Background: Medical diagnosis may be thought of as a categorization task. Research and theory in psychology as well as medical decision making indicate at least 2 processes by which this categorization task may be accomplished: (a) analytic processing, in which one makes explicit use of clinical features to reach a diagnosis, and (b) similarity-based processing, in which one makes use of past exemplars to reach a clinical diagnosis. Recent research indicates that these 2 processes are complementary.
Purpose: We investigate the coordination of analytic and similarity-based processes in clinical decision making to examine if the relative reliance on these 2 processes is (a) amenable to instruction and (b) dependent on level of clinical experience.
Methods: The reliance of these 2 processes was indexed by the performance of 12 preclinical medical students on cases dichotomized as typical and atypical (analytic processing) and on cases dichotomized as similar or dissimilar to cases seen previously in a training phase (similarity-based processing).
Results: The results indicated that both processes are operative. Of particular interest was that preclinical medical students enhanced their performance by adopting a similarity-based strategy. This was especially so for atypical cases. These results are in contrast to residents, who enhanced their performance by adopting an analytic strategy.
Conclusions: The relative reliance on analytic and similarity-based processes is amenable to instruction and dependent on expertise.