Evolutionary consequences of behavioral diversity

TL;DR

This paper investigates how increased behavioral diversity in iterated social games influences evolutionary dynamics, revealing complex effects on cooperation stability, fitness landscapes, and strategy invasibility in finite populations.

Contribution

It demonstrates that greater behavioral choices can both promote and hinder cooperation, and that multi-choice strategies tend to invade populations, expanding understanding beyond binary strategies.

Findings

Some two-choice strategies resist invasion by multi-choice strategies.

Greater behavioral diversity creates rugged fitness landscapes with multiple stable cooperation levels.

Multi-choice strategies can invade and resist invasion, promoting behavioral diversity.

Abstract

Iterated games provide a framework to describe social interactions among groups of individuals. Recent work stimulated by the discovery of "zero-determinant" strategies has rapidly expanded our ability to analyze such interactions. This body of work has primarily focused on games in which players face a simple binary choice, to "cooperate" or "defect". Real individuals, however, often exhibit behavioral diversity, varying their input to a social interaction both qualitatively and quantitatively. Here we explore how access to a greater diversity of behavioral choices impacts the evolution of social dynamics in finite populations. We show that, in public goods games, some two-choice strategies can nonetheless resist invasion by all possible multi-choice invaders, even while engaging in relatively little punishment. We also show that access to greater behavioral choice results in more "rugged " fitness landscapes, with populations able to stabilize cooperation at multiple levels of investment, such that choice facilitates cooperation when returns on investments are low, but hinders cooperation when returns on investments are high. Finally, we analyze iterated rock-paper-scissors games, whose non-transitive payoff structure means unilateral control is difficult and zero-determinant strategies do not exist in general. Despite this, we find that a large portion of multi-choice strategies can invade and resist invasion by strategies that lack behavioral diversity -- so that even well-mixed populations will tend to evolve behavioral diversity.