Cognitive Psychology Class Notes > Semantic Memory
Definition of Semantic Memory:
- relatively permanent memory store for general world knowledge
Models of Semantic Memory Organization
Feature Comparison Model:
Demo: Sentence Verification Task
True or false:
A robin is a bird.
A bulldozer is a bird.
A bat is a bird.
A chicken is a bird.
- 2 Types of Features:
1. characteristic features:
- features that are descriptive, common, and frequent, but not essential to the meaning of the item
- ROBIN: flies, perches in trees
- the robin does not have to fly or perch to be considered a robin
- features absolutely essential to the meaning of the item
- ROBIN: animate, has feathers, has red breast
2. defining features:
- 2 Stages of Processing:
1. Process all features of subject with predicate; comparison of characteristic features.
- if low similarity between features --> respond 'false'
- if high similarity between features --> respond 'true'
- if intermediate similarity, Stage 2 processing
2. Create comparison question; comparison of defining features.
- A bat is a bird --> a bat is a mammal; is a bird a mammal? A chicken is a bird. --> does not fly, does chicken have feathers?
- takes more time to respond
- Research FOR Feature Comparison Model:
- typicality effect:
A carrot is a vegetable.
A rutabaga is a vegetable.
- we make faster sentence verification decisions when an item is a typical member of a category, rather than an unusual member
- WHY? high similarity between features allows for Stage 1 processing only for 'A carrot is a vegetable'; Stage 1 and Stage 2 processing is necessary for 'A rutabaga is a vegetable'
- Research AGAINST Feature Comparison Model:
- category size effect:
A poodle is a dog.
A squirrel is an animal.
- we make faster sentence verification decisions when an item is a member of a small category
- small categories contain more defining features; therefore, FC model would predict that there should be more Stage 2 processing for small categories and thus longer RTs
Semantic Network Models:
- PDP approach
- Collins & Loftus (1975)
- ACT*, ACT-R
- concepts represented as nodes in network
- nodes are linked together by pathways
- proposition = node 1 --- pathway --- node 2
- spreading activation
- frequently used links have greater strengths
- intersection search
- prototypes best represent categories
- prototypes need not really exist
- degrees of prototypicality (prototypical to nonprototypical)
- apple is a prototypical fruit
- tomato is a nonprototypical fruit
- Empirical Characteristics of Prototypes:
- Prototypes are often supplied as better examples of a category (Mervis, Catlin, & Rosch, 1976).
- Prototypes serve as reference points (Rosch, 1975a)
- Prototypes receive more priming from category names and are judged more quickly (Rosch, 1975b) 'fire engine red' vs. 'muddy red'
- Prototypes can substitute for a category name in a sentence (Rosch, 1977)
- Prototypes share common attributes in a family resemblance category (Rosch & Mervis, 1975)
- Levels of Categorization:
- superordinate level --> musical instruments
- basic level --> guitar
- subordinate level --> Fender Stratocaster
- Basic-level categories have special status (Rosch et al., 1976):
- share more attributes
- have shapes in common
- are used to identify objects
- produce priming effect
- are first learned by children
- experts use subordinate level as basic level