Semantic System Flashcards
What is Implicit / non-declarative memory?
What is Implicit / non-declarative memory
- Information that you know, but you cant verbalize out loud
- Includes:
- Emotional: How emotional states
- Procedural: How you do things; eg, driving a car
What is Explicit / Declarative memory?
Explicit / Declarative memory
- Information that can be verbalized
- Semantic: what; e.g. facts
- Episodic: when information occurred; when you learnt that fact
What is the difference between autobiographical and semantic memory?
Difference between autobiographical and semantic memory
- Autobiographical Memory
- Personal information
- Specific Events
- Semantic Memory
- Knowledge about the world
- How you know how to use tools, objects, cook
- Facts
- Knowledge about the world
Why is semantic memory important?
Most everyday cognitive activities rely on semantic memory…
- How to recognise and use objects
- Represent concepts in the form of language
- Fluid and flexible knowledge manipulation, association and combination of concepts
- Reasoning, planning the future or remembering the past doesn’t occur without conceptual content
What is meant by category specific impairment?
What is meant by category specific impairment?
- A patient is unable to name specific categories of objects
- E.g. unable to name body parts, but they are fine at categorizing other objects
What is the Picture Naming Task?
Picture Naming Task
Task: say line drawings out loud
- includes animals, fruits/vegtables, artefacts
Picture naming task for pictures from standardised set that were matched for familiarity and frequency and visual complexity and familiarity
- Used to test category specific impairments
What is the Sound Identification Task?
Sound Identification Task
- Task: you get sound characteristics and you need to name what is making the sound;
- e.g. dog barking, or car horn
Used to test category specific impairments
What is the Object Decision Task?
Object Decision Task
- Task: presented with objects that are either real or two other objects put together
- decide if the object is real of not
Used to test category specific impairments
What is the Parts Decision Task?
Parts Decision Task
- Task: given a picture of a body and a number of heads
- Which head goes with the body
used to test category specific impairments
What is Visual Processing?
Visual Processing
- visual matching and face recognition tasks
used to test category specific impairments
What is the Central Attribute Judgement Task?
Central Attribute Judgement Task
- Task: asks questions that tap into…
- visual/perceptual features
- E.g. does a cow have a mane? Does a whale have a large tail fin?
- And functional/associative features
- Does a whale fly? Does an eagle lay eggs?
used to test category specific impairments
What is the Processing Difficulty Hypothesis?
Early researchers were confused by why people were much poorer at categorizing living apposed to non-living things
- Task differences could be the result of…
-
Familiarity (how familiar people are with a word/object)
- People arent as familiar of living things
-
Frequency (how often the word/object appears in usage)
- People don’t see living things as frequently
-
Visual complexity
- Living things are more visually complex than non-living
What is the Neural structure principle?
Explains how semantic knowledge is organised/structured.
Neural structure principle – conceptual knowledge is organised based on neurally specific areas (a link between mind and brain - isomorphism) that store categorical information (e.g living things, non-living things)
- These are known as Modality specific theories, which includes…
- Sensory/Functional Theory
- Domain Specific Hypothesis
What is isomorphism?
a link between mind and brain - isomorphism
What is the Correlated structure principle?
Explains how semantic knowledge is organised/structured.
Correlated structure principle – conceptual knowledge (semantic system) is organized in the brain based on the statistical cooccurrence of different features of objects. Brain damage results in category specific impairments for correlated features; due to the inter relationship between the features
- These are known as Statistical Cooccurrence, which includes…
- Organised Unitary Content Hypothesis (OUCH)
- Conceptual-Structural Account
What is the Sensory/Functional Theory?
Theory of Semantic memory
Adheres to neural-structure principle
Semantic knowledge is organized into perceptual (sensory) and non-perceptual (functional) information
- Thus there are two dimensions…
-
Visual/Perceptual characteristics (auditory, visual, tactile)
- Naming living things
-
Functional/Associative characteristics (functions of objects and associated objects)
- Naming non-living things
-
Visual/Perceptual characteristics (auditory, visual, tactile)
Example
- describe characteristics of an apple
- Would say things about
- Colour
- How it tastes
- How it smells
- Would say things about
Description of the apple is consistent with the notion of living things - Visual/perceptual representation
- Describe characteristic of a hammer
- Would say things about
- Function
- Associates (hammer and nail)
- Uses
- Would say things about
Description of the hammer would be consistent with non-living things - functional/associative information representation
What are the Predictions of Sensory/Functional Theory?
- and are these predictions supported?
Prediction 1: Recognition of all living things depends on representations in the same semantic sub-system (visual/ perceptual) therefore….
- Thus, there should not be a patient who has a specific category deficits within the living things
Prediction 2: Patients with category specific deficits (e.g. living vs. non-living) will also have disproportionate deficits for the modality or type of information tapped into via the impaired category (e.g. functional/associative verse visual/perceptual)
- e.g. If you have an impairment for living things, you will also have problems providing information or knowledge about visual/perceptual characteristic
Prediction 3: Patients with a deficit for visual/ perceptual knowledge or functional/ associative knowledge should show a categorical deficit that is most dependent on that type of knowledge
- impaired visual/ perceptual knowledge = impairment for living things
- impaired functional/ associative knowledge = impairment for non-living things
However, these predicitons are not supported
What is the Domain-Specific Hypothesis?
Theory of Semantic memory
neural-structure principle
Domain-Specific Hypothesis
- Assumes evolutionary pressures resulted in specialised and functionally distinct neural circuits that process perceptually and conceptually distinct categories of objects/information
- Semantic knowledge is organised into categories (domains) that reflect evolutionary salient distinctions (relevant for our survival)
categories include
- Animals category
- fruits/vegetables category
- Conspecifics category (other humans)
- possibly tools category
Limitation: does not say how items are represented within a category
What are the predictions of the Domain-Specific Hypothesis?
Prediction 1: Assumes distinct neural systems dedicated to animals, fruits/vegetables, conspecifics (humans) and tools, due to these distinct systems the other systems cannot compensate for the damaged neural system.
Prediction 2: No association between a deficit for a type or modality of knowledge and a conceptual deficit for a specific category
- For any given category specific impairment this will be for all types of knowledge within the category
- Patients with category-specific semantic deficits present with equivalent impairments to visual/ perceptual and functional/ associative knowledge
Prediction 3: Perceptual stages of object recognition models might be functionally organised by domain specific constraints and this predicts category specific visual agnosia despite intact early visual processes
- The structural description stage of object representations might have those functional domains (such as functional/associative information and visual/perceptual information), but these domains do not apply to the semantic system (conceptual information is not represented this way)
What are the limitations of the Domain-Specific Hypothesis?
Problems with Domain-Specific Hypothesis
- Lack specificity how knowledge is represented within categories
- Selective deficits → categorical organisation but approach does not explain how things are represented within each category
- Plants – food or poison
- Animals – attack or food
- Tools – function, developed later
- It is not clear how these categories are represented
What is the Organised Unitary Content Hypothesis?
Theory of Semantic memory
(OUCH)
We have categories within our semantic system, categories comprise of highly correlated concepts because of overlapping/common features
-
Example
- Humans and other animals would all cluster together in the animal category because they breathe, composed of flesh,
Assumption 1: How concepts are represented within semantic memory
- Members of a semantic category cluster close together in feature space
- Within a category representation occurs within semantic space and is lumpy
- Items with a higher number of features are more central - have features in common with typical items (picture)
Assumption 2: Category specific patient deficits due to damage to lumpy region(s) within semantic spaceBrain damage affects category members because it
- Affects objects/concepts with similar properties and these are stored in adjacent neural areas OR
- Affects the highly correlated features of category members
What is the benefits of the Organised Unitary Content Hypothesis (OUCH)?
Benefits of the Organised Unitary Content Hypothesis (OUCH)
- Can account for very severe deficits
- e.g., problem with animal category is a problem with the lumpy semantic space representation for animals and associated features
What are the predictions of the Organised Unitary Content Hypothesis (OUCH)?
Organised Unitary Content Hypothesis (OUCH) predictions
Prediction 1: OUCH predicts modality specific semantic effects
- Category impairments would occur due to disruption of feature representations of items within the impaired category, and not others
Prediction 2: OUCH predicts relative sparing of categorisation performance
- While you might have damage to features within a category, you will have some level of category representation
Prediction 3: OUCH predicts category specific deficits
- Category impairments would occur due to disruption of feature representations of items within the impaired category
- You might have a specific deficit for plants, gem stones or furniture. The reason is the brain damaged caused disruption to the features that are most relevant to that category
What are the strengths and limitations of the Organised Unitary Content Hypothesis (OUCH)?
Strengths
- OUCH is consistent with patient data showing category specific deficits
Limitations
- But the type of featural representation not defined
- Animals for example; is it represented through pets, farm animals, sound characteristics
- Ways information clusters together not specified
- How do the items categories together
- Functional rather than neural approach
- May not be linked with neural deficits
