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14 Seiten, Note: 1,0
2. Prototype theory
2.1 Development and general notions
2.2 The structure of conceptual categories
2.2.1 The horizontal dimension
2.2.2 The vertical dimension
3. Problems of prototype theory
3.1 Problems of componential analysis
3.2 ‘Prototype’ as a prototypical notion
3.3 The Odd Number Paradoxon
3.4 The Problem of Ignorance and Error
3.5 The Missing Prototypes Problem
3.6 Context-dependency of dimensional concepts
This paper will deal with prototype theory and its problems. The first part of the paper will provide a brief introduction into prototype theory. It will be based on the experimental and theoretical work done by Eleanor Rosch and her colleagues in the 1970s. Rosch’s work can easily be considered the most important work in the field of prototype theory as Rosch’s work marked the beginning of prototype theory. The focus of the first and more theoretical part of the paper lies on the structure of conceptual categories, as this is where most critics of prototype theory take aim at. The second part of the term paper will be dedicated to a selection of the most commonly brought up problems of prototype theory. In the conclusion it will be discussed whether or not prototype theory is relevant for linguistics.
Prototype theory is part of the large field of cognitive linguistics, which interests both cognitive psychologists and linguists. It deals with the human “ability to identify perceived similarities (and differences) between entities and thus group them together” (Evans & Green 2006: 248), which is per definition called categorization. Prototype theory replaced or at least challenged the ‘classic theory’ of categorization, which had been in charge since Aristotelian times and progressively been regarded as more and more insufficient for adequately explaining the human categorization system, as it searched to explain categorization solely by means of necessary and sufficient conditions (ibid.: 251-253). The central problem of the ‘classic theory’ is the problem of conceptual fuzziness. The ‘classic theory’ “permits only two degrees of membership, i.e. member and non-member” (Taylor 1990: 54f), while linguistic reality proves that there are cases in which it is difficult or even impossible to decide whether a given entity is member of a certain category or not, e.g.: “Consider the category bird. While it is obvious that birds like robin and sparrow belong to this category, it is less obvious that animals like penguins and ostriches do, neither of which can fly” (Evans & Green 2006: 253f). This is where the ‘classic theory’ fails and prototype theory comes into play.
It is suggested that prototype theory should rather be regarded as “less a theory of knowledge representation than a series of findings” (ibid.: 249), as it “emerged from the research of Eleanor Rosch and her colleagues” (ibid.) done in the 1970s. Rosch’s findings and her theoretical work were based on earlier works by e.g. Brown and Wittgenstein (Croft & Cruse 2004: 77).
Rosch formulates two central principles which give insight into the human categorization system. The first principle (principle of cognitive economy) says that categories help organisms, and consequently human beings, to gather and store information about their environment as efficiently as possible:
The first principle contains the almost common-sense notion that, as an organism, what one wishes to gain from one's categories is a great deal of information about the environment while conserving finite resources as much as possible (Rosch 1978: 28).
In her second principle (principle of perceived world structure) Rosch claims that the world organisms perceive is structured:
The second principle of categorization asserts that unlike the sets of stimuli used in traditional laboratory-concept attainment tasks, the perceived world is not an unstructured total set of equiprobable co-occurring attributes. Rather, the material objects of the world are perceived to possess […] high correlational structure (ibid.: 29).
It is also pointed out that the perception of the world is species-specific and determined by the functional needs of the one perceiving. When it comes to human beings, which are prototype theory’s main focus of interest, the perception of the world is also culture-specific:
It should be emphasized that we are talking about the perceived world and not a metaphysical world without a knower. What kinds of attributes can be perceived are, of course, species-specific. […] What attributes will be perceived given the ability to perceive them is undoubtedly determined by many factors having to do with the functional needs of the knower interacting with the physical and social environment. One influence on how attributes will be defined by humans is clearly the category system already existent in the culture at a given time (ibid.).
According to Rosch, conceptual categories have a vertical and a horizontal dimension:
[…] [W]e may conceive of category systems as having both a vertical and a horizontal dimension. The vertical dimension concerns the level of inclusiveness of the category – the dimension along which the terms collie, dog, mammal, animal and living thing vary. The horizontal dimension concerns the segmentation of categories at the same level of inclusiveness – the dimension on which dog, cat, car, bus, chair, and sofa vary (ibid.: 30).
Rosch’s example provides one with an idea of what the term inclusiveness means in this context, but Evans & Green make it even clearer: “[i]nclusiveness relates to what is subsumed within a particular category” (Evans & Green 2006: 256).
What is most essential about the distinction between the vertical dimension and the horizontal dimension is that the vertical dimension deals with taxonomic – this term will be introduced in 2.2.2 – structures between categories, while the horizontal dimension deals with internal structures of categories.
When discussing internal structures of categories, the question of how humans decide whether or not a given entity belongs to a certain category is central. This is a matter of family resemblance. As Hampton (1997: 87) states, the term family resemblance goes back to philosopher Wittgenstein, who suggested that members of categories with no clear defining features resembled each other like close relatives do:
[…] [T]here might be a characteristic family nose, and family eye colour, and family hair type, and different family members would be expected all to have at least some of these characteristic, although not all (ibid.: 87).
Rosch Mervis (1975: 574f) performed a series of experiments which showed that there are similar relationships between members of a category:
In the present research, we viewed natural semantic categories as networks of overlapping attributes; the basic hypothesis was that members of a category come to be viewed as prototypical of the category as a whole in proportion to the extent to which they bear a family resemblance to (have attributes which overlap those of) other members of the category. Conversely, items viewed as most prototypical of one category will be those with least family resemblance to or membership in other categories. (Rosch & Mervis 1975: 575).
Nevertheless, sometimes it is very hard if not impossible to decide whether or not a given entity belongs to a certain category, which is due to the fact that “[m]ost, if not all, categories do not have clear-cut boundaries” (Rosch 1978: 35). Miller tries to give evidence for this:
[…] [M]any category boundaries are […] vague and […] movable; an object that would be accepted as a table in one context may be identified as a bench on some other occasion (Miller 1978: 308).
Another question that needs to be considered is whether or not all category members hold the same status within a category? Rosch’s research showed that there are so-called prototype effects, which are per definition “asymmetries among category members and asymmetric structures within categories” (Lakoff 1987: 40), i.e. some category members are regarded to be better exemplars of their categories than other category members. Rosch & Mervis found out that “the more prototypical of a category a member is rated, the more attributes it has in common with other members of the category and the fewer attributes in common with members of the contrasting categories” (Rosch 1978: 37), which already provides one with a slight idea of what prototypical members are, but Lakoff makes it even clearer: “The most representative members of a category are called ‘prototypical’ members (Lakoff 1987: 41)”.
Lakoff (ibid.: 41f) presents various experimental paradigms used in order to uncover prototype effects and determine the prototypical members of a category. All of these involve Goodness of exemplar (GOE) ratings, i.e. the subject has to, either directly or indirectly, rate how representative of its category a category member is. Referring to her own empirical studies, Rosch states that subjects mostly agree concerning GOE ratings:
It is by now a well-documented finding that subjects overwhelmingly agree in their judgments of how good an example or clear a case members are of a category, even for categories about whose boundaries they disagree (Rosch 1978: 36).
As already briefly mentioned earlier, the vertical dimension is concerned with taxonomic structures between categories. Rosch provides one with a definition of the term taxonomy: “A taxonomy is a system by which categories are related to one another by means of class inclusion” (Rosch 1978: 30). Taxonomy is closely linked to the level of abstraction, as “[t]he greater the inclusiveness of a category with a taxonomy, the higher the level of abstraction” (ibid.). Taylor illustrates the notion of taxonomy with the following example:
A given entity may be categorized in many alternative ways. Chair, piece of furniture, artefact, and indeed entity, are all equally true ways of describing the thing I am sitting on as I write this chapter. chair, furniture, artefact, and entity represent four levels of categorization, each more inclusive than the preceding one. The category chair is included in the superordinate category furniture, which in turn is included in the even higher category artefact. On the other hand, kitchen chair is a subordinate member of the category chair (Taylor 1990: 46).
It is also worth mentioning that not all levels of categorization share the same status within the human categorization system:
There is […] a level of categorization which is cognitively and linguistically more salient than the others. This is the ‘basic level’ of categorization. It is at the basic level of categorization that people conceptualize things as perceptual and functional gestalts ” (ibid.: 48).
 gestalt – central term of Gestalt psychology, a branch of psychology “which is interested in the principles that allow unconscious perceptual mechanisms to construct wholes or ‘gestalts’ out of incomplete perceptual input” (Evans & Green 2006: 65).
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