The characteristics of early diagnostic hypotheses generated by physicians (experts) and students (novices) at one medical school.

How hypotheses generated at the outset of a physician-patient encounter influence the physician's diagnostic reasoning has received relatively little attention in the literature. Yet, this activity modulates the efficiency and accuracy of the diagnostic process. The authors proposed the theory that physicians (experts) would generate less specific initial diagnostic hypotheses than would students (novices). In 1988 and 1989, the hypotheses generated by 32 practicing physicians and 39 third-year medical students at one medical school were analyzed for number, specificity, and breadth (i.e., range) of diagnoses, and for differences between those generated by the physicians and by the students. The hypotheses were formulated on the basis of the initially available data--chief complaint and its duration, and basic demographic descriptions--from patients in three clinical scenarios. Compared with the physicians, the students generated significantly more hypotheses and significantly more specific hypotheses. There was no significant difference between the groups in the breadths of the hypotheses they selected, that is, the numbers of broad categories of diagnosis covered by individuals' hypotheses.