Why do some decision makers prefer big multilateral agreements while others prefer cooperation in small clubs? Does enforcement encourage or deter institutional cooperation? We use experiments drawn from behavioral economics and cognitive psychology-along with a substantive survey focused on international tradeto illustrate how two behavioral traits (patience and strategic reasoning) of individuals who play key roles in negotiating and ratifying an international treaty shape their preferences for how treaties are designed and whether they are ratified. Patient subjects were more likely to prefer treaties with larger numbers of countries (and larger long-term benefits), as were subjects with the skill to anticipate how others will respond over multiple iterations of strategic games. The presence of an enforcement mechanism increased subjects' willingness to ratify treaties; however, strategic reasoning had double the effect of adding enforcement to a trade agreement: more strategic subjects were particularly likely to favor ratifying the agreement. We report these results for a sample of 509 university students and also show how similar patterns are revealed in a unique sample of ninety-two actual US policy elites. Under some conditions certain types of university student convenience samples can be useful for revealing elite-dominated policy preferences-different types of people in the same situation may prefer to approach decisionmaking tasks and reason through trade-offs in materially different ways.What determines preferences for international legal cooperation? What determines how decision makers prefer to design or whether they aspire to ratify international

One of the best-known and most replicated laboratory results in behavioral economics is that bargainers frequently reject low offers, even when it harms their material self-interest. This finding could have important implications for international negotiations on many problems facing humanity today, because models of international bargaining assume exactly the opposite: that policy makers are rational and self-interested. However, it is unknown whether elites who engage in diplomatic bargaining will similarly reject low offers because past research has been based almost exclusively on convenience samples of undergraduates, members of the general public, or small-scale societies rather than highly experienced elites who design and bargain over policy. Using a unique sample of 102 policy and business elites who have an average of 21 y of practical experience conducting international diplomacy or policy strategy, we show that, compared with undergraduates and the general public, elites are actually more likely to reject low offers when playing a standard "ultimatum game" that assesses how players bargain over a fixed resource. Elites with more experience tend to make even higher demands, suggesting that this tendency only increases as policy makers advance to leadership positions. This result contradicts assumptions of rational self-interested behavior that are standard in models of international bargaining, and it suggests that the adoption of global agreements on international trade, climate change, and other important problems will not depend solely on the interests of individual countries, but also on whether these accords are seen as equitable to all member states.self-interest | bargaining | elites | ultimatum game | game theory

Centralized sanctioning institutions have been shown to emerge naturally through social learning, displace all other forms of punishment and lead to stable cooperation. However, this result provokes a number of questions. If centralized sanctioning is so successful, then why do many highly authoritarian states suffer from low levels of cooperation? Why do states with high levels of public good provision tend to rely more on citizen-driven peer punishment? Here, we consider how corruption influences the evolution of cooperation and punishment. Our model shows that the effectiveness of centralized punishment in promoting cooperation breaks down when some actors in the model are allowed to bribe centralized authorities. Counterintuitively, a weaker centralized authority is actually more effective because it allows peer punishment to restore cooperation in the presence of corruption. Our results provide an evolutionary rationale for why public goods provision rarely flourishes in polities that rely only on strong centralized institutions. Instead, cooperation requires both decentralized and centralized enforcement. These results help to explain why citizen participation is a fundamental necessity for policing the commons.A centuries-old debate exists on how to best govern society and promote cooperation: is cooperation best maintained by a central authority [1,2] or is it better handled by more decentralized forms of governance [3,4]? The debate is still unresolved, and identifying mechanisms that promote cooperation remains one of the most difficult challenges facing society and policymakers today [4].Decentralized, individual sanctioning of non-cooperators (also known as free-riders or defectors) is one of the main tools used by societies to promote and maintain cooperation [5]. Individuals can sanction free-riders implicitly via behavioural reciprocity (as in the case of the highly successful tit-for-tat strategy [6]) or explicitly via costly punishment [7]. Both of these forms of peer punishment have been widely studied using evolutionary models and behavioural experiments [8][9][10]6,11].Recently, however, Sigmund et al. [12] showed that centralized institutions can have an evolutionary advantage over peer punishment because, unlike peer-punishers, these institutions may eliminate 'second-order' free-riding. Second-order free-riders cooperate with other players but they do not pay the cost of punishing defectors and this can allow defectors to re-emerge [13][14][15]. To address this problem, Sigmund et al. present a model of 'pool' punishment, where agents commit resources to a centralized authority that sanctions freeriders [12,16]. Pool punishment avoids the second-order free-rider problem because the centralized authority punishes any individual who does not

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