Freedom to choose between public resources promotes cooperation

As cooperation incurs a cost to the cooperator for others to benefit, its evolution seems to contradict natural selection. How evolution has resolved this obstacle has been among the most intensely studied questions in evolutionary theory in recent decades. Here, we show that having a choice between different public resources provides a simple mechanism for cooperation to flourish. Such a mechanism can be at work in many biological or social contexts where individuals can form different groups or join different institutions to perform a collective action task, or when they can choose between collective actions with different profitability. As a simple evolutionary model suggests, defectors tend to join the highest quality resource in such a context. This allows cooperators to survive and out-compete defectors by sheltering in a lower quality resource. Cooperation is maximized, however, when the qualities of the two highest quality resources are similar, and thus, they are almost interchangeable.Author summary: How is selfishness curbed in many biological populations to solve collective action problems? A simple answer to this question arises by noting that, in many populations, individuals can join different groups to perform a collective action task. Similarly, individuals often face situations where they can join different collective action tasks with different profitability. As we show here, this provides a natural mechanism for solving collective action problems. In such contexts, defectors predominantly join the higher quality public resource. This enables cooperators to survive and out-compete defectors by working cooperatively in a lower quality resource. However, cooperation is maximized when different public resources have similar qualities, and thus, similar attractiveness for the individuals.