Early exclusion leads to cyclical cooperation in repeated group interactions

TL;DR

This paper demonstrates that early social exclusion in repeated group interactions can sustain cooperation among selfish individuals by preventing defection, leading to oscillations among strategies and dominance of cooperation.

Contribution

It introduces a model where early exclusion with monitoring costs promotes cooperation and reveals oscillatory dynamics among strategies in repeated interactions.

Findings

Early exclusion prevents cooperation breakdown.

Oscillations among cooperators, defectors, and excluders occur.

Cooperators dominate most of the time with early exclusion.

Abstract

Explaining the emergence and maintenance of cooperation among selfish individuals from an evolutionary perspective remains a grand challenge in biology, economy, and social sciences. Social exclusion is believed to be an answer to this conundrum. However, previously related studies often assume one-shot interactions and ignore how free-riding is identified, which seem to be too idealistic. In this work, we consider repeated interactions where excluders need to pay a monitoring cost to identify free-riders for exclusion and free-riders cannot participate in the following possible game interactions once they are identified and excluded by excluders in the repeated interaction process. We reveal that the introduction of such exclusion can prevent the breakdown of cooperation in repeated group interactions. In particular, we demonstrate that an evolutionary oscillation among cooperators, defectors, and excluders can appear in infinitely large populations when early exclusion is implemented. In addition, we find that the population spends most of the time in states where cooperators dominate for early exclusion when stochastic mutation-selection is considered in finite populations. Our results highlight that early exclusion is successful in solving the mentioned enigma of cooperation in repeated group interactions.