Lecture 12: Categorization

Question 1

Taxonomy of Memory

Answer 1

○ Split up into sensory, working, and long term memory
§ Then Split into Explicit and implicit
□ Explicit is split into semantic and episodic
□ Implicit: Subconscious memory
□ Explicit: Conscious memory
® Episodic: Memories of personal episodes from your own life
® Semantic: General knowledge, memory of facts

Question 1

Categorization

Answer 1

Organizing the brain’s knowledge into categories, allows inferences about members of a class, i.e. living lings breathe

Question 1

Pigeons (Wasserman)

Answer 1

§ Trained pigeons to peck in one of four holes in a screen based on the picture in the hole (peck the flower)
§ Pigeon was 81% accurate with old exemplars, and 64% accurate with new exemplars (new flowers)

Question 2

Physical Similarity vs Conceptual Knowledge Experiment (Gilman)

Answer 2

○ Had children look at pictures of a flamingo, bat, and hawk
§ Hawk looks more like bat, but bat is not a bird
□ Kids say that the hawk feeds its kids mashed up food like the flamingo, not milk like the bat

Question 2

Classical View of Categorization

Answer 2

○ Defining Properties: Necessary and sufficient features to put something into a category
○ Problem: what defines game?
§ So many different things can be games; basketball, chess, etc.
§ Would you consider a monk a bachelor?

Question 2

Probabilistic View

Answer 2

• Psychologically, properties/features are characteristic, not defining
  ○ Something belongs to a category if it is similar to members of that category
  ○ Some members have more characteristic properties than others
  ○ Category boundaries are fuzzy

Question 3

Typicality Evidence

Answer 3

○ Order fruits from typical to least typical
§ Most people agree on the ranking
○ People are faster to verify the truth of sentences when the example is more typical vs less typical

Question 4

Hedges

Answer 4

§ Used to not commit entirely to a POV
□ “A whale is technically a mammal” is a normal sentence, but you wouldn’t say “a cow is technically a member,” making the cow the more typical member of the group mammals

Question 5

Exemplar Theories

Answer 5

○ We have examples of each category stored away in memory, and categorize new things based on the similarity to the stored exemplar
○ Multiple exemplars are stored in memory
○ Categorize based on similarity to stored exemplars

Question 6

Prototype Theories

Answer 6

○ We have a prototype, a best, ideal, or average example
○ Only the prototype is stored in memory
- Categorize based on similarity to prototype

Question 7

Geometric Approach

Answer 7

Concepts may lie in a geometric space, or similarity may be based on concordance of multiple features

Question 8

Similarity rating task

Answer 8

○ Asked question about similarities between objects on a scale of 1-6
- Made a geometric space based on these responses

Question 9

Metric Axioms

Answer 9

○ If concepts are represented in a geometric space, similarities should satisfy certain properties (axioms) or geometric space
○ Minimality: The dissimilarity between a concept and itself must always be the smallest possible
§ Suggests geometry is wrong?
○ Symmetry: The similarity between two concepts must be the same regardless of order
§ Proves not to be true

Question 10

Triangle inequality

Answer 10

If one concept is similar to a second, and that to a third, then the first and third must be reasonable similar

Question 11

Tversky’s Featural Approach

Answer 11

○ People give similarity ratings inconsistent with geometric space
○ Feature-based similarity approaches do not require these metric axioms
- Feature based approaches look at features in common and different features