2Categorization.pptx

,单击此处编辑母版标题样式,单击此处编辑母版文本样式,二级,三级,四级,五级,#,Categorization,Outline,Classical Theory of Categorization,Early Empirical Research into Lexical Categories,The Internal Structure of Categories:Prototypes,Attributes,Family Resemblances and Gestalt,Context Dependence of Categorization,The Classical Theory,The classical theory of categorisation was the prevalent model since the time of Aristotle and holds that conceptual and linguistic categories have,definitional structure,.This means that an entity represents a category member by virtue of fulfilling a set of,necessary and(jointly)sufficient conditions,for category membership.,A category is defined by a limited set of necessary and sufficient conditions.These conditions are conceived as clear-cut,“discrete”features(or essential features),which can be either present or absent.,The classical Aristotelian view claims that categories are discrete entities characterized by,a set of properties which are shared by all of their members,.These properties are assumed to establish the conditions which are both necessary and sufficient to capture meaning.,According to the classical view,categories should be clearly defined,mutually exclusive and collectively exhaustive.This way,any entity of the given classification universe belongs unequivocally to one,and only one,of the proposed categories.,Classical Definition of Bachelor,BACHELOR+unmarried+male+adult,a.The Pope,b.An adult male living with his girlfriend,c.A male homosexual,d.A male homosexual living with his boyfriend,e.A seventeen-year-old living on his own,running his own Internet firm,and dating several women.cf.a seventeen-year-old living with his parents and going to school,who virtually all agree is not a bachelor,The definitional problem of the classical theory,It is remarkably difficult to identify a precise set of conditions that are necessary and sufficient to define a category.This requires the identification of all those features that are shared by all members of a category(necessary features)and that together are sufficient to define that category(no more features are required).,Game Example,The game example by Wittgenstein reveals that there is no single set of conditions that is shared by every member of the category GAME.While some games are characterised by AMUSEMENT,like tiddlywinks,others are characterised by LUCK,like dice games,still others by SKILL or by COMPETITION,like chess.,In other words,it appears to be impossible to identify a definitional structure that neatly defines this category.,The problem of conceptual fuzziness of the classical theory,A second problem with the classical view is that definitional structure entails that categories have definite and distinct boundaries.In other words,an entity either will or will not possess the right properties for category membership.,FURNITURE:table chair TV set comb,BIRD:robin sparrow penguin ostrich,The problem of prototypicality of the classical theory,The problem of prototypicality concerns what happens at the,centre,of a category.,If each member of a category shares the same definitional structure,then each member should be equally typical.,Table or chair are good(typical)examples of the category FURNITURE.Carpet is a less good example.,From Classical Theory to Prototype Theory:Two Experiments,Experiment by Berlin and Kay,Experiment by Labov,Early Empirical Research into Lexical Categories(Munsell Color Chips),Early Empirical Research into Lexical Categories,The result of the comparison of the focal colors,Focal colors are not only shared by the speakers of one and the same language but they are also very consistent across different languages,Color categorization is anchored in focal colors.,The boundaries of color categories vary between languages and even between speakers of one language.,Focal colors are shared by different speakers and different language communities.,Focal colors are perceptually more salient than non-focal colors.The attention of 3 year olds is more often attracted by focal than by non-focal colors,and 4 year olds match focal colors more accurately to a given display of other focal colors than non-focal colors.,Focal colors are more accurately remembered in short-term memory and more easily retained in long-term memory.,The names of focal colors are more rapidly produced in color-naming tasks and are acquired earlier by children.,Focal colors appear to possess a particular perceptual-cognitive salience,which is probably independent of language.,The salience of focal colors reflects certain physiological aspects of mans perceptive mechanisms.,Focal color might relate to certain universally occurring phenomena like day and night(white and black),the sun(red),vegetation(green),the sky(blue)and the ground(brown)(Wierzbicka 1990).,Rosch replaced Berlin and Kays“focus”with prototype since“focal”suggests a central position.“Prototype”stood for artificially created“best examples”and focal colors were natural prototypes.,Experiment by William Labov(1973,1978),The fuzziness of category boundaries has many facets,of which context-dependence is one of the most important.,Labovs Findings,Categories do not represent arbitrary divisions of the phenomena of the world,but should be seen as based on the cognitive capacities of the human mind.,Cognitive categories of colors,shapes,but also of organisms and concrete objects,are anchored in conceptually salient prototypes,which play a crucial part in the formation of categories.,The boundaries of cognitive categories are fuzzy,i.e.,neighboring categories are not separated by rigid boundaries,but merge into each other.,Between prototypes and boundaries,cognitive categories contain members which can be rated on a typicality scale ranging from good to bad examples.,Prototype theory,Prototype theory is most closely associated with the experimental research of cognitive psychologist Eleanor Rosch and her colleagues.,Principles of categorisation,(1)the,principle of cognitive economy,(2)the,principle of perceived world structure,Principle of cognitive economy,This principle states that an organism,like a human being,attempts to gain as much information as possible about its environment while minimising cognitive effort and resources.This cost-benefit balance drives,category formation,.In other words,rather than storing separate information about every individual stimulus experienced,humans can group similar stimuli into categories,which maintains,economy,in cognitive representation.,Principle of perceived world structure,The world around us has,correlational structure,.For instance,it is a fact about the world that wings most frequently co-occur with feathers and the ability to fly(as in birds),rather than with fur or the ability to breathe underwater.This principle states that humans rely upon correlational structure of this kind in order to form and organise categories.,The categorisation system,Good examples,bad examples,and,category boundaries,Category membership is not a yes-or-no distinction.Rather it involves different degrees of typicality.,Categories are formed around prototypes,which function as cognitive reference points.,Some concrete entities do not have clear-cut boundaries in reality:e.g.,body parts,Vagueness applies to boundaries of entities.Mountains are vague because they are not clearly delimited as individual entities.,Fuzziness/fuzzy category boundary applies to boundaries of the cognitive categories.The cognitive category of MOUNTAIN(or KNEE or FOG)is fuzzy because it does not have clear boundaries either.,Comparison of some attributes for ROBIN and OSTRICH,The Internal Structure of Categories:Prototypes,Attributes,Family Resemblances,Categorization,is the process in which experiences and concepts are recognized and understood.Categorization implies that concepts are classified into categories based on commonalities and usually for some specific purpose.Categorization is fundamental in decision making,in all kinds of interaction with the environment,and in language.Categorization is central issue in Cognitive Linguistics in which it is argued to be one of the primary principles of conceptual and linguistic organization.,Prototype,A relatively abstract mental representation that assembles the key attributes or features that best represent instances of a given category.Accordingly,the prototype is viewed as a schematic representation of the most salient or central characteristics associated with members of the category in question.According to,Prototype Theory,the prototype provides structure to and serves to organise a given category,a phenomnon known as,prototype structure,.An important consequence of this is that categories exhibit,typicality effects,.,The Attribute Structure of Prototype Categories,Prototypical members of cognitive categories have the largest number of attributes in common with other members of the category and the smallest number of attributes which also occur with members of neighbouring categories.This means that in terms of attributes,prototypical members are maximally distinct from the prototypical members of other categories.,Bad examples(or marginal category members)share only a small number of attributes with other members of their category,but have several attributes which belong to other categories as well,which is,of course,just another way of saying that category boundaries are fuzzy.,Family Resemblance,The principle of family resemblances:raised by Ludwig Wittgeinstein in his much-quoted passage about the category GAME.,Wittgensteins Conclusion:Games are connected by a network of overlapping similarities,which he called family resemblances.,On a somewhat more abstract level,the principle of family resemblances has been defined as a set of items of the form AB,BC,CD,DE.That is,each item has at least one,and probably several,elements in common with one or more other items,but no,or few,elements are common to all items.(Rosch and Mervis 1975:575),The Structure of Categories,Categories form part of a hierarchical taxonomic structure organized in accordance with at least three structural principles:radial structure,inheritance,and levels of categorization.,Radial structure,The notion of radial structure with introduced by Lakoff(1987),and implies that categories do not have symmetric structures.A radial structure is a taxonomy that has a center-periphery structure,such that the center of the category provides the schema of prototypical properties.The center is itself an idealization over what the members of the category have,or should have,in common.,The more in common a member has with the prototypical center,the closer to the center it is located.That is,those members that do not share a lot of features with the center are peripherally located.Thus categories display graded centrality and degree of membership,with good members towards the center and bad members towards the boundary.,Inheritance,Members of categories,which are also called instances of categories,are said to inherit properties from the schema-the more they inherit,the better members,they are.However,sometimes members of a category are categories themselves,in which case they are called subsets or subcategories.Subcategories are considered extensions of the schema,because they provide a sets of properties themselves,only some of which are inherited from the schema.,Levels of Categorization,Taxonomies of categories are organized into levels of categorization.There are three levels:,Superordinate level:Superordinate categories are the most general ones.They are the ones that are at the top of a folk taxonomy).,Basic,or generic,level:categories at the basic,or middle,level are perceptually and conceptually the more salient.The generic level of a category tends to elicit the most responses and richest images,providing a basic gestalt,and seems to be the psychologically basic level.Basic level categories are members of superordinate level categories.,Subordinate level:Subordinate level categories are the most specific ones.They are the members of the basic level categories.They have clearly identifiable gestalts and many individuating specific features.,Levels of Categorization,达克斯猎狗,Characteristics of prototypicality,1)categories are defined in terms of a family of resemblance rather than by means of a set of necessary and sufficient features,2)membership in a category is determined by the perceived distance of resemblance of the entity to the prototype,there is no clear-cut boundaries.But there is a continumm,3),All members of a category dont enjoy equal status.,Context Dependence,The prototypes of cognitive categories are not fixed,but may change when a particular context is introduced,and the same is true for category boundaries.More generally,the whole internal structure of a category seems to depend on the context and,in a wider sense,on our social and cultural knowledge,which is thought to be organized in cognitive and cultural models.,Prototypes are not all the fixed reference points for cognitive categories that we have assumed them to be,but that they are liable to keep shifting as the context changes.,The context-dependence of prototypes,The hunter took his gun,left the lodge and called his dog.(retriever),Right from the start of the race the dogs began chasing the rabbit.(greyhound),She took her dog to the salon to have its curls reset.(poodle),The policemen lined up with the dogs to face the rioters.(Alsatian),What turns out the most likely member of a certain category depends on the context.,The two-fold effect of context,The context can change the weight of attributes that seem to be relevant for a certain category.,The context can emphasize attributes that are not prominent and even introduce new attributes which would not be mentioned at all in non-contextualized attribute-listing experiments.,Problems with the Prototype Theory,肯定类典型论不等于说它已完美无缺。其倡导者否认“必要且充分的特征”作为判定范畴成员的标准,但未对语义特征作直接论述。如果抛开“必要且充分”,语义特征是不是判定范畴成员的标准,?,假如回答是否定的,那么凭什么判断某一认识对象为典型,?,假如回答是肯定的,那么具备多少特征才称得上是典型,?,Prototype of a word sense?,Topics for Research,Linguistic categories,Language acquisition,（,vocabulary,teaching,&,learning,construction,teaching,&,learning),Categorization across cultures or languages,