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Concepts and Categories. Concepts and Categories. Concept – a mental representation Category – the set of things picked out by the concept Why do we need them? To make predictions To prevent information overload. Effects of Categorization. 1. categorical perception

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Concepts and categories2 l.jpg
Concepts and Categories

  • Concept – a mental representation

  • Category – the set of things picked out by the concept

  • Why do we need them?

    • To make predictions

    • To prevent information overload


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Effects of Categorization

1. categorical perception

  • categorical perception = perceiving things in discrete categories rather than as points on a continuum.

  • Characteristics:

    • sharp change in probability of category labeling at the category boundary

    • greater between-category than within-category discriminability

      2. category labels' effect on perception(Tajfel & Wilkes, 1963)

      3. implications: stereotypes


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What is Categorization Based on?

  • Similarity?

  • Similarity as shared features

  • But which features?


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Semantic Feature Models of Concepts

  • The classical view: defining features

  • The probabilistic view:

    • prototypes (Rosch, 1977)[Coglab demo next slide]

    • exemplars (Medin & Schaffer, 1978; Hintzman, 1986)

    • What’s the difference? Internal structure

  • Hybrid models: defining & characteristic features


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Prototypes: Coglab Results

Pattern type Reaction time (ms)

Prototypes 718.68335

Variants 752.62085

SOURCE: grand mean

A N MEAN SD SE

50 752.0379 228.3917 32.2995

SOURCE: A

A N MEAN SD SE

Variant 25 778.1483 246.9372 49.3874

Prototy 25 725.9275 210.0015 42.0003

FACTOR : RANDOM A DATA

LEVELS : 25 2 50

TYPE : RANDOM WITHIN DATA

SOURCE SS df MS F p

===============================================================

mean 28278051.3746 1 28278051.3746 297.222 0.000 ***

R/ 2283391.4564 24 95141.3107

A 34087.6919 1 34087.6919 3.430 0.076

AR/ 238495.4094 24 9937.3087


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Different kinds of concepts?

  • dog, tree, diamond (natural kind objects, basic level)

  • Collie, oak, industrial diamond (natural kinds, subordinate level)

  • animal, plant, geographical feature (natural kinds, super-ordinate level)

  • hammer, chair, cup (artifact objects)

  • felony, majority, contract (abstract, conventionally defined)

  • candy cigarette, dog bed, phone book (non-novel noun-noun combinations)

  • apple chair, carpet light, ear filter (novel noun combinations)

  • Brazil, Richard Nixon, Jupiter (names)

  • wife, senator, friend (social roles)

  • justice, peace, existence (abstract nouns)

  • bake, eat, explode (verbs)

  • red, hot, large (perceptual adjectives)

  • entropy, genus, photosynthesis (technical terms)


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Types of Concepts

  • Natural kind concepts

  • Artifacts

  • Conventionally defined

  • Other types?


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Similarity Re-examined

  • non-reflexivity of similarity

  • non-transitivity of similarity

  • context-dependence of similarity(Tversky, 1977)

  • similarity can not simply equal the number of shared features

  • similarity does not always predict categorization

    • Psychological Essentialism (for natural kinds)

    • Ad-hoc categories: not defined by similarity


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Theory Theories of Concepts

  • Organization of concepts is knowledge-based rather than similarity-based(Keil, 1986, 1987; Murphy & Medin, 1985).

  • People's intuitive theories are the basis for categorization of natural kind objects. This has particularly been argued for biological kinds.


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Conceptual Combination

  • Modification? (brown apple)

  • Separate Prototypes? (big wooden spoon)

    • But sometimes the combination has a prototypical feature that is not typical of either noun individually (pet birds live in cages, but neither pets nor birds do)

  • Extending salient characteristics?

    • When nouns are “alignable” (zebra horse)

    • But non-alignable nouns are combined using a different mechanism (zebra house)


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Context-Dependence of Conceptual Combination

  • “Sit in the apple-sauce chair.”

  • Is conceptual combination really about the structure of concepts, or is it about the pragmatics of language use?


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