Small groups and long memories make for cooperation

At Phys.org:

In a new paper, published in the journal Scientific Reports, University of Pennsylvania researchers use game theory to demonstrate the complex set of traits that can promote the evolution of cooperation. Their analysis showed that smaller groups in which actors had longer memories of their fellow group members' actions were more likely to evolve cooperative strategies.

The work suggests one possible advantage of the human's powerful memory capacity: it has fed our ability as a society to cooperate.

"In the past we've looked at the interactions of two players to determine the most robust evolutionary strategies," said Joshua B. Plotkin, a professor in Penn's Department of Biology in the School of Arts & Sciences. "Our new analysis allows for scenarios in which players can react to the behaviors and strategies of multiple other players at once. It gives us a picture of a much richer set of social interactions, a picture that is likely more representative of the complexities of human behavior."

For the original researh: Alexander J. Stewart et al, Small groups and long memories promote cooperation, Scientific Reports (2016). DOI: 10.1038/srep26889

Abstract: Complex social behaviors lie at the heart of many of the challenges facing evolutionary biology, sociology, economics, and beyond. For evolutionary biologists the question is often how group behaviors such as collective action, or decision making that accounts for memories of past experience, can emerge and persist in an evolving system. Evolutionary game theory provides a framework for formalizing these questions and admitting them to rigorous study. Here we develop such a framework to study the evolution of sustained collective action in multi-player public-goods games, in which players have arbitrarily long memories of prior rounds of play and can react to their experience in an arbitrary way. We construct a coordinate system for memory-m strategies in iterated n-player games that permits us to characterize all cooperative strategies that resist invasion by any mutant strategy, and stabilize cooperative behavior. We show that, especially when groups are small, longer-memory strategies make cooperation easier to evolve, by increasing the number of ways to stabilize cooperation. We also explore the co-evolution of behavior and memory. We find that even when memory has a cost, longer-memory strategies often evolve, which in turn drives the evolution of cooperation, even when the benefits for cooperation are low.