Прототиптік теория: санаттарды жіктеудің дәрежелік ұғымы

Theory of categorization based upon degrees of similarity to a central case

Prototype theory is a theory of categorization in cognitive science, particularly in psychology and cognitive linguistics, in which there is a graded degree of belonging to a conceptual category, and some members are more central than others. It emerged in 1971 with the work of psychologist Eleanor Rosch, and it has been described as a "Copernican Revolution" in the theory of categorization for its departure from the traditional Aristotelian categories. It has been criticized by those that still endorse the traditional theory of categories, like linguist Eugenio Coseriu and other proponents of the structural semantics paradigm.

The term prototype, as defined in psychologist Eleanor Rosch's study "Natural Categories", was initially defined as denoting a stimulus, which takes a salient position in the formation of a category, due to the fact that it is the first stimulus to be associated with that category. Rosch later defined it as the most central member of a category. Rosch and others developed prototype theory as a response to, and radical departure from, the classical theory of concepts, which defines concepts by necessary and sufficient conditions. Necessary conditions refers to the set of features every instance of a concept must present, and sufficient conditions are those that no other entity possesses. Rather than defining concepts by features, the prototype theory defines categories based on either a specific artifact of that category or by a set of entities within the category that represent a prototypical member. The prototype of a category can be understood in lay terms by the object or member of a class most often associated with that class. The prototype is the center of the class, with all other members moving progressively further from the prototype, which leads to the gradation of categories. Every member of the class is not equally central in human cognition. As in the example of furniture above, couch is more central than wardrobe. Contrary to the classical view, prototypes and gradations lead to an understanding of category membership not as an all or nothing approach, but as more of a web of interlocking categories which overlap. Further development of prototype theory by psychologist James Hampton, and others replaced the notion of prototypes being the most typical exemplar, with the proposal that a prototype is a bundle of correlated features. These features may or may not be true of all members of the class (necessary or defining features), but they will all be associated with being a typical member or the class. By this means, two aspects of concept structure can be explained. Some exemplars are more typical of a category than others, because they are a better fit to the concept prototype, having more of the features. Importantly, Hampton's prototype model explains the vagueness that can occur at the boundary of conceptual categories. While some may think of pictures, telephones or cookers as atypical furniture, others will say they are not furniture at all. Membership of a category can be a matter of degree, and the same features that give rise to typicality structure are also responsible for graded degrees of category membership. In Cognitive linguistics it has been argued that linguistic categories also have a prototype structure, like categories of common words in a language.

The notion of prototypes is related to Wittgenstein's (later) discomfort with the traditional notion of category. This influential theory has resulted in a view of semantic components more as possible rather than necessary contributors to the meaning of texts. His discussion on the category game is particularly incisive:Consider for example the proceedings that we call 'games'. I mean board games, card games, ball games, Olympic games, and so on. What is common to them all? Don't say, "There must be something common, or they would not be called 'games'" but look and see whether there is anything common to all. For if you look at them you will not see something common to all, but similarities, relationships, and a whole series of them at that. To repeat: don't think, but look! Look for example at board games, with their multifarious relationships. Now pass to card games; here you find many correspondences with the first group, but many common features drop out, and others appear. When we pass next to ball games, much that is common is retained, but much is lost. Are they all 'amusing'? Compare chess with noughts and crosses. Or is there always winning and losing, or competition between players? Think of patience. In ball games there is winning and losing; but when a child throws his ball at the wall and catches it again, this feature has disappeared. Look at the parts played by skill and luck; and at the difference between skill in chess and skill in tennis. Think now of games like ring a ring a roses; here is the element of amusement, but how many other characteristic features have disappeared! And we can go through the many, many other groups of games in the same way; can see how similarities crop up and disappear. And the result of this examination is: we see a complicated network of similarities overlapping and criss crossing: sometimes overall similarities, sometimes similarities of detail. Wittgenstein's theory of family resemblance describes the phenomenon when people group concepts based on a series of overlapping features, rather than by one feature which exists throughout all members of the category. For example, basketball and baseball share the use of a ball, and baseball and chess share the feature of a winner, etc., rather than one defining feature of "games". Therefore, there is a distance between focal, or prototypical members of the category, and those that continue outwards from them, linked by shared features. Recently, Peter Gärdenfors has elaborated a possible partial explanation of prototype theory in terms of multi dimensional feature spaces called conceptual spaces, where a category is defined in terms of a conceptual distance. More central members of a category are "between" the peripheral members. He postulates that most natural categories exhibit a convexity in conceptual space, in that if x and y are elements of a category, and if z is between x and y, then z is also likely to belong to the category.

Within language we find instances of combined categories, such as tall man or small elephant. Combining categories was a problem for extensional semantics, where the semantics of a word such as red is to be defined as the set of objects having this property. This does not apply as well to modifiers such as small; a small mouse is very different from a small elephant. These combinations pose a lesser problem in terms of prototype theory. In situations involving adjectives (e. g. tall), one encounters the question of whether or not the prototype of [tall] is a 6 foot tall man, or a 400 foot skyscraper. The solution emerges by contextualizing the notion of prototype in terms of the object being modified. This extends even more radically in compounds such as red wine or red hair which are hardly red in the prototypical sense, but the red indicates merely a shift from the prototypical colour of wine or hair respectively. The addition of red shifts the prototype from the one of hair to that of red hair. The prototype is changed by additional specific information, and combines features from the prototype of red and wine.

Mikulincer, Mario & Paz, Dov & Kedem, Perry focused on the dynamic nature of prototypes and how represented semantic categories actually changes due to emotional states. The 4 part study assessed the relationships between situational stress and trait anxiety and the way people organize the hierarchical level at which semantic stimuli are categorized, the way people categorize natural objects, the narrowing of the breadth of categories and the proneness to use less inclusive levels of categorization instead of more inclusive ones.

Prototype theory has been criticized by those that still endorse the classic theory of categories, like linguist Eugenio Coseriu and other proponents of the structural semantics paradigm.

Linguists, including Stephen Laurence writing with Eric Margolis, have suggested problems with the prototype theory. In their 1999 paper, they raise several issues. One of which is that prototype theory does not intrinsically guarantee graded categorization. When subjects were asked to rank how well certain members exemplify the category, they rated some members above others. For example, robins were seen as being "birdier" than ostriches, but when asked whether these categories are "all or nothing" or have fuzzier boundaries, the subjects stated that they were defined, "all or nothing" categories. Laurence and Margolis concluded that "prototype structure has no implication for whether subjects represent a category as being graded" (p. 33).

Daniel Osherson and Edward Smith raised the issue of pet fish for which the prototype might be a guppy kept in a bowl in someone's house. The prototype for pet might be a dog or cat, and the prototype for fish might be trout or salmon. However, the features of these prototypes do not present in the prototype for pet fish, therefore this prototype must be generated from something other than its constituent parts. James Hampton found that prototypes for conjunctive concepts such as pet fish are produced by a compositional function operating on the features of each concept. Initially all features of each concept are added to the prototype of the conjunction. There is then a consistency check for example pets are warm and cuddly but fish cannot be. Fish are often eaten for dinner, but pets are never. Hence the conjunctive prototype fails to inherit features of either concept that are incompatible with the other concept. A final stage in the process looks for knowledge of the class in long term memory, and if the class is familiar may add extra features a process called "extensional feedback". The model was tested by showing how apparently logical syntactic conjunctions or disjunctions, such as "A sport which is also a game" or "Vehicles that are not Machines", or "Fruits or Vegetables" fail to conform to Boolean set logic. Chess is considered to be a sport which is a game, but is not considered to be a sport. Mushrooms are considered to be either a fruit or a vegetable, but when asked separately very few people consider them to be a vegetable and no one considers them to be a fruit. Antonio Lieto and Gian Luca Pozzato have proposed a typicality based compositional logic (TCL) that is able to account for both complex human like concept combinations (like the PET FISH problem) and conceptual blending. Their framework shows how concepts expressed as prototypes can account for the phenomenon of prototypical compositionality in concept combination.