11 units of profit, Joe gets -1
cooperate	defect	Joe gets 11 units of profit, Sam gets -1
cooperate	cooperate	Both get 10 units of profit

In this game, the best option for each herder is to maximise their cattle grazing and screw the other herder. This way, the most time you do is 2 years.