Social dilemmas among unequals

This is the author accepted manuscript. The final version is available from Nature Research via the DOI in this record.Direct reciprocity is a powerful mechanism for evolution of cooperation, based on repeated interactions. It requires that interacting individuals are sufficiently equal, such that everyone faces similar consequences when they cooperate or defect. Yet inequality is ubiquitous among humansand is generally considered to undermine cooperation and welfar. Most previous models of reciprocity neglect inequality. They assume that individuals are the same in all relevant aspects. Here we introduce a general framework to study direct reciprocity among unequals. Our model allows for multiple sources of inequality. Subjects can differ in their endowments, their productivities, and in how much they benefit from public goods. We find that extreme inequality prevents cooperation. But if subjects differ in productivity, some endowment inequality can be necessary for cooperation to prevail. Our mathematical predictions are supported by a behavioral experiment where we vary the subjects’ endowments and their productivities. We observe that overall welfare is maximized when the two sources of heterogeneity are aligned, such that more productive individuals receive higher endowments. In contrast, when endowments and productivities are misaligned, cooperation quickly breaks down. Our findings have implications for policy-makers concerned with equity, efficiency, and public goods provisioning.European Research Council Start GrantGraph GamesAustrian Science Fund (FWF)Office of Naval ResearchJohn Templeton FoundationISTFELLOW program

A research agenda for malaria eradication: diagnoses and diagnostics.

Many of malaria's signs and symptoms are indistinguishable from those of other febrile diseases. Detection of the presence of Plasmodium parasites is essential, therefore, to guide case management. Improved diagnostic tools are required to enable targeted treatment of infected individuals. In addition, field-ready diagnostic tools for mass screening and surveillance that can detect asymptomatic infections of very low parasite densities are needed to monitor transmission reduction and ensure elimination. Antibody-based tests for infection and novel methods based on biomarkers need further development and validation, as do methods for the detection and treatment of Plasmodium vivax. Current rapid diagnostic tests targeting P. vivax are generally less effective than those targeting Plasmodium falciparum. Moreover, because current drugs for radical cure may cause serious side effects in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency, more information is needed on the distribution of G6PD-deficiency variants as well as tests to identify at-risk individuals. Finally, in an environment of very low or absent malaria transmission, sustaining interest in elimination and maintaining resources will become increasingly important. Thus, research is required into the context in which malaria diagnostic tests are used, into diagnostics for other febrile diseases, and into the integration of these tests into health systems