Thursday, February 21, 2019

Another logical problem of language acquisition: Part 1

Some of you may recall that I invited FoLers to submit stuff for blog fodder on the site. I have received a few takers, but not as enthusiastic as Callum Hackett.  Below is the first part of an extended discussion based on his thesis topic. I like the idea of being in on the ground floor wrt this kind of stuff; new thoughts by young colleagues that leads me by the hand in new directions. I hope that Callum is the first of many who decide to educate the rest of us. Thx.


Another logical problem of language acquisition: Part 1

Following on from various interesting discussions here on FoL, I’ve been meaning to elaborate on some of the comments I’ve made in places about how we might want to reconsider our grammatical architecture if we want generative theory to be a truly successful contributor to cognitive and evolutionary science. To help frame the major issues, in this first post I’m going to examine the basic logic of the competence/performance distinction, as well as some of its complications. Then, in a second, I’ll consider in more detail the actual relationship between competence and performance, and the implications this has for what our theory of competence ought to look like, if indeed having a theory of competence is what should qualify generative grammar as a science of the mind.

To advertise—these posts being a truncation of some of my doctoral work—so long as what we mean by ‘competence’ is the system of linguistic knowledge represented in the mind of a speaker, independent of any use that’s made of it, then my conclusion will be that any model of competence we can identify as a T-model (so, basically everything since Aspects) logically cannot work because the T-model misunderstands the relationship between knowledge and use.

Having said this, I also believe that we can devise a different architecture that preserves the best of the rest of generative theory, that gives us better stories to tell about cognition and evolution (and so better chances of being funded), and—my personal favourite—that allows us to make some strategic concessions to behaviourists that in the end seal the deal for nativism.

To make a start on all this, first we should recognize that a theory of competence is wholly inaccessible to us unless we have some idea of how competence relates to performance, simply because all of our analytical methods deal exclusively with performance data, due to the mental representations that are constitutive of competence being by definition inscrutable.

Of course, this quite trivial observation doesn’t mean that linguists need to know any of the details about howcompetence gets performed; it just means that, because all the data available to us always isperformed, we need at least an abstract conception of what performance amounts to, purely so we can factor it out.

So far, so uncontroversial. Didn’t generative theory already have this sorted by 1965? Chomsky does after all give a description of what we need to factor out at the very beginning of Aspects, where he introduces the competence/performance distinction with the remark that we’re interested in:

 “an ideal speaker-listener, in a completely homogeneous speech-community, who knows its language perfectly and is unaffected by such grammatically irrelevant conditions as memory limitations, distractions, shifts of attention and interest, and errors (random or characteristic) in applying his knowledge of the language in actual performance.”

Of course, lots of (silly) people have objected to this as being much too idealistic but my complaint would be that it isn’t nearly idealistic enough, in that I don’t believe it properly circumscribes competence to the genuine exclusion of performance, as it has too narrow a view of what performance is.

The reasons for this are straightforward enough, though a little pedantic, so we need to think carefully about what idealization actually achieves for linguistic theory. Note foremost that, given the inscrutability of mental representations, there can never, even in principle, be circumstances that are somehow soideal that we could make direct observations of a speaker’s competence. In ideal conditions, we might eliminate all the distortions that can be introduced in performance, but we would still always be dealing with performed data.

Indeed, if you read the above quotation from Aspectsagain, you’ll see that Chomsky plainly isn’t talking about getting at mental representations directly, and he doesn’t mean to be. He’s still talking about performance, only perfectperformance—the ideal speaker-listener demonstrates unhindered applicationof knowledge, not knowledge itself. Thus, note how the distortions that Chomsky lists are not only grammatically irrelevant, they are also irrelevant to the successful performance of whatever a grammar contains.

Crucially, what this limitation to performance data means is that the role of idealization is not (and cannot be) to eliminate everything that impinges upon competence, so that we can get a good look at it. It’s rather to eliminate everything that impinges upon performance of competence—to make performance perfect—so that performance is left as the only thing to factor out of the data, just as soon as we have an independent idea of what it is.

This subtlety is vital for assessing a claim Chomsky subsequently makes about the basic methodology of linguistics: that we can construct a theory of competence from observations of performance guided by the principle that “under the idealization set forth [...] performance is a direct reflection of competence.” Straightforward though this seems, it does not follow as a simple point of definition.

We’ve just observed that idealization on its own does nothing to define or eliminate the influence of performance on our data—it just makes the data ready for when we have an independent idea of what performance is—so we can only take perfectperformanceto directlyreflectcompetence if we help ourselves to an ancillary assumption that performance itself just isthe reflection of competence (i.e. its externalization). This of course goes hand-in-hand with a definition of competence as the internal specification of what can be performed.

To use the somewhat more transparent terminology of Chomsky’s later I-language/E-language distinction, what this means altogether is that the theory of competence we have built using the Aspectsmethodology depends not only upon the basic distinction between competence and performance as a distinction between whatever’s internal and whatever’s external, but also upon a strictly additionalassumption that the internal and the external are related to one another in the way of an intension and extension.

So, why be pedantic about this? It may seem that defining the relationship between competence and performance as an intension and extension is so obviously valid—perhaps even a kind of logical truth—that observing it to be implicit from the get go in Aspectsis hardly worth comment. However, even if this definition is sound, it isn’t anything at all like a necessary truth, meaning that some justification must be found for it if we are to have confidence in a theory that takes it for granted.

To understand why, consider the fact that treating competence and performance as intension and extension casts performance as an entirely interpretativeprocess, in the sense that every performance of a structured sound-meaning pair is no more than the mechanical saying and understanding of a sound-meaning pair that is first specified by the competence system (and notice, here, how having an intensional specification of sound-meaning pairs is, by definition, what commits us to a T-model of competence).

Another conceptual possibility, however, is that the competence system might furnish certain resources of sound, structure and meaning for a performance process that is creative, in the sense that sounds and meanings might be paired afresh in each act of performance, totally unrestricted by any grammatical specification of how they should go together. This might seem like such a crazy alternative that it is no alternative at all, but in fact I’ve just described in quite uncontroversial terms the task of language acquisition.

We already knowthat performance has to be to some extent creative rather than interpretative because the competence system at birth is devoid of any language-specific content, so it initially has no capacity to specify any sound-meaning pairs for performance. Moreover, as the associations between sound and meaning that we learn are arbitrary, and are thus not predictable from purely linguistic input, the only way children have of formulating such associations is by observing in context how sounds are used meaningfully in performance. Thus, our question is really: to what extent is performance notcreative in this way, or to what extent does its creative element give way to interpretation?

Here, our standard story first concedes (at least implicitly) that, given the arbitrariness of the sound-meaning relation, performance must be involved at least in the creation of atomic sound-meaning pairs, or whatever else it is that constitutes the lexicon (it makes no difference, as you’ll see later). But, because the proper structural descriptions for sentences of these atoms cannot be inferred from their performance, given the poverty of the stimulus, there must also be an innate syntactic competence that generates these structures and thereby accounts for speakers’ unbounded productivity.

These propositions are, I believe, totally beyond reproach, and yet, taken together, they do notlicense the conclusion that linguists have drawn from them: that language-specific atoms created in performance therefore serve as input to the innate syntax, such that structured sound-meaning pairs are only ever interpreted in performance, rather than being created in it.

To expose why this inference is unwarranted, one thing we have to bear in mind in light of our consideration of the proper role of idealization is that there is simply nothing about the data that we study that can tell us directly whether performance is interpretative or not. Because we are always looking at performed data, the limit of what we can know for certain about any particular sound-meaning pair that we bring before our attention is just that it is at least one possible outcome of the performance process in the instance that we observe. To know furthermore whether some pairing originates in competence or performance requires us to know the cognitive relationship that holds between them, and this is not manifest in performance itself. In order to establish that relation, like any good Chomskyan we must draw on the logic of acquisition.

Now, before we can give a satisfying treatment of the poverty of the stimulus, we need to be a little more precise about what it means for performance to be involved in pairings of purely atomic sounds and meanings—whatever they are—as there are two possibilities here, one of which we must reject.

On the one hand, we might imagine that the meaning of an expression is somehow a property of the expression’s uses in communication, such that sound-meaning pairs are constructed in performance because meanings themselves are derived entirely from behaviour. This is the Skinnerian or Quinean view and, for all of Chomsky’s original reasons, we can dismiss it out of hand.

The alternative we might imagine is that the meaning of an expression is some sort of mental representation, independent of any behaviour (i.e. a concept, or something like one), and, following a Fodorian line of argument, if these mental representations cannot be derived from experience of language (and they can’t), then they must be pre-linguistic. Thus, the role for performance here is not to create meanings(in the sense of concepts), but rather to create the relationsbetween an innate repertoire of possible meanings and whichever pieces of language we observe to represent them (schematically, this is something like taking the innate concept BIRD and assigning it either ‘bird’ or ‘Vogel’, though there is a lot wrong with this description of the lexicon, as I’ll get to later).

A crucial corollary of this construction of atomic sound-meaning relations in performance is that at least our initial knowledge of such relations must not (indeed, cannot) consist of having mentally represented lexical entries for them, as the fact that we have to construct our lexicons by observinglanguage use, given the arbitrariness of their contents, means they cannot also in the first instance determinelanguage use, as that would be circular (another way of stating this is to ask: if you know that ‘bird’ means BIRD only because your lexicon tells you so, how did that information ever get into your lexicon when it was empty?).

But by now, it should be clear that the competence/performance distinction is not so straightforward as a distinction between knowledge and use because the means by which we come to know at least some sound-meaning relations is a matter of performance. This being the case, an important question we must ask is: why can’t we go on constructing such relations in performance indefinitely, becoming better and better at it as we gain more and more experience? What need do we have of a competence system to at some point specify such relations intensionally in the form of mentally represented sound-meaning pairs?

To pose this question more starkly, we have traditionally assumed that a person understands the meanings of words by having a mentally represented dictionary, somehowacquired from the environment, yet given the fact that children are not born with lexicons and nonetheless come to have lexical knowledge, isn’t the lesson to learn from this that a lexicon is not necessary for such knowledge, and so the specification of word meanings is just not what lexicons are for? Note that these questions apply if you suppose a mental lexicon to list pairings of sounds and anysorts of mental representation, be they atomic concepts, feature sets, chunks of syntactic structure, or whatever else your derivational framework prefers.

As it happens, the lexicon in linguistic theory was never really devised to account for lexical knowledge in any straightforward way. Ever since Aspects, the lexicon has been little more than a repository for just whatever speakers seem to need as input to syntactic derivation in order to produce and understand structured expressions, without there being any independent constraints on what a lexicon can or cannot contain. So, to see where this acquisition conundrum really leads, we finally have to turn to the poverty of the stimulus.

Here, though, I will leave you with a cliff-hanger, for two reasons. First, in the next section of the argument, we’ll have to deal with some subsidiary misconceptions about descriptive and explanatory adequacy, as well as what (an) E-language is (if anything at all), yet I’ve already gone on quite enough for one post.

Second, though the poverty of the stimulus introduces some new dimensions to the argument, the logical structure of what follows will in essence be the same as what you’ve just read, so that the conclusion we’ll come to is that the fact that children are not born with language-specific grammars and yet nonetheless come to understand specific languages entails that it cannot be the function of an acquired grammar to specify the meanings of the expressions of a language, yet this is precisely what T-model grammars are designed to do. It’s no use getting on with the extra details needed for that conclusion, however, if you’re not at least on board with what I’ve said so far. I think it should all be rather uncontroversial for the FoL audience, but I’d like to invite comments nonetheless, in case it might be helpful to express the second half a little differently.


  1. "isn’t the lesson to learn from this that a lexicon is not necessary for such knowledge, and so the specification of word meanings is just not what lexicons are for?"

    I feel there is a bit of a non sequitur here, but maybe I am misreading.

    A car is not necessary for me to get to work since I can walk, but walking is much slower. This doesn't imply that the function of my car is not to drive me about.
    Similarly one can indeed learn the structure of a sentence by looking at a million utterances from the language, but obviously if you know the language, then the whole process can be done a lot quicker.

    1. I should perhaps have said more cautiously at this point, "isn't the lesson to learn from [lexicons not being] necessary for such knowledge [that] the specification of word meanings might not be what lexicons are for?"

      Certainly, the fact that there may be performance-based alternatives for understanding words does not preclude the possibility of lexicons also specifying word meanings intensionally. As it turns out, there are other reasons why lexicons cannot have this function, which appear in the second part of the argument (hence why I got slightly ahead of myself here) and which will therefore mean that your analogy does not hold.

      I think the rest of your comment introduces some hidden assumptions about alternative processes for meaning construction that I simply don't share. On the one hand, I have pointed out that I will argue for an alternative to the T-model for how we understand expressions that still acknowledges the poverty of the stimulus, so I don't agree at all that one can learn the structure of a sentence from looking at a million example sentences.

      And, as for the handiness of having a competence system to do the work of specifying the meanings of expressions, it would of course be a lot quicker for everyone if we were all born speaking English, but that doesn't mean that such a thing is possible. Naturally, I am not arguing that people don't "know a language", so in saying that "knowing a language" is a more plausible treatment of speakers' understanding, I think you're imagining some sort of psychological model that I haven't and won't argue for.

    2. I feel like there are some fine distinctions that I am not paying attention to here: maybe learn/acquire is one of them; does my remark make more sense with acquire in place of learn?

      I didn't follow the final paragraph, sorry.

    3. I'm not entirely sure but maybe using the word 'acquire' suggests that you're privileging a particular variety of knowledge that I tried to argue we may simply not need in order to have an explanatory theory.

      If you take it very coarsely, the term 'acquisition' suggests that the child must look in their environment for clues about the nature of the language they're learning and then represent certain conclusions inside their mind in order to have facility with the language. My argument is that those conclusions, which we typically identify as being constitutive of linguistic knowledge, are necessarily predicated upon knowing the language first in performance, so that we at least have to ask if we actually need to posit the mental representations that we're positing.

      So, for example, stating more briefly what I said in the post, if you're going to end up with a lexical entry that says {'bird'=BIRD}, you're only going to be able to formulate this on the basis of knowing by means other than the lexical entry (because your lexicon is initially empty) that 'bird' means BIRD in some observed speech act. Then, as the lexical entry was not needed to know the meaning of 'bird' in this speech act, why suppose that the entry is needed specifically to know the meaning of 'bird' in subsequent speech acts? One might instead approach speech acts 2, 3, 4 and so on until the end of time using exactly the mechanisms of understanding that were used in speech act 1.

      To restate my reply to your first comment, the shape of this argument so far is indeed not sufficient to conclude that lexicons don't specify word meanings, it's only sufficient to conclude that lexicons are not a priori necessary for this, so that we must have independent justifications for supposing that this is what they're for. It seemed earlier that the justification you were suggesting is that having such knowledge mentally represented would make the whole language task easier, but there are various impossible things that would make the whole language task easier, so we have to be wary of arguing from plausibility.