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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
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
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

what is categorization based on
What is Categorization Based on?
  • Similarity?
  • Similarity as shared features
  • But which features?
semantic feature models of concepts
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
prototypes coglab results
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

different kinds of concepts
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)
types of concepts
Types of Concepts
  • Natural kind concepts
  • Artifacts
  • Conventionally defined
  • Other types?
similarity re examined
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
theory theories of concepts
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.
conceptual combination
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)
context dependence of conceptual combination
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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