What is a concept?

1. What is a concept? • Part of semantic memory (vs. episodic memory) • A class of items that seem to belong together • ‘dog’, ‘balloon’, ‘terrorist’ (things) • ‘tall’, ‘ugly’ (properties) • ‘walk’, ‘jump’ (actions) • A mental construct (vs. the outside world) • Abstract knowledge

2. How are things clustered into categories? Based on similaritybig birdnsesame jump)t Sesamestreet_bigbird Sesametstree_jump

3. fido jessie puppy formerly known as prince prince bingo German Shepherd - Abstract representation

4. What does it mean to know what a ‘dog’ is? • Classical View: • To know what a ‘dog’ is, is to know its definition. • Dog = mammal, four legs, barks, wags tail • These properties are • Singly necessary: every member must have them • Jointly sufficient:everything that have them is a member • Categories have sharp boundaries • Either you are in or you are out • Categories have a homogeneous space • Everyone that is ‘in’ is equally good member of the category

5. Classical View: Problems • Good definitions are hard to find! • Example: A bachelor is an unmarried man • is my kid a bachelor? Adult • is the pope a bachelor? intention to get married • Some members are more typical than others(Categories have internal structure) • Basketball, golf, mini-golf • Cup, tea cup, stanley cup, C-cup Solution: • There are no defining properties, but rather • properties characteristic of the group (typical features)

6. Birdie bird Bird?

7. Is Pluto a planet or a ‘dwarf planet’? Npr (silly question) Mother: • ‘working’ mother • ‘adoptive’ mother

8. A prototype: • is an abstract representation (usually the average) • contains salient features that are true of most instances e.g., birds usually can fly (but not always) => ‘ability to fly’ is a salient feature of the category ‘bird’ A prototypical bird is one that flies (& have feathers, etc) A bird that doesn’t fly is atypical (weird: penguin, ostrich)

9. Prototype Theory (Rosch) • specify the “center” of the category, • leave ‘fuzzy’ boundaries • graded category membership (tea cup vs. Stanley cup) • some categories don’t obey these properties • Things that have ‘essence’ (‘human’ ‘marriage’)??

10. Prototypes and Basic Level • Physical Object • Living Thing • Animal • Mammal • Carnivore • Canine • Dog • Australian Shepherd

11. Superordinate BASIC Subordinate

12. Superordinate: Low similarity within category (low coherence) Animals look different from each other BASIC level: -High similarity within category All fish look the same -Low similarity between categories Fishes look different from other animals Subordinate: High similarity between categories (low discriminability) Different types of fish look similar to each other Except to Experts

13. Properties of the Basic Level Categories • Maximize within-category similarity • Minimize between- Category similarity • Maximum level of abstraction while maintaining physical similarity • Shorter name

14. Basic Level • “There is generally one level of abstraction at which the most basic category cuts can be made. .. • …the basic level of abstraction in a taxonomy is the level at which categories carry the most information.” Rosch et al. 1976) • One privileged level

15. Why are concepts useful? Functions • Coding of experience: Classification of items as members of the same category • Reduces cognitive demands • Facilitates communication • Inductive Inferences • Natural kinds vs. artifacts • Combines to create complex categories • Contact lens • Digital Camera

16. Concepts and Misconceptions • Stereotypes (social categories) • Blacks, Republicans, Arab Nations • Stereotypes reduce complexity • The reduction in complexity leads to errors

17. Stereotypical biases • Extreme examples of the category are more heavily weighted • same is true for some other categories, e.g. trees • Within-category variability is underestimated • “all Bush supporters are the same” • Insensitivity to disconfirmation • Members who challenge the stereotype are thought to be ‘special cases’ (poor examples of the category). Therefore • they are thought not to be diagnostic of the category. • “No women is a good soldier. A good female soldier, is less of a woman” • Stereotypes are more stable than is warranted by evidence • test-retest reliability: after one week .94 after 4 years .92 • Illusory correlation • Distinctive behavior - Distinctive individuals are perceived to ‘go together’ even when they are independent (e.g., antisocial behavior - blacks) • Misattribution (race – poverty – education- neighborhood) • Racial stereotypes are thought as ‘essential’ categories