Mathematicians called game theorists often program computers to run game after game of Prisoner’s Dilemma, recording the acts of both Charlie and Al in each round. By programming each of the players to respond to defection and cooperation in a variety of ways, game theorists began to discover some definite response patterns that resulted in better survival.
One of these successful patterns was “tit for tat” – in other words, Charlie cooperates with Al unless Al snitches on Charlie; in which case Charlie retaliates by defecting in the next round, and only gradually puts more trust in Al as Al proves his trustworthiness. But if Charlie has the chance to snitch on a prisoner he may never see again – let’s call this guy Vito – then Charlie has no reason not to defect on Vito. The decision of whether or not to defect on old Al, on the other hand, would consider cooperation a much more reasonable option.
However, this new study provides a revolutionary Prisoner’s Dilemma strategy. A team led by psychologists Andrew Delton and Max Krasnow of the University of California, Santa Barbara showed mathematically that cooperation was a more evolutionarily stable strategy regardless of whether or not an agent reasoned that it would encounter the same partner again. Even when the likelihood was more than 90 percent that Charlie would never see Vito again, he still tended to cooperate.
This stands in stark contrast to those earlier mathematical models, which tended to predict that the best strategy is to be generous with one’s regular reciprocal partners, but selfish in one-time-only interactions. Instead, this research shows that the cost/benefit ratio for both these kinds of generosity is about the same.
If the researchers are right, this means that generosity has a strong tendency to co-evolve with social cooperation.
It’s also interesting to note that this model predicts the same sort of generosity regardless of the size of the group – what’s important isn’t how likely you are to meet the same person again, but simply that there is a chance, however slight, that they might help you in the future. But even if they don’t, it costs nothing to be nice.