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==Iterated Prisoner's Dilemma==

==Iterated Prisoner's Dilemma==

The Iterated Prisoner's dilemma is when the basic game is played multiple times (sometimes infinitely many times). Here, co-operation can be a Nash equilibrium. This requires that each player pays attention to what the other player does on previous "rounds", and punish or reward the other player as appropriate. The best strategy in the Iterated Prisoner's dilemma is the "t*t for tat" strategy. The "t*t for tat" strategy is to cooperate the first time and then on all subsequent times the strategy is to do whatever the opponent did on the turn prior to the one you are on.

The Iterated Prisoner's dilemma is when the basic game is played multiple times (sometimes infinitely many times). Here, co-operation can be a Nash equilibrium. This requires that each player pays attention to what the other player does on previous "rounds", and punish or reward the other player as appropriate. The best strategy in the Iterated Prisoner's dilemma is the "tit for tat" strategy. The "tit for tat" strategy is to cooperate the first time and then on all subsequent times the strategy is to do whatever the opponent did on the turn prior to the one you are on.

An additional strategy that is often followed and debated is the "Grim Trigger": that is to say, cooperate until the first defection, and from then on out, defect every turn.  Grim Trigger tends to work only when there is informational exchange.

An additional strategy that is often followed and debated is the "Grim Trigger": that is to say, cooperate until the first defection, and from then on out, defect every turn.  Grim Trigger tends to work only when there is informational exchange.