Transcript CATEGORIZATION - University of Connecticut

CATEGORIZATION
• Classical view (Aristotle): categories
are defined by a set of necessary and
sufficient conditions
– example: BACHELOR
– each of these four features (human,
unmarried, adult, male) is necessary
– Together, the four features are
sufficient.
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• Problem: difficult to identify the
necessary and sufficient features
• Ludwig Wittgenstein used as an
example the category GAME.
• Another problem: no basis for
distinguishing among the members of
a category - no levels of membership
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• Categories should have clear and welldefined boundaries
• experimental observation suggests
that categories have a graded
structure with fuzzy boundaries
• some members of a category are
better members than others
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• Returning to our example…
• BACHELOR:
–
–
–
–
35 year-old unmarried man?
21 year-old unmarried man?
17 year-old unmarried man?
Is a divorced man a bachelor? A priest?
The Pope?
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• Eleanor Rosch - proponent for the
view that categories have a fuzzy and
graded structure
• investigated how people use
categories
• she asked people to simply rate on a
7-point scale how well a word fits a
category
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• Example: category = VEGETABLE
• PEA and CARROT were rated as very
good exemplars (1.07 and 1.13)
• ONION (2.52) and YAM (3.31) =
moderately good exemplars
• PEANUT (5.36) and RICE (5.59) =
poor exemplars
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• it takes a shorter amount of time to
decide that POTATO is a
VEGETABLE than to decide that
OLIVE is a VEGETABLE
• This finding is known as the
Typicality Effect
• in contradiction with the view that
category judgments are based solely
on a fixed set of necessary and
sufficient features
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• Two main theories of categorization:
• prototype theory:
– a mental representation of the average
or most typical member of a category
– prototype does not exist, abstract
notion
• exemplar theory
– individual entities representative of a
category
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EXPERIMENTAL
PROCEDURE
• TASK: is this word a member of the
given category?
• 64 trials
• 8 with each of 8 categories:
• FURNITURE, FRUIT, WEAPON,
VEHICLE, TOOL, BIRD, SPORT,
CLOTHING
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• On half of the trials the exemplars
will be category members, on the
other half not.
• On half of the YES trials the
exemplar will be a highly typical
member
– (BIRD-ROBIN).
• On the other YES trials the exemplar
will be moderate or low in typicality
–
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(FURNITURE-BENCH, BIRD-PENGUIN).
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• The experimental trials are
presented in a different random
order for each student.
• The task is to decide whether the
probe is a member of the category.
• If the answer is incorrect, feedback
will be given
• respond as fast as possible, but also
try to avoid making errors.
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Design
• IV: typicality (high, low)
• DV1: RT
• DV2: accuracy
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DISCUSSION
• Compare means of RT and accuracy
• benefits: enables useful and
intelligent inferences
• costs: stereotyping
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How This Experiment
Relates to the Real World
• Categorization is fundamental to
almost everything we do.
• How do children learn categories?
• Are categories real or in the mind of
the categorizer?
• Stereotypes illustrate the costs of
categorization
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