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6) Semantic Memory (Theories of semantic memory organisation (Feature…
6) Semantic Memory
Theories of semantic memory organisation
Sentence verification experiments
DV: Reaction time (seeing if TRUE or FALSE)
Sentence: Subject-predicate (a canary is a bird)
Set inclusion:
A canary is a bird
Property-attribute:
A canary has feathers
Network models
(localised representation)
Hierarchal Network Model
Concepts organised with property attribute stored at highest level
Cognitive economy: limited capacity save storage space
Increased reaction time = as you go up the levels
Problems
Frequency of co-occurances: associative strength is better predictor of reaction time
RTS do not always mirror heirarchial relationship
Within character typicality effects
False judgements are not faster for closer concepts
Assumptions
Concepts represented by nodes (localist representation)
Relationships between concepts represented as links (set inclusion= isa, property attribute has)
Spreading activation model
Links vary in associative strength: explains typicality effect
Activation of concepts: spreads to other concepts linked to it: explains
semantic priming effect
Feature comparison model
(distributed representation)
Explains partial degradation (how many animals did moses take on ark?)
Bundle of features for an object (visual features, tactile, auditory, gustatory)
Two stage decision model: defining (bird has wing, a beak) VS characteristic features (can fly, build nests)
Linguistic hedges
1) compare all features
2) compare defining features (look for match)
Typicality effect (positive decisions), Similarity effect (negative decisions)
Problem
Lacks a clear definition of defining & characteristic features
Disorders of semantic memory
Perceptual-functional theory
Category-specific impairments reflect different types of property distinguishing
Living: visual features
Musical instruments considered by visual
Non-living: actions you perform
Thats why have less impairments
Problems
Some paitents are impaired for all
Some are conceptual: not perceptual/functional
Distributed-plus-hub theory
There is a hub for each concept, or object
in addition
to distributed modality specific information
ATL: concept hubs
Neurospsycological studies
Show
Selective impairment of categories
Impairment of Living things with preserved knowledge of NON living things = more common
Gets even more specific
Preseved body parts with impairment of living things
Persevered knowledge of non living, with impaired knowledge of musical instruments
Patient JFR
Episodic Memory VS Semantic memory
Episodic
Memories for events in specific temporal & spatial context
Semantic
Conceptual knowledge, linguistic knowledge, memories for general facts
Impairments
: can't comprehend meanings of words, pictures, express ideas