AIMS & OBJECTIVES: The aim of this lecture is to review current approaches to understanding knowledge At the end of the lecture you will have learned What is meant by the term propositional knowledge The difference between a category and a prototype Typicality effects
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The aim of this lecture is to review current approaches to understanding knowledge
At the end of the lecture you will have learned
What is meant by the term propositional knowledge
The difference between a category and a prototype
Parkin, A. (2000). Essential Cognitive Psychology. Psychology Press, Chapter 8.
Larochelle S, et al., (2000). What some effects might not be: The time to verify membership in "well-defined'' categories. Quarterly Journal of Experimental Psychology-A, 53(4), 929-961.Knowledge
If x and y then z
If 4 legs and barks=dog
Oldest living creature
Buries eggs etc..
Store of facts (LTM).
Allows language etc..
Also, allows us to make inferences about the external environment.
This enables us to solve novel problems (1+4=5)
Adaptive and productive.What is knowledge?
We categorise each object as an exemplar of a “type” on the basis that it shares featurese.g. a turtle
an amphibious creature
slower than a hare.
Abstract common features form a category.
A category is a class or description of objects or events with common attributes and the members of categories are called instances.
People tend to think in taxonomiccategories
Furniture, vegetable..Exemplars and categories
Concepts defined by necessary and sufficient attributes.
An instance is a member of a conceptual category only if it meets minimal properties e.g., a triangle
a two dimensional geometric figure
with three straight sides joined at their ends
with angles adding up to 180o
Prediction: DFT assumes clear boundaries between members and non-members of a category.
All members of category should be equallyrepresentative of the conceptual category.
All people should represent categories in the same way.
BUT category boundaries are not clearly defined or discrete.
Typicality effects.Defining feature theory
More typical fish
Fruit or vegetable?
Typicality effects (1975, JEP, 104, 192-233).
People tend to decide that some instances are better members than others.
Most typical furniture
Instances are not literally defined as members of a category on basis of logic.
Instances have an internal abstract relative structure.
This structure needs an organising principle.Eleanor Rosch
Conceptual categories are represented by a prototype.
A prototype is a composite or abstraction of features.
This combines all of the characteristics of the most typical members of a category (fruit - seeds, edible).
Is this a fish?
This is based on overall similarity of an exemplar to the abstract prototype rather than on the features of the items themselves.
This theory explains the typicality effect because not all instances precisely resemble the prototype.Rosch’s prototype theory
Collins and Quillian (1969) taxonomies.
Knowledge about biological forms is organised in a hierarchy.
General concepts are at the apex and specific concepts are at the base.
The superordinate level is the most inclusive category e.g., animal.
The superordinate category subsumes more specific subordinate categories e.g., category “animals”
birds, fish etc
canary, ostrich, shark, salmonNetwork Theory
This is a type of distributed network
A canary is a canary can sing 0
A canary is a bird can fly 1
A canary is an animal has flesh 2
A canary is a fish has gills false
number of levels =
Patients with dementia seem to lose subordinate information (e.g. canary) before superordinate name (e.g. animal) on tests of concept knowledge.
Data consistent with idea of hierarchical knowledge in semantic memory that supports Collins model.
Evidence from brain imaging suggests category specific regions in the brain (e.g. Thompson-Schill, 1999).Neuropsychological evidence