In Reply to Croskerry and Tait:
We thank Drs. Croskerry and Tait for their interest in our report, which showed that there was a moderately strong inverse relationship between reading time and diagnostic accuracy. Croskerry and Tait interpret these results as “consistent with [the view that] intuitive decisions are more vulnerable to error than those made in the analytic system.” This conclusion derives from their interpretation that solution time reflects problem difficulty. Unfortunately, they miss a crucial point in the methodology: All subjects saw essentially the same cases. Thus, the inverse relation between time and accuracy reflects differences in participants, not cases. Further, in Table 2 we showed that this inverse relationship between time and accuracy holds for 23 of the 25 cases.
We agree that there is no exact correspondence between length of time and reliance on System 1 or System 2 thinking. But if one accepts a strict dual-process theory, with a faster, contextual, nonanalytical System 1 and a slower, conceptual, analytical System 2, then faster times are likely a consequence of increased reliance on System 1 processes, and our conclusion—that “we found no support for the assertion that a longer time to diagnosis (typically associated with more deliberate, or System 2, processing) results in fewer errors”—follows directly.
We recognize that reading a case is not the same as practice. But to assert without proof that “the exercises in the authors’ experiment do not reflect the actual complex processes involved in patient assessment” is too strong. We remind the authors that virtually all the evidence in support of dual-process theory, both in medicine and in the research program of Kahneman,1 derives from performance on written cases. Furthermore, many of the studies that have looked at the relationship between errors and System 1 and System 2 processes in real-world tasks and stimuli2–3 would support our conclusion that expert clinicians can use rapid and efficient heuristics to solve problems with fewer errors than when they use slower deliberative processes.
We are puzzled by the authors’ statement that “faster responses … occur when the participants have the knowledge base to quickly arrive at the correct conclusion using System 2.” Our understanding is that System 1 thinking, based on knowledge related to prior experience, leads to rapid and (usually) correct solutions. Croskerry and Tait appear to assume three processes: slow and correct System 2, fast and error-prone System 1, and fast and correct System 2. This is clearly not what Kahneman,4 one of the founders of dual-processing theories, believes when he states that
the operations of System 1 are fast, automatic, effortless, associative, and difficult to control or modify. The operations of System 2 are slower, serial, effortful, and deliberately controlled.
Finally, we do not “promote the notion … that speed increases accuracy.” In our report, we stated, “as educators we should not encourage learners to speed up or avoid any reflection.” But we do want to stress that, even if one accepted a strict dual-process theory, System 1 thinking should not be blamed for all diagnostic errors.
Jonathan Sherbino, MD
Associate professor of emergency medicine, McMaster University Faculty of Health Sciences, Hamilton, Ontario, Canada.
Geoffrey R. Norman, PhD
Professor of clinical epidemiology and biostatistics, McMaster University Faculty of Health Sciences, Hamilton, Ontario, Canada; firstname.lastname@example.org.
Wolfgang Gaissmaier, PhD
Chief research scientist, Max Planck Institute for Human Development, Harding Center for Risk Literacy, Berlin, Germany.
1. Kahneman D Thinking Fast and Slow. 2011 New York, NY Farrar, Straus and Giroux
2. Kahneman D, Klein G. Conditions for intuitive expertise: A failure to disagree. Am Psychol. 2009;64:515–526
3. Gigerenzer G, Gaissmaier W. Heuristic decision making. Annu Rev Psychol. 2011;62:451–482