Offering payment for research participation is commonplace, ethical, and sometimes necessary. Nevertheless, this practice remains a source of debate in academia.

A 2017 study published in the Yale Journal of Health Policy, Law, and Ethics found that the total amount of compensation offered for a complete study in the United States varies from $5 to $2,000, while nearly two-thirds of studies offer $250 to participants.

The correlation between money and study participation has not been thoroughly explored, however.

New University of Pennsylvania School of Medicine research answers a looming question: Do people lie and deceive when study participation pays?

Published in JAMA Network Open, and authored by Holly Fernandez Lynch, Steven Joffe, Harsha Thirumurthy, Dawei Xie, and Emily A. Largent, “Association Between Financial Incentives and Participant Deception About Study Eligibility” is the first study of its kind.

For the study, the researchers recruited 2,275 individuals to participate in a randomized and nationally representative survey on vaccination status. Participants were randomly assigned into seven groups, with 325 respondents in each group.

Control group — whose results were used to determine the true rates of vaccination across all groups — participants had no incentive to lie or deceive, as they were told to be eligible if they had received any vaccine in their lifetime. In the six experimental groups, respondents were offered $5, $10, or $20 for participation, and were told they were eligible only if they had (or had not) received an influenza vaccine in the past six months.

In the control group, 52.2 percent of respondents reported receiving an influenza vaccine in the past six months. In three of the six remaining groups, when offered $5, $10, or $20 as compensation, reports of vaccination were significantly higher, jumping up to 62.8 percent in one of the groups ($10). Reports of vaccination jumped to 63.1 percent in the $5 group, and 62.1 percent in the $20 group.

In the remaining three groups, where respondents were told that eligibility depended on having not received an influenza vaccine in the past six months, reports of vaccination dropped. In the $5 group, the reports dropped to 46.5 percent, in the $10 group to 41.8 percent, and among respondents in the $20 group the reports of vaccination dropped to 46.7 percent.

Since the only differences between the groups were payment amounts and eligibility, University of Pennsylvania School of Medicine researchers attributed the differences in reported vaccination rates to deception. In conclusion, between 10.5 and 22.8 percent of the respondents were lying.

Interestingly, higher rates of payment were not associated with higher rates of deception.

“This type of behavior not only undermines a study’s integrity and its results, but in a study with eligibility criteria that are intended to protect participants, it also has the potential to put participants at risk,” lead author author Holly Fernandez Lynch said in a press release supplied to Eurekalert.

The researchers explained that their findings do not suggest that research participation compensation should be eliminated or reduced. Rather, researchers should “use objective metrics whenever possible” instead of “relying on self-reporting by participants.”