Categorization and structured extensions Bárbara Eizaga Rebollar May

Categorization and structured extensions Bárbara Eizaga Rebollar May 2015

Mental representations: Introduction Intension or sense: set of criteria for identifying a concept & the properties relating it to other concepts (Unit 2). Here we study the relationship between words & the world: a level of mental representation. A noun denotes because it’s associated with something in the speaker/hearer’s mind. Relation between the mental representation (image) & the real-world entity: Resemblance

Mental representations: Introduction F. ins. Imaginary entities of Batman. Problem: Different images that different speakers have of a common noun like house depend on their experience.

Mental representations: Concepts So even if images are associated with words, this can’t be the whole story. The sense of some words, while mental, isn’t visual but a more abstract element: a concept Lexicalized non-lexicalized a single word concept phrases On the shopping channel, I saw a tool for compacting dead leaves into garden statuary.

Mental representations: Concepts The reason why some concepts are lexicalized & others not is utility. If we refer to something very often, it will become lexicalized: Microwave oven for a while a 2 -word label. With frequency of use microwave A traditional approach to describing concepts defines them by using sets of necessary and sufficient conditions. If we have a concept like WOMAN, it must contain the info necessary to decide when something in the world is a woman or not.

Attributes, necessary & sufficient conditions How can be this information organized? As a set of attributes or characteristics, i. e. x is a woman iff L. Where L is a list of attributes, like: x is human; x is adult; x is female, etc. These attributes can be seen as: Ønecessary conditions: sth must have them to be a woman. Øsufficient conditions: when a set is enough to describe a concept, i. e. it has the right amount of information.

Attributes, necessary & sufficient conditions So this theory views concepts as bits of knowledge: the necessary & sufficient conditions for sth to be an example of that concept. Problem 1: if speakers share the same concept they will agree on the necessary and sufficient conditions. But it has proved difficult to set these up even for concrete nouns like cat & dog. F. ins. the noun zebra: is an animal, has 4 legs, is striped, is a herbivore, etc. Which of these are necessary? The 1 st obviously; the rest are problematic.

Attributes, necessary & sufficient conditions If we find a pure white or black zebra, we might still call it a zebra. Or if, by some birth defect, a 3 -legged zebra comes into the world, it’d be still a zebra. Or if a zebra ate a few insects, would it cease to be a zebra? Problem 2: Speakers use words whose identifying attributes are hardly known. F. ins. difference between cookie and biscuit, yet they are regularly used. As with gold or platinum, we can use words without knowing much about the referent. Conclusion: It seems unlikely that a word is referring to a concept composed of a set of necessary & sufficient conditions, i. e. a definition.

Prototypes Because of problems with necessary & sufficient conditions, Rosch proposed a more elaborated theory of concepts: the prototype theory. Concepts are viewed as structured so that there are central or typical members of a category, but then a shading off into less typical or peripheral members: Chair > + central member of category FURNITURE > lamp. Sparrow > + typical member of category BIRD > penguin. Speakers tend to agree more on typical members than on less typical ones. This approach allows borderline uncertainty: an item may bear resemblance to 2 different prototypes.

Prototypes F. ins. If an English speaker is unsure about whether whale is a mammal or a fish. Prototype theory explains this by the fact that whales are far from the central prototype of the category MAMMAL. And they resemble prototypical fish in some features: they live underwater in oceans, have fins, etc. Conclusion: Some members of a category are better exemplars than others; so members of a category are graded with respect to one another. BUT establishing a prototype depends upon experiences and beliefs of the population investigated.

Prototypes Rosch listed 6 exemplars of the category Diseases & asked people to rank them. The result was: cancer> measles> malaria> muscular dystrophy> rheumatism > cold Cold is the mildest of the diseases, but the number of people suffering from colds at the time of the experiment would affect its saliency. Prototypicality isn’t valid for all speakers of a language, or even the same speakers on different occasions. Experiments to identify prototypes may identify exemplars of a category, but they aren’t necessarily what we think of when a category is named.

Family resemblances A prototype for categories named by superordinates with many hyponyms (fish, vegetable, etc. ) don’t have clear prototypes as BASIC LEVEL CATEGORIES… BUT family resemblances between category members, associated through substance, shape, configuration, …: Root vegetables: carrot, turnip, potato. Green vegetables: cabbage, spinach, broccoli. - perceived shape homogeneity , neutrality Basic level - fast identification of categ. members category - single mental image st - 1 learnt by children - most common label for categ. members

Family resemblances chair Superordinate lamp desk lamp floor lamp table furniture desk chair easy chair rocking chair dining room table coffee table Basic Subordinate

Conceptual networks An alternative approach to prototype discovering is to present subjects a set of picture & ask the name for them. Decisions were made on: a. Shape & configuration of container. b. Container material. c. Purpose to which it is put.

Conceptual networks One kind of family resemblance is the CHAIN OF SIMILARITY. In top row, object 3 is a better exemplar of a cup than 2, which is better than 1; in the left column, 5> 6> 7> 8> 9. The chain is extended by chaining to various types of contexts: -From sticks to martial arts contests that use sticks or swords. From these to judo contests, and contests between Zen master and student. -From ropes & the contest chain to the trajectory of a ball in a game: hits and pitches in baseball, shots in basketball. -From ropes to rolls of tape or films and hence to movies.

Conceptual networks: Radial structures Semantic extension proceeds along a chain in which the 1 st & the last link are semantically quite distant. F ins. mother: 1. Prototypical mother: woman who produces the ovum, conceives, gestates, gives birth, & nurtures ego. Radiating from this are more peripheral attributes of mother. 2. Natural or biological mother: woman who produces the ovum, conceives, gestates & gives birth to ego. 3. Genetic or donor mother: supplies the ovum that becomes ego to a surrogate mother. 4. Nurturant mother: adoptive mother, a foster mother, the genetic mother, or the surrogate mother.

Radial structure of mother The radial structure of this category is defined with respect to the different models. Genetic mother Single mother Surrogate mother Stepmother Adoptive mother Central case Biological mother Foster mother Birth mother Natural mother

Radial structure Concepts can be the prototype of their category in various ways: o Central subcategory : others relate to this ØAmble and swagger relate to WALK ØShove relates to PUSH o Essential: meets a common definition: birds have feathers, lay eggs ØMove involves change of location. o Typical case: most are like this: sparrow Ø Going to a conference involves air travel. o Ideal/anti-ideal case: positive social standard: parent/ negative social standard: terrorist o Salient exemplar: individual chosen as example

Category structure • Classical Category: necessary and sufficient conditions • Radial Category: a) a central member branching out to less-central and non-central cases; b)degrees of membership, with extendable boundary • Family Resemblance: a) every family member “looks” like some other family member(s); b) there is no one property common across all members (e. g. polysemy) • Prototype-Based Category • Ad-hoc Category: things you can fit inside a shopping bag.

Stereotypes & Gestalten Stereotype Semantics holds that the meaning of a language expression is not a well-defined set of properties, but rather a MINIMUM SET OF STEREOTYPICAL FACTS. ØThe stereotypical bird flies, even though penguins don’t. ØThe stereotypical politician is economical with truth when his/her credibility is threatened. Experts usually have more knowledge than their fellows and so their stereotypes would be different from the layperson: a male chauvinist & a radical feminist different stereotypes for man & woman.

Stereotypes & Gestalten Similar to the stereotype is the notion of a prototype as a GESTALT, which means ‘single mental image’. Classic examples of Gestalten in perception are: a. Knowing the configuration of a chair even though one can only see parts of it from a single point. b. Recognizing a melody without being conscious of the individual notes from which it is created. c. Having a Gestalt of a word that enables you to feel that it is spelt correctly or incorrectly on a given occasion. When people conjure a mental image of dog, some people would call it a Gestalt, others a prototype & others a stereotype.

References o Allan, K. 2000, Natural Language Semantics. Cornwall: Blackwell. o Rosch, E. H. (1973). "Natural categories". Cognitive Psychology 4 (3): 328– 50. o Rosch, E. H. ; Mervis, C. B. ; Gray, W. D. ; Johnson, D. M. ; Boyes-Braem, P. (1976). "Basic objects in natural categories". Cognitive Psychology 8 (3): 382– 439. o Saeed, J. I. 1997. Semantics. Oxford: Blackwell Publishing.