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Chapter 7

Cognitive Psychology - In and Out of the Laboratory: Chapter 7

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Psychology 2135A/B
Robert Brown

Chapter 7 - Concepts and Categorization - grouping of things into larger groups is categorization - mental representation of a category is a concept - doctors categorize illnesses to determine diagnosis - Medin (1989) argues concepts and categories serve as building blocks for human thought and behaviour - Lamberts and Shanks (1997) argue how concept are mentally represented is a central concern to cognitive psychology - concept: mental representation of some object, event, or pattern that has stored much of the knowledge typically thought relevant to the thing - category: class of similar things that share one of two things: - an essential core - or some similarity in perceptual, biological, or functional properties - Medin says categories are existing objectively in the world and concepts are mental representations of categories - Medin & Smith (1984) argue concepts help us establish order in knowledge base - concepts allow us categorize, to treat new things in same way we treat familiar things that we perceive to be in the same set (Neisser, 1987) - categorization allows us to make predictions and act accordingly - concepts play important role; reduces too much new information and allows easy language and communication (Smith and Medin, 1981) Theoretical Descriptions of the Nature of Concepts The Classical View - dates back to Aristotle to 1970s - features: a component of an object, event, or representation - classical view of concepts: all instances of a concept share fundamental features - features represented are individually necessary and collectively sufficient - assumes that concepts mentally represent lists of features - assumes that membership in a category is clear-cut - implies all members within a category are created equal - Eleanor Rosch criticized view - found that people judge different members of a category as varying in "goodness" - people more likely to list typical than atypical instances of a concept - people respond faster to typical examples - highly typical instances often led to better priming in semantic priming studies - McCloskey and Glucksberg (1978) found people do not have clear boundaries, especially for atypical instances - concluded that membership is graded and boundaries are fuzzy - most people cannot generate lists of features that are individually necessary and collectively sufficient to specify membership The Prototype View - prototype view of concepts: all concepts are organized around idealized mental representations of examples - denies existence of necessary and sufficient feature lists, except for a limited number of concepts like mathematical ones - prototypes: abstract representation of an idealized member of a class of things - prototypes include features that are characteristic - no individual feature, except very trivial ones, need be present to count as member - more characteristic features an instance has, more likely to be regarded as member - family resemblance structure of concepts: Wittgenstein (1953); each member shares different features with different members; few, if any, features shared by each member; more features a member possesses, more typical it is - Rosch and Mervis (1975) had people list features of individual items in categories and found very few features true of all items for a category - often thought of as mental summaries or averages of all instances - concepts have one or more core representations but not rigid boundaries - concepts exist at many different levels of a hierarchy; higher-level (superordinate), lower-level (subordinate) - Rosch and colleagues found another level, the basic level - basic level of categorization: hypothesized type of concept thought to be at a psychologically fundamental level of abstraction - compromise between grouping similar objects and distinguishing among objects - superordinate levels of categories: broader than basic level, including exemplars that can be quite dissimilar from one another - subordinate level of categories: thought to make fewer distinctions than basic level - criticisms of prototype view: - fails to capture people's knowledge about limits of conceptual boundaries - Rosch and colleagues counter-argued that some constraints come from environment itself, from the way world works; we just pick up information about world's regularities, not impose arbitrary groupings - typicality ratings depend to some extent on context; varies with way concept itself is being thought about - Armstrong, Gleitman, and Gleitman (1983) found that typicality ratings task is flawed, at least for discovering underlying representation of concepts Thee Exemplar View - exemplar view of concepts: concept consists of mental representations of actual instances or examples - people categorize new instances by comparing them to representations of previously stored instances, called exemplars - no necessary and defining features to be stated - explains difficulty in categorizing unclear, atypical instances - typical instances thought to be more likely to be stored than less typical ones, or to be more similar to stored exemplars, or both; therefore faster processing for typical - Allen and Brooks (1991) - trained people on fictional creatures and gave defining features for each - people took longer to classify and made many more errors in categorizing negative matches that others - concluded that previous exemplars stored in memory influenced categorization even though a simple categorization was given - criticisms of exemplar view: - too unconstrained; which will become exemplars and which will not - how are different exemplars called to mind at time of categorization - model has difficult accommodating data from large and complex categories The Schemata View - concepts are schemata - schemata can embed themselves in one another hierarchically; therefore possible to have subschemata and/or superschemata - schemata/scripts view of concepts: idea that all concepts are schemata - schemata store abstracted information across instances and from actual instances - does not specify clear boundaries among individual schemata - not sufficiently empirically testable The Knowledge-Based View - concepts have much more to do with people's knowledge and world-views - knowledge-based view of concepts: concepts function in relation to their instances as a scientific theory does to data supporting it (Murphy & Medin, 1985) - a person uses their knowledge of how the concept is organized to justify classification and to explain why certain instances happen to go together - people's theories or mental explanations about the world are intertwined with their concepts and provide basis for categorization (Heit, 1997) - lets people explain instances that go together and why, features that are important and why, and features that are irrelevant and why - Goodman (1972) criticized that similarity is empty without some specification of what the relevant respects are e.g., things share infinite similarities, less than 100kg, 101kg... - Komatsu (1992) created explanation-based category - people base classifications on meaningful relationships among instances and categories - based on degree to which people focus on superficial, perceptual information versus deeper, knowledge-derived information about function or role - any theory of concepts must balance between cognitive economy and informativeness - must also explain a concept or category's coherence Forming New Concepts and Classifying New Instances - to form concept, must have some basis for generalization, for grouping certain things but not others Concept Attainment Strategies - Bruner, Goodnow, and Austin (1956) did some of the earliest work - acquire information necessary to isolate and learn a concept - retain the information for later use - transform the information to make it usable when testing ideas about new possible instances - looked for strategies people used when trying to guess what concept experimenter had in mind - one strategy was simult
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