Wahl L M, Nowak M A
Institute for Advanced Study, Olden Lane, Princeton, NJ, 08540, USA.
J Theor Biol. 1999 Oct 7;200(3):307-21. doi: 10.1006/jtbi.1999.0996.
We present a general model for the Prisoner's Dilemma in which variable degrees of cooperation are possible, and payoffs are scaled accordingly. We describe a continuous strategy space, and divide this space into strategy families. We derive the payoff function for these families analytically, and study the evolutionary outcome when a wide range of strategies play against each other. Our results show that the initial degree of cooperation offered by a strategy is a decisive factor for evolutionary robustness: the most successful strategies in our model offer full cooperation as an initial move, but thereafter cooperate fully only if their opponent does the same. These strategies gradually raise the stakes when playing a strategy which is initially reticent to cooperate, but differ from the strategies predicted by other continuous models in that they are not only generous, but are also consistently optimistic and uncompromising.
我们提出了一种囚徒困境的通用模型，其中合作程度可变，收益也相应地进行了缩放。我们描述了一个连续的策略空间，并将这个空间划分为策略族。我们通过解析得出这些策略族的收益函数，并研究当多种策略相互对抗时的进化结果。我们的结果表明，一种策略所提供的初始合作程度是进化稳健性的决定性因素：在我们的模型中最成功的策略以完全合作作为初始行动，但此后只有当其对手也这样做时才会完全合作。当与最初不愿合作的策略博弈时，这些策略会逐渐提高赌注，但与其他连续模型预测的策略不同的是，它们不仅慷慨，而且始终乐观且毫不妥协。
