Objective: This paper aims to summarise the evidence supporting the role of experience-based, non-analytic reasoning (NAR) or pattern recognition as a central feature of expert medical diagnosis.
Methods: The authors examine a series of studies, primarily from their own research programme at McMaster University, that demonstrate that expert and novice diagnostic problem solving is based, to some degree, on similarity to a prior specific exemplar in the memory.
Results: The studies reviewed have shown NAR to be a component of diagnostic reasoning at all levels from novice to subspecialist, and in dermatology, electrocardiography and psychiatry. The retrieval process is rapid and is not available to retrospect. It may be based on visual similarity, but can also be present in verbal descriptions. Some evidence exists that the process is unlikely to be available to introspection. Further, early hypotheses based on NAR can result in the re-interpretation of critical clinical findings.
Conclusions: Non-analytic reasoning is a central component of diagnostic expertise at all levels. Clinical teaching should recognise the centrality of this process, and aim to both enhance the process through the learning of multiple examples and to supplement the process with analytical de-biasing strategies.