Determinants of diagnostic hypothesis generation: effects of information, base rates, and experience.

Physicians generated diagnostic hypotheses for case histories for which 2 types of diagnoses were plausible, with one having a higher population base rate but less severe clinical consequences than the other. The number of clinical and background symptoms pointing towards the 2 diagnoses was factorially manipulated. The order and frequency with which physicians generated hypotheses varied with the amount of relevant clinical and background information and as a function of population incidence rates, with little evidence of base rate neglect. Availability of a hypothesis, made possible by diagnosis of a similar case before, also made doctors generate this diagnosis earlier and more frequently. Physicians' experience affected hypothesis generation solely by increasing the availability of similar cases. The results are consistent with the use of similarity-based hypothesis generation processes that operate on memory for prior cases.