W3 Organisation of concepts ✅

Question 1

What are the 2 proposed models for how concepts are organised in semantic memory?

Answer 1

Definition: Concepts - mental representations and the fundamental units of thought e.g., concept of bird, animal etc.

1. Hierarchical Network model
2. Spreading Activation model

Question 2

Features of the Hierarchical Network Model, its supporting evidence and issues?

Answer 2

• Semantic memory organized into a series of hierarchical networks
• Major concepts are represented as nodes
• Properties/features are associated with each concept
  ____
  Supporting evidence: sentence verification task
  -> decides asap if sentences are true or false
  Result: Greater distances between semantic concepts and categories are associated with longer RTs
  Conclusion: Unless information is directly linked with a concept in semantic memory, we infer the answer from properties of higher nodes
  -> Making more inferences slows verification
  ______
  Problems:
  1. Familiarity: issues with verified statements used
  -> when controlled, reduced the hierarchical distance effect
  2. Typicality: verification is faster for more representative member (penguin < canary), independent of hierarchical distance

Question 3

Features of the spreading activation model, its supporting evidence & problems?

Answer 3

• Semantic memory is organized by semantic relatednes
• Length of links indicates the degree of semantic relatedness
• Activity at one node causes activation at other nodes
  via links
• Spreading activation decreases as further away from OG activation
  _____
  Supporting evidence:
  1. Semantic priming tasks: semantically related stimuli makes subsequent processing faster
  => Semantic links and distance determine the strength and the speed of activation
  2. DRM paradigm: Ps mistook a word at the central of the paradigm (related concepts) as having studied when it was not present. (false memory)
  => Activation spread from all presented words to related words
  ____
  Evaluation:
  1. Pros: more flexible -> account for more empirical findings
  2. Cons: reduce specificity of the model’s prediction + difficult to test
  3. Limitations:
• Oversimplified (notion that each concept is represented by one node only)
• Fixed mental representation? (individuals experience different contexts to the word)
• No method to measure semantic distance

Question 4

What is the role of context? (Situated Simulation theory)

Answer 4

• Concepts are processed differently in different situations (context-dependent)
• Concepts incorporate perceptual properties (colour, model) and motor properties (e.g. ride, buy)

Question 5

What is the supporting evidence and limitations of the Situated Simulation Theory?

Answer 5

Supporting evidence:
1. Neurological evidence:
- Brain areas activated by action words are adjacent to and partly overlap with activations produced by the corresponding movement
- E.g. Words such as lick, pick, and kick activate parts of the motor cortex similar to doing those movements.

2. Role of motor in accessing mental concepts:
   - Understanding of action verbs requires activation of the motor areas used to carry out the named action
   - E.g. faster RTs when ‘hand-related action’ words correspond with hand movements
   —
   Limitations:
3. How variable are concepts across situation? (stable core + context-dependent element - secondary)
4. Is context necessary to assessed the main concept meaning?

Question 6

How is semantic memory organised at the brain level (2 neurological theories)?

Answer 6

1. Grandmother cell hypothesis
   - Semantic memories are represented in the brain as whole objects
   - Each object/concept has its own node or neuron (e.g. a special neuron representing your grandmother)
   - Semantically similar nodes are grouped together

2. Feature-based approach
   - Different kinds of information about a given object are stored in separate brain regions (modality-specific)

=> This view is becoming increasingly popular

Question 7

What is meant by Hub-and-Spoke model?

Answer 7

A hybrid model of semantic memory, 2 components:
1. Hub: Modality-independent conceptual representations
-> Anterior temporal lobe (ATL)
2. Spokes: Modality-specific
brain areas (e.g. sensory and
motor processing)
-> Inferior temporal lobe (ITL)

Question 8

What are the 2 supporting evidence for Hub-and-Spoke model?

Answer 8

1. tDCs study - Ask 2 question types about tools (function & manipulation) then apply electrical current to stimulate brain activity.
   -> applied to IPL (Spoke): tool manipulation task was enhanced (motor system)
   -> applied to ATL (Hub): increased performance in both tools and tool manipulation (connected to spoke, provide uniform semantic concepts)
2. Neuropsychological study

General semantic deficit (e.g. naming, sorting objects)
-> Damaged ATL region

Category-specific deficits (Patients K.C & E.W) - can do one semantic task correctly but not the other
-> Damaged in specific ITL regions

Question 9

Evaluation of the Hub-and-Spoke model?

Answer 9

Increasing evidence that concepts are organized in hub (core) + spokes (modality-specific)

Limitations (open issues):

• The role of ATL may be more complex (oversimplification)
• Does familiarity with concepts affect their organization in the
  hub? (difficult to measure)
• How many ”spokes”? (problems with variability)
• How is information integrated between the spokes and the
  hub? (links)