Knowledge Based Solution Strategies in Medical Reasoning

The techniques of propositional analysis are used to examine the protocols of seven cardiologists in a task involving the diognosis of a case of acute bocterial endocarditis and an explonotion of its underlying pathophysiology. It is shown that the explanations of physicians making an accurate diagnosis can be accounted for in terms of a model consisting of pure forword reasoning through a network of causal rules, actuated by relevant propositions embedded in the stimulus text. These rules appear to derive from the physician’s underlying knowledge base rather than any information in the text itself. In contrast. subjects with inocurote diognoses tend to make use of a mixture of forward and backward reasoning, beginning with a high level hypothesis and proceeding in a top-down fashion to the propositions embedded in stimulus text, or to the generation of irrelevant rules.