Pill or bill? Influence of monetary incentives on the perceived riskiness and the ethical approval of clinical trials

In clinical trials, incentivizing human research subjects with large amounts of money is often considered unethical, as it may coerce people to participate. This argument implies that people perceive rewards (i.e., incentives) independently of risks (i.e., probability of side-effects) or that they assume that larger rewards are associated with lower risks. However, past research on risk perception indicates that people associate higher rewards with higher risks. To test whether people treat incentives in clinical trials as a proxy for risk, we conducted an online experiment (N = 483) in which people estimated the riskiness of hypothetical clinical trials. We manipulated the monetary incentives that participants of the clinical trials were offered. The results show that people expect more side effects if the monetary incentives for participation are higher. Results further show that the majority of participants were more likely to ethically approve a trial if it offered a high monetary incentive. In contrast to existing ethical guidelines these results suggest that paying large rewards may be less problematic because people implicitly associate them with higher risk and because they trade-off risks and financial benefits.