Table 1. Taxonomy of proposed interventions.
• Descriptive norms• Relatively inexpensive• If norm of participation is low, normative information may reduce desire to participate
• Injunctive norms• Informed participants are less likely to make mistakes during clinical trial
• Reciprocity
• Personalization• Serves ethical goal of informed consent• Too much information can reduce desire to engage
• Simplified consent forms
• Providing information at appropriate times• Depends on trust in the source of the information
• Defaults• Recruitment procedure has to be developed anyway, so little added effort to incorporate choice architecture• Some procedures are not fully transparent
• Active choice
 • Enhanced active choice• May backfire, by introducing “no” options or by asking wrong questions
 • Expanded active choice• Grant greater sense of control/autonomy to participants
• Ethical concerns about fully informed consent
• Structured decision flow• Relatively inexpensive
 • Foot-in-the-door
 • Self-prophecy
• Incentives• Direct financial payment• Compensates participants for time, opportunity cost, and taking on risk• Can be expensive
• Lottery payment• Undue inducement
• Material prizes• Delivery of incentives can be structured to motivate continued participation• Unjust inducement
• Rewards that facilitate participation (e.g., bus pass)• Potential participants may fail to disclose exclusion criteria
• Social recognition
• Providing RCT results