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10 The Poverty of the Stimulus Argument

10 The Poverty of the Stimulus Argument - 10 The Poverty of...

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Unformatted text preview: 10 The Poverty of the Stimulus Argument 1 General data Except for congenital defect or trauma we all end up using (at least) a particular language, although we might have ended up using any other language. Our brains, unlike those of other species, are such as to enable us to acquire language as such, although they are not primed to acquire any particular language. 2 The acquisition of language is species specific. Whatever distinguishes us from other animals must be specific enough (not necessarily specific to language) for us to arrive at English or Italian or Navajo, etc. It must also be general enough to target any language with equal ease. 3 Innateness Humans possess innate equipment, whether specific to language or not, that enables them to acquire any language. So far, then, we don’t have any argument for the claim that the human child begins with something specifically linguistic. Some other, species specific, capacity could do the job. 4 The languages we speak are very different. There might be universal features shared by all languages, but they are not apparent in the seemingly infinite variety of data to which children are exposed. What else does the child have other than the data? It seems that we are infinitely far from the explanatory ideal situation, i.e., the more languages there are, the more inclusive must be our initial capacity to represent language. 5 Triviality. That the child begins with innate equipment is true enough, but we seem to require something decidedly less trivial. What the child’s innate equipment is required to actively constrains its ‘choices’ as to what is part of the language to be attained. But no child is wired to target any particular language: the child can make the right ‘choices’ about any language with equal ease. 6 Initial stage The children must begin with ‘knowledge’ specific to language, i.e., the data to which the child is exposed is ‘understood’ in terms of prior linguistic concepts as opposed to general concepts of pattern or frequency, say. E.g.: children distinguish phonemes from rumours. 7 Poverty of the stimulus A child may acquire a language even though the data itself is too poor to determine the language: the child needs no evidence for much of the knowledge she brings to the learning situation. Children acquire language from pidgin. Roughly, children always make the right ‘hypotheses’ as a function of their genetic endowment. 8 Since the child can fixate on any language in the face of a poverty of stimulus about each language and since all languages are equally acquirable, children all begin with the same universal linguistic knowledge. This is the essence of the poverty of stimulus argument. 9 The poverty of the stimulus argument does not tell us: 1. What information is innate. 2. How the innate information is represented in the mind/brain. 3. Whether the information is available to a general learning mechanism or specific to a dedicated one (i.e. general intelligence or language module). These issues are to be decided by the normal scientific route of the testing and comparison of 10 hypotheses. Positive data tells the child that some construction is acceptable. Negative data tells the child that some construction is unacceptable. There is much discussion of this difference, for it has been claimed that negative evidence is typically unavailable and not used by the child even where it is available. 11 Children are innately constrained to initially ‘chose’ the smallest possible language compatible with their positive data. 12 Much of the debate around the Poverty of the Stimulus Argument focuses on negative evidence. If there is lot of negative evidence there are more chances that the child’s learning is based on trial and error. Even if there is plenty of negative data (which is questionable), the Poverty of the Stimulus Argument is not refuted. 13 The relative neutrality of the Poverty of the Stimulus Argument suggests something surprising: the fact that the child can acquire any language without seemingly enough data to do so, indicates, counter­intuitively, that languages are not so different. The innate ‘hypotheses’ the children employ must be universal, rather than language particular. Imagine that each language is radically distinct, an effect of a myriad of contingent historical and social factors. This seems to be what the pursuit of descriptive adequacy tells us. Now, if this were the case, then the child’s data would still be poor. 14 But how would innate knowledge help here? Since, ex hypothesi, each language is as distinct as can be, there is no generality which might be encoded in the child’s brain. That is, the child would effectively have to have separate innate specific knowledge about each of the indefinite number of languages it might acquire. 15 This is just to fall foul of the Poverty of the Stimulus Argument: how does the child know that the language it is exposed to is a sample of grammar X as opposed to any of the other grammars? The best explanation. The specific conjecture is that we all begin with universal grammar (UG), the one language, as it were. UG is innate and is informed in the sense that it encodes certain options or parameters which are set by exposure to certain data. 16 To acquire a language is simply for the values of UG’s parameters to be set in one of a finite number of permutations (given the acquisition of a lexicon.) Chomsky understands UG to be the initial state of the language faculty (an abstractly specified system of the brain.) 17 To acquire a language is to acquire a particular systematic mapping between sound and meaning. How do we fixate on such a pairing? Think of the language faculty as a genetically determined initial state prior to experience. Experience triggers the setting of values along certain parameters that determine the output conditions. Experience also provides the assignment of features in the lexicon, although not the features themselves. 18 From the Initial State to I­Language Different experiences set the parameters to different values (cf. switch analogy). This finite variation ramifies to produce languages of seemingly infinite variety. Once all parameters are set, the faculty attains a steady state we call an I­language. I­language is a generative system which explains an individual’s competence with her idiolect. 19 UG is not implied by the above general reasoning about acquisition in the face of the poverty of the stimulus. It is, rather, a somewhat speculative hypothesis based upon a myriad of considerations, both empirical and theoretical. The form of the Poverty of the Stimulus Argument is quite general and based on what Chomsky has called Plato’s problem. The problem occurs wherever a competence is exhibited which we have apparently too little data to acquire. 20 The Poverty of the Stimulus Argument is not employed in direct defence of UG (under some proprietary specification). On the contrary, UG is supported to the extent that it is the best theory of the knowledge which the Poverty of the Stimulus Argument tells us exists. UG is a scientific hypothesis. 21 What must a child know such that it can correctly go from this kind of data to the correct interrogative form in general? (1) a. b. That man is happy Is that man happy? (2) a. b. That man can sing Can that man sing? Chomsky asked this question as a challenge to Putnam, who had contended that the child need only have at her disposal general principles (not domain specific linguistic ones). 22 The empiricist challenge. SI: Go along a declarative until you come to the first ‘is’ (or, ‘can’, etc.) and move it to the front of the sentence. SI is structure independent in that it appeals merely to the morphology and linear order of the declarative. 23 The important point here is that an empiricist may happily appeal to SI as the rule upon which the child fixates, for it involves no linguistic concepts and so is one at which a child may arrive without the benefit of specific linguistic knowledge. 24 Now the child would proceed correctly with SI so long as she continued to meet such monoclausal constructions as (1)+(2). (1) a. That man is happy b. Is that man happy? (2) a. That man can sing b. Can that man sing? 25 But the rule does not generalise. (3) a. That man who is blonde is happy Application of SI would produce the nonsensical (3) b. * Is that man who blonde is happy? (3) c. [NP That man [CP who is blonde]] is happy 26 It is unreasonable to assume that, for a child to fixate on a rule R, it needs exposure to all the distinct types of construction to which R applies, i.e., all those construction types which would refute potential prior hypotheses of ‘false’ rules. 27 This is the gift of Plato’s point in the Meno. There is nothing in particular being withheld from the slave boy, but he arrives at an understanding of Pythagoras’ theorem on the basis of data that would not be sufficient were he relying on just that data. Hence, we conclude (non­demonstratively) that he has prior knowledge about the domain. 28 The Rarity of Negative Evidence. The kind of negative evidence putatively exploited by children is very weak, only appears in mothers with young children. Crucially, the relatively rich mother­child interaction observed is typical of the Western middle­class, but it is far from universal. The fact that children acquire normal competence without negative evidence shows that the children who do have it do not need it. 29 There is no need of negative evidence. This is corroborated by the fact that there is no correlation between negative evidence supplied by an attentive mother and the rapid acquisition of mature competence. So, (i) children don’t require negative evidence and (ii) even when they have it, they don’t use it. This observation is also supported by a wealth of anecdotal data on the sheer recalcitrance of children’s errors. 30 Children’s errors. All the data we have indicate that children’s errors (morphological, semantic, syntactic) are quite rare, certainly rarer than they would be were the child seeking to falsify or test initial hypotheses. Moreover, the errors made are neither random nor occur equally for all constructions. For example, usually, children (as well as adults, of course) make regularisation errors with the past tense affix ­ed. 31 It is very difficult to talk sensibly about children’s errors in the absence of an acquisition model, for, whether rare or legion, the pattern of errors remains unexplained. A theory of language acquisition must explain what we get ‘right’ just as much as what we get ‘wrong’. As the specific complexity of our competence leads to a theory of UG, so the specific systematicity of our errors leads to the thought that we are not, in general, falsifying hypotheses. 32 The mere existence of errors doesn’t militate for empiricism, or, rather, some as yet unspecified learning regime based on general principles. The crucial issue is how errors are explained, and there are many ways of classifying and explaining errors that are perfectly consistent with the nativist stance. E.g.: a child’s errors should be consistent with some parametric value of UG, i.e., the errors are only relative to the target language, not UG. 33 Motherese and Empiricism. It provides an initial framework from which the child may proceed to abstract statistically syntactic categories. The unpopularity of the Motherese hypothesis has two principal sources: 1. Motherese is not a universal phenomenon: some cultures and communities either lack Motherese all together ­ parents speak to their children with no peculiar prosody ­ or parents actually tend not to talk to their children much at all; even so, the children acquire their respective languages perfectly well. 34 2. Differential exposure to Motherese is not correlated with differential rates of language acquisition. Whatever Motherese is for, it does not appear to have a decisive role in language acquisition. Prosody, especially that of Motherese, might reflect word boundaries, but it is far from clear if phrasal boundaries are reflected (see e.g. Pinker). 35 In effect, then, what the child must be able to do, if she is to progress from words to phrases, is recognise that Daddy, as it might be, is the head of a subject NP, but this is something that looks not to be either phonetically or morphologically marked. The child may analyse (parse) its input stream, but to do so the child requires some structural constraints (phrase bracketings/parsing) specific to language and there is no data to suggest that this is encoded in the input. 36 Semantic Bootstrapping: Abstraction vs. Innateness Semantic bootstrapping refers to the hypothesis that children utilize conceptual knowledge to create grammatical categories when they’re acquiring their mother tongue. E.g.: categories like “type of object/person” maps directly onto the linguistic category “noun” while category like “action” onto “verb”, etc. This helps children start on their way to acquiring part of speech. 37 The hypothesis received support from the experiments that showed that three­to five­year­olds do, in fact, generally use nouns for things and verbs for actions more often than adults do. Theta­roles are understood to be innate. If not the child would have to hypothesise along, ‘All objects are named by count nouns’. Where does object come from? (See Fodor 1998. Concepts: Where Cognitive Science Went Wrong, OUP. ch. 3). 38 Since the bootstrapping mechanism need not be understood as a property of UG it doesn’t challenge the nativist hypothesis. Bootstrapping could be construed as a separate mechanism that maps semantic properties onto the syntax proper. Bootstrapping offers no reason to favour a statistical model of learning rather than a rule­ constraint based one. 39 Moral: Bootstrapping doesn’t seem to call into doubt the rationalist (anti­empiricist) claim that syntactic categories are not learned by abstraction. The poverty of stimulus argument doesn’t necessarily demonstrate the falsity of empiricism. It is not, though, a question of demonstration. Like in any other science these are empirical and theoretical considerations. 40 It is not good enough to talk vaguely of a mechanism that has a “preference for rules stated in terms of unobservables over those stated in terms of observables” (Cowie 1999. What’s Within: Nativism Reconsidered, OUP: 189). It is not as if any old unobservables will do. The constraint is quite specific. We want to know specifically how the child can have a “preference” for ‘rules’ involving, say, subject NP and matrix auxiliary verb. 41 The question is straightforwardly empirical. There is evidence that the child is able statistically to recover some information from phonetic streams, but there is no evidence that the child can statistically induce syntactic categories. 42 Rules Are epiphenomena: they are neither formulated, nor represented, nor tested by the learner; nor are they theoretical postulates. We can talk about rules, but only for taxonomic convenience. It is thus simply false that Chomsky or others think of a given grammatical rule as crucial; it is a mere taxonomic effect, whose interpretation and explanation can changed radically with the development of linguistics. 43 Linguistics per se is not in the business of refuting empiricism. Linguistics attempts to construct theories that, as in any other science, have universal scope, economy, and predictive success. This is in itself independent of claims of nativism. 44 The psychology proper begins when one construes the theories as answers to the question of what speaker­hearers know; consequently, the questions are raised as to how we acquire the information and put it to use. Such a construal places constraints on the theories (explanatory adequacy), but these are quite innocent, for there is no a priori bar on empiricist answers to the problems. 45 ...
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