LECTURE NINE Flashcards
WHY CATEGORIZE?
- Organize a complicated, messy world
- Many regularities in the environment
- Generalization and discrimination
- Prediction – if an object is determined to be a member of a category, it can be treated like others
DARK SIDE OF CATEGORIZATION
- Stereotyping: Judgments about
people determined by category membership - Prejudice and bias: Incorrect prediction. Could have disastrous
consequences!
CONDITIONS FOR CATEGORIES
Qualities that an item must have to be in a category as well as discriminate from other category membership
FUNCTIONAL HYPOTHESIS
Categorization might be based on functionality of object
CASUAL HISTORY
Sometimes what matters most for categorization is not similarity or function, but history
FUNCTIONAL VS CASUAL
Depends on point of categorization
* For man-made objects, tools, manipulable objects – probably function
* For biological entities, or objects where history matters – probably history (casual)
PROTOTYPE THEORY
- Maybe it’s not strict rules, function, or history, but family resemblance
- Every concept is typified by a certain prototypical instance of that concept
- Things that are more similar to the prototype are better members of that category; more typical
- “Fuzzy” category boundaries (as opposed to strict)
- Representation is “idealized” and “averaged” across all category members
- Might not actually correspond to anything in reality!
- Abstract representation generated by everything seen
- A typical member of the category generated internally
PROTOTYPE FORMATION
- Prototypes are developed through experience: Average of all members of the category you have perceived
- Importance of language: When first forming prototypes and categories, need to explicitly label category. Often leads to overgeneralization errors (look at all those chickens!)
BASIC LEVEL CATEGORIES
- Recall what we discussed during object recognition – first term used to describe the object is the “basic” level
- Example of “painting”, not “paint drops” or “photograph”
- Basic-level categories based on prototypical category membership
- “Chair” (basic) vs. “furniture” (superordinate) vs. “upholstered armchair” (subordinate)
EVIDENCE FOR PROTOTYPES
- Sentence verification tasks: “A penguin is a bird” slower to confirm vs. “A robin is a bird”
- Response time correlated with typicality ratings
- Production tasks: Ask people to name as many birds as they can
- Start at “center” (typical members) and move outward to less typical
ATTRACTIVENESS
- Another interesting note – more typical category members are often rated as more attractive
- Which fish is the most “attractive”
- This holds true for human faces as well – typical features are rated as more attractive
*Most (conventionally?) attractive people cluster around the average for all facial features - Closer to prototype
ARE FUZZY BOUNDARIES IN CATEGORIZATION GOOD
- One of main strengths of prototype theory is fuzzy boundaries – don’t need to abide by strict rules and category membership
- Problem – how fuzzy are the boundaries?
- How atypical can we move things from a prototype
before it no longer matches?
EXEMPLAR THEORY
Representation corresponds to actual category member
* Exemplar of a category existed at one point and you saw it
* “Best example(s)” of the category you have actually perceived * Collection of numerous specific members of the category
HIERARCHICAL CATEGORIES
- Categories are hierarchical * For a given category…
- More specific categories (subordinate)
- More general category (superordinate)
- Knowledge can be represented hierarchically
- Don’t need to store in memory specifically that “cats breathe” if you know cats are animals and animals breathe
- Empirical results support this organization
- Faster at verifying sentences if statement is on the same hierarchical level
- Slower when needing to traverse the hierarchy
- Note though – no accounting for similarity to prototypical members in this model
- Generally faster when more prototypical
- Sometimes there is redundancy
- Peacocks directly linked with have feathers – very prominent characteristic
CATEGORICAL PERCEPTION
Although categorization might be thought of as solely following perception, mental categories can affect perception in a top-down fashion
* Continuous sensory data can be binned into categories, due to category learning and linguistic knowledge (but to what extent?)
