Ethical oversight of clinical research is one of the primary means of ensuring that human subjects are protected from the natural bias of researchers and research institutions in favor of experimentation. At a minimum, effective oversight should ensure that risks are minimized and reasonable in relation to anticipated benefits, protect vulnerable subjects from potential coercion or undue influence, ensure full and informed consent, and promote the equitable distribution of the risks and benefits of research. Because these assessments often involve value (...) judgments for which there are no agreed-upon objective standards, we rely on deliberative procedures thought to have the greatest likelihood of producing the right or best outcomes. Concerns about the potential for improperly functioning IRBs to waste scarce human and institutional resources and impede biomedical progress have motivated a surge in empirical research assessing their procedures and outcomes. Yet within this literature, there has been minimal attention paid to the social scientific evidence regarding how individuals and deliberating groups make decisions, nor how those data might inform IRB practice. This essay seeks to fill that gap, locating recent empirical data on IRB composition and process within the context of data regarding what I call “deliberative pathologies,” or instances when deliberation fails to live up to one or more aspect of the deliberative ideal because of systematic biases in the ways participants interact. The paper goes on to make evidence-based recommendations to reduce the vulnerability of IRB deliberations to the kinds of pathologies discussed and indicate directions for future research. (shrink)