1. Semantic Memory Memory for meaning
Permanent memory store of general world knowledge
Mental thesaurus, dictionary, or encyclopedia
Language, concepts, decisions, etc.
Whereas episodic memory differs widely from individual to individual, semantic memory is similar across individuals

2. Two Models of Semantic Memory
Collins and Quillian Network Model
Smith Feature Comparison Model
Each makes two assumptions of semantic memory:
1) Structure
2) Process of retrieval

3. Collins and Quillian Network Model
Two fundamental assumptions of semantic memory:
Structure: Nodes in a network
Process of retrieval: Spreading activation

4. Collins and Quillian Network Model
Structure: Nodes in a network
Each concept in semantic memory is represented by a node, a point or location in semantic space

5. Collins and Quillian Network Model
Structure: Nodes in a network
Each concept in semantic memory is represented by a node, a point or location in semantic space.

6. Collins and Quillian Network Model
Structure: Nodes in a network
Nodes are linked together by pathways, directional associations between concepts. Every concept is related to every other concept.

7. Collins and Quillian Network Model
Structure: Nodes in a network
Each pathway has a label defining the relationship between the concepts: Isa statements and property statements form propositions

8. Collins and Quillian Network Model
Process of Retrieval: Spreading Activation
An individual concept becomes activated

9. Collins and Quillian Network Model
Process of Retrieval: Spreading Activation
This activation spreads to adjacent nodes, activating them as well

10. Collins and Quillian Network Model
Process of Retrieval: Spreading Activation
Activation continues to spread through the network, but the level of activation decreases with each “step”

11. Collins and Quillian Network Model
Process of Retrieval: Spreading Activation
Consider the activation caused by “Can a robin can breathe?”

12. Collins and Quillian Network Model
Process of Retrieval: Spreading Activation
The nodes ROBIN and BREATHE spread activation through the network.

13. Collins and Quillian Network Model
Process of Retrieval: Spreading Activation
The intersection of two spreads of activation is found indicating critical concepts; a decision stage operates to determine validity of intersection

14. Smith’s Feature Comparison Model
Two fundamental assumptions of semantic memory:
Structure: Feature lists
Process of retrieval: Feature comparison

15. Smith’s Feature Comparison Model
Structure: Feature Lists
Semantic memory is a collection of Feature Lists
Each concept represented as a list of semantic features: simple, one-element characteristics of the concept
Features are ordered in a list in terms of definingness: The most defining features for a concept are at the top of the list

16. Smith’s Feature Comparison Model
Structure: Feature Lists
Defining features: Features absolutely essential to the concept (e.g. Birds are living objects)
Characteristic features: Features common to, but not essential to, a concept’s meaning (e.g. Birds fly)

17. Smith’s Feature Comparison Model
Process of Retrieval: Feature Comparison
General example: True or false: “An A is a B”?
Stage 1: Global Feature Comparison
Access required concepts and randomly select features about each concept
Features compared and similarity score determined
High: “Yes”, Low: “No”, or Intermediate: Go to Stage 2

18. Smith’s Feature Comparison Model
Process of Retrieval: Feature Comparison
General example: True or false: “An A is a B”?
Stage 2: Comparison of Defining Features
Access defining features of each concept
Determine if defining features match
Features match: “Yes”
Features mismatch: “No”

19. Smith’s Feature Comparison Model
Process of Retrieval: Feature Comparison

20. Clashing Evidence for the Models
General Task: Sentence Verification
Key issues:
Cognitive Economy
Property Statements
Typicality Effects

21. Clashing Evidence for the Models
Cognitive Economy (Bad for: C & Q; Good for: S)
Wings
Wings
Bird
Bird
Feathers
Feathers
Robin
Robin
Red Breast
Wings
Blue Eggs
Feathers

22. Clashing Evidence for the Models
Property Statements (Bad for: S; Good for: C & Q)
E.g.: A canary is a small bird with yellow wings
According to Smith: Look up feature lists for five concepts CANARY, BIRD, SMALL, YELLOW, and WINGS
This requires a list of “Things that are small”; “Things that are yellow”; “Things with wings”
Collins & Quillian incorporate property statements into their network so it doesn’t face this problem

23. Clashing Evidence for the Models
Typicality Effects (Bad for: C & Q; Good for: S)
Not all members of a category are equal
Typical members of a category can be judged faster
This is captured with Smith’s similarity score but not explained by Collins & Quillian:
Robin
Sparrow
Bird
Chicken
Penguin

24. A Hybrid Model No strict cognitive economy
Property statements available
Typical members of a category stored more closely
Properties more important to concept stored more closely

25. A Final Wrinkle
Recent ERP research is now suggesting that RT effects (e.g. typicality effects) in semantic memory may be associated with decision processes rather than retrieval processes
What’s the problem? Such effects have lead to model revisions that add semantic distance between nodes (e.g. the hybrid model just described.) Such revisions may not be appropriate.
Current models of semantic memory have yet to adequately address this finding

26. Categorization
Concept Formation
Traditional Research:
Show subjects a series of arbitrary patterns and have them judge whether each is an example of the concept being tested.
Limitations are that they are not related to the real world

27. Categorization Natural Categories
Concepts and categories that occur in the real world
Members do not belong to their categories in simple yes/no fashion
Categories have fuzzy boundaries with ill-defined membership for many category instances
No single feature is absolutely necessary as a criterion of category membership
Membership in a category is a matter of degree

28. Back to Spreading Activation
Four important principles associated with this idea:
1) Activation spreads
2) Spreading takes time
3) Activation becomes diffuse as it spreads
4) Activation decays over time
If semantic relatedness is the organizing principle of semantic memory, then relatedness should play a big role in these principles
The test: Priming

29. Priming in Semantic Memory
In essence: How does the processing of a prime affect the processing of a target?
Does thinking about one concept “bring to mind” other concepts? If so, they are “connected” in semantic memory

30. Priming in Semantic Memory
How can we use this to test the association between semantic relatedness and spreading activation?
- Distance of spread
- Speed of spread

31. Priming in Semantic Memory
Distance of Spread: Vary “steps” between prime and target
STIMULUS 1: ROBIN
Activation added to Robin

32. Priming in Semantic Memory
Distance of Spread: Vary “steps” between prime and target
STIMULUS 1: ROBIN
Activation spreads through network

33. Priming in Semantic Memory
Distance of Spread: Vary “steps” between prime and target
STIMULUS 2: BIRD
Does activation get this far?

34. Priming in Semantic Memory
Distance of Spread: Vary “steps” between prime and target
STIMULUS 2: FEATHERS
Does activation get this far?

35. Priming in Semantic Memory
Distance of Spread: Vary “steps” between prime and target
STIMULUS 2: BREATHES
Does activation get this far?

36. Priming in Semantic Memory
Speed of Spread: Vary time between prime and target
How long does it take activation to go from Robin to Bird?

37. Priming in Semantic Memory
There are two major ways to set up these experiments:

38. Empirical Demonstrations of Priming
Freedman and Loftus (1971)
Name a member of a category defined by a prime and a target
Conclusion: Category faster than letter or color
Prime Target Result
P Fruit No Priming
Red Fruit No Priming
Fruit P Priming
Fruit Red Priming

39. Empirical Demonstrations of Priming
Loftus and Loftus (1974)
Same methodology as Freedman & Loftus
Difference: Trials have various SOAs (within trials) and sometimes repeated the category of a previous trial (across trials)
TRIAL 1 TRIAL 2 TRIAL 3 TRIAL 4
Lag 0: Fruit-P Fruit-B Animal-D Building-L
Lag 2: Fruit-P Animal-D Building-L Fruit-B

40. Empirical Demonstrations of Priming
Loftus and Loftus (1974)

41. Empirical Demonstrations of Priming
Loftus and Loftus (1974)
Within trials: Category more facilitation than letter or color
Across trials: Facilitation less at longer lags
SOAs: Facilitation better at longer SOAs

42. Empirical Demonstrations of Priming
Rosch (1975)
Are two things members of the same category?
Prime: Category name (related) or “Blank” (neutral)
Targets: Typical or atypical category members
Trout
Sparrow
BLANK
No priming
Robin
Sparrow
BIRD
Lots of priming
Penguin
Ostrich
BIRD
Less priming

43. Empirical Demonstrations of Priming
Meyer and Schvaneveldt (1971)
Lexical Decision Task

44. Empirical Demonstrations of Priming
Neely (1977)
Insert figure 7-13

45. Empirical Demonstrations of Priming
Neely (1977)
At small SOAs, there is facilitation between related words even tough it is unexpected.
At larger SOAs, this facilitation disappears.

46. Empirical Demonstrations of Priming
Marcel (1980)
Immediately after prime, present a mask
Prevents conscious awareness of seeing prime
Even without conscious awareness, prime affects target
Child
Infant

47. Summary of Priming
Related primes speed processing: Activation spreads from one concept to another
Reduced relatedness or typicality of concepts decreases priming: Activation spreads to most related concepts
Longer SOAs increase priming: Spreading activation takes time

48. Summary of Priming Longer lags decrease priming: Activation decays
Priming at very short SOAs and despite conscious expectations: Priming is automatic
Priming occurs without awareness: Priming is implicit

49. Context and Priming
Work in context is interested in large-scale semantic representations that involve episodic and semantic knowledge
- Comprehension of sentences and paragraphs
- Comprehension of spoken conversations

50. Contextual Ambiguity and Priming
What does the word bank mean?
1. We had trouble finding the bank.
2. We were swimming at the bank.
3. We were making a deposit at the bank.
Sentence 2 primes RIVER; Sentence 3 primes MONEY
Context primes a particular concept of bank