The history of science is littered with violations of the human rights of research participants (1, 2). One response has been regulation. In the United States, the Belmont Report lays out ethical principles for human subjects research (3), which form the foundation of modern-day institutional review boards. According to the Belmont Report, ethics committees and investigators need to determine whether the benefits of the research outweigh the costs and whether the costs unevenly burden particular groups. However, the assumptions underlying such assessments can be flawed (4, 5). Without evidence about the causal effects of social science research on participant welfare, researchers risk causing unexpected harms or missing unexpected benefits.