Proceedings of the Annual Meeting of the Cognitive Science Society

What role does causal knowledge play in categorization? The current study tested the hypothesis that weight given to features is determined by the specific role they play within a causal structure. After learning typical symptoms of a disease, participants were asked to judge the likelihood that new patients had that disease. Half of the patients were missing one of the typical symptoms, and the other half had an extra symptom (a symptom typical of an alternative disease). For patients with a missing symptom, likelihood ratings were lower if the missing symptom was a cause of other symptoms than if it was an effect. However, for patients with an extra symptom, there was no difference between likelihood ratings when the extra symptom was a cause or an effect. These results suggest one mechanism underlying differences between experts and novices in categorization, and suggest an explanation for why different kinds of features (e. g., molecular or functional) are important for different kinds of categories (e.g., natural kinds or artifacts).