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Two CompetingAttentional Mechanisms in Category Learnin

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Journal of Experimental Psychology: Learning, Memory, and Cognition 1998, Vol. 24, No. 6, 1437-1458 Copyright 1998 by the American Psychological Association, Inc. 0278-7393f)8/$3.00 Two CompetingAttentional Mechanisms in Category Learning Alan W. Kersten, Robert L. Goldstone, and Alexandra Schaffert Indiana University This research provides evidence that there are 2 competing attentional mechanisms in category learning. Attentionai persistence directs attention to attributes previously found to be predictive, whereas attentional contrast directs attention to attribute values that have not already been associated with a category. Three experiments provided evidence for these mechanisms. Experiments 1 and 2 provided evidence for persistence because increased attention to an attribute followed training in which that attribute was relevant. These experiments also provided evidence for contrast because attention was also increased to the values of an attribute when the values of another, more salient attribute had already been associated with categories. Experiment 3 provided evidence that persistence operates primarily at the level of attributes, whereas contrast operates at the level of attribute values. Learning theorists have relied on the notion of attention to explain how learning one discrimination can be facilitated or hindered by the prior learning of another discrimination. In particular, learning a discrimination is dependent on atten- tion to the relevant attribute. Two seemingly contradictory mechanisms have been proposed for the changes in attention following a successful discrimination. According to one mechanism, which we call attentionalpersistence, increased attention is allocated to attributes that have been found to be predictive of an outcome. This mechanism is involved in the analyzer theory of Sutherland & Mackintosh (1971). Accord- ing to the analyzer theory, when a discriminative stimulus in an operant conditioning paradigm is found to be predictive of reinforcement, greater attention is devoted to the relevant attribute of the discriminative stimulus. Because the total pool of attentional resources is fixed, this requires a decrease in attention to other attributes. As a result, a learner is better able to learn a second discrimination involving the same attribute but is less able to learn a discrimination involving a different attribute. Attentional persistence plays a role not only in theories of operant conditioning but also in promi- nent theories of categorization (e.g., Kruschke, 1992; Nosof- sky, 1986). A second attentional mechanism, which we call atten- tional contrast, works in the opposite direction. In particular, once a value of an attribute has been associated with a category, attention is allocated to other attribute values when another category must be learned. This mechanism is involved in the Pearce-Hall model of learning (Pearce & Alan W. Kersten, Robert L. Goldstone, and Alexandra Schaffert, Department of Psychology, Indiana University. We thank Julie Earles for helpful comments on a previous version of this article. Examples of the events used as stimuli in this research are available over the World Wide Web at http://www.psy.fau.edu/chez/ awk/home.html. Correspondence concerning this article should be addressed to Alan W. Kersten, who is now at the Department of Psychology, Florida Atlantic University, 777 Glades Road, Boca Raton, Florida 33431-0991. Electronic mail may be sent to [email protected]. Hall, 1980). According to this model, stimuli receive attention only to the extent that their consequences are unclear. Thus, once an attribute value has been found to be reliably associated with a given outcome, attention to that attribute value is reduced. This theory thus appears to stand in opposition to the analyzer theory, in which a consistent predictor of an outcome receives greater attention. Evidence for Attentional Persistence Early evidence for attentional persistence can be found in the classic study of Lawrence (1949). In the first stage of this study, rats in the experimental condition were placed in a maze with one white arm and one black arm. We refer to such dimensions of variation, regardless of whether they vary quantitatively or qualitatively, as attributes (e.g., color). We refer to specific points along these dimensions as values (e.g., black). Rats were reinforced for entering the black arm. Attentional persistence would thus predict increased attention to the color attribute following this discrimination. In contrast, rats in a control condition were trained in a gray maze with texture rather than color predicting reinforce- ment. After this first stage of learning, rats were placed in mazes that had either two white arms or two black arms. Rats were reinforced for entering the right arms of black mazes and the left arms of white mazes. Thus, prior associations learned in the first stage involving specific values of color would not help rats learn these new contingencies. Consistent with attentional persistence, experi- mental rats learned these contingencies faster than control rats, presumably because of increased attention to color following the first stage of training. Further evidence for persistence has come from studies of intradimensional versus extradimensional shifts in discrimi- nation. For example, Mackintosh and Little (1969) pre- sented pigeons with pairs of stimuli that varied on both the color and orientation of a stripe. One group of pigeons was reinforced for pecking a stripe of a particular color, whereas a second group was reinforced for pecking a stripe of a particular orientation. Following this initial training, both groups were transferred to a task in which only color was 14371438 KERSTEN, GOLDSTONE, AND SCHAFFERT relevant. Two new colors and two new orientations were used so that prior associations would presumably not directly affect pigeons' performance. Pigeons that were subject to an intradimensional shift (i.e., those that were initially trained on color) performed better on this transfer task than did pigeons who were subject to an extradimen- sional shift. This


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