Concept and Categories (1) Flashcards
What is the ‘Classical View’ of concepts?
Assumptions:
- Concepts mentally represent lists of features
- membership is an all or nothing affair: an object either has all pf the necessary and sufficient defining features (category memory) or it doesn’t (not a member)
- implies that all members of a category are equally good examples e.g. an isosceles triangle isn’t a better or worse example of a triangle than an equilateral triangle
What evidence is there for defining features?
Rips, (1989):
- Gave participants a scenario in which a bird that had come into contact with a toxic substance had mutated so that it (superficially) resembled an insect
- this mutant bird was able to mate with a normal bird and the offspring would be a normal bird
- (is this ‘insect-looking-bird’ still a bird?
- subjects/participants invariably said “yes” - independently of descriptions varying the degree of mutation
- if the mutant was able to breed normally then it was adjudged to be a bird
- is being able to ‘breed true’ a defining feature?
- being able to breed true is NOT a defining feature (in the classical sense) - according to Pothos and Han, (2000)
- In a variant of Rip’s study they gave undergraduate students stories about an imaginary bird (a ‘Gobble’) and a blackbird and a story relating the 2 that varied the degree of mating success between and within species
- participants’ task was to say whether the animals were the same or not - 7/10 participants said that the ability to mate was NOT a necessary feature
What is feature centrality?
- Features may not be defining but they do appear to differ in their importance
- in a series of experiments, Malt, (1994) asked subjects to come up with different types of water and to rate their H2O content/level
- classification was not reliably related to ‘H2O content’
Sloman, Love and Ahn, (1998):
- Asked people to imagine common objects and to imagine/rate a category member missing a number of features
- they found that features didn’t act in a necessary/sufficient way i.e. the presence or absence of a feature didn’t guarantee/prevent group membership but that features DID differ in terms of how central they appeared
What is the Prototype view?
- Theory suggests that concepts/categories are organised around a central ‘ideal’ or prototype
- The boundaries of a category are therefore ‘fuzzy’ because membership is determined by comparison to this ‘ideal’: the nearer the new item is to the prototype then the more likely it is to be included as a memnber
- membership is graded: some members of a category are better examples than others (are more similar to the prototype)
What evidence is there for the Prototype view?
McCloskey and Glucksber, (1979); Rosch, (1973); Rosch, Simpson and Miller, (1976); Smith, Shoben and Rips, (1974):
Lexical decision tasks:
- Some items are more quickly identified than others e.g. ‘a robin is a bird’ is identified faster than ‘a chicken is a bird’
- this finding suggests that some category members are closer to a ‘prototypical’ member than others
Barsalou, (1983 and 1985); Barsalou and Sewell, (1985); Mervis, Caitlin and Rosch, (1976):
Production:
- Subjects are asked to come up with the names of members of a particular category
- items that are the closest to the prototype are produced more frequently and earlier on the list than other members
Rosch, (1976); Mervis et al., (1976); Smith, Balzano and Walker, (1978):
Picture identification:
- Subjects are told they will see a picture that they have to identify as belonging to a particular category or not
What other evidence is there for the Prototype view?
Rosch, (1975); Malt and Smith, (1984):
Typicality ratings:
- Subjects are asked to rate how ‘typical’ various category members are
- there is consistency in rating a number of items: these are presumably nearer to the prototype
Induction:
- Tests of subject’s willingness to extrapolate information. Rips, (1975) told participants a new fact about robins
- the subjects were willing to apply this new fact to ducks as well
- participants told a new fact about ducks were less willing to apply this to robins
- Rips suggested that extrapolation moves from prototypical members (robins) to less typical members (ducks) but not vice versa (the other way round)
Sentence production tasks:
- Subjects/participants are asked to make up sentences about a category e.g. birds
- the subjects may produce sentences like “I like to feed birds in the park”
- these sentences are re-written with the category name substituted for either a prototypical member e.g. robins or a non-prototypical member e.g. penguins
- i.e. “I like to feed robins in the park”
- “I like to feed penguins in the park”
- these modified sentences are then given to another group of subjects
- these subjects rate the sentences containing the non-prototypical examples as being less plausible than the sentences containing a prototypical example
- this is suggested by Rosch, (1977a0 to be because subjects are actually thinking about a prototypical member when they are asked about the category
- hence the sentences about the category name with the name of a prototypical category name with the name of a prototypical example
What are the Positives and potential Problems of the Prototype view?
Positives:
- There is a lot of support for the prototype view and the evidence is convergent (helps reduce circulatory of argument)
Potential Problems:
- Cognitive economy: how many prototypes?
- e,g, do we have a prototype for fish and pet fish?
What is the Exemplar view?
Brooks, (1978 and 1987); Hintzman, 91986); Medin, (1975 and 1976); Medin and Schaffer, (1978); Shin and Nosofsky, (1992):
- Very similar to the prototype view
- except different because it suggests that instead of an abstract prototype we think of an actual example when we carry out a categorisation task
- suggests that in carrying out
- this view is therefore able to explain all of the findings that had been attributed to the prototype view (all of the tasks were discussed involved subjects producing the name - or an exemplar - of a category member or producing some kind of typicality rating)
What findings can the Exemplar view explain that the Prototype view can’t?
Preservation of variability information:
Rips, (1989a) and Rips and Collins, (1993):
- Asked subjects/participants the typical sizes of objects e.g. rules and pizzas (both typically 12 inches long)
- subjects were then asked whether or not a new object 12 inches in length was more likely to be a ruler or a pizza
- participants said that the new object was more likely to be a pizza
- they knew that there was more variability in sizes of pizzas than in sizes of rulers
- this supports and exemplar view because it is only by referring to actual examples of each category that you’re able to establish the amount of variability within a category
- if we think of theories of concepts as being like statistics then the prototype view would be the ‘mean’ whilst the exemplar view would be the ‘mode’
What is meant by Conceptual Flexibility?
- The Exemplar view of conceptualisation suggests that categorisation will be affected by the examples that subjects/participants/people have been exposed to priming
- the prototype view and the classical view both imply that categories will be stable
- Baron, (1977) gave subjects English words and non-words (words that conform to English spelling rules but aren’t actual words) to pronounce e.g. tave
- this may be pronounced according to a rule (a consonant-vowel-consonant ending with e results in a long vowel sound e.g. cave, save) or with a short vowel sound like ‘have’ (an exception to the pronunciation rule given above)
- participants were significantly more likely to pronounce ‘tave’ with a short vowel sound if they’d previously seen the word ‘have’ in the list
What are ‘Ad-Hoc’ Categories?
Barsalou, (1983 and 1988):
- Suggested that ‘Ad-Hoc’ Categories also have a graded structure found in pre-existing common categories e.g. fruit
What is Cognitive Economy?
- The exemplar view doesn’t require an extra level of representation
- in the prototype view we need to represent a prototype and also the actual members of a category
- in the exemplar view then we don’t need a prototype - this role is taken on by an actual example
- also allows for a smaller number of categories as they are more flexible
What are the problems with Similarity?
Medin, (1989):
- Points out a number of problems with the prototype view
- essentially this view operates by comparing how ‘like’ a prototypical category member a new stimulus s
- the more ‘like’ the prototype, the higher the typicality rating/faster the lexical decision/more frequently the new stimulus will be produced in production tasks
- Medin suggests our knowledge of concepts CAN’T operate this way
- one could argue that comparing similarities is no use as they have more similarities than differences
- it only seems certain features are important in categorisation: Conceptual rules or theories specify which of these feature are important
What is Psychological Essentialism?
- Medin (1989):
- Argues that concepts are rules that highlight certain features of an object/example
- the possession of these features is what prompts us to include them into a particular category
- whilst probabilistic theories rely on features and the classical view relies on rules, Psychological Essentialism argues for a fusion of theory based approaches to conceptualisation and feature, or similarity based approaches
There is some experimental support for these claims: - In simple terms, relationships between objects (rules) are independent of similarity (features)
- simply possessing similar features doesn’t guarantee conceptual stability (Goldstone, Medin and Gentner, 1991); (Bassok and Medin, 1997)
