This paper offers a new and robust model of the emergence and persistence of cooperation. In the model, interactions are anonymous, the population is well-mixed, and the evolutionary process selects strategies according to material payoffs. The cooperation problem is modelled as a game similar...

Indirect reciprocity is generally considered one of the leading mechanisms to explain how cooperation may emerge by natural selection. The basic intuition is that establishing a reputation of being a helpful individual increases the probability of being in turn helped. Two models have been...

The objective of this paper is to illustrate a potential problem in Samaritan's dilemmas: that Samaritans have a vested interest in encouraging parasitism. In effect, they gain from their altruism. To demonstrate this result, we show that the Nash equilibrium in a Samaritan's dilemma is a Pareto...