Advances in Health Sciences Education

, Volume 2, Issue 2, pp 173–184 | Cite as

The Non-Analytical Basis of Clinical Reasoning

  • Geoffrey R. Norman
  • Lee R. Brooks


This paper explores the assertion that much of clinical diagnostic thinking is based on the rapid and unconscious matching of the presenting problem to a similar, previously encountered, problem. This ‘non-analytic’ form of concept formation has been described in the psychology literature for over a decade. From this theory, we deduce and test several hypotheses: 1) Diagnosis is based in part on similarity to a particular previous example. In studies in dermatology, specific similarity accounts for about 30% of diagnosis. 2) When experts err, these errors are as likely as novices to occur on typical presentations. For residents, general practitioners and dermatologists, about 40% of errors were on typical slides. 3) Features are re-interpreted in light of diagnostic hypotheses. In radiology, attaching a standard positive history to the film bag increased the number of features seen on both normal and abnormal films by about 50%. 4) Experts cannot predict errors of other experts. In dermatology, experts predicted only 11–60% of errors committed by their colleagues. We conclude that amassing prior instances is an important component of expertise, and education should recognize this element.


Contact Dermatitis Clinical Reasoning Lichen Planus Diagnostic Hypothesis Typical Slide 
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Copyright information

© Kluwer Academic Publishers 1997

Authors and Affiliations

  • Geoffrey R. Norman
    • 1
  • Lee R. Brooks
    • 1
  1. 1.Health Science CenterMcMaster UniversityHamiltonCanada

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