HOW TO COPE WITH NOISE IN THE ITERATED PRISONERS-DILEMMA

Noise in the form of random errors in implementing a choice is a commo n problem in real-world interactions. Recent research has identified t hree approaches to coping with noise; adding generosity to a reciproca ting strategy; adding contrition to a reciprocating strategy; and usin g an entirely different strategy, Pavlov, based on the idea of switchi ng choice whenever the previous payoff was low. Tournament studies, ec ological simulation, and theoretical analysis demonstrate (1) a genero us version of tit-for-tat is a highly effective strategy when the play ers it meets have not adapted to noise; (2) if the other players have adapted to noise, a contrite version of tit-for-tat is even more effec tive at quickly restoring mutual cooperation without the risk of explo itation; and (3) Pavlov is not robust.