Christoph Hauert, at the Program for Evolutionary Dynamics at Harvard (update: now at British Columbia), and colleagues have a recent paper which addresses the “second order social dilemma” that arises from cooperators who may free-ride by failing to engage in the costly punishment of defectors in public goods games. Here, they consider four strategies, 1) nonparticipation, 2) participators who defect, 3) participators who cooperate, but fail to punish defectors, and 4) participators who cooperate and engage in costly punishment of defectors.
Noting that cooperative behavior in many joint enterprises that can be characterized as public goods games is enforced through institutions that impose sanctions on defectors, and that in the absence of such institutions, individuals are generally willing to engage in punishment of defectors, even when costly, they ask how this costly punishing behavior may have become established in the first place. It turns out that the ability to choose not to participate is key. Their findings suggest that circumstances where the engagement in the joint enterprise is voluntary are more likely to promote cooperation than those where participation is mandatory. The paper is available here.
Christoph Hauert, Arne Traulsen, Hannelore Brandt, Martin A. Nowak, and Karl Sigmund, Via Freedom to Coercion: The Emergence of Costly Punishment, 316 Science 1905-1907 (2007).