Anthropologists have documented substantial cross-society variation in people’s willingness to treat strangers with impartial, universal norms versus favoring members of their local community. Researchers have proposed several adaptive accounts for these differences. One variant of the pathogen stress hypothesis predicts that people will be more likely to favor local in-group members when they are under greater infectious disease threat. The material security hypothesis instead proposes that institutions that permit people to meet their basic needs through impartial interactions with strangers reinforce (...) a tendency toward impartiality, whereas people lacking such institutions must rely on local community members to meet their basic needs. Some studies have examined these hypotheses using self-reported preferences, but not with behavioral measures. We conducted behavioral experiments in eight diverse societies that measure individuals’ willingness to favor in-group members by ignoring an impartial rule. Consistent with the material security hypothesis, members of societies enjoying better-quality government services and food security show a stronger preference for following an impartial rule over investing in their local in-group. Our data show no support for the pathogen stress hypothesis as applied to favoring in-groups and instead suggest that favoring in-group members more closely reflects a general adaptive fit with social institutions that have arisen in each society. (shrink)

“How social norms change” is not only a theoretical question but also an empirical one. Many organizations have implemented programs to abandon harmful social norms. These programs are standardly monitored and evaluated with a set of empirical tools. While monitoring and evaluation (M&E) of changes in objective outcomes and behaviors is well developed, we will argue that M&E of changes in the wide range of beliefs and preferences important to social norms is still problematic. In this paper, we first present (...) a theoretical framework and then show how it should guide social norms measurement. As a case study, we focus on the harmful practice of child marriage. We show how an operational theory of social norms can guide the design of surveys, experiments and vignettes. We use examples from existing research to illustrate how to study social norms change. (shrink)