Martin Nowak and Cooperation

Martin A. Nowak, the master of the spatial games published two years ago a book, entitled "Evolutionary Dynamics: Exploring the Equations of Life" (Belknap Press, 2006). We remark some references by Nowak about cooperation in this book.

According to Nowak, experimental game theory shows that humans do not behave rationally. They are guided by instincts that might have evolved via different situations. In the Prisoner´s Dilemma, humans often try to cooperate. Cooperation means not to cooperate with the state attorney but to cooperate with your partner and remain silent. If both of you defect, both will get a long prison sentence. No matter what your partner does, it is better for you to defect. The rational analysis suggests that both prisoners will confess and spend a long time in jail. Defector always have a higher fitness than cooperators. Natural selection increases the frequency of defectors until cooperators have become extinct. But cooperation becomes a promising option when the game is repeated several times between the same two players. Consider a strategy in which an agent cooperates on the first move and then cooperates as long as the opponent does not defect. If the opponent defects once it will switch permanently to defection and it will never forgive. This strategy is a strict Nash equilibrium versus a strategy consisting in always defect. In terms of evolutionary dynamics, if the whole population uses the first strategy, then the second one cannot invade. Obviously, human strategic instincts are not formed by playing games with a well-defined number of rounds. In the lifetime there might always be another round. There is always a tomorrow in our plans.