Complexity redux redux

Alex has had some interesting comments on an earlier post. I thought that I would move the discussion from the comments to the main text.  Thanks Alex.

I think that I have found the nub of my disagreement with Alex. It can be localized to the first sentence of paragraph 2 of his last comment. 

We don't know what the grammars are so *of course* we have to abstract away from the properties of grammars.

No, No, No!!! We know a great deal about grammars. What I want from computational theories/considerations is an explanation of why what I know to be the case has the properties it does.  For Alex, grammatical properties have to earn their computational keep by solving antecedent problems of various sorts.  For me the shoe is on the other foot: I am interested in computational theories to the degree that they earn their linguistic keep by enlightening me as to why grammars have the properties I know that they have. For example: Why are there locality restrictions like minimality?  Why are the phase heads v, C and D?  Why do antecedents of moved elements c-command their launch sites?  Note that these why questions all presuppose that there are locality restrictions like minimality, and "subjacency." That there is displacement and that c-command describes a required grammatical restriction etc.  I go further: I think that we KNOW that the structure of FL/UG are roughly described by the generalizations outlined in LGB. This I know. What I don't know is why, and here is where I look to computational considerations to possibly enlighten me. If such enlightenment is forthcoming, great. If not, I look somewhere else. This opportunism has led me to the tentative conclusion that much of what goes on in CS is beside the point.  Oddly some of what goes on in software design is not.  So, maybe the right way of thinking of computation in linguistics should look to what they are doing in software engineering rather than in CS departments.  I am not dogmatic about this for after all I am being deliberately opportunistic (a variant on Tom Lehrer’s Lobyachevsky strategy).  So were there to be something interesting coming from core CS considerations, I would be happy to embrace the results. Here I am open minded. Where I am not open-minded concerns whether we know what FL/UG (roughly) looks like. We do. There’s more to discover, but we know a lot and should NOT set this knowledge aside in doing our computational investigations.

My impression is that this is not how Alex see things. What he wants is a computational theory able to handle linguistic data without assuming that these properties of grammar hold. He is skeptical about them and so wants to finesse them. I am convinced they are true and so they form boundary conditions on further discussion.  We have made different judgments and they determine what we are looking for. Much of our disagreement stems from this, I believe.

There is one further source: we have very different conceptions concerning the utility of formalization.  I am not sold on the view that without formalization science grinds to a halt. Indeed, I might go further, it often impedes. I was recently reminded of the fact that physics used the calculus quite effectively for about 200 years before it was put on solid foundations (Cauchy-Wierstrass). Till then it was riddled with all sorts of foundational problems that philosophers and mathematicians were eager to parade and probe.  Doing so was, I have been told, very central to work on physics in England post Newton.  The problems were ignored on the continent. Consequently, physics thrived on the continent and died in England for about 100 years.  It seems that despite the foundational flaws lots of good work could be done and was done. 

The tools we use in syntax are clear enough in my view and formalization has (putting a few exceptions aside) yet to reveal anything very deep, at least in syntax.  I have nothing against people working on doing this, but I don't really see this as a pressing need. Our problems in linguistics don't arise, I believe, because we misunderstand our tools.  Nor, have I so far seen many deep results arise from the various formalizations that have been wrought. Formalizations can be useful, but are by no means required. Indeed, my impression from Stabler’s work is that should one want to formalize GB or Minimalism or GPSG or whatever it seems doable.  The question then is not if it can be done, but why, and here I am less sanguine than Alex seems to be that it is worth the effort.

Very last point: Alex notes that the ease of parsing long sentences needs explanation. Yup. In fact, Berwick and Weinberg in other work provide one. Certain left corner parsers seem to do the trick. However, as BW show, these require bounded left contexts. Interestingly, as they show, grammars that embed something like phases/subjacency/barriers deliver a grammar format of the right type, one that snugly fits into an efficient left corner parser. Now, I don't know if left corner parsers are the "right" parsing theory. BW’s was deterministic for example and whether grammars are deterministic is contentious, I am told. But I do like the style of argument: it provides a nice computational reason for a certain kind of grammatical code. One might be tempted to say that a grammar would be well designed (i.e. the code would be “efficient,” “optimal”) to efficiently parse language, if it had  subjacency/phases/barrier like restrictions as a design characteristic. I like this kind of computational explanation.  It aims to explain a known design feature of FL/UG in computational terms. We need more results like this. Get to work Alex!

Minimalism and the Language Specificity of UG

For this post let’s assume that the Minimalist project has entirely succeeded. What implications does this have for the structure of FL/UG? In particular: if MP is right does this reduce the linguistic particularity of UG? Does it mean that FL is just general intelligence plus the super special Merge sauce (with even Merge not necessarily parochial to language)?  I believe the answer is no. Let me explain.

I understand the Minimalist project as follows: It starts from the observation that humans are specially built for language. When more and more details are considered, this suggests a dedicated, pretty articulated, innate faculty of language with its own peculiar principles and organization. However, this is a problem for it seems that linguistic facility is a recent evolutionary addition to the cognitive repertoires so there is not enough time for the kind of complexity that theories of UG (e.g. LGB) attribute to FL to arise.  This is a kind of “poverty of stimulus” reasoning applied to the emergence of UG in a background where evolutionary change is gradual and complexity only emerges slowly. At any rate, Minimalism embraces “Darwin’s Problem” and considers it together with Plato’s Problem and so concludes that there is less linguistically specific to FL/UG than we earlier believed.  Does this support the conclusion that FL/UG is not a linguistically dedicated device with scads of innate structure just ready to pounce on PLD to produce grammars of specific languages? No. Why not?

The reason is that the Minimalist answer does not preclude a richly structured linguistically dedicated UG in FL and the evidence is overwhelming, that it is richly structured and very language specific. To show this, let me give another version of the Minimalist project using terminology I stole from David Poeppel.

Linguistic cognition is different. Say that cognitive theories explain some domain of cognitive facility by specifying the kinds of circuits minds/brains use to execute that kind of cognition and showing how these circuits interact to produce that cognitive capacity (think circuit diagram): so, e.g. the visual system deploys specific circuits organized in a certain way to segregate scenes and identify objects. Similarly with auditory systems, causal identification systems, numerosity systems, etc.  Now, the fact that humans seem uniquely gifted when it comes to language suggests that they are endowed with circuitry specifically dedicated to linguistic tasks. This would, for example, explain why humans do language and nothing else does. The most famous Minimalist suggestion on offer is that the special circuit is Merge. Add that circuit to those that are already there and out pops the capacity to develop linguistic facility (note: on this view Merge need not be linguistically specific, just unique to humans, see here for discussion). The project on this view is to show how the circuits that cognition in general makes available plus the Merge circuit plus whatever background “laws” of biology, physics and computation we can avail ourselves of lead to the kinds of linguistic facility we see in humans. What facility is that? The one described to a decent first approximation in LGB, for example (though you can sub the operations and principles of GPSG, LFG, HPSG, RG if they are more congenial to you, without affecting the main point). So the Minimalist project amounts to finding how a few (in the best case, just one) special circuits can combine together with those available in general cognition to derive the operations and generalizations of LGB, which we can take to be an accurate description of FL/UG (at least for present discussion). Assume we can do this, show how the LGB framework can be coded in Merge plus a bunch of other all purpose cognitive circtuis. Doesn’t it imply that there is at most a very weak sense in which FL/UG has dedicated linguistically specific structure? Nope.

To see this, consider Chomsky’s analogy between mental and bodily organs.  There are stomachs and there are kidneys. Stomachs don’t do what kidneys do and kidneys don’t do what stomachs do. GI specialists are not nephrologists and vice versa (in fact medical friends tell me that they even have very different personalities!). However, this is not because there are special stomach cells that do stomaching and special kidney cells that do kidneying. Rather the same kinds of cells, with the same kind of biological, chemical and physical properties organized in one way give stomachs and in another kidneys. So stomachs are very different from kidneys and we assume that the “genes” code specifically for stomach organizations and specifically for kidney organizations and this drives the development of these specialized organs dedicated to digestion and waste removal respectively.

I hope the analogy to FL is obvious (if not, read on).  FL differs from other areas of cognition the way that stomachs differ from kidneys. The minimalist conceit is that this is not by and large due to possessing different circuitry. The guess is that there is at most one (or two) specialized circuit (e.g. Merge) with everything else the same. On this conception, FL can be quite distinct in its properties from those of the other mental just like there is a big difference between kidneys and stomachs. In sum, the genes build stomachs with their special features, kidneys with theirs and FLs with theirs.

So, is there a rich innate structure to FL? Yes, the evidence is overwhelming.  Is this structure peculiar to linguistic cognition? Yes, the evidence is overwhelming. Does this mean that Minimalism is wrongheaded? No, new circuits added to old can produce qualitatively new things. Indeed old circuits combined in new ways can yield qualitatively different things.  Minimalism is not warmed over Piaget. There is a faculty of language with rich innate linguistically dedicated structure and even a complete realization of Minimalist ambitions does not in and of itself gainsay this.  What there may not be are many many linguistically specialized components. The Minimalist bet, indeed, is that there are very few, maybe just one. And, it is entirely consistent with a triumphant Minimalism that the structure of FL is comprised of innate linguistically dedicated structure. In other words, Minimalism does not imply that linguistic cognition it’s just (or largely) general intelligence applied to language and it's entirely consistent with rich linguistically dedicated innate conceptions of UG.