Concepts

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Concepts Categorization

• Internal Structure of Concepts

2
Outline

• What is a concept?
• Similarity-based Views
• The Classical View
• Probabilistic Views
• The Exemplar View
• The Prototype View

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What is a Concept?

• Concept mental representation of a class (cars,
  cats, oaks, chairs) and associated knowledge and
  beliefs.
• List all of the kinds of BIRDS you can think of.

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Living Thing
Breathes
Animal
Plant
Feathers
Mammal
Bird
Ostrich
Barks
Bat
Dog
Canary
Yellow
5
Living Thing
Breathes
Animal
Plant
Bird
Feathers
Mammal
Ostrich
Barks
Bat
Dog
Canary
Yellow
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What do Concepts do for us?

• Cognitive Economy
• Inferences
• Combine to form Complex Thoughts
• Communication

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The Classical View

• Features are singly necessary and jointly
  sufficient to define the concept.
• Singly necessary every member must have that
  feature.
• Jointly sufficient everything that has all
  features must be a member.
• Categorization gt comparing properties of
  instance to definition

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Classical View Problems

• Definitions are difficult to specify
• Typicality Effects

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Typicality Effects

• Some things are better examples of a concept than
  others.
• Categorization
• Retrieval
• Acquisition
• Reasoning

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Probabilistic Views

• How can the Classical View explain typicality
  effects?
• Probabilistic Views Category membership is
  graded.
• Prototype View
• Exemplar View

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The Prototype View

• Prototype abstracted representation of a
  category containing salient features that are
  true of most instances.
• Bird
• Categorization gt comparison to prototype

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Prototype v. Classical

• Features arent necessary or sufficient.
• Features can be weighted.
• Category membership can be graded.
• Categories can have internal structure.

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The Exemplar View

• Similar to Prototype View
• Representation is not a definition
• Different Representation is not abstract
• Descriptions of specific examples
• Bird
• Categorization gt comparison to stored exemplars

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Typicality Effects

• How do Probabilistic Views explain typicality
  effects?
• Categorization
• Retrieval
• Acquisition
• Reasoning

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Probabilistic Views

• Thought question How did you come up with the
  features weights for the prototype of bird?

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Distribution Exam 1
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Within-Category Structure

• Similarity-Based Views
• Classical
• Probabilistic
• Prototype
• Exemplar
• Similarity-Based Views fail to explain...
• Relations among features
• Feature centrality
• Which features are part of representation

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Similarity Depends on Context

• White Cloud
• Gray Cloud
• Black Cloud

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Similarity Depends on Context

• White Cloud
• Gray Cloud
• Black Cloud

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Similarity Depends on Context

• White Cloud
• Gray Cloud
• Black Cloud

• White Hair
• Gray Hair
• Black Hair

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Similarity Depends on Context

• White Cloud
• Gray Cloud
• Black Cloud

• White Hair
• Gray Hair
• Black Hair

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Is Similarity Enough?

• Is similarity sufficient for category membership?
• Imagine an object 3 inches in diameter. (Rips,
  1989).
• Is it more similar to a pizza or a quarter?
• Is it more likely to be a pizza or a quarter?

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Is Similarity Enough?

• Is similarity necessary for category membership?
• Sorp/Doon Story. (Rips, 1989).
• Accident v Essence
• Is it more similar to a bird or an insect?
• Is it more likely to be a bird or an insect?

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Theory-based Approach

• Similarity is not enough.
• Knowledge of the world informs and shapes our
  concepts folk theories
• Features embedded in complex network of causal
  and explanatory links. Folk theories point out
• Relative importance of features
• Relations among features
• Objects classified into concept that best
  explains their pattern of attributes.

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Flies
Small
Cares for Young
Two Legs
Has Wings
Eats Bugs
Has Feathers
Tasty
Lays Eggs
Lives in a Nest
Sings
Colorful
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Theory-based Approach

• Similarity is not enough.
• Knowledge of the world informs and shapes our
  concepts folk theories
• Features embedded in complex network of causal
  and explanatory links. Folk theories point out
• Relative importance of features
• Relations among features
• Objects classified into concept that best
  explains their pattern of attributes.

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Psychological Essentialism

• Previous accounts emphasize perceptually salient
  surface features.
• Non-obvious underlying features related to folk
  theories are often crucial for understanding
  concepts.
• A Dolphin is more similar to a shark than a deer.
• Dolphins and deer are both mammals because of
  internal properties.
• Peoples representations of concepts include an
  essence.

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Flies
Small
Cares for Young
Two Legs
Has Wings
Eats Bugs
Has Feathers
Tasty
Lays Eggs
Lives in a Nest
Sings
Colorful
29
Flies
Small
Cares for Young
Two Legs
Has Wings
Eats Bugs
Has Feathers
Tasty
Lays Eggs
Lives in a Nest
Sings
Colorful
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What is an Essence?

• Theory-related
• Causes observable properties
• Ultimately determines category membership
• Definition?
• Could be very vaguely understood or even taken on
  faith.

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Psychological Essentialism

• People act as though things have essences
  (underlying natures) that make them the thing
  they are.
• Essences constrains/generates properties that
  vary in their centrality.
• Essence is tied to Informal Theories
• Essentialist Heuristic Things that look alike
  tend to share deeper properties.

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Psych. Esslism Implications

• Transformations
• Change in surface features dont change category
  membership
• Removing pigeons wings or feathers
• Change in essential features DO change category
  membership
• Changing a pigeons DNA structure
• Categorization ultimately based on essence
• Expertise
• Category membership all-or-none

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Is Category Membersip REALLY graded?

• Coley Luhmann
• Three kinds of concepts
• Natural Kinds (bird, fish, tree, chemical
  element)
• Social Kinds (occupation, relative)
• Artifacts (furniture, vehicle, clothing)
• Ratings
• Typicality
• Absolute Category Membership (yes, no, sorta)
• Expert Judgments

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Results Does Typicality Predict
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Summary

• Similarity-Based Views
• Classical
• Probabilistic
• Prototype
• Exemplar
• Similarity alone is not enough
• Theory-Based Views
• Psychological Essentialism