Association Between Financial Incentives and Participant Deception About Study Eligibility

Offers of payment for research participation are ubiquitous but may lead prospective participants to deceive about eligibility, jeopardizing study integrity and participant protection. To date, neither the rate of payment-induced deception nor the influence of payment amount has been systematically studied in a nationally representative randomized survey experiment.

To estimate payment-associated deception about eligibility for an online survey and to assess whether there is an association between payment amount and deception frequency.

Randomized, 7-group survey experiment. Data were collected in March 2018 and analyzed from March to August 2018. The setting was a nationally representative online survey among US adults drawn from the GfK KnowledgePanel.

Varying payment amounts for participation ($5, $10, or $20 cash equivalent) and direction of eligibility criterion (having received or not having received an influenza vaccination in the past 6 months).

Proportion of respondents reporting recent influenza vaccination.

In total, 2275 individuals participated in the survey, a 59.4% (2275 of 3829) response rate; 51.8% (1108) were female, and 21.1% of respondents (399) were aged 18 to 29 years, 24.9% (532) were aged 30 to 44 years, 26.0% (601) were aged 45 to 59 years, and 28.0% (738) were 60 years or older. For participants offered a $5 incentive, the reported frequency of recent influenza vaccination was 16.6% higher (95% CI, 9.1%-24.1%) among those told that eligibility (and thus payment) required recent vaccination than among those told that eligibility required no recent vaccination. The corresponding differences were 21.0% (95% CI, 13.5%-28.5%) among those offered $10 and 15.4% (95% CI, 7.8%-23.0%) among those offered $20. Estimated proportions of ineligible individuals who responded deceptively regarding eligibility ranged from 10.5% to 22.8% across study groups. There was no evidence that higher payment was associated with higher frequency of deception.

In a nationally representative randomized survey experiment to evaluate whether and to what extent payment is associated with participants misleading investigators about their research eligibility, this study found evidence of significant deception. However, no association was observed between payment amount and frequency of deception. Further research is needed to extend these findings to clinical research. These data suggest that, when possible, investigators should rely on objective tests of eligibility rather than self-report.