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BMJ Qual Saf. 2016 Jan 29. pii: bmjqs-2015-005014. doi: 10.1136/bmjqs-2015-005014. [Epub ahead of print]

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

Author information

  • 1Institute 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.
  • 2Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada.
  • 3Department of Medicine, McMaster University, Hamilton, Ontario, Canada.
  • 4Department of Medicine, University of Washington, Seattle, Washington, USA.
  • 5Program 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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