Fig. 1.

A: Category structure of a rule-based category-learning task. The optimal rule is: Respond A if the background color is blue (depicted as light gray), and respond B if the background color is yellow (depicted as dark gray). B: Category structure of an information-integration category-learning task. In this example, shape is irrelevant. For the three relevant dimensions, one level is arbitrarily assigned a numerical value of +1: symbol color of green (depicted as black), background color of blue (depicted as light gray), and numerosity of two. The other levels are assigned a numerical value of 0: symbol color of red (depicted as white), background color of yellow (depicted as dark gray), and numerosity of one. If the sum of the values on the relevant dimensions is greater than 1.5, the stimulus is assigned to Category A; if less than 1.5, the stimulus is assigned to Category B. Copyright © 2003 by the American Psychological Association. Reproduced with permission: Ashby, F.G., Noble, S., Filoteo, J.V., Waldron, E.M., & Ell, S.W. (2003). Category learning deficits in Parkinson’s disease. Neuropsychology, 17, 115–124. (The use of APA information does not suggest endorsement by APA.)