The political scientist Robert Axelrod invited experts to submit computer programs that played a repeated game, the Prisoner’s Dilemma, in which each player chooses to cooperate or to betray. “I ran the fourteen entries and a random rule against each other in a round robin tournament,” he wrote.
The winner was a very simple strategy called “tit for tat,” sent in by Anatol Rapoport. In Axelrod’s words, it was “merely the strategy of starting with cooperation, and thereafter doing what the other player did on the previous move.” Axelrod published the results in 1980. His book The Evolution of Cooperation followed in 1984.