Promoting cooperation in the field

• We review randomized field experiments in real-world cooperation settings.
• Material rewards and increasing efficacy change costs and benefits of cooperating.
• Observability and descriptive norms harness reciprocity and reputation concerns.
• Results: Cost–Benefit Interventions are mixed, Social Interventions are effective.
• Policymakers can use theory, lab and field experiments to increase social welfare.

We review the growing literature of field experiments designed to promote cooperative behavior in policy-relevant settings outside the laboratory (e.g. conservation, charitable donations, voting). We focus on four categories of intervention that have been well studied. We find that material rewards and increased efficacy, interventions focused on altering the costs and benefits of giving, have at best mixed success. Social Interventions based on observability and descriptive norms, conversely, are consistently highly effective. We then demonstrate how a theoretical framework based on reciprocity and reputation concerns explains why Social Interventions are typically more effective than Cost–Benefit Interventions, and suggests ways to make Cost–Benefit Interventions more effective. We conclude by discussing other less-studied types of intervention, and promising directions for future research.