Tit for tat is an English saying meaning "equivalent retaliation". It is also a highly effective strategy in game theory for the iterated prisoner's dilemma. The strategy was first introduced by Anatol Rapoport in Robert Axelrod's two tournaments, held around 1980. Notably, it was (on both occasions) both the simplest strategy and the most successful.
An agent using this strategy will first cooperate, then subsequently replicate an opponent's previous action. If the opponent previously was cooperative, the agent is cooperative. If not, the agent is not. This is similar to superrationality and reciprocal altruism in biology.
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Famous quotes containing the word tat:
“Older women can afford to agree that femininity is a charade, a matter of coloured hair, écru lace and whalebones, the kind of slap and tat that transvestites are in love with, and no more.”
—Germaine Greer (b. 1939)