Classical Categories versus Experientially Based Categories

1. Classical Categories versus Experientially Based Categories Prototypes and the Basic Level Linguistics 3430

2. What’s Important about Categorization? • Most words refer to classes rather than to specific entities. • Perception, motor activity, linguistic behavior all involve categories. • We infer based on category: • Linnaean taxonomy: genus homo entails family hominid, which entails order primate,whichentails class mammalia, which entails phylum chordata. • Medical diagnosis: doctors must make quick judgments using ‘heuristics’, which can lead to reasoning errors like ‘availability’ and ‘confirmation bias’.

3. The Mysteries of Categorization • Using a common noun requires us to categorize. • But what does it mean to know the name of something—knowing a description, a context, an image? • How do we use names appropriately? • How do our purposes affect the way we categorize?

4. The Classical Model of Categorization • The classical model says that to know a category is to know the properties that define it (a description). • Categories have no internal structure; all members are equal. • Categories are based on inherent properties. • Humans have access to category structure, but may make naïve errors. • Categories are independent of humans or human purposes.

5. Philosophers Reject the Classical Model • The challenges starts with proper names. • The classical model is description theory: to know a name is to know facts about the person who carries the name (Russell). • It accounts for the coherence of sentences like Santa Claus does not exist. • S. Kripke argues that it’s wrong: we use a name because other people in the community use the name in certain contexts. • H. Putnam extends the causal theory to natural kind terms like gold and elm.

6. Extension to Natural Kinds • Putnam says: for me, both elms and beeches are ‘deciduous trees growing in North America’. • Yet if he says, ‘The elm is the most popular ornamental tree in North America’ this statement can be evaluated as true or false. • Nothing in Putnam’s head fixes his elm reference; rather, the community contains people who know what a technical elm is. • The experts ensure that when he says elm he is talking about elms, so we folk are free to talk loosely.

7. Linguists Reject the Classical Model • Putnam is pretty much right: category boundaries aren’t fixed, but defined by the context in which the category is used. • Human categorization is a matter of human experience and imagination—of perception, motor activity and culture (on the one hand) and of metaphor, metonymy and mental imagery on the other (on the other). • To change our view of categories is to change our view of the world, since categories are categories of things: animals, substances, artifacts, colors, kinsmen, emotions, etc.

8. The Alternative Model • Since humans create categories, their organization reflects human needs and creativity. • Categories are organized by prototypes. • Prototypes give rise to: • membership gradience • meaning extensions (polysemy) • contested categories • stereotype-based reasoning • When categories are nested, one level is more basic than the others: beverage/alcoholic beverage/beer.

9. The Alternative Model • There may be no property which characterizes all members of a category, whether necessary or sufficient. • This doesn’t necessarily mean that the category has unclear boundaries. • It does mean that the category may be extensible. • The SALAD example

10. Radial Categories • Lakoff (1987) proposes to model prototype-based categories as radial categories. • In such categories, the central member is defined by a cluster of converging properties (torn lettuce is basic ingredient, it is served cold, it is served as a side dish, it contains acidic sauce, it contains other vegetables). • Peripheral members lack one or more of the properties that jointly define the central member.

11. Experiments on Prototypes • Eleanor Rosch described asymmetries that she called prototype effects: subjects judged members of some categories as more representative than others. • Paradigms included: • direct rating • reaction time • production of examples • asymmetry in similarity ratings • directionality of generalizations

12. The Basic Level • Roger Brown: “While a dime can be called a coin or money or a 1952 dime, we somehow feel that dime is its real name”. • Categorization “begins at the level of distinctive action”; superordinate and subordinate names are “achievements of the imagination”. • This means that in a taxonomy one level is more important to us than the others.

13. The Basic Level • The level of distinctive actions. • The level which is learned earliest and at which things are first named. • The level at which names are shortest, most frequent, and least likely to be borrowed. • The highest level at which a single image can stand for the whole. • The level at which most the knowledge is concentrated.

14. The Basic Level • The level at which folk categories align best with technical categories: • order: rodentia • family: muridae • genus: mus, rattus,cricetus, meriones • species: rattus norvegicus, rattus rattus • The level with the greatest cultural significance. • The level at which distinctions are made most easily.

15. Prototypes and the Basic Level • How are prototype-based categories distinct from basic-level categories? • Not all prototype-based categories are in a taxonomy. • But all basic-level categories have prototypical members (e.g., BIRD).