Effects of initial choices in the prisoner's dilemma

In the two-person prisoner's dilemma game (PDG), there is considerable evidence that the tit-for-tat (TFT) strategy is most effective in inducing the other person to cooperate. One of the important features of the TFT strategy is that it cooperates on the first trial. We varied the initial choices of a simulated other, and tested the effects of (a) initial choices (cooperation or defection), and (b) persistence of initial choices: unilateral cooperation (or defection) on the first trial, first two trials, or first four trials. Results showed that a cooperative strategy-one that starts with cooperative choices-induced greater cooperation than a strategy that started with defections. The results of this study clearly show that (a) a cooperative strategy-one that initiates unilateral cooperation at the outset and then adopts a TFT strategy-is very effective in inducing subsequent cooperation from the other party, (b) the effectiveness of a cooperative strategy varies directly with the cooperative orientation of the other party (a cooperative strategy is more effective against a cooperative than a competitive person), and (c) initial cooperation is more effective if it is repeated more than once. Copyright (C) 2002 John Wiley Sons, Ltd.