He started a computer tournament for people to submit prisoner's dilemma strategies and discovered, much to his surprise, that a very, very simple strategy won -- it won the first tournament, and even after everyone knew it won, it won the second tournament -- that's known as tit for tat.
Mise in piedi un torneo al computer dove le persone elaboravano strategie da dilemma del prigioniero, e scoprì, con sua grande sorpresa, che la strategia vincente era molto molto semplice. Vinse il primo torneo, e vinse anche il secondo, benché tutti, ormai, già la conoscessero.