Meta-consent in research on decisional capacity: a "Catch-22"?

Empirical studies of ethical issues, which have increased in number and scope in recent years, may themselves raise both practical and ethical issues. One example of such an issue is the question of who may be legitimately enrolled in studies of decision-making capacity; must all participants in studies of consent capacity have capacity to consent? This question may pose a "Catch-22": For example, if some of the participants in a study of consent capacity are deemed by a particular standard to be incapable of consent. In weighing the risks and benefits of studies of consent capacity, how should reviewers consider the context of actual versus hypothetical trials for which the participant's consent is being sought? Here, we explore these "meta-consent" issues by describing the dimensions of the issue and potential solutions, centering around the concept of "active assent" (requiring expressed understanding of the purpose of the study and its voluntary nature, as well as expression of a choice to participate).