Equitable governance of common goods

 The bulk of EEP's work in this area is theoretical, and applies the mathematical techniques of evolutionary game theory and adaptive-dynamics theory. In addition, an experimental study has been completed investigating social choice between different types of social contracts (Zhang et al., in revision).

In an article published in the Proceedings of the National Academy of Sciences of the USA (PNAS), the impact of voluntary participation in public good games has been investigated (Sasaki et al., 2012b). The study shows that positive incentives (rewards) cannot engender full cooperation at reasonable institutional cost, while negative incentives (penalties) can do so under compulsory participation only when a group’s initial level of cooperation is already high, implying a social trap (Figure 3 ). The study’s main result is that such social traps can be overcome, and full cooperation be established at surprisingly modest institutional cost, when negative incentives are combined with voluntary participation.

Evolution of cooperation in public-good games with compulsory participation and incentives. (a) Very small incentives cannot take a group away from full defection (D). (d) Very large incentives establish full cooperation (C), but are inefficiently costly. (b) Intermediate positive incentives (rewarding) can establish merely partial cooperation, while (c) intermediate negative incentives (punishing) lead to bistability: when the group’s initial level of cooperation is high, the incentives engender full cooperation, whereas when the group’s initial level of cooperation is low, it collapses to full defection despite the incentives. The latter effect is known as a social trap and fundamentally impedes the evolution of cooperation.

Similar issues arise in efforts directed at curbing corruption (Lee et al., in preparation). A related study has analyzed the impact of social exclusion, an approach frequently used in human interactions (Sasaki and Uchida, 2013). Variable group sizes also play a role for synergistic interactions in microbial population (Cornforth et al., 2012), and also occur when agents in wellmixed populations use reputation information to decide whether or not to interact with other agents: in the latter case, cooperation is maximized when the agents employ optimal tolerance levels (Chen et al., 2012b). Various approaches to indirect reciprocity based on reputation information were compared in an article by Sigmund (2012).

Studies of cooperation evolution in spatially structured groups of agents have examined the “win-stay, lose-shift” principle (Liu et al., 2012b), adaptive cooperative investments (Chen et al., 2012a), different learning rules and local information for resolving local social dilemmas (Wang et al., 2012b), successdriven migration and its sometimes counter-intuitive consequences (Liu et al., 2012a), probabilistic connections among agents (Wang et al., 2012a), and generalized benefit functions in spatial public goods games with continuous strategies (Chen et al., 2012e). A canonical equation for adaptive dynamics with interaction structure was derived by Allen et al. (2013) and applied to social dilemmas; this has revealed how cooperation levels vary with the so-called structure coefficient characterizing the social dynamics in a group of interacting agents.

Offering important models for understanding anthropogenic ecological hazards, EEP has studied collective-risk dilemmas (Chen et al., 2012c). In this context, risk-driven migration has been shown to provide an efficient strategy for boosting cooperation (Chen et al., 2012d). The latter study also shows that if the joint goal in a collective-risk dilemma is overambitious, a relatively weak feedback between group performance and risk level is socially optimal.

For the Encyclopedia of Theoretical Ecology, Sigmund and Hilbe (2012) have been invited to contribute a survey article on game theory. 

Last edited: 31 October 2013