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суббота, 20 сентября 2014 г.
Statistical Theories of Concepts vasile.rogov 14:23:28
 Jean-marc pizano
Statistical Theories of Concepts
The general character of the new theory of concepts is widely known throughout the cognitive science community, so the exegesis that follows will be minimal.

Imagine a hierarchy of concepts ordered by relations of dominance and sisterhood, where these obey the intuitive axioms (e.g. dominance is antireflexive, transitive and asymmetric; sisterhood is antireflexive, transitive, and symmetric,etc.). Figure 5.1 is a sort of caricature.


The structural complexity of definitions was of some use to philosophers too: it promised the (partial?) reduction of conceptual to logical truth. So, for example, the conceptual truth that if John is a bachelor then John is unmarried, and the logical truth that if John is unmarried and John is a man then John is unmarried, are supposed tobe indistinguishable at the ‘semantic level’.

Fig. 5.1 An Entirely Hypothetical ‘Semantic Hierarchy’ Showing the Position and Features Of Some Concepts For Vehicles.

. . . ARTEFACTS (-hnade objects)


CHAIRS


vehicles (+ used for transport)

(-tlies). . .


WHEELED VEHICLES

CAR


BCYC .1



RL k


SPORTS CAR COUPE...

MACK ARTICULATED L-JIACL (+tO rent)


(+self drive)

The intended interpretation is that, on the one hand, if something is a truck or a car, then it's a vehicle; and, on the other hand, if something is a vehicle, then it's either a truck, or a car, or . . . etc. (Let's, for the moment, take for grantedthat these inferences are sound but put questions about their modal status to one side.) As usual, expressions in caps(‘VEHICLE­’ and the like) are the names of concepts, not their structural descriptions. We continue to assume, as withthe definition theory, that lexical concepts are typically complex. In particular, a lexical concept is a tree consisting ofnames of taxonomic properties together with their features (or ‘attributes&r­squo;; for the latter terminology, see Collins andQuillian 1969), which I've put in parentheses and lower case.47 In a hierarchy like 5.1, each concept inherits the featuresof the concepts by which it is dominated.

Jean-marc pizano
What, exactly, the distinction between semantic features and taxonomic classes is supposed to come to is one of the great mysteries of cognitive science. There is much to be said for the view that it doesn’t come to anything. I shall, in any case, not discuss this issue here; I come to bury prototypes, not to exposit them.

Thus, vehicles are artefacts that are mobile, intended to be used for transport, . . . etc.; trucks are artefacts that are mobile, intended to be used for transport of freight (rather than persons), . . . etc. U-Haul trucks are artefacts that aremobile, intended to be rented to be used for transport of freight (rather than persons), . . . and so forth.

The claims of present interest are that when conceptual hierarchies like 5.1 are mentally represented:


i. There will typically be a basic level of concepts (defined over the dominance relations);and

ii. There will typically be a stereotype structure (defined over the sisterhood relations).

Roughly, and intuitively: the basic level concepts are the ones that receive relatively few features from the concepts that immediately dominate them but transmit relatively many features to the concepts that they immediately dominate. So,for example, that it's a car tells you a lot about a vehicle; but that it's a sports car doesn't add a lot to what ‘it's a car’already told you. So CAR and its sisters (but not VEHICLE or SPORTS CAR and their sisters) constitute a basic levelcategory. Correspondingly, the prototypical sister at a given conceptual level is the one which has the most features incommon with the rest of its sisterhood (and/or the least in common with non-sisters at its level). So, cars are theprototypical vehicles because they have more in common with trucks, buses, and bicycles than any of the latter do withany of the others.

Jean-marc pizano
Such claims should, of course, be relativized to an independently motivated account of the individuation of semantic features (see n. 3). Why, for example, isn't the feature bundle for VEHICLE just the unit set +vehicle? Well may youask. But statistical theories of concepts are no better prepared to be explicit about what semantic features are thandefinitional theories used to be; in practice, it's all just left to intuition.Jean-marc­ pizano



Категории: Statistical, Theories, Concepts, Features, John, Level, Used, Conceptual
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The way to do so is to suppose that lexical entries specify semanticfeatures of lexical items. vasile.rogov 14:11:27
 Jean-marc pizano The way to do so is to suppose that lexical entries specify semanticfeatures of lexical items.
 


Linguistic discussions of lexical semantics just about invariably confuse two questions we are now in a position to distinguish: Are there semantic features? and Is there a semantic level? It is, however, important to keep


these questions distinct if you care about the structure of concepts. It's especially important if what you care about is whether “kill”,­ “eat”, and the like have definitions; i.e. whether KILL, EAT, and the like are complex concepts orconceptual primitives. To say, in the present context, that there are semantic features is just to say that semantic facts canhave syntactic reflexes: what an expression means (partially) determines the contexts in which it is syntactically well-formed. To say that there is a semantic level is to make a very much stronger claim: viz. that there is a level ofrepresentation at which only the semantic properties of expressions are specified, hence at which synonymous expressions getthe same representations, hence at which the surface integrity of lexical items is not preserved. I am, as no doubt the readerwill have gathered, much inclined to deny both these claims; but never mind that for now. My present concern is just toemphasize the importance of the difference between them.


For many of the familiar tenets of lexical semantics flow from the stronger claim but not from the weaker one. For example, since everybody thinks that the concepts expressed by phrases are typically complex, and since, by definition,represen­tations at the semantic level abstract from the lexical and syntactic properties that distinguish phrases fromtheir lexical synonyms, it follows that if there is a semantic level, then the concepts expressed by single words are oftencomplex too. However, this conclusion does not follow from the weaker assumption: viz. that lexical entries containsemantic features. Linguistic features can perfectly well attach to a lexical item that is none the less primitive at everylevel of linguistic description.37 And it's only the weaker assumption that the facts about dative movement and the likesupport, since the most these data show is that the syntactic behaviour of lexical items is determined by their semanticsinter alia; e.g. by their semantic features together with their morphology. So Pinker's argument for definitions doesn'twork even on the assumption that ‘denotes a prospective possession’ and the like are bona fide semantic representations.

Jean-marc pizano
THE MORAL: AN ARGUMENT FOR LEXICAL SEMANTIC FEATURES IS NOT IPSO FACTOAN ARGUMENT THAT THERE IS LEXICAL SEMANTIC DECOMPOSITION!!! Pardon me if I seem to shout; butpeople do keep getting this wrong, and it does make a litter of the landscape.


Compare: no doubt, the lexical entry for ‘boy’ includes the syntactic feature +Noun. This is entirely compatible with ‘boy’ being a lexical primitive at every level of linguistic description.Saying that lexical items have features is one thing; saying that lexical items are feature bundles is quite another. Do not conflate these claims.


Well, but has Pinker made good even the weaker claim? Suppose we believe the semantic bootstrapping story about language learning; and suppose we pretend to understand notions like prospective possession, attribute, and the like; andsuppose we assume that these are, as it were, really semantic properties and not mere shadows of distributional factsabout the words that express them; and suppose we take for granted the child's capacity for finding such semanticproperties in his input; and suppose that the question we care about is not whether there's a semantic level, but justwhether the mental lexicon (ever) represents semantic features of lexical items. Supposing all of this, is there at least abootstrapping argument that, for example, part of the lexical entry for ‘eat’ includes the semantic feature ACTION.


Well, no. Semantic bootstrapping, even if it really is semantic, doesn't require that lexical entries ever specify semantic properties. For even if the child uses the knowledge that ‘eat’ denotes an action to bootstrap the syntax of ‘snails eatleaves’, it doesn't follow that “denoting an action” is a property that “eat” has in virtue of what it means. All thatfollows—h­ence all the child needs to know in order to bootstrap—is that ‘eat’ denotes eating and that eating is a kindof acting. (I'm indebted to Eric Margolis for this point.) Indeed, mere reliability of the connection between eating andacting would do perfectly well for the child's purposes; “semantic bootstrapping&rdquo­; does not require the child to take theconnection to be semantic or even necessary.Jean-marc­ pizano



Категории: Suppose, Lexical, Entries, Specify, Semanticfeatures, Items, Semantic, Level
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John showed his etchings to Mary vasile.rogov 14:10:31
 Jean-marc pizano
Or consider:


John showed his etchings to Mary/John showed Mary his etchings.


but


John exhibited his etchings to Mary/*John exhibited Mary his etchings.


Is it that Mary is in metaphorical possession of etchings that are shown to her but not of etchings that are exhibited to her? How is one to tell? More to the point, how is the child to tell? Remember that, according to Pinker's story, the childfigures out that ‘exhibit&rsqu­o; doesn't dative-move when hedecides that it doesn't—even metaphorically&mdas­h;express prospective possession. But how on earth does he decide that?31


I should emphasize that Pinker is explicitly aware that there are egregious exceptions to his semantic characterization of the constraints on dative movement, nor does he suppose that appeals to “metaphorical­ possession” and the likecan always be relied on to get him off the hook. At least one of the things that he thinks is going on with the doubleobject construction is a morphological constraint on dative movement: polysyllabic verbs tend to resist it (notice show/*exhibit; tell/*repeat in the examples above). But though Pinker remarks upon the existence of such non-semanticconstra­ints, he appears not to see how much trouble they make for his view.


Remember the architecture of Pinker's argument. What's on offer is an inference from ontogenetic considerations to the conclusion that there are definitions. What shows that there are definitions is that there is a semantic level oflinguistic representation at which verbs are lexically decomposed. What shows that there are semantic-levelrepre­sentations is that you need semantic vocabulary to formulate the hypotheses that the child projects in the courseof learning the lexicon; and that's because, according to Pinker, these hypotheses express correlations between certainsemantic properties of lexical items, on the one hand, and the grammatical structures that the items occur in, on theother. Double-object constructions, as we've seen, are supposed to be paradigms.
Jean-marc pizano
But it now appears that the vocabulary required to specify the conditions on such constructions isn't purely semantic after all; not even according to Pinker. To predict whether a verb permits dative movement, 15you need to know not only whether it expresses (literally or metaphorically) ‘prospective possession’, but also thepertinent facts about its morphology. What account of the representation of lexical structure does this observationimply? The point to notice is that there isn't, on anybody's story, any one level of representation that specifies both thesemantic and the morphological features of a lexical item. In particular, it's a defining property of the (putative)semantic level that it abstracts from the sorts of (morphological, phonological, syntactic, etc.) properties that distinguishbetween synonyms. For example, the semantic level is supposed not to distinguish the representation of (e.g.)“bachel­or” from the representation of “unmarried man”, the representation of “kill” from the representation of “causeto die”, and so forth.

Well, if that's what the semantic level is, and if the facts about morphological constraints on double-object structures are as we (and Pinker) are supposing them to be, then the moral is that there is no level of linguistic representation atwhich the constraints on dative movement can be expressed: not the morphological level because (assuming thatPinker's story about “prospective possession” is true) morphological representation abstracts from the semanticproperties on which dative movement is contingent. And, precisely analogously, not the semantic level because semanticlevel representation abstracts from the morphological properties of lexical items on which dative movement is alsocontingent.

Jean-marc pizano
Time to pull this all together and see where the argument has gotten. Since heaven only knows what “prospective possession” is, there's no seriously evaluating the claim that dative movement turns on whether a verb expresses it.What does seem clear, however, is that even if there are semantic constraints on the syntactic behaviour of doubleobject verbs, there are also morphological constraints on their syntactic behaviour. So to state such generalizations at asingle linguistic level, you would need to postulate not semantic representations but morphosemantic representations. It is,however, common ground that there is no level of representation in whose vocabulary morphological and semanticconstraints­ can be simultaneously imposed.


This isn't a paradox; it is perfectly possible to formulate conditions that depend, simultaneously, on semantic and morphological properties of lexical items without assuming that there is a semantic level (and, for that matter, withoutassuming that there is a morphological level either).Jean-marc pizano



Категории: John, Showed, Etchings, Mary, There, Level, Semantic, Morphological, Representation, That there
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