The Benefit of Diagnostic Hypotheses in Clinical Reasoning: Experimental Study of an Instructional Intervention for Forward and Backward Reasoning

Two approaches to electrocardiogram (ECG) diagnosis were examined in a series of 2 experiments. The first approach, based on forward reasoning, asked participants to carefully obtain all the data, then synthesize the data into a diagnosis using provided rules. The second, based on backward reasoning, asked participants to try to work out the diagnosis then identify supporting features. Participants were undergraduate psychology students. In the first experiment, the forward reasoning group had the ECG removed after listing features. Accuracy of the forward reasoning group was 41.9% and accuracy of the backward reasoning group was 61.3%. In the second experiment, the forward reasoning group was permitted to retain the ECG; this time accuracy rose to 49.4% versus 61.9% for the backward reasoning group. The difference remained statistically significant. Thus, the results showed a consistent advantage for holistic, backward reasoning in an ECG diagnostic task with novices.