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Journal of Experimental Psychology: Human Perception and Performance

Summary: Journal of Experimental Psychology:
Human Perception and Performance
1992, Vol. 18, No. 1, 50-71
Copyright 1992 by the American Psychological Association. Inc.
Complex Decision Rules in Categorization: Contrasting Novice and
Experienced Performance
F. Gregory Ashby and W. Todd Maddox
University of California, Santa Barbara
The ability of novice and experienced Ss to learn complex decision rules was tested with 3
categorization tasks. Each task involved 2 categories with exemplars that were normally distrib-
uted on 2 stimulusdimensions. 3 separate sets of stimuliwere used, and in each task the decision
rule that maximized categorization accuracy was a highly nonlinear function of the stimulus
dimension values. In the 3 tasks, all experienced Ssused highly nonlineardecision rules. Quadratic
rules were supported over bilinear rules, and in many cases, Ss used nearly optimal decision
rules. These findings did not depend on whether the stimulus components were integral or
separable. Novice Ss also did not use simple linear rules. A model that assumed Ss tried a
succession of different linear rules was also rejected. Instead, novices appeared to use quadratic
rules, although less consistentlythan experienced Ss.
Humans are remarkably accurate at categorizing a huge


Source: Ashby, F. Gregory - Department of Psychology, University of California at Santa Barbara


Collections: Biology and Medicine; Computer Technologies and Information Sciences