1. Concepts and General Knowledge Semantic Memory Stores
Chapter 10
Concepts and General Knowledge
Semantic Memory Stores
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2. Building Blocks of Thought
Concepts— a mental representation representing a category of objects: stored in long-Term Memory
Category – a set or class of objects that belong together (e.g., groupings of similar objects, events, ideas, or people)
Concepts provide a kind of mental shorthand, economizing cognitive efforts.
Automatic animation
The cartoon humorously provides an example of a concept: a chair, or something with legs to sit on. Imagine it every time we needed to refer to the different kinds of chairs, we didn’t have the basic concept of “chair” to make our references easier and quicker.
APA Learning Goal 1: Knowledge Base of Psychology
APA Learning Goal 4: Application of Psychology
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3. Classical Approach: Concepts
Concepts viewed as definitions with lists of necessary (properties that instances of the concept MUST have) and sufficient (a set of properties that fully define all members of the concept.
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4. Defining the properties or features on a Concept
Formal Concept – clear cut defining rules
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5. Chapter 7 General Knowledge
“Real-World” or Natural Concepts– Fuzzy defining rules
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6. Classical Approach Assumes: Sharp category boundary (in or out)
Equality of members
Representation of category is list of necessary and sufficient features
If an entity meets the conditions it is a member
If an entity is a member we know it meets the conditions

7. Ludwig Wittgenstein (1953)
Used examples such as triangle and square (text example) and friends and games(text example) to demonstrate the amazing ability of humans to conceptualize thoughts that they could not define.
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8. Chapter 7 General Knowledge
While there are a small set of formals concepts such as scientific categories and geometric shapes, there are vastly more concepts that humans are able to understand that are “real-world”. There is no set of necessary and sufficing properties that define them. Instead they are defined by a set of properties that are likely to be true, but not all members of the concept need to have each property, nor is there a set of properties that fully define the concept.
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9. Family Resemblance (Wittgenstein)
No one feature that all have in common….
… Yet all are in some way similar to the other category members
Variation within categories allowed

10. Family Resemblance Assumes:
No strict “definition” of what’s in/out based on individual features
Membership based on similarity
Some members can be “better” examples than others
Problem: If category membership is based on similarity, the question remains; similar to what?

11. McCloskey & Glucksberg (1978)
McCloskey & Glucksberg – subjects disagree about whether atypical items belong in a category:
30/30 apple is a fruit, chicken is not a fruit
16/30 pumpkin is a fruit
Subjects change their minds when tested later.
Conclusion: Category Boundaries are not always clear-cut.

12. Chapter 7 General Knowledge
Is X a member of the category Y?
Not all members of a category are equally as good members of those categories. Some members are more typical than others. We are able to more quickly respond to typical than to atypical instances. This is called the typicality effect. Therefore, membership is not equal.
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13. Rosch and Mervis (1975)
Participants got category names (bird) and lists of 50 members (robin, canary, ostrich, penguin, sparrow…)
Provided rating on how well the item represented the category (typicality ratings)
Results: Much agreement on ratings between participants

14. Rosch (1975) Bat Penguin Owl Sparrow CATEGORY: BIRDS Telephone Mirror
Poor
Very Good
CATEGORY: BIRDS
Telephone
Mirror
China Closet
Chair,
Sofa
Very Good
Poor
CATEGORY: FURNITURE

15. Rosch & Mervis (1975) continued
New participants list attributes (properties) of each of the instances. Some attributes were listed more frequently than others. e.g., can fly vs. lives on a farm Results: Typical instances had more frequently listed features than did less typical instances.
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16. Rips, Shoben & Smith, 1973 Verification Task
Press a button to answer TRUE or FALSE to the following statements
Question Response
A canary is a bird
A ostrich is a bird
TRUE
fast
Typicality effect
TYPICALITY EFFECT
Rips, Shoben & Smith, 1973
slow

17. Other Support Mervis, Catlin & Rosch, (1976)
When asked to list instances of a category, typical instances are generally listed first, indicating that they come more quickly to mind.
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18. Typicality and Language
Typical instances are acquired earlier in life than atypical instances. When mentioning two category members together, the more typical member generally is mentioned first.
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19. Semantic Dementia (Fronto-Temporal Degeneration)
A syndrome of progressive deterioration in semantic memory (knowledge of objects, people, concepts and words). 
can still speak fluently (good grammar and pronunciation)
Lose of words for certain items and the knowledge of the meaning of the word. For example, someone may not only forget the word hippopotamus when shown a picture, but also loses all the knowledge they once had about this (e.g. that it is an African animal that lives in rivers).
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20. Chapter 7 General Knowledge
may also have difficulty recognizing what things are.
Effects all modalities (sound, taste, empathy)
Unlike Alzheimer's disease, memory for day-to-day events may be good.
Visuo-spatial skills intact.
At later stages, personality is often affected.
Deterioration of left anterior temporal lobes.
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21. Chapter 7 General Knowledge
Animal copies by patient B.F. (shown on right) demonstrate retention of visuo-perceptual ability in SD patients. Naming tests highlight their semantic deficits. When asked to name these animals, B.F. called the cow a ‘dog’ and the elephant a ‘cow’.
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22. Chapter 7 General Knowledge
Drawings by patient G.W. show semantic deficits in spontaneous recall. Distinguishing features are absent: the fish lacks fins, the first bird lacks wings and the elephant lacks a trunk.
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23. Alternative Approaches to Concepts
Prototypes
Exemplars
World Knowledge
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24. Chapter 7 General Knowledge
Prototype Approach a.k.a. Family Resemblance or Probabilistic approach) Eleanor Rosch
A Prototype is an abstract, typical representation of the category members. You can think of it as the weighted average of the important features of members of the category.
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25. Prototype Approach
The guy in the center is closest to the prototype (highest prototypically) but he isn’t the prototype
Prototype isn’t here
Prototype is abstract

26. Prototype Approach Features: Prototype Glasses (yes/no)
Hair (dark/light)
Nose (big/small)
Ears (big/small)
Mustache (yes/no)
Prototype
2/3 glasses, 7/9 light hair, 7/9 big nose, 7/9 big ears, 5/9 mustache
Center guy has the highest prototypicality

27. Chapter 7 General Knowledge
Probabilistic (not all or none). Prototypes include characteristic features that are usually
present, not only necessary or sufficient features.
Objects that do not share all the characteristics of the prototype are still members of the category but not prototypical ones.
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28. Chapter 7 General Knowledge
Prototype Theory
Rosch (1970s) suggested that when people categorize items they match them against a "prototype" which contains the most representative features inside the category. .
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29. Chapter 7 General Knowledge
Novick (2003) – Exemplars Change with Experience Extensive media coverage following 9/11 effected the typicality of airplane as a response to the category of vehicle. Airplane was judged to be a more typical vehicle for 1 month following the attacks, relative to a baseline calculated from data collected yearly for 5 years preceding the attacks. By 4.5 months, however, typicality was back to baseline.
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30. Exemplar Approach Medin & Schaffer
Exemplars are specific examples
Examples of category members are saved in memory (typical as well as atypical)
Potential members compared to all exemplars
Those with high family resemblance are like more of the exemplars
May be more useful for smaller categories (US presidents, very tall mountains)

31. Evidence supporting Exemplars
Much of the evidence that supports the prototype model also predicts the exemplar model.
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32. Exemplars or Prototypes Brooks & Allen (1991)
Asked subjects to discriminate between two animals (Diggers and Builders) Two kinds of animals could be distinguished in two different ways (“two-out-of-three” rule). 3 Relevant Features (leg length, angularity of body, spotted/not spotted). 2 non-relevant features (number of feet and length of neck).
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33. Chapter 7 General Knowledge
Half of the participants explicitly told rule, others not told.
Classification rule:
2 of (long legs, angular body, spots) => Builder
2 of (short legs, curved body, not spots) => Digger
Example of Builder Example of Digger
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34. Chapter 7 General Knowledge
Learning Phase: Rule (Prototype) Condition: Participants explicitly told the rule and used it to categorized 8 exemplars. Memory (Exemplar) Condition: Shown 8 exemplars and told which were diggers and which builders without being told the rule.
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35. Generation of new items for Test phase.
New items that varied from the learning phase exemplars were generated by manipulating relevant or non-relevant features.
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36. Chapter 7 General Knowledge
Good Matches: Changed a feature that did not change the category. In the example below shortening the neck does not change the category.
Original
New
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37. Chapter 7 General Knowledge
Bad Matches: change a relevant feature so that the new item is now a member of the other category. Adding spots
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38. Chapter 7 General Knowledge
Results
Participants made errors that indicated they were relying on similarity to known exemplars rather than on the rule (prototypes). Even when a rule is known and easy to explicitly state, past examples can override application of the rule!
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39. Chapter 7 General Knowledge
A Caveat
Evidence shows that we use both prototypes and exemplars depending on context. Natural categories – we may have richer prototypes and more complex rules, therefore we rely on prototypes. For Artificial categories we rely on exemplars.
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40. World Knowledge Approach
When we do “real-world” categorization tasks we don’t just rely on prototypes or remembered exemplars, we also call on our world knowledge which included richer conceptual representations (uses for, causal and contextual information).
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41. Example: Goal-Derived Categories
Goal-derived categories are those that satisfy some goal (e.g., birthday gifts that make the recipient happy or what you would take with you if your fire alarm went off). Family resemblance scores and prototypes are of little value for these categories since membership is based on goal satisfaction rather than sharing some particular attribute or set of attributes.
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42. The Role of Knowledge in Concept Learning Lin and Murphy (1997)
People learned about objects used in foreign countries. One group learned that the tuk is used for hunting. The hunter holds the handle (3) with one hand behind the hand guard (2) and pulls the end of the rope (4) while slipping the noose (1) around the animal’s neck.
People learned about objects used in foreign countries. One group learned that the tuk is used for hunting. The hunter holds the handle (3) with one hand behind the hand guard (2) and pulls the end of the rope (4) while slipping the noose (1) around the animal’s neck. The other group was told that the tuk was a fertilizing tool. Liquid fertilizer is held in the tank(2), the knob (3) is turned to allow it to come through the outlet pipe (4). The loop is used to hang the tuk up. After learning a variety of concepts, items were then prsenting missing one or more of the parts in the original object. What was found that the effect of a missing part really had a big effect on the subjects’ classification of the object as a tuk. Those learning that Part 1 was a noose were far less likely than those learning that Part 1 was a loop hanger to classify the object missing Part 1 as a tuk, presumably because the missing part was more central to its function.

43. Chapter 7 General Knowledge
Lin and Murphy (1997)
The other group was told that the tuk was a fertilizing tool. Liquid fertilizer is held in the tank(2), the knob (3) is turned to allow it to come through the outlet pipe (4). The loop is used to hang the tuk up.
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44. Chapter 10 – 1 Concepts and Knowledge
After learning a variety of concepts, items were then presenting missing one or more of the parts in the original object. The missing part really had a big effect on the participants’ classification of the object as a tuk. Those learning that Part 1 was a noose were far less likely than those learning that Part 1 was a loop hanger to classify the object missing Part 1 as a tuk, presumably because the missing part was more central to its function.
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45. Tomato: Fruit of Vegetable?
Depends on your reason for categorizing! Definitions If you are a gardener, it is a fruit. In the kitchen, it is a vegetable.
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