To the Editor: We read with anticipation Sherbino and colleagues’1 recent article. However, we find it ironic that there are some cognitive shortcuts made in the authors’ premise, analysis, and conclusion that may limit the practical implications of their study.
The premise asserts that “according to the literature, diagnostic errors arise primarily from System 1 reasoning, and therefore they are associated with rapid diagnosis.”1 This interpretation of the literature commits what is referred to as “the round trip fallacy”2 (e.g., no evidence of disease means that there is evidence of no disease). The statement that System 1 reasoning is more error prone (which we believe the literature does support) does not necessarily lead to the round-trip assumption that errors in diagnostic reasoning primarily arise from System 1. The authors correctly point out that there are many other potential reasons for errors. Their premise also conflates the concept of System 1 reasoning with diagnostic error and rapid time, which we do not believe is consistent with the descriptions of System 1 and System 2 thinking by Kahneman and others.3-5
A possibly erroneous assumption in the analysis is that a categorical variable (System 1 versus System 2) can be directly equated with a continuous variable (time). Fast(er), in relative terms, does not necessarily confer a change in categories of reasoning. Therefore, unless an answer is immediate (not just relatively faster), and prior to our awareness,2,5 it is difficult to choose whether to ascribe System 1 or System 2 based on time alone.
It may be less important in the conclusion to assign causality to error and fall victim to the narrative fallacy2,5 (the tendency to perceive, or impose, causality based on the plausible) than it is to contribute to a robust model of how clinical reasoning may “really” work. As Groves6 suggests, (1) clinical reasoning is complex and involves a number of interacting elements, (2) it involves a dynamic interaction of content knowledge and critical thinking, (3) analytic and nonanalytic processes work in tandem, and (4) a definitive model of clinical reasoning includes the overarching role of metacognition.
In that broader framing, perhaps error can occur at any time or place in the process, so System 1 and System 2 reasoning can be both functional and/or dysfunctional depending on the context.
The above considerations make clear that it is easy to be too quick when arriving at conclusions about response times and diagnostic accuracy.
David Petrie, MD, FRCP
Professor and head, Department of Emergency Medicine, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada; David.firstname.lastname@example.org.
Sam Campbell, MD
Professor of emergency medicine, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada.
1. Sherbino J, Dore KL, Wood TJ, et al. The relationship between response time and diagnostic accuracy. Acad Med. 2012;87:785–791
2. Taleb NN The Black Swan—The Impact of the Highly Improbable. 2007 New York, NY Random House
3. Croskerry P. A universal model of diagnostic reasoning. Acad Med. 2009;84:1022–1028
4. Evans JS. Dual-processing accounts of reasoning, judgment, and social cognition. Annu Rev Psychol. 2008;59:255–278
5. Kahneman D Thinking Fast and Slow. 2011 New York, NY Macmillan
6. Groves M. Understanding clinical reasoning: The next step in working out how it really works. Med Educ. 2012;46:444–446