The main goals have been, first, to investigate the extent to which large-scale cooperation problems differ from small-scale cooperation problems, second, to apply and combine multiple methods to study human cooperation, and, third, to derive implications for the protection of the global commons.
Regarding the first objective, we have conducted a series of experiments to better understand if and how groups respond differently to interventions than individuals. An important conclusion of this work is that group behavior is more difficult to influence than individual behavior, especially when soft mechanisms are used, based on internal motivations such as reputation, guilt, approval seeking or disapproval avoidance, making more stringent measures necessary for groups. Furthermore, we have studied the endogenous formation of institutions for a better understanding of large-scale cooperation. Importantly, we have focused on institutions that are chosen and implemented by the actors involved rather than imposed from the outside because there is no outside for international problems. Our research shows that the preconditions for successful cooperation are fundamentally different from the factors identified by previous literature on small-scale cooperation. Strategic skills are more important than cooperativeness, with negotiators setting the institutional framework to minimize the need for voluntary cooperation.
With regard to the second objective, a large part of our work has again focused on the formation and impact of institutions. We first conducted a meta-study to evaluate all existing experimental research on the endogenous formation of institutions, which among other things shows that standard economic theory has weak explanatory power for the choice of institutions. We then investigated whether the experimental results could be better explained by an evolutionary model, which is indeed the case. The results also show the importance of social learning, information about other actors and groups, and intergenerational memory. The findings can explain, for instance, why institutions that are generally seen as successful, such as the EU or the UN, can nevertheless be at risk of losing support. The combination of case studies, theoretical modeling, experimental investigations, and evolutionary simulations has proven to be highly valuable in the project and beyond. To verify the research results with regard to their methodological robustness, we have used diverse samples of participants in the experiments and surveys, including students, representative national samples, and international samples of negotiators and scientists. Studies with the latter samples are particularly difficult to implement and therefore especially valuable.
Regarding the third objective, climate change has played a dominant role throughout the project. By means of theoretical modeling, experimental investigations, and expert surveys, we have attempted to provide a comprehensive assessment of what has been achieved and possible ways forward. The mechanisms included in the Paris Agreement can be expected to exert an influence on climate change mitigation efforts, but stronger measures are needed. The linkage of climate policy with international trade is increasingly receiving attention. Our research shows that such linkage has a higher chance of success if the gains from trade are relatively large and if countries use a coordinated multilateral approach rather than a unilateral approach. As another example of possible ways out of the crisis, we have examined the acceptance of geoengineering technologies and their determinants. Our results show that the views of climate experts do not only depend on their expectations of global damages but also on the expectations for their own home country, highlighting another layer of the dilemma between global appropriateness and the personal or national perspective.
