Chapter12- readings

Chapter12- readings - Chapter 12 The Exemplar View Edward...

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The Exemplar View Edward E. Smith and Douglas L. Medin Rationale for the Exemplar View - The exemplar view holds that concepts are represented by their exemplars (at least in part) rather than by an abstract summary. -however, exemplars themselves can be abstractions - The term exemplar is often used ambiguously; it can refer either to a specific instance of a concept or to a subset of that concept - Some models based on the exemplar view do not exclude summary-type information - These models claim that the exemplars usually play the dominant role in categorization because they are more accessible than summary information - A number of studies in different domains indicate that people frequently use exemplars when making decisions and categorizations. One such study was by Kahneman and Tversky (1973). - In studies of categorization, subjects use exemplars to determine if a test item is an instance of a target category but sometimes decide that the test item is not such an instance by retrieving a counterexample. Concept Representations and Categorization Processes The Critical Assumption - The representation of a concept consists of separate descriptions of some of its exemplars (either instances or subsets). - If the exemplar is a subset, its representation can consist either of other exemplars, or of a description of the relevant properties, or both. - If the exemplar is an instance, it must be represented by a property description; the representation is explicitly disjunctive, and the properties of a concept are the sum of the exemplar’s properties - Three Criteria used for a summary representation - it is the result of an abstraction process - it need not correspond to a specific instance - it is always applied when a question of category membership arises - The Critical Assumption violates the criteria of summary representation - Some exemplars are subsets and therefore have at least some abstraction - for this reason, lack of abstraction is a matter of degree, and the best assumption is that exemplar based representations show a greater lack of abstraction than those based on the classical or probabilistic view. This is the meat of the Critical Assumption because it is the only thing common to all present models based on the exemplar view. - whether or not part of a representation corresponds to an instance is a point on which various exemplar models vary and is not criterion for being an exemplar model. The Proximity Model as an Extreme Case
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This note was uploaded on 04/18/2008 for the course PSYC 213 taught by Professor Levitin during the Winter '08 term at McGill.

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Chapter12- readings - Chapter 12 The Exemplar View Edward...

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