Factors Associated With Payments to Research Participants: A Review of Sociobehavioral Studies at a Large Southern California Research University.

Along with a dearth of regulatory guidance, little empirical research has examined factors related to participant payment in research. We conducted a cross-sectional study of 100 institutional review board (IRB)-approved sociobehavioral human subjects research protocols at a large research university in Southern California. The proportion of studies that paid participants differed significantly by type of research (p < .001) and study population (p = .009). The average payment amount also differed significantly by study population (p < .001) and type of participation (in-person vs. remote; p < .001). In addition, studies that required more visits (p < .001) and more time (p = .011) paid significantly more than studies with fewer and shorter visits, respectively. These findings provide data to help inform future ethical payment practices.