Semantic Memory Flashcards
What is declarative memory made up of?
Semantic memory and episodic memory
What is semantic memory?
Semantic memory: conceptual knowledge, linguistic knowledge, memories for general facts
Impairments in semantic memory - can’t comprehend meaning of words/pictures, can’t express ideas
What is the sentence verification task?
To decide whether the sentence is true or false - the DV is reaction/response time.
The sentence types are:
- set inclusion: describing if a subject belongs to a category [IS A]
- property-attribute: describing a property of the subject [HAS A]
Describe a network model:
- concepts are represented by nodes (localist representation)
- relationships between concepts are ‘links’
Describe the hierarchical network model:
concepts are organized in a hierarchy
cognitive economy –> a property attribute is represented only at the highest level, rather than redundantly at every level (so in order to get all the information, you must travel between levels) –> therefore it should take you longer to verify a statement represented at a higher level than at the level of the subject
Limitations of the hierarchical model.
Conrad:
- better explained in ‘frequency of co-occurence of concept and property’ rather than ‘levels’
- RT varied with the subject-property frequency within a level –> i.e. ‘peacocks have feathers’ and ‘canaries have feathers’ did not have the same reaction time despite being same level
Other issues
- RTs do not always mirror hierarchical relationship (quicker to identify a dog as an animal than a dog as a mammal, this isn’t consistent with the hierarchy)
- within category typicality effects (typical items are more easily judged as members of a category than atypical items)
- negative judgements are not faster for closer concepts
Discuss the Spreading Activation model
- Network model but concepts are organized non-hierarchically (explains the lack of hierarchical effect)
- links vary in associative strength (explains typicality effect, but does not explain how negative judgements are made)
- activation of concept spreads to other concepts linked to it (explains semantic priming effect - this is when a response to a word is faster following a semantically related word)
Discuss the difference between network models and feature comparison model
Network models assume knowledge is represented within a concept node (localist representation) –> doesn’t represent similarity between concepts well
Feature comparison model assumes concept is represented as distributed features in semantic space –> “sheep” is represented in terms of visual, tactile, auditory and gustatory features
Discuss the feature comparison model
Feature comparison model assumes concept is represented as distributed features in semantic space.
Two stage decision model: Decisions are made by comparing the similarity of features of subject and predicate terms –> canary (subject) is a bird (predicate)
Features can be defining features (essential to the concept) or characteristic features (non-essential)
The two stage decision process explains
- typicality effect (on positive decisions)
- similarity effect (on negative decisions)
Limitations:
- clear definition of defining and characteristic features is lacking – i.e. more difficult to reject a sentence that has some similarity than those that have no similarities
Neuropsychological studies of semantic memory showed that:
- selective impairment of categories (selective impairment of living things together with preserved knowledge of non living things is more common than the opposite)
- even more specific category-specific impairment is also observed (preserved knowledge of body-parts with impairment of living things, or impaired knowledge of musical instruments together with preserved knowledge of non-living things)
Discuss the two theories of organisational concepts in the brain
- Perceptual function theory: category specific impairments reflect different types of property
- Distributed-plus-hub theory: there is a hub for each concept or object in addition to distributed modality specific information
Describe the perceptual function theory
Category specific impairments reflect different types of properties that distinguish between category members: living things are distinguish from each other on the basis of perceptual properties, while non-living things are distinguished on the basis of functional properties
This explains more common impariment with living things
Explains category specific impariments where members are distinguished by visual properties (musical instruments)
Limitations
- patients do not necessarily show impairments of one type of knowledge
- some properties are neither sensory/perceptual nor functional - they can be conceptual / verbal knoweldge
Describe distributed plus hub theory
There is a hub (anterior temporal lobes) for each concept in addition to distributed modality specific information (spokes)
- hubs provide an efficient way of integrating our knowledge across different sensory modalities of a given concept
- make it easier for us to detect semantic similarities across concepts
- concept hubs are located in the anterior temporal lobes (the left atl is important for verbal concepts)
