Prediction and diagnosis: An experimental comparison

Diagnostic tasks differ from predictive tasks in two respects (1) the direction of the inference in diagnosis (from effect to cause) is inverse to that in prediction (from cause to effect), and (2) the event to be inferred is more distal in diagnostic tasks than in predictive tasks. These task features led to the hypothesis that a diagnostic task would be harder to learn than a predictive task. This hypothesis was tested in an experimental situation in which the causal mechanism was random sampling with replacement. Five groups of subjects with 10 subjects in each (two predictive and three diagnostic groups) were run in individual sessions with 100 trials of feedback training. The two predictive groups learned more rapidly and to a higher level compared to the diagnostic groups. Conclusion: the present data support the hypothesis that predictive tasks are easier to learn than comparable diagnostic tasks.