Five Rules for the Evolution of Cooperation

The paper Five rules for the evolution of cooperation seeks to explain some of the conditions under which evolution favours cooperation over defection. It discusses five mechanisms: kin selection, direct reciprocity, indirect reciprocity, network reciprocity, and group selection. Cooperation necessarily involves paying a cost yourself such that someone else receives a benefit. Cooperators, by definition, are willing to pay this cost to help others, while defectors are not. Without any mechanisms for the evolution of cooperation, defectors tend to win over cooperators, as illustrated by the classical prisoner’s dilemma. The paper argues that there are mechanisms which strengthen the strategy of cooperation relative to defection.

The first mechanism is kin selection. Paying a cost to increase the likelihood of a relative reproducing can indirectly help your own genetic success, since you both share genetic material. The second is direct reciprocity. When two individuals meet repeatedly, as in a repeated prisoner’s dilemma, paying a cost to benefit someone else in the present can improve the likelihood that they will reciprocate by paying a cost to help you in the future. The third is indirect reciprocity: helping others because reputation matters. Someone else is more likely to help you in the future if they know that you are helpful, so it pays to develop a reputation of being helpful. The fourth is network reciprocity, where cooperators cluster with other cooperators. Cooperators mostly interact with their neighbours in a network, who are more likely to be cooperators as well. This allows cooperators to benefit each other within their network clusters while limiting exploitation by defectors. The fifth is group selection. While defectors may dominate cooperators within groups, cooperative groups are more likely to dominate selfish groups. There exists an evolutionary bias for cooperative groups relative to selfish groups, even if selfish individuals have an advantage within groups. Although cooperation is naturally unstable, because cooperators pay costs and defectors avoid them, the paper shows that cooperation can evolve when some mechanism makes helping others ultimately beneficial for cooperators too.

I am particularly interested in indirect reciprocity. The concept of reputation and its implications within games seems difficult to define and quantify effectively. It may be possible to expand the mechanism of indirect reciprocity to the group level and even the geopolitical level. The United States took on a role of supporting global development without clear, direct, or immediate benefits in the post-war world order, in policies ranging from the Marshall Plan to USAID. It would be interesting to investigate whether other nations throughout history have adopted similar strategies, and to determine whether these can indeed be classified as strategies of indirect reciprocity.