Categories and Concepts Flashcards
Category
set of things that are grouped together on the basis of something
Concept
mental representation of a category
You must…
remember previous experiences
recognize similarity
have a concept “lion”
Concept increases processing efficiency for
Memory
Reasoning
Communication
Complex Concepts
Cat
both a category and a concept
concept within category of animals
category that includes all the types of different cats
Basic Level
neither too general nor specific
tends to be used in speaking and reasoning about categories
ex: airplane, apple, etc.
Basic Level of Categorization
represented in language by a single word
in naming, we are likely to use the basic level
easier to explain what features are common to members of basic level categories than for other levels
Inductive Inference
reaching a general conclusion based on specific examples
use examples to build up general rule
categorization is itself an inductive inference
Deductive inference
reaching a conclusion about a specific instance, based on general principles
Gelman and Markman
Shown flamingo "bird feeds its babies mashed up food" Shown Bat "bat feeds its babies milk" Shown blackbird "what does this bird feed its babies?"
Inductive inference from categories
85% of preschoolers guess blackbird feeds its babies mashed up food. Used category information, rather than perceptual similarity to make inference
Three classes of theories
Classical, Probabilistic, Exemplar
Classical Theory
Rules
category defined in terms of necessary and sufficient features
representation is abstract, does not store any information about specific exemplars
Probabilistic Theory
Failure of classical theory led to proposal that category representation may be probabilistic rather than deterministic
Prototype theory: prototypes
Exemplar theory: individual instances
both based on idea of similarity
Theory Theory
categories provide explanations for how things work in the world
center on causal relations between entities in the world
guide perception by leading us to believe that particular features are interesting and others are not
Criticisms of Classical theory
defining features often can’t be found
you can often remove any particular feature and some object will still be a category member
Non-necessary features affect categorization
violation of any one defining feature does not seem to affect our categorization
Ludwig Wittgenstein
What is a game?
for many categories there are no clear defining features
various members share various features, but there is no single feature that is necessary
Challenges for Classical Theory
it is impossible to give adequate definitions
graded membership
typicality effects
(robin is more typical bird than a penguin)
Family Resemblance
Wittgenstein proposed that members of a category have a family resemblance to each other
no defining features that one must have but there are common/typical features
membership is a matter of degree, not all or nothing
Graded family membership
items are in a category, qualify based on necessary and sufficient rules
items are not in a category, do not meet the necessary and sufficient rules
Typicality effects
Name fruit: most common ones (most typical) are named most frequently
Prototype Theory
categories are represented by the average of all members of the category
items can be better or worse examples of a category
Prototype Theory cont.
prototype need not exist in real world
category representation is abstract, does not store information about specific exemplars
graded category membership
Posner & Keele
two prototypes created and never shown to the participants.
distortions of each prototype are created. Subjects learn to classify the distortions. New distortions, (variations of the old ones) were shown, then prototypes were shown
Posner and Keele results
subjects were more likely to endorse the prototype as a category member than they were for a new distortion
Old (studied) distortions were classified just as well as the unseen prototype. Suggests that subjects store an average of their experiences
Problems with Prototype Theory
assumes that information about individual instances is not stored. People do seem to store information about individual exemplars
Exemplar thoery
concepts are represented by all of the exemplars that have been experienced
Category “bird” is represented by memories of all previous experiences of birds. When we categorize, we compare to all exemplars in memory
category representation is concrete
Natural vs. Artifact
Natural: groupings that occur naturally (bird, trees)
Artifact: designed/invented (computers, sports cars)
Stable vs. Ad-hoc
Stable: people generally agree on what goes into them, what the criteria of inclusion are
Ad-hoc: unstable categories defined for a special purpose or within a specific context
What is a drunk?
knowledge based causal theory: late at night, someone jumps into pool fully clothed
concept of drunk involves a theory of impaired judgment which explains the man’s behavior so you induce he must be drunk
Schema
large, complex units of knowledge that encode properties which are typical of instances of general categories and omit properties which are not typical of the categories
Summary of Approaches to categorization
Classical theory: concepts have definitions
Prototype: summary representation for each category
Exemplar: no summary representation, concept is a collection of individual instances
Theory based: categories include causal explanations
