Another interesting expansion of the basic model is to include strategies that consider both the recipient’s and the donor’s image score. We explored two types of strategies. ‘And’ strategies involve cooperation if the image score of the recipient is larger than a certain value and the image score of the donor is less than a certain value. The idea is that if an individual has already a high image score, it is not necessary to aim for a still higher image score (by helping others). On the other hand, ‘or’strategies result in cooperation if the image score of the recipient is larger than a certain value or the image score of the donor is less than a certain value. Here the idea is that if an individual has a low image score it may be advantageous to increase the score by helping others regardless of how low their image score is. In both cases, highly cooperative societies form (Fig 4). If, in contrast, we simulate strategies that only consider their own image and do not take into account the image of the recipient, cooperation does not emerge.

XREF: Connects to indirect reciprocity and reputation-based cooperation work in evolutionary game theory. Builds on: "A minimum number of rounds per generation is needed for cooperation to prevail."

Nowak, M. A., & Sigmund, K, Evolution of Indirect Recip…, loc. 73