Ethnocentrism: Strategy for winning a large scale Prisoner's Dilemma game

We decided to play the prisoner’s dilemma game on a large population scale and thus find out what is the best possible strategy for the game, given certain conditions. It is a tough task to infer any trends by observing Nature because the biological processes that we need to observe have a large time-scale. For this reason, we write certain computer programs based on theoretical models, run these, and get approximate results. We try to analyse these results and find their implications.

In NetLogo, there’s already an available library model-program on ethnocentrism that we may run. The place where all the events happen is called the playground. It has a grid-pattern, and individuals are randomly distributed among these grids. There are four kinds of individuals, each denoted by a symbol:

1.Altruists: they co-operate with everybody
2.Ethnocentrists: they co-operate only with the individuals who have a certain cognitive tag indicating that both of them belong to the same ethnic group. Or else, they defect.
3.Defectors: they defect everyone, no matter who.
4.Cosmopolitans: they have a strange behaviour- they defect individuals of the same etnic group but co-operate with those of others

Each individual interacts with each of its four neighbours based on its strategy in the prisoner’s dilemma game. So who will win this game?
After running the program several times, we concluded that ethnocentrism dominates.

Why is it so?

From our prior discussions on myxobacteria, we know that co-operation among individuals of the same species tends to increase the reproductive potential. Thus, altruists and ethnocentrists would have the best chances of dominating due to high reproductive potential. This holds, given that there are not too many defectors and cosmopolitans to take advantage of the co-operation. However, this scenario does not arise. The count of defectors in the population is low due to their inherently low reproductive potential. The number of cosmopolitans is even lower since they defect their own ethnic group and help other ethnic group(s).

In the case of altruists and ethnocentrists, there is co-operation within the ethnic group. However, when ethnocentrists come face-to-face with altruists, it is ethnocentrism that wins because ethnocentrists get extra benefit by defecting the co-operative altruists. Moreover, ethnocentrists fare better with the defectors of other ethnic groups by defecting them, unlike the altruists.

Thus, ethnocentrism is, logically, the best strategy in this game. Indeed it is a logical conclusion that the success of an ethnic group should stem from these two factors: how much co-operation there is within the group, and how much the group members can exploit individuals from other groups for their own benefit.