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BMJ Qual Saf. 2017 Feb;26(2):104-110. doi: 10.1136/bmjqs-2015-005014. Epub 2016 Jan 29.

Is bias in the eye of the beholder? A vignette study to assess recognition of cognitive biases in clinical case workups.

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Institute of Medical Education Research Rotterdam, Erasmus MC, Rotterdam, The Netherlands.
Department of Public and Occupational Health, VU University Medical Center/EMGO Institute, Amsterdam, The Netherlands.
Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada.
Department of Medicine, McMaster University, Hamilton, Ontario, Canada.
Department of Medicine, University of Washington, Seattle, Washington, USA.
Program for Educational Research and Development, McMaster University, Hamilton, Ontario, Canada.



Many authors have implicated cognitive biases as a primary cause of diagnostic error. If this is so, then physicians already familiar with common cognitive biases should consistently identify biases present in a clinical workup. The aim of this paper is to determine whether physicians agree on the presence or absence of particular biases in a clinical case workup and how case outcome knowledge affects bias identification.


We conducted a web survey of 37 physicians. Each participant read eight cases and listed which biases were present from a list provided. In half the cases the outcome implied a correct diagnosis; in the other half, it implied an incorrect diagnosis. We compared the number of biases identified when the outcome implied a correct or incorrect primary diagnosis. Additionally, the agreement among participants about presence or absence of specific biases was assessed.


When the case outcome implied a correct diagnosis, an average of 1.75 cognitive biases were reported; when incorrect, 3.45 biases (F=71.3, p<0.00001). Individual biases were reported from 73% to 125% more often when an incorrect diagnosis was implied. There was no agreement on presence or absence of individual biases, with κ ranging from 0.000 to 0.044.


Individual physicians are unable to agree on the presence or absence of individual cognitive biases. Their judgements are heavily influenced by hindsight bias; when the outcome implies a diagnostic error, twice as many biases are identified. The results present challenges for current error reduction strategies based on identification of cognitive biases.


Cognitive biases; Diagnostic errors; Patient safety

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