Categorization and Concept Formation

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Categorization and Concept Formation

• What does the child know about the world?
• How does the child come to know what she knows?
• Is the childs mind different from the adults
  mind, or does the child just know less?
• Does the child come factory equipped with any
  knowledge of the world?
• What does learning mean?

2
Why categorize things in the world?

• Conserve on memory
• What if your memory had to store every single
  instance of every thing you ever saw??
• Support inferences
• This cat has fur and meows. Will this be true of
  the next cat I see?
• What kind of thing is it? What kind of
  inferences/ explanations apply to that kind of
  thing?

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Concepts and Categories

• A concept picks out a set of things in the world
• A category is the set of things it picks out
• Meaning of a word the concept it expresses
• What are our concepts like?
• Are there different kinds of concepts?

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Possible Bases for Categorization

• Taxonomic (same kind of thing)
• Thematic or event-based
• Spatial relations (next to, on top of)
• Next to groups desk and chair
• Causal relationship between kinds
• Can opener cans one category because use
  opener to open cans
• Participate in same event
• Dog bone one category because dogs chew bones
• What if child thought animal refers to
• Dog, leash, cow, grass, cat, milk
• Inference problems if categories do not capture
  same kind of thing (taxonomic)

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Views of the structure of concepts

• Classical concepts
• Philosopher Aristotle
• Family resemblance concepts
• Philosopher Wittgenstein
• Natural kinds / essentialism
• Philosopher Kripke
• Domain-specific concepts (theory based)

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Views of concept structure flow from views of the
mind

• Blank slate/ driven by perception
• Classical concepts
• Family resemblance concepts
• Mind provides structure/ privileged hypotheses
• Natural kinds / essentialism
• Domain-specific concepts (theory based)

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Classical View of the Structure of Concepts

• Concept is defined by a set of necessary and
  sufficient conditions
• Blue triangle
• Intension of a category (the concept itself)
• the set of attributes or features that define the
  category (its meaning)
• bachelor unmarried man of marriageable age
• Concept a mental representation specifying the
  conjunction of these defining features
• Extension of category
• the set of objects that fulfill the criteria of
  the intensional definition (actual bachelors)

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Classical View of the Structure of Concepts

• Concept set of necessary and sufficient
  conditions
• Isolable, uncorrelated dimensions (blue,
  triangle)
• Sharp boundary conditions
• No internal structure to the category
• One blue triangle cannot be a better example of
  the category than another
• Concepts are INVENTED, not discovered
• They are imposed by minds on the world. They do
  not capture something that is already true of the
  world
• Classical concepts are arbitrary. Free to vary
  from person to person and culture to culture.

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Abilities needed to acquire classical concepts

• Analytic abilities for decomposing an object into
  its properties.
• A powerful hypothesis-testing system, for
  generating possible properties and evaluating
  them against new exemplars, as well as for
  revising, rejecting, or maintaining hypotheses in
  the face of new evidence
• An ability to use the intensional criteria to
  evaluate subsequent objects to determine whether
  they are members of the category

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Abilities needed to acquire classical concepts

• Analytic abilities for decomposing an object into
  its properties.
• Here are gorbs
• What makes these members of the same category?
• Decompose objects into properties
• These gorbs are blue. They are triangles
• Which properties does the mind use??
• Usual answer perceptual properties
• Still, which ones?

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Abilities needed to acquire classical concepts

• Hypothesis-testing system, for generating
  possible properties and evaluating them against
  new exemplars
• Hypothesis Gorbs are blue triangles
• Are these gorbs?
• Need new hypothesis!
• Hypothesis 2 Gorbs are triangles

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Abilities needed to acquire classical concepts

• Hypothesis 2 Gorbs are triangles
• Need new hypothesis!
• Gorbs are red or blue triangles
• New tests...
• An ability to use the intensional criteria to
  evaluate subsequent objects to determine whether
  they are members of the category
• Is this a gorb?

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Babies categorize the world. But do babies have
these abilities? Do other animals?

• Abilities needed to acquire classical concepts
• Analytic abilities for decomposing an object into
  its properties.
• A powerful hypothesis-testing system, for
  generating possible properties and evaluating
  them against new exemplars, as well as for
  revising, rejecting, or maintaining hypotheses in
  the face of new evidence
• An ability to use the intensional criteria to
  evaluate subsequent objects to determine whether
  they are members of the category

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Family Resemblance (Eleanor Rosch)

• Cateories have family resemblance structure
• No necessary or sufficient conditions
• Game Wittenstein example
• characteristic features no defining features
• Categories are DISCOVERED, not invented
• detecting the correlational structure of world
• Fuzzy boundaries, internal structure
• Internal structure Better and worse examples of
  a fruit
• Fuzzy boundaries Eggplant? Tomato?

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Family Resemblance (Eleanor Rosch)

• Detecting structure in the world
• Start with features, which are correlated?
• Other animals can categorize. Do other animals
  have family resemblance categories?
• Pigeons tree, individual woman (not arbitrary
  cultural inventions)
• To distinguish categories
• Which features are highly correlated?
• degree of overlap of cues
• Compute cue validities (feathers v. fur)

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Family Resemblance (Eleanor Rosch)

• Taxonomic structure of categories
• Fruit superordinate
• Apple basic level
• Grannysmith apple subordinate level
• Basic object level The level where there is
• Maximum similarity between members within the
  category and
• Minimal similarity between members of contrasting
  categories
• Grannysmith apple v. Macintosh apple
• Subordinate level because so much more overlap in
  features, compared to (e.g.) apple pear

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Family Resemblance (Eleanor Rosch)

• Taxonomic structure of categories
• Fruit superordinate
• Apple basic level
• Grannysmith apple subordinate level
• Fruit (apple, pear, grape)
• Superordinate level because so few features
  overlap between instances (compared to basic
  level)
• Test ask people to generate features in common
• Note What counts as basic level depends on
  expertise (culture relative)
• tree basic to me
• maple v. oak v. beech basic to forest
  forager or nursery owner

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• At basic level some category members have lots
  of high cue validity features, others have fewer
• Robin Sparrow versus Ostrich
• Prototypical or central members of the category
• Members with lots of characteristic features,
  lots of high cue validity features
• Is this psychologically real? Tests
• Which is a better example of a bird?
• Not seen as silly similar answers across
  subjects
• Reaction time Is this sentence true?
• A robin is a bird faster than An ostrich is a
  bird

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Is basic level psychologically real (continued)...

• Children usually learn words for basic level
  category before superordinate or subordinate
• Remember taxonomic assumption in word learning
• Children usually learn prototypical members of a
  category before atypical members
• (robin before ostrich)
• Category learning in adults
• Create new categories vary their correlational
  structure. Adults learn prototypical members
  most easily
• Dani (New Guinea) only two color terms (light,
  dark)
• Learn color categories organized around focal
  colors faster, more easily

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Problems with the family resemblance view...

• Some evidence for prototypicality etc can also be
  found for classical categories (odd numbers)
• Which is a better example of an odd number, 3 or
  17?
• How can there be prototypic odd numbers?
• Save Contrast identification function with
  conceptual core. 2 different mental structures?

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Problems with the family resemblance view...

• Bottom up starts with features
• Which features?
• Are all features equal? (color v. self-propelled
  motion)
• Do features dominate over other considerations?
• Only perceptual features possible on any blank
  slate (empiricist) account

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Problems with the family resemblance view...

• Do relationships among features matter?
• Birds. Feathers, beak, wings.
• Beak on the wings?
• Feathers on the feet?
• Do we then need higher level features?
• Are there theory-like mental structures
  organizing these features?
• Is it true that children and adults are dominated
  by perceptual similarity???

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Natural Kinds and Essentialism

• Natural kinds categories found in nature
• Horse mammal gold water lemon
• Rich correlational structure
• Contrast White things (soap cloud sink...)
• Knowing kind category allows you to infer many
  things
• Anteater is a mammal. What else do you know?
• Here is a skunk. Properties... New skunk Same
  properties

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Natural Kinds and Essentialism

• Can discover new things about natural kinds. Can
  have a science of a natural kind category (but
  not of white things)
• Not just correlations among features Causal
  structure very important for kind categories
• Causal structure gives rise to surface features
• Being a racoon gives rise to surface features
  like black eye patches striped tail. Perceptual
  features may be used to identify a kind category
  member, but they do not define what counts as a
  member.

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Natural Kinds and Essentialism

• What causes you to BE a racoon?
• Something inside, some essence
• Not looks like a skunk (Frank Keil)
• Color racoon fur black with white stripe down
  back, use surgery to implant bag of stinky stuff,
  so now can squirt stinky stuff.
• Is it still a racoon, or is it now a skunk?
• Does it have racoon innards or skunk innards?
• Will it have racoon babies or skunk babies?
• 7 year olds racoon, racoon, racoon
• 5 year olds less sure, but do better if you make
  it a really tight fitting costume

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Natural Kinds and Essentialism

• What causes you to BE a racoon?
• Something inside, some essence
• Perceptual features do not CAUSE internal
  similarity (arabian v. thoroughbred horse)
• Internal features cause perceptual features
• Albino tiger is still a tiger, even though no
  stripes

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Natural Kinds and Essentialism

• What causes you to BE a racoon?
• Something inside, some essence
• Post-hoc cultural explanation of what the essence
  is
• Genes
• Has skunk spirit
• Captures intuition that there is something
  essential that makes you a member of the
  category, not just what you look like

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Natural Kinds and Essentialism

• Because causal structure is important
• Natural kind categories are more theory-like
• Beak cannot be on wings
• Some features more critical to essence than
  others has racoon babies more important than
  has eye patches
• Applies only to animals, plants, and minerals?
  Or can artifacts be natural kinds too?
• Milk carton to bird feeder What is it now?
• Tools versus animals, plants, minerals...

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Natural Kinds and Essentialism

• Causal theory of reference (Saul Kripke)
• Kind categories are baptised with a name
• Category description functions like a name it
  does not specify criterial features.
• Did Shakespeare write Hamlet?
• Makes no sense if concept Shakespeare is
  defined as he who wrote Hamlet
• Makes sense if an individual is called
  Shakespearethen can ask if that individual
  wrote Hamlet

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Natural Kind Categories Support Induction

• When children make inferences, are they dominated
  by perceptual similarity? Or do they take natural
  kind category into account?
• Pit category name against perceptual similarity
  (Susan Gelman Ellen Markman)
• First pretest, show that children do not know
  whether target has property
• Do dolphins breathe under water or do they pop up
  above the water to breathe?
• Do fish breathe under water or do they pop up
  above the water to breathe?
• Choose animals/substances and features where they
  do not know. E.g., 53 correct on this property
  (chance)

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Category membership vs. perceptual similarity
See this fish? It breathes under water.
See this dolphin? It pops up above the water to
breathe.
What does this fish do? Does it pop up above the
water to breathe, or does it breathe under water?
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Category label over-rides perceptual similarity

• 4 year olds
• When Category and Perceptual similarity in
  Conflict
• 68 go with category (breathes under water)
• When Category Perceptual in sync 88
• No child consistently used perceptual
• 37 consistently (15/20 times) used category
  label
• 3 year olds simpler task. Tell about shark
  This fish breathes under water which other does?
• Same pattern
• Also with gold, pearls (minerals)

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Will any arbritrary feature elicit same pattern?
Or is this pattern particular to category labels?

• Put different colored dots next to bird, bat
• Children at chance

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Is it just having the exact same label?Or does
it have to be the same natural kind?

• Test with synonyms the child knows
• Rabbit versus Bunny
• Not just identity of word label
• Children prefer kind category even when labeled
  with different words

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Do all features generalize in the same way? Or
are the childs inferences more theory-guided?

• For animals
• Physiological features like breathes under
  water generalize by kind category
• Size generalizes by perceptual similarity (200
  pounds versus 2 pounds)
• Some features do not generalize by kind category
  at all
• Is dirty
• Fell on floor
• Is a year old

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Natural kind categories and inferences

• By 3-4 years of age, children use natural kind
  category to infer properties
• They only use kind category for some properties
  the ones that are in fact likely to be a function
  of membership in a natural kind category
  (breathes, what it eats, lays eggs)
• They do not use it for properties that are likely
  to generalize by perceptual similarity (weight)
• They do not generalize some properties at all
• The pattern suggests a sophisticated theory of
  how animals work!!

37
Categorization and Concept Formation

• What does the child know about the world?
• How does the child come to know what she knows?
• Is the childs mind different from the adults
  mind, or does the child just know less?
• Does the child come factory equipped with any
  knowledge of the world?
• What does learning mean?

38
Questions to think about throughout 142...

• What does the child know about the world?
• How does the child come to know what she knows?
• Is the childs mind different from the adults
  mind, or does the child just know less?
• Does the child come factory equipped with any
  knowledge of the world?

39
Questions to think about throughout 142...

• How does the environment affect development?
• How does maturation affect development?
• Why did scientists underestimate how much infants
  know?
• What is the competence/ performance distinction?
• Can one part of the brain know something that
  another part of the brain does not know?

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Questions to think about throughout 142...

• What is the difference between studying natural
  competences and side-effects?
• What does learning mean?
• How many learning processes are there?
• Is instinct the opposite of learning?
• What is the design of the instinct that causes
  learning in a given domain?