PSY246 Lecture Notes - Lecture 7: Rca Dimensia, Celery, Neurodegeneration
2 Jun 2018
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Semantic memory – Week 7 Lecture PSY246:
Lecture outline;
• Episodic vs. semantic memory
• Theories of semantic memory organization
o Word meanings (lexical semantics): led to computational
investigations of natural language processing (machine translation; text
corpus analysis)
o Sentence verification experiments
o Network models
▪ Hierarchical network model
▪ Spreading activation model
o Feature comparison model: distributed representation
• Disorders of semantic memory:
o Neuropsychological studies (category-specific deficits)
▪ Perceptual-functional theory
▪ Distributed-plus-hub (‘hub and spoke’ model) theory
Division of long term memory –
• Declarative memory (facts)
• Procedural memory (actions, motor skills)
• UNDER declarative memory;
o Semantic memory (general knowledge)
o Episodic memory (dated recollections of events) → events tied to
temporal and spatial context
Semantic memory (also called conceptual knowledge) is the aspect of human memory
that corresponds to general knowledge of objects, word meanings, facts and people,
without connection to any particular time or place. Knowing that you ate Szechuan
scallops at the Peking Restaurant in Cambridge last Thursday evening is episodic, not
semantic, memory. Knowing that Szechuan refers to a province of China, that food
from this region tends to be spicy and that scallops are sea-creatures that live in
brittle bivalve shells are all forms of conceptual knowledge. Memory for episodic
events is not only specific to times and places, it is also largely specific to an
individual. Conceptual knowledge on the other hand, is mostly shared across
individuals in a given culture, although its precise scope depends on the individual’s
experience.
Episodic vs. semantic memory –
• Semantic memory = conceptual knowledge, linguistic knowledge, memories
for general facts
• E.g. dogs have fur, Ottawa capital of Canada
• Impairments in semantic memory = cannot comprehend meanings of words or
pictures or express ideas
Experiments on semantic memory organisation –
find more resources at oneclass.com
find more resources at oneclass.com
• Early studies used the sentence verification task
• DV = reaction time
• Subject-predicate: ‘a canary is a bird’
• Sentence types
o Set inclusion; describe the subject being a member of a category = a
canary is a bird (true), a whale is a fruit (false)
o Property-attribute = a canary has feathers (true), a whale has seeds
(false)
Network models –
• Concepts are represented by nodes (localist representation)
• Relationships between concepts are represented by links
o Set inclusion (canary is a bird): isa
o Property attribution (canary can sing): has
Hierarchical network model (Collins and Quillian, 1969)
• Concepts are organised in a hierarchy
• Cognitive economy
o Property attribute is stored non-redundantly at the highest (most
general) level → e.g. “Leonardo da Vinci had knees”; da Vinci is a
human being – human beings have knees
• Sentence verification RT is a function of levels – in order to verify info like
‘canary has skin’ – you need to access the canary node AND the animal node
• In order to verify info, you need to traverse two links
• ‘A canary can sing’ is verified quicker than ‘a canary can fly’ or ‘a canary has
skin’
• Hierarchy e.g. canary to bird to animal
Problems with the hierarchical network model:
• Challenge to the cognitive economy
• Conrad (1972)
o Argued that RT data better explained in terms of frequency of co-
occurrence of concept and property rather than levels
▪ RT varied with the subject-property frequency (associative
strength: determined from norms) within a level
▪ E.g. within Level-1 sentence: birds have feathers
▪ High frequency property = peacock has feathers
▪ Low frequency property = canary has feathers
o Results showed RT is a function of frequency of co-occurrence
(associative strength)
Other problems with the hierarchical network model:
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Division of long term memory : declarative memory (facts, procedural memory (actions, motor skills, under declarative memory, semantic memory (general knowledge, episodic memory (dated recollections of events) events tied to temporal and spatial context. Semantic memory (also called conceptual knowledge) is the aspect of human memory that corresponds to general knowledge of objects, word meanings, facts and people, without connection to any particular time or place. Knowing that you ate szechuan scallops at the peking restaurant in cambridge last thursday evening is episodic, not semantic, memory. Knowing that szechuan refers to a province of china, that food from this region tends to be spicy and that scallops are sea-creatures that live in brittle bivalve shells are all forms of conceptual knowledge. Memory for episodic events is not only specific to times and places, it is also largely specific to an individual.
