Impersonal cooperation among strangers enables societies to create valuable public goods, such as infrastructure, public services, and democracy. Several factors have been proposed to explain variation in impersonal cooperation across societies, referring to institutions (e.g., rule of law), religion (e.g., belief in God as a third-party punisher), cultural beliefs (e.g., trust) and values (e.g., collectivism), and ecology (e.g., relational mobility). We tested 17 preregistered hypotheses in a meta-analysis of 1,506 studies of impersonal cooperation in social dilemmas (e.g., the Public Goods Game) conducted across 70 societies (k = 2,271), where people make costly decisions to cooperate among strangers. After controlling for 10 study characteristics that can affect the outcome of studies, we found very little cross-societal variation in impersonal cooperation. Categorizing societies into cultural groups explained no variance in cooperation. Similarly, cultural, ancestral, and linguistic distance between societies explained little variance in cooperation. None of the cross-societal factors hypothesized to relate to impersonal cooperation explained variance in cooperation across societies. We replicated these conclusions when meta-analyzing 514 studies across 41 states and nine regions in the United States (k = 783). Thus, we observed that impersonal cooperation occurred in all societies—and to a similar degree across societies—suggesting that prior research may have overemphasized the magnitude of differences between modern societies in impersonal cooperation. We discuss the discrepancy between theory, past empirical research and the meta-analysis, address a limitation of experimental research on cooperation to study culture, and raise possible directions for future research.

Blood donors are indispensable for enabling a myriad of medical procedures and treatments. We examined how public trust in the healthcare system and healthcare quality relate to individuals’ likelihood of donating blood, using survey data from representative samples of 28 European countries ( N = 27,868). Our preregistered analyses revealed that country-level public trust, but not healthcare quality, predicted individual propensity to donate blood. Notably, public trust decreased over time in many countries, while healthcare quality increased. Our results highlight the role of subjective perceptions of the healthcare system, rather than the objective state of healthcare, for blood donation behavior in Europe.