Principio de temporalidad

The traditional view of categorization is shaped by the model of ‘necessary and sufficient conditions’ (NSC model for short) that goes back to Aristotle. According to the NSC model, a category is defined by a set of necessary con- ditions, which together are sufficient. For example, if we assume that the cat- egory WOMANis defined by the three conditions of being human, female and adult, each one is necessary. If someone is not human or not female or not adult, he or she is not a woman. On the other hand, the condition of being human and female and adult, is sufficient for membership in the category WOMAN. It does not matter what other conditions someone or something may fulfil. Being a woman or not depends on these three conditions.

As you will have noticed, the NSC model of categorization, also called the check-list model, exactly matches with the BFA notion of meaning (7.3). 09-UnderSemantics-Ch9-cp 04/04/2002 7:51 am Page 174

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The binary features that make up the meaning of a word according to BFA directly correspond to the necessary conditions of the NSC model.

The Aristotelian model can be characterized by the following points: ● Categorization depends on a fixed set of conditions or features. ● Each condition is absolutely necessary.

● The conditions are binary (yes-or-no) conditions. ● Category membership is a binary (yes-or-no) issue. ● Categories have clear boundaries.

● All members of a category are of equal status.

That categories have clear boundaries is a direct consequence of the fact that the defining conditions are binary. Everything either fulfils this set of conditions or it does not. If it does, it belongs to the category, otherwise it does not. As a consequence, categories have clear boundaries, and within their boundaries all members enjoy the same status of full members. Each single point of the NSC model was challenged in Prototype Theory, the result of the first extensive studies in categorization undertaken by cognitive psychologists and semanticists.

9.2.2 Prototypes

The findings on colour terms, which at the same time were findings on colour categorization, did not seem to fit the NSC model at all. Clearly, the subjects did not categorize the colour chips by checking a list of binary features. The basic colour categories are primarily defined by focal colours. A definite boundary between neighbouring categories cannot be drawn. ‘Category boundaries … are not reliable, even for repeated trials with the same informant’ (Berlin and Kay, 1969, p. 15). When one moves from focal red to focal brown in a system that has BCTs for both, one somewhere leaves the range of red hues and enters that of brown hues. Furthermore, the categories REDand BROWNintuitively overlap. Brownish red is predominantly red but still more or less brown, and reddish brown is vice versa. Thus, it appears, a colour belongs to a category if it is sufficiently similar to the focal hue, i.e. the best example. Since, however, similarity is a matter of degree, category membership too is a matter of degree, rather than a yes-or-no issue. Linguists and psychologists set out to investigate other areas for similar phenomena. They found that for many different categories best examples can be empirically established. These come to mind first and are consistently considered ‘better members’ than less typical cases. Such central examples came to be called prototypes. Experiments were carried out to examine whether category membership in general is a matter of similarity to the prototype and hence a matter of degree; whether categories have fuzzy boundaries; whether the defining conditions, or features, are binary and always strictly necessary.

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It soon turned out that, apparently, many categories have a ‘graded structure’. They contain prototypical exemplars that represent the category best and other exemplars that do it to a lesser extent but are still good examples, while others only enjoy a marginal status. For example, in a famous study cited in every textbook on cognitive semantics, Eleanor Rosch, whose name is inextricably linked with the early development of Prototype Theory, established a ranking within the general category BIRD. The subjects participating in the study were asked to rate on a scale from 1 (for best) to 7 the ‘goodness-as-example’ of different kinds of birds. The results were surprisingly consistent. Robins were considered the best examples, followed by doves, sparrows and canaries; owls, parrots, pheasants and toucans occupied a medium position, ducks and peacocks were considered even less good examples, while penguins and ostriches ranked lowest. Similar results were obtained for the categories FURNITURE, FRUIT, CLOTHING, etc. Furthermore, the rankings were consistent with other findings, such as the time it took the subjects to answer questions of the type ‘Is a penguin a bird?’, ‘Is an eagle a bird?’, etc.; the less typical the examples were, the longer the reaction time.

Since prototypical examples are what we think of first, we will exclude other cases when a category is mentioned, as long as there is no reason to do otherwise. Thus prototypes play an important role in what is called default

reasoning, i.e. reasoning in terms of assumptions which replace specific actual information as long as none is provided. For example, when Mary tells John,

(1) Look, there’s a bird on the window sill.

John will think of a prototypical bird, not of an owl, a condor, an ostrich or a penguin. If someone mentions a ‘car’, we will not think of a truck or a veteran car. It is therefore misleading to use the general terms for non- prototypical cases, misleading – but not semantically incorrect. Penguins are birds and we can refer to them as birds in appropriate contexts. For example, (2a) and (2b) are perfectly acceptable:

(2)a. The only birds that live in the Antarctic are penguins. b. Penguins come ashore to nest. The birds lay one to three eggs.