Tit for tat
The Prisoner's Dilemma is a famous thought experiment that illustrates the challenges of cooperation and competition. Imagine two prisoners are arrested for a crime. The police offer each prisoner a deal: if one denounces the other and the other stays silent, the rat will be released, and the other will receive a long sentence. If both accuse each other, they both receive an average sentence. If both are silent, only a short sentence will be received.
The dilemma is that each prisoner is incentivized to denounce the other, even though both would benefit from cooperating and remaining silent. This simulates real-life situations like the Cold War arms race, where each side built weapons out of fear the other would do the same, even though both would be safer with fewer weapons.
In the 1980s, scientist Robert Axelrod organized a computer tournament where different strategies for solving the prisoner's dilemma competed. People submitted programs with names like Jesus, Lucifer, and Tester. Axelrod has received submissions ranging from a few lines of code to tens of thousands.
The simplest strategy, called Tit for Tat, won. It starts with cooperation, then simply copies what the opponent did last time. It therefore rewards cooperation but punishes betrayal, while leaving room for forgiveness. This "nice but retaliatory" strategy has proven effective and parallels real-world strategies such as the "live and let live" system that emerged in World War II trench warfare. The story illustrates how cooperation, reinforced by measured retaliation, can arise, even in difficult conditions.