The mere fact that study participants are paid “cannot render a study unethical,” according to Holly Fernandez Lynch, JD, MBe, assistant professor of medical ethics at the University of Pennsylvania Perelman School of Medicine. “We pay people for lots of different reasons: To reimburse their expenses, to compensate their time and effort, and to incentivize their participation above and beyond reimbursement and compensation rates.”

There are two central ethical concerns. One is undue inducement, meaning an offer so attractive it leads to bad judgment. “This is typically overblown if the IRB is doing its job of making sure that no research is approved where risks outweigh benefits,” Fernandez Lynch argues.

It is not undue inducement for someone to be willing to do something only if they are offered enough payment. “Most of us feel that way about our jobs,” Fernandez Lynch offers.

Second is unjust inducement, meaning payment is more attractive to lower-income people, putting too much of the burden of research participation on them. “This is a legitimate ethical concern, but the response should not necessarily be to pay less. It could be to pay more,” Fernandez Lynch says.

Offering incentives to research participants did not result in undue or unjust inducement.1 Researchers randomly assigned patients to incentives of $0, $200, or $500 to participate in an actual smoking cessation trial from 2017-2019 or $0, $100, or $300 to participate in an actual ambulation intervention trial from 2018-2019. The authors compared the percentage of people who decided to consent and found no evidence of undue or unjust inducement.

Fernandez Lynch says IRBs and researchers should be considering if they are offering participants too little, given what they are asked to contribute. “Payment is often important as a matter of fairness and avoidance of exploitation,” Fernandez Lynch says. “Yet attention is typically around whether payment is too high.”

Fernandez Lynch and colleagues recently addressed whether and how much participants in COVID-19 human infection challenge studies should be paid. They created a payment worksheet to help researchers and IRBs assess ethically justifiable payment amounts.2 “The worksheet is not specific to challenge studies, per se,” Fernandez Lynch notes. “It should be easily adjusted to serve as a model for all clinical research.”

IRBs look carefully at both the amount and the method of payment for research participation, says Janet Usinger, PhD, associate professor, state extension specialist emeritus, and IRB co-chair at the University of Nevada, Reno. For IRBs, the most important question is: Is this a fair amount of money (or gift) for the research conducted? An incentive for research that requires a great deal of time and complexity should be higher than for simple procedures of short duration. “The basic principle is that incentives should be fair, but should not be perceived as coercive, particularly for studies that are more than minimal risk,” Usinger says.

The method of payment also is a consideration. “Incentives are used to recognize the time and effort for participating in a research study; they are not payment for participation,” Usinger notes. In other words, completion of the research activities should not be a criterion for receiving the incentive.

For research that involves a lengthy commitment, payment can be made as the study progresses. “This encourages continued participation and allows participants to receive the incentive for as long as they are active participants in the research,” Usinger explains.

Risk usually is the primary consideration of unethical incentives. “There are numerous examples of offering a great deal of money to individuals who have limited resources for participating in biomedical research that involves a great deal of risk,” Usinger says. “However, this equally applies to the social sciences.”

Giving a young adult who is homeless several hundred dollars to provide data that may put the person at legal risk would be considered unethical. Usinger says IRBs should ask: Is the person’s participation voluntary, or is the incentive unduly coercive? “The incentive should reflect a fair and just thank you for their participation,” Usinger says. “It is not a hard and fast rule. Rather, an incentive should be reasonable for the research activities involved.”


  1. Halpern SD, Chowdhury M, Bayes B, et al. Effectiveness and ethics of incentives for research participation: 2 randomized clinical trials. JAMA Intern Med 2021;181:1479-1488.
  2. Lynch HF, Darton TC, Levy J, et al. Promoting ethical payment in human infection challenge studies. Am J Bioeth 2021;21:11-31.