Summary: This research was supported in part by Public Health Service Grant MH3760. We thank Vince
Filoteo for his helpful suggestions. Correspondence concerning this article should be addressed to
F. Gregory Ashby, Department of Psychology, University of California, Santa Barbara, CA 93106
(2006). In B. H. Ross (Ed.), The Psychology of Learning and Motivation,
Vol. 46 (pp. 1-36). New York: Elsevier.
THE ROLE OF THE BASAL GANGLIA IN
F. Gregory Ashby and John M. Ennis
Categorization is the act of responding differently to objects or events in separate
classes or categories. It is a vitally important skill that allows us to approach
friend and escape foe, to find food and avoid toxin. Every organism must have
some categorization ability. Even bacteria categorize. For example, the bacterium
e. coli tumbles randomly until it encounters a substance that it categorizes as a
nutrient. It then suppresses its tumbling behavior and swims up the concentration
gradient in search of the nutrient's source.
The scientific study of human category learning has a long history. For most
of this time, the focus was on the cognitive processes that mediate categorization.
Within the past decade, however, considerable attention has shifted to the study of