Implications of Reciprocity in the Evolution of Ethnocentrism and Cooperation

Background: Ethnocentrism is defined as an individual’s tendency to favor in-group members at the expense of out-group members. Recent computer simulations have studied its evolution by modelling cooperative and defective behaviours in a Prisoner’s Dilemma framework. Methods: This paper introduces reciprocity to the study of ethnocentrism and extends Hammond and Axelrod’s agent-based model by simulating the effects of five new genotypic strategies. (1) Results: In stable-state outcomes, although ethnocentrism still dominates, moderate ethnocentrism (in-group cooperation and out-group reciprocity) is more frequent than humanitarianism and is by far the most adaptive out of all reciprocal strategies. Because it is the only reciprocal strategy that cooperates with in-group members, we conclude that it is thanks to in-group cooperation that moderate ethnocentrism is successful, which confirms previous research findings. Additionally, throughout early and late evolutionary patterns, we see that moderate ethnocentrism benefits and suffers from the characteristics of both ethnocentrism and humanitarianism, which may explain why ethnocentrism still emerges as the dominant strategy overall. Conclusion: The strengths of the present model lie in its ability to abstractly model reciprocal behaviours in the study of ethnocentrism and may be more externally valid than Hammond and Axelrod’s original agent-based model. (1) However, this model does not take in account other factors that play a role in human decision-making, such as social context, learning, or development, which could be topics of future computational simulations on ethnocentrism.