Proceedings of the Annual Meeting of the Cognitive Science Society

This paper investigates the process of hypothesis generation and the coordination of hypothesis and evidence in medical diagnostic tasks. Two issues are addressed: the generation of hypothesis and the directionality of reasoning. Two problems whose initial presentation suggested an initial hypothesis were presented to subjects with different degrees of expertise in clinical medicine. When faced with contradictory evidence against the initial hypothesis, 1) early novices either modified the initial hypothesis, or ignored, or reinterpreted the cues in the problem to fit the hypothesis; 2) intermediate novices generated concurrent hypotheses to account for different sets of data; and 3) advanced novices generated several initial hypotheses and subsequently narrowed the hypothesis space by generating a single coherent diagnostic hypothesis. All subjects, used a mixture of forward reasoning and backward reasoning. A more forward-directed reasoning was related to diagnostic accuracy. These results on diagnostic reasoning are discussed in relation to findings on scientific reasoning.