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Behavioural Processes 66 (2004) 309332 Dissociating explicit and procedural-learning based

Summary: Behavioural Processes 66 (2004) 309332
Dissociating explicit and procedural-learning based
systems of perceptual category learning
W. Todd Maddoxa,, F. Gregory Ashbyb
a Department of Psychology, 1 University Station A8000, University of Texas, Austin, TX 78712, USA
b University of California, Santa Barbara, CA, USA
A fundamental question is whether people have available one category learning system, or many. Most multiple systems
advocates postulate one explicit and one implicit system. Although there is much agreement about the nature of the explicit
system, there is less agreement about the nature of the implicit system. In this article, we review a dual systems theory of
category learning called competition between verbal and implicit systems (COVIS) developed by Ashby et al. (1998). The
explicit system dominates the learning of verbalizable, rule-based category structures and is mediated by frontal brain areas such
as the anterior cingulate, prefrontal cortex (PFC), and head of the caudate nucleus. The implicit system, which uses procedural
learning, dominates the learning of non-verbalizable, information-integration category structures, and is mediated by the tail
of the caudate nucleus and a dopamine-mediated reward signal. We review nine studies that test six a priori predictions from
COVIS, each of which is supported by the data.
2004 Elsevier B.V. All rights reserved.
Keywords: Categorization; Classification; Memory; Caudate nucleus; Working memory; Prefrontal cortex
1. Introduction
Categorization is a vitally important skill. The feed-


Source: Ashby, F. Gregory - Department of Psychology, University of California at Santa Barbara
Maddox, W. Todd - Department of Psychology, University of Texas at Austin


Collections: Biology and Medicine; Computer Technologies and Information Sciences