Lecture 8 - Concepts and Categories Flashcards
What influences the meaning of language? (define them)
- Semantics: Meanings of words
- Syntax: Roles/themes (who, what, to whom)
- Pragmatics: Influence of context
Why are concepts important?
- Allow predictions and inferences (e.g., sabre-tooth tiger = dangerous)
- Enable cognitive economy (grouping experiences)
- Facilitate communication (shared understanding of categories)
What is the structure of natural categories? What is the basic level preferred for?
- Superordinate (e.g., animal)
- Basic (e.g., dog)
- Subordinate (e.g., border collie)
- Basic level is preferred for:
- Spontaneous naming, efficient recognition, unique features, first acquired (Rosch et al.)
What are defining attributes? Any support?
- Concepts described by set of individually necessary and collectively sufficient features, e.g., bachelor = male, adult, unmarried
- Supported by Collins & Quillian’s hierarchal model
What are some problems with defining attributes?
- Some definitions are hard to specify (e.g., “chair”)
- Features may be:
- Not necessary (not all chairs have 4 legs)
- Not sufficient (other things can match the features but not be a chair)
What did Roach (1973) find?
- People rate category members by typicality, e.g., “A robin is a bird” verified faster than “An ostrich is a bird”
- Typicality effects undermine strict definitions
What di McCloskey & Glucksberg (1978)?
- Concept boundaries are fuzzy
- Is a stroke a disease? - Even participants changed answers a month later
What is the Prototype Theory? (Rosch, 1973, 1975)
- A concept is represented by a prototype (most typical instance), e.g., birds = flies, has wings, lays eggs
- Categorisation is based on similarity to the prototype
What are some problems with the Prototype Theory?
- It loses information about category variability (e.g., small birds are more likely to sing)
- It doesn’t explain relational knowledge
- Rips (1989): Category judgments based on explanations, not similarity
What is the Exemplar Theory? (Medin & Shaffer, 1978)
- Concepts consist of all known category members, e.g., bird = robin, eagle, penguin…
- Categorisation = similarity of stored exemplars
- Retains variability information (unlike prototype theory)
What are some problems of similarity theories (prototype & exemplar)?
- Concept combinations: “pet fish” is not typical of either category
- Ad hoc categories: created on-the-fly, not similarity-based (e.g., things to save in a fire)
What is the Explanation-Based Theory (Theory Theory)?
- Proposed by Murphy & Medin (1985)
- Concepts involve relational knowledge, e.g., feathers + wings + light bones –> enables flight
Also explains: - Different developmental stages = one concept
Rips (1989): 25c coins judged as same category due to explanation
What are some problems with Explanation-Based Theories?
- Vague definition of what counts as a “theory”
- Assumes unconstrained knowledge (not always realistic)
Name the three influences on word meaning
Semantics, syntax, prgmatics
Concepts help with…? (short answer)
Prediction, cognitive economy, communication
Which level is preferred for naming and recognition?
Basic level
Example of defining attributes?
Bachelor = male, adult, unmarried
Who critiqued definitions with typicality ratings?
Rosch (1973)
Who found that category judgments can change over time?
McCloskey & Glucksberg (1978)
Prototype theory suggests concepts are based on…? (short)
A single ideal instance with typical features
Which theory retains variability information?
Exemplar theory
Who proposed Theory theory/Explanation-Based Theory?
Murphy & Medin (1985)
Rips (1989) showed that category judgments are often based on…?
Explanations
