Haven’t I seen this before? The downside of doctors relying on their intuition when making diagnoses

author approved badgeReference: Mamede, S., van Gog, T., van den Berge, K., Rikers, R. M., van Saase, J. L., van Guldener, C., & Schmidt, H. G. (2010). Effect of availability bias and reflective reasoning on diagnostic accuracy among internal medicine residents. JAMA304(11), 1198-1203.

Guest post by Lucia Chisari

An experienced doctor is working at an urgent care center. One by one, patients come into her office and describe their symptoms. She takes notes, examines the patients’ history, and looks at the results of their clinical examinations. Eventually, she makes a diagnosis and prescribes a treatment. On that particular day, she has met two patients with viral hepatitis. Now the next patient comes in. His symptoms are extremely similar to those of hepatitis, but in truth, what is afflicting him is cirrhosis, a different disease requiring a different treatment. Is the doctor more likely to conclude that this person has hepatitis, and not cirrhosis, due to her previous experience during the day?


While thinking about a particular case and its diagnosis, clinicians may engage in one of two types of clinical reasoning. The first type, non-analytical reasoning, is unconscious and rapid, and develops with increasing expertise. The second type, analytical reasoning, is slower (think: Sherlock Holmes) and involves careful reflection. Non-analytical reasoning is highly efficient, but can also be subject to cognitive biases (1).

Mamede et al. (2010) asked whether non-analytical reasoning is affected by the availability bias, or the likelihood to think something is happening because it comes to mind more easily (as in our doctor’s situation). The authors tested two additional hypotheses: 1) that more experienced clinicians engage in non-analytical reasoning more than less-experienced clinicians, and thus experienced clinicians are more affected by availability bias, and 2) that the bias can be remedied by inducing doctors to reflect; that is, engage in analytical reasoning.

(2) Dr. Watson (left) and Sherlock Holmes (right), possibly engaging in a session of analytical reasoning?

Participants were thirty-six internal medicine residents. Half were in their first year of the residency and half in their second year (presumed to be more experienced). The study consisted of three phases. In the first phase, each participant was exposed to summaries of six cases (i.e., symptoms, signs, test results) and had to come up with a diagnosis for each case as quickly as possible. To ensure any effects found were due to the experimental manipulations and not the particular characteristics of the cases, two sets of cases were randomly assigned to participants

In the second phase, participants were exposed to eight new cases, four of which were similar to two cases from the first phase. Again, participants had to deliver a diagnosis as soon as possible. In the final phase, the four cases that were similar to phase 1 cases were presented again to the participants, this time with a set of questions that invited them to reflect on the given diagnosis and gave them the option to switch to another disease.

(3) Phase 2 results from Mamede et al. (2010). Second year participants had significantly lower scores in similar cases than in other cases (1.55 vs. 2.19), and lower scores in similar cases than first year students (1.55 vs 2.03).

The results revealed a significant interaction between years of training and recent experience with similar cases. Specifically, second year residents had significantly lower diagnostic scores on cases similar to the previously seen in the first phase than on the cases that were not preceded by similar ones. That is, second year residents seemed to be affected by the availability bias.

However, when invited to reflect on the four similar cases, both first and second year residents significantly improved their diagnostic scores. This shows that mistakes in diagnosis possibly due to availability bias can be corrected by introducing a reflective session while considering a patient’s case.

This study’s results suggest that availability biases may particularly affect experienced clinicians’ diagnoses in the context of non-analytical reasoning. The results also show that this availability bias can be counteracted by inducing clinicians to engage in analytical reasoning.

Limitations of the study, as stated by the authors, are related to facts that impede generalizing these results to real-world situations. In particular, the study participants were first and second-year residents, which leads us to wonder if, for example, the bias could be remedied by a reflective session in professionals with several years of experience. Furthermore, the order and manner in which similar cases present themselves in clinics are arguably quite different to those used in the study. Nonetheless, the study provides valuable experimental evidence as to the undesirable effects of availability bias in experienced medical students. It also demonstrates the potential of training medical students in different types of reasoning.

Lucia is a second year Research Master luciastudent at the program Educational Sciences: Learning in Interaction, at Utrecht University, the Netherlands. She has a Bachelor’s degree in Biological Sciences (University of Buenos Aires) and for the past three years she has been doing research and working in science education. Currently she is assisting in research on faculty’s development as teachers and education for sustainable development. Connect with her on LinkedIn.

Images: (1) Photo by Bill Branson (November, 1990). Source: Wikimedia Commons. (2) Illustration by Sidney Paget in Strand Magazine (September, 1893). Source: Wikipedia. (3) Results from Mamede et al. (2010), Table 2.

 Additional Reference:  (1) Schmidt, H. G., & Boshuizen, H. P. (1993). On acquiring expertise in medicine. Educational Psychology Review, 5, 205-221. doi:10.1007/BF01323044