21. How successful, in your view, is Chomsky’s
attempt to interpret the theory of grammar as an investigation of a human
biological capacity?
The research programme that
Noam Chomsky began in linguistics, starting with the publication of his
monograph, Syntactic Structures, in
1957, and properly expounded in his 1965 work Aspects of the Theory of Syntax, is not very well understood by the
majority of its popular and even academic critics. Chomsky’s frequent failure
to hedge his claims about the postulated “language organ” (and his penchant for
overly strong pronouncements) has contributed to this failure of understanding,
since few critics bother to understand how he explicates these terms in his
methodological framework or where they sit in his metaphysics of mind. Of
course, at the same time, he has himself ignored some issues in biology that ought
to have compelled him to slightly change his tune on “innateness”. Nevertheless,
in this essay, I claim that, if one does properly understand the methodological
and philosophical foundations of the generative-grammar-based research
programme into the “Universal Grammar”, two things are evident: 1.) that the
programme has been about as successful as its progenitors hoped, if not more
(with no degeneration, in Lakatos’
terms), and 2.) that the programme has been successful in the independent sense
that it has led to genuine insights about the human mind.
One of the major things that
critics of ‘UG’ are wont to gloss over is that, strictly speaking, there is no
one “theory of Universal Grammar”. Instead, there is only a general ‘UG’-research programme based on the
construction of generative grammars held to capture the innate implicit knowledge
which is falsifiably (and each model
ought to be falsifiable individually) held to be required for the achievement
of human linguistic competence (the
generative grammar in the human mind).[1]
As this implies, the empirical support is (and could not be) uniform for ‘UG’,
understood as the UG-research programme;
instead, because the approaches to generative grammar that have been developed
as part of this overall research programme since Chomsky’s exposition of a
Transformational Grammar approach in Aspects
to the Theory of Syntax (1965) vary in the level of ‘innate’ ‘knowledge’
they postulate, different evidence is required to falsify each of these
approaches, and to confirm any one of them relative to the others. In
particular, a stronger version of the famous “Poverty of the Stimulus” argument
– one which draws on more evidence of linguistic universals, infant reliance on
rules and hard-to-empirically-explain examples of “structure-dependence” – are needed to support the early Transformational
Grammar models than for the models proposed since the Principle and Parameters
paradigm shift, with the Minimalist Program starting from the postulation that the
generative system is simpler than a grammar
(per se), and therefore probably being more prone to rejection by evidence
of too many universals and such (this
would, of course, be rejection relative to another model of generative grammar).
It is very important to
acknowledge, of course, that there are some very sensible philosophical critics
of the UG research-programme, like the Australian-born philosopher of biology,
Fiona Cowie [1999], who see Chomsky’s very use of the word “innate” as problematic from a scientific viewpoint. One of
Cowie’s motivations for her, in the end, quite moderate critique of “nativist”
theories in What’s Within? is the
fact that the word has no clear scientific interpretation. She shares this view
with her fellow philosopher of biology, Paul Griffiths (of the University of
Sydney), who in his 2002 paper “What is innateness?” points out that the word
“innate” is no longer used in any field of biology except cognitive science,
and argues that it ought to be discarded in cognitive science, too, since
innateness is a “folk-biological” concept which yokes together three biologically
separate notions: species-typicality, developmental fixity and intended design
[Griffiths, 2002: 2].
Whilst I myself agree with
this critique, I do not think it is in the least bit destructive of Chomsky’s
research-programme, because I also think (and Griffiths does not explicitly
deny) that the generativist talk of an “innate language faculty” can simply be substituted
for one of two other phrases: a “developmentally canalised, species-typical
language faculty” (in the case of Chomsky and his fellow non-adaptationists (spandrelists)
about the evolution of the language faculty) or “an adaptive, environmentally canalised, species-typical language
faculty” (in the case of Pinker, Jackendoff and the other adaptationists about the
evolution of the language faculty).[2] One
small criticism I have of Chomsky (along with fellow generativists like Charles
Yang, Robert Berwick, Steven Pinker, Ray Jackendoff, etc) is that he hasn’t made
this terminological alteration himself, still using the language of Cartesian
or Humboldtian rationalism, of which he has always regarded his work a direct descendant [Chomsky, 1965, 1986]. However, since I don’t think that the use of
this unscientific language is a significant problem for the UG-research
programme, I will myself, in the rest of this essay, always type the folk term in
single inverted commas while still assuming that I am defending Chomsky.
Past this terminological
hurdle, the single biggest reason why I think that Chomsky’s research programme
has been a success in both the senses I outlined in my introduction is empirical validation. It seems to me
quite clear that the theory that Homo
sapiens does have a developmentally canalised, species-typical language
faculty has not been falsified over
the decades, but is instead clearly still the best (indeed, the only)
explanation for the empirical evidence of rapid language acquisition and human
linguistic competence.
Despite the impression evoked
by some critics, Chomsky’s generative research-programme did not begin as a scholastic,
a priori enterprise, but was motivated
by empirical considerations of a fairly fundamental kind. The reason that Chomsky’s
famous 1957 monograph, Syntactic
Structures, is often heralded as the founding document of modern cognitive
science, despite not framing itself as a work of mentalistic investigation (and
containing no argument for the existence of an ‘innate’ “language faculty”) is
that Chomsky’s formal conclusions in SS
directly entail the powerful scientific conclusion that at least one language
(English) cannot be understood in behaviourist terms, and that English speakers
must ‘possess’ (in some vague sense, leaving representational and acquisitional
issues aside) what Chomsky would later call, in Aspects of the Theory of Syntax, “a system of generative processes”
[1965: 4]. The most pivotal part of
Chomsky’s monograph is his chapter 3 proof
that a finite-state or Markov model (a model which involves the
mono-directional chaining of words) is simply inadequate to generate all the grammatical sentences of English,
and the implication, explored in the next two chapters (“Phrase Structure Grammar”
and “Limitations of Phrase Structure Description”, in which he introduces the
notion of a “transformation” to complement the inadequate phrase structure
grammar), that an adequate generative grammar must be a hierarchical or syntax-based grammar
of some kind.[3]
Although the inadequacy of the finite-state model perhaps should have been
obvious, it was no trifling result, because it refutes the strongest empiricist
view about language production. If it is impossible to formally generate English sentences by a finite-state model, then
it is also impossible to generate English sentences by the kind of finite-state
model one might want to implement in a computer, or one might imagine existing
in a brain: a complicated word-chain device relying on transitional probabilities. One instead needs generative principles, and this fact literally precludes the strongest empiricist
understanding of language production.[4]
Evidently, behaviourists
wanted to avoid talking about mentation at all, but the theory of language
production found within works like Skinner’s Verbal Behavior (the subject of Chomsky’s famously destructive 1959
review) clearly rules out the
possibility that human language is produced by a generative grammar. As Steven
Pinker writes in The Language Instinct, the
finite-state model is directly “congenial to stimulus-response theories: a
stimulus elicits a spoken word as a response, then the speaker perceives his or
her own response, which serves as the next stimulus, eliciting one out of
several words as the next response, and so on” [1994: 93].
Of course, in Syntactic Structures itself, Chomsky uses his chapter 3 proof to
motivate a more purely methodological conclusion: that linguistics ought to shift
from static, structural description of corpora – the behaviourist methodology
of American Structuralism[5] – towards
the construction of the kind of descriptively adequate generative grammar he
attempts to construct for English in SS
(a transformational phrase structure grammar). Yet it is not hard to see how this
led to the far bolder scientific shift expounded in Aspects of the Theory of Syntax. In order to make the case for an
entirely new vision of linguistics in Aspects,
Chomsky extended his insight about the necessity of a creative model for English sentence-production
into all languages (on the strongly empirically
based contention that no other human language can be adequately described by a
finite state model either, supplemented by the empirically based assumption of strong
human cognitive universality), and combined this with an argument in support of
(essentially) 18th Century Rationalism. His new claim was that the
aim of the discipline should be to construct generative grammars that are descriptively
adequate for all natural languages, and explanatorily
adequate as “universal grammars”. That is to say, linguists should attempt
to describe the ‘innate’ linguistic competence or “system of generative
processes” held to be necessary for the acquisition of any natural language by
a child [1965: 6].
At this point, I should
point out that, whilst I am claiming that Chomsky’s research-programme was empirically
motivated at its inception, I am not claiming that all its empirical
presuppositions were thoroughly confirmed in 1965. It clearly might have been the case that the
evidence collected after 1965 strongly disconfirmed these empirical
presuppositions, and thus rendered the research programme untenable. If it had
turned out that there were
significant cognitive group-differences in Homo
sapiens – that some populations don’t have (and couldn’t have) language
with any recursion (as Daniel Everett claimed to show, falsely[6]) – then that would be a kind of
falsification of the universalist aspect of the programme (although,
presumably, that wouldn’t sound the death-knell for the investigation of the
linguistic competence of the human populations with the developmentally
canalised language faculty). Similarly, if “Nim Chimpsky” (or, for that matter,
some other animal) had proven capable of learning actual grammar, rather than
mere sign-strings, then that would have been a blow to Chomsky’s pretty
significant working assumption that the language faculty is unique to humans
(and it would probably have forced him to attribute to the ‘language faculty’ a
lower degree of developmental canalisation).
More interestingly, it might
have been the case that the evidence gathered after 1965 strongly favoured the hypothesis
that language acquisition occurs by means of solely domain-general cognitive processes, as Michael Tomasello’s
“usage-based theory of language” holds (a theory of language which, despite its
domain-generality, avoids getting wrecked on Chomsky’s SS proof about the inadequacy of Markov word-chains by positing that
speakers learn entire grammatical constructions
by means of a powerful “theory of mind” and contextual-awareness) [Tomasello,
2003]. If it had turned out that the condition known as “Specific Language
Impairment” was in all cases actually just a misdiagnosed general cognitive impairment,
or that all fully articulate older children diagnosed with autism or an
autism-spectrum disorder have either been misdiagnosed or had full cognitive
empathy in the critical period for acquisition, then that would lend strong
support to a Tomasello-type theory over one which postulates a language
faculty.
As it stands, however, things
have not turned out this way. Thus, the UG-research programme has been
completely justified in continuing to exist and grow.
In more recent years, some subtler empirical objections
to the UG research-programme have come from the AI community, which has had far
more success with trained statistical models (for example, probabilistic context-free grammars) than categorical models (any
of the ‘pure’ models created by generativists). The schism between these two
worlds – one practical, one theoretical – came to the fore in 2011 after
Chomsky made some highly disdainful comments about statistical approaches to “various
linguistic problems” (accusing statistical modellers of doing ‘butterfly-collecting’
rather than “science”) at the Brains, Machines and Minds symposium held on MIT’s
150th Anniversary. Soon after, the Director of Research at Google,
Peter Norvig, published an essay on Chomsky online in which he argued that the
father of linguistics was entirely in the wrong, since probabilistic models
have been far more successful in actual implementations than any categorical
ones [Norvig, 2011]. Nevertheless, as Chomsky’s student Charles Yang has argued
in response to similar critiques, whilst there is now “a good deal of evidence
against the ‘triggering’ model of learning” (which, Yang happily concedes, deserves
to be replaced by a “probabilistic model”, which is domain-general) “one
needn’t, and shouldn’t, abandon the categorical theory of GRAMMAR”, which is
domain-specific [Yang, 2007: 215]. In other words, it is still perfectly cogent
to study the abstract generative processes, because, as Chomsky has always
claimed, they represent the underlying linguistic
competence and nothing more.
There is one kind of critique of Chomsky’s
research-programme which has nothing to do with the empirics of ‘UG’, but the metaphysics. Towards the end of her
critique of ‘UG’ in What’s Within? Fiona
Cowie brings up an objection of exactly this metaphysical kind. Tapping into a
broader philosophical doubt many hard-line connectionists and ‘Churchlandian’ eliminativists
have about the computational theory of mind in general, Cowie claims that it is
deeply problematic that Chomsky cannot specify what the implicit “knowledge of
language” [7]
he theorises about actually is [Cowie,
1999: 274]. In particular, it is unclear, she claims, in what sense grammar
actually could be “represented” [1999: 274].
Despite the seeming
importance of this line of objection, Chomsky is simply a deflationist about
this question of “representation”, and I think he is right to be so. The reality
is that there is no possible theory of linguistic-competence – no possible explanatory scientific theory of
language – other than one which posits ‘knowledge’ in the form of a system of
“rules and representations” [Chomsky, 1980]. This means that Chomsky’s UG
research-programme is the only possible scientific research programme into the
faculty of language. The fact that, as Chomsky himself says in a reply to the
philosopher Georges Rey (quoting Randy Gallistel) “we clearly do not understand
how the nervous system computes,” or even “the foundations of its ability to
compute,” should not put a halt to the only scientific investigation into the
human language faculty, just as it shouldn’t put a halt to any other cognitive
scientific studies (including in other species) [Chomsky in Chomsky and his Critics, 2003: 276]. As
Chomsky says in that same reply, “surely no one expects that some isolable part
of the organism is dedicated to digestion, or navigation, or language, or any
other component that is singled out for investigation in any rational approach
to the study of a complex system” [Chomsky, 2003: 276].
In
summary, I believe that Chomsky’s attempt to interpret the theory of grammar as
an investigation of a human biological capacity has been highly successful, according to any reasonable criteria
for such things. The Universal Grammar-research programme he began in the early
1960s has enjoyed significant internal development while its core presuppositions
have been strongly confirmed. This has, in turn, revealed to us important
insights about the human mind.
[1] Of
course, the “theory of Universal Grammar” might then be understood as the empirical
presuppositions necessary for the tenability of this programme in general.
However, across the history of
the UG-research programme, it seems to me that the only constant empirical presuppositions
are: 1.) human cognitive universality (no significant cognitive group-differences
in Homo sapiens), and 2.) the
existence, in all humans without severe impairment, of a developmentally canalised,
domain-specific, computational ‘module’ (in the vaguest possible sense) which
explains human “linguistic competence” (and possibly several other human
abilities) for which we can construct generative models (not even grammars per
se) by investigating the syntax of the world’s languages. It seems to me that many
critics who mount general attacks on “Universal Grammar” believe they are
attacking a stronger thesis than the conjunction of these two propositions.
[2] Strictly speaking, it would be best
to rephrase Chomsky’s usage of “innate language faculty” with “a
developmentally canalised, species-typical language faculty which originated as
a spandrel but proved adaptive and was then selected for” [Chomsky, 2012: 14].
[3] He doesn’t use the word “hierarchical”
in SS.
[4] Of course, this in itself shows
nothing about the ‘innateness’ (more properly, developmental canalization, etc)
of the generative processes necessary for language production in an adult
speaker. In itself, it also clearly doesn’t rule out the possibility of
probabilistic language models more sophisticated than Markov chains (i.e.
probabilistic generative grammars), or, arguably, Michael Tomasello’s
usage-based theory of language [2003], which I’ll discuss later.
[5] Of which one of the major proponents
was Chomsky’s teacher and mentor, Zellig Harris.
[6] Pirahã
does have recursion, and (more fundamentally) Piraha speakers can learn
Portuguese, so Everett’s ‘argument’, such as it is, poses no problem for the
research programme at all [Nevins, Pesetsky, Rodrigues: 2009].
[7] Which
he has tried to re-term the “cognizance of language” in an attempt to stop the
philosophical controversy.
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