Lecture 16: Knowledge 16 Flashcards
According to the theory: Classical view, how do we represent concepts
Intuition: Concepts have definitions, a list of necessary and sufficient conditions for membership in a category. Concepts can be defined in terms of individually necessary and jointly sufficient features
Ex: a square: closed figure, four sides and corner, equal side lengths and equal angles.
Bachelor: Adult, unmarried, male (wrong)
According to the theory: Prototype view, how do we represent concepts
Concepts do not have definitions. They are represented by a prototype. Other members share a family resemblance relation to the prototype, and typicality is a function of similarity to the prototype.
According to the theory: Exemplar model, how do we represent concepts
Concepts do not have definitions or summary representations. A concept is the set of all examples of the concept that are stored in memory.
Exp: Concept bird: all exemplars of birds in memory.
In what ways are basic Level categories special
Basic level names are used to identify objects, they are moderately specific. Privileged level of categorization: bird, screwdriver, chair. ppl list many common attributes at the basic level.
Category
a group of objects in the world
Concept
a mental representation of a group of objects
Categorization
to think of an object X as an instance of a category
Why we love the classical view
- cognitive economy = just need definition
- generalization = must have necessary features
- communication = everyone has same concept
Why do we hate the classical view
- failure to find definitions for real-world concepts (e.g., game, bachelor)
- borderline cases (e.g., is a lamp/rug furniture?)
- some members are better than others (e.g., 3 is a “better” prime # than 2, robins are “better” birds than penguins) AKA typicality effects
Typicality effects
phenomena in which some examples seem like “better” category members than others
typicality predicts a variety of behavioral measures:
- RT to identify picture/word as category member –> fast for best, slow for worse
- generalization: lions express protein X, what about whales? (high prob) vs. whales express protein X, what about lions? (low prob); more likely to go from typical –> atypical
Prototype view
1 of 3 theories on how we represent concepts; concepts do not have definitions, they are represented by a prototype; other members share a family resemblance relation to the prototype, and typicality is a function of similarity to the prototype
prototype maximizes average similarity
graded membership
Family resemblance
the notion that members of a category (e.g., all dogs, all games) resemble each other; in general, relies on some number of features being shared by any group of category members, even though these features may not be shared by all members of the category; therefore, the basis for family resemblance may shift from one subset of the category to another
Graded membership
the idea that some members of a category are “better” members and therefore are more firmly in the category than other memebrs
Posner & Keele’s study
evidence for prototype view
see dot patterns, judge whether each belongs to category A or B –> guess at first, but will get better with feedback; then show old, new, and prototype (new) dot patterns and judge whether you had seen it before
results: prototypes were judged to be familiar, categorized as much as “old” even though they were new
–> automatic abstraction of prototypes
Exemplar Model
1 of 3 theories on how we represent concepts; concepts do not have definitions or summary representations; a concept is the set of all examples of the concept that are stored in memory (e.g., concept bird: all exemplars of bird in memory)
