How Much Are Subjects Paid to Participate in Research?

Grady's current article (2001) addresses a difficult and enduring issue in research ethics: how much compensation may be offered to subjects without creating an "undue inducement" (McNeill 1997; Dickert and Grady 1999; Macklin 1981; McGee 1997). To shed a little light on this topic, we reviewed published biomedical and psychosocial studies to examine how much people are being paid. During the summer of 2000 we reviewed all studies published during 1997-1998 in ten journals, ¹ identifying those performed in the United States and indicating use of a payment or incentive. We abstracted information about incentive form and amount, duration of and/or active time spent in the study, and types of activities involved.

We identified a total of 126 studies. Of these, 56 papers included details about time and incentives. With Institutional Review Board (IRB) approval, we solicited missing information from the remaining authors by e-mail and phone, and received 53 responses (76%). This yielded 109 (71%) studies for analysis, involving 146 different subject populations or compensation groups.

Participants were drawn from students (77), community members (46), patients (12), "normal controls" (7), and children (4). Incentives for participation included reimbursement (1), fixed payments (74), hourly wage (8), course credit (50), and other incentives such as lottery or movie tickets, snacks, or pens (13). In seven studies involving multiple populations, no incentive was provided to one group. Of the 66 studies involving students, 64 appeared in psychology journals, and students only received course credit for participation in 49 (74%).

Cash payments ranged from $1 to $730. Greater amounts were paid for studies involving:

1. multiple interactions between subjects and researchers (generally over a period of weeks or months);
2. longer time in active participation;
3. any invasive tasks (including taking drugs, bodily measurements, blood draws or other interventions); or
4. a greater number of research tasks (any of the above categories of invasive activities, surveys, interviews, stimulus/response tasks, and focus groups).

We summarize the amounts paid for different research activities in Table 1. Note that all studies involving drugs also involved other activities.

In a multiple regression analysis, we find that subjects were paid on average about $9.50 per hour of active participation (t = 7.2, p < 0.001), plus an average sum of over $12 (t = 3.3, p = 0.001) for each additional separable task involved in the study. See Figure 1.

This small study shows that payments are related to the time and level of activity requested of participants. This data itself does not suggest that untoward monetary payments are regularly being offered to subjects of published studies to entice them to participate in research. Of course, there may be studies not included in our sample—such as Phase I clinical trials in healthy subjects—where larger payments are used to induce participation.

Our study does show, however, that course credit remains a common form of compensation offered to college students for research participation. Clearly, the potential for coercion from granting course credit for participation is a source of concern, and we unfortunately have no data regarding whether these subjects are offered a reasonable alternative to participation.