***
Linking syntactic
theory to behavior and brains
It is very frustrating to work in the cognitive neuroscience
of syntax within the mainstream Generative Grammar (GG) framework when there
are essentially no real linking theories on offer between syntactic theory and
online sentence processing. At present, the connection between syntactic theory
and whatever people do when they hear and produce sentences is completely
opaque, as is how the mature language system develops during acquisition. My present point is to underscore the
essentiality of establishing such a linking theory. I truly believe that any
cognitive neuroscience of language that seeks to incorporate the insights of
Generative Grammar absolutely needs such a linking theory. Of course, cognitive
neuroscience of language can proceed without
incorporating the insights of syntactic theory, and this is often done – most
people working on syntax attempt to localize some vague, a-theoretical notion
of “syntactic processing” without clearly defining what this is. An even
clearer example of departure from syntactic theory is recent work by that
posits certain brain areas that are “core” language areas, without defining
what language is beyond “you know it when you see it” (Fedorenko et al., 2011).
Is that what we want for neuroscience investigations of language – near total
disregard for GG? I don’t. The whole reason I am (was) here at UMD is because I
find syntactic theory very deep, both for descriptive and explanatory adequacy,
and I in fact think that the Minimalist program in particular may allow
bridging the gap between linguistics and the fields of neuroscience and
evolutionary biology.
There are reasons for this disregard, a major one being that
nobody talks about how a Minimalist grammar is used. We certainly have plenty of insightful work in acquisition
and psycholinguistics that tell us when children know certain grammatical
constructions (e.g., Lukyanenko et al., 2014) or when certain grammatical
constraints are used online (e.g., Phillips 2006), but we don’t have any
strongly plausible suggestions as to what happens mechanistically. For example, it seems that people don’t search for
gaps inside of islands, but why don’t
they? How is the grammatical knowledge deployed in real time such that people
don’t try to find a gap inside an island? This issue is a fundamental question
for my line of work, and one that remains unanswered. For a related example in
the world of brains, there is a very close connection between the syntactic
properties of sentences and activation in language-relevant brain areas (e.g.,
Pallier et al., 2011; Matchin et al., 2014) – but what does this mean with
respect to the function of these
brain areas? Are these areas “Merge
areas”, or something else? If something else, what is our theory of this
something else (that takes into account the fact that this area cares about
structure)? This sort of question applies to pretty much every finding of this
sort in psycholinguistics, language acquisition, and cognitive neuroscience.
My work rests on experiments of language use, in normal
people during brain scanning or in patients with brain damage. I attempt to
explain why brain areas light up the way that they do when people are producing
or comprehending language, or why patients have particular problems with
language after damage to certain brain areas, and I try to connect these
notions with syntactic theory. However, it is very hard to proceed without
knowing how the postulates of syntactic theory relate to behavior. Here are
just a sample of major questions in this regard that exemplify the opacity
between syntactic theory and online processing:
·
When processing a sentence, do I expect Merge to be active? Or not?
·
What happens when people process things less
than full sentences (like a little NP – “the dog”)? What is our theory of such
situations?
·
Do derivations really proceed from the bottom
up, or can they satisfactorily be switched to go top-down/left-right using
something like Merge right (Phillips
1996)?
·
What happens mechanistically when people have to
revise structure (e.g., after garden-pathing)?
·
Are there only lexical items and Merge? Or are there stored complex
objects, like “treelets”, constructions, or phrase structure rules?
·
How does the syntactic system interact with
working memory, a system that is critical for online sentence processing?
These things are not mentioned in syntactic theory because
of the traditional performance/competence separation (Chomsky, 1965). There did
use to be some discussion of these linking issues in work that sought to bridge
the gap between syntactic theory and online sentence processing (e.g., Miller
& Chomsky, 1963; Fodor et al., 1974; Berwick & Weinberg, 1983), but it
does not seem so for currently, at least for Minimalism. In order for me to do
anything at all reasonable in neuroscience with respect to syntax, I need to
have at least a sketch of a theory that provides answers to these questions,
and such a theory does not exist.
There are syntactic theories on the market that do connect
(somewhat) more transparently to behavior than mainstream GG – those of the
“lexicalist” variety (e.g., Bresnan, 2001; Vosse & Kempen, 2000; Frank,
2002; Joshi et al., 1975, Lewis & Vasishth, 2005), with the general virtues
of this class of theory, including the very virtues of transparency to online
behavior, summarized by Jackendoff (2002) and Culicover and Jackendoff (2005;
2006). In my mind, Jackendoff and Culicover are right on the point of
transparency – this kind of grammatical theory does connect much better with
what we know about behavior and aphasia. At the very least, it seems to me
impossible to even get of the ground in discussions of psycholinguistics,
neuroimaging or aphasia without postulating some kind of stored complex
structures, “constructions” or “treelets”, or perhaps old-fashioned phrase
structure rules that might fill an equivalent role to treelets (see Shota
Momma’s 2016 doctoral dissertation for an excellent review of this evidence for
psycholinguistics, hopefully available soon J). Minimalist grammars do not provide this level of
representation, while lexicalist theories do.
Here is a set of fundamental observations or challenges from
psycholinguistics and neurolinguistics that any kind of linking theory between
syntax and online sentence processing should take into account:
·
Online processing is highly predictive and
attempts to build dependencies actively (Omaki et al., 2015; Stowe, 1986 –
filled-gap effect)
·
Online processing very tightly respects grammatical
properties (e.g., phrase structure, Binding principles, Island structures)
(Lewis & Phillips, 2015)
·
Stored structures of some kind seem necessary to
capture many behavioral phenomena (Momma, 2016; see also Demberg & Keller,
2008)
·
The memory system involved in language appears
to operate along the lines of a parallel, content-addressable memory system
with an extremely limited focus of attention (Lewis et al., 2006)
·
The main brain “language areas” are highly
sensitive to hierarchical structure and other grammatical properties (Embick et
al., 2000; Musso et al., 2003; Pallier et al., 2011)
·
Damage restricted to Broca’s area (the main
language-related brain region) results in only minor language impairments, not
fundamental issues with language (Linebarger et al., 1983; Mohr et al., 1978)
·
Contra Grodzinsky (2000), there doesn’t seem to
be any class of patients that is selectively impaired in a particular component
of grammar (e.g., Wilson & Saygin, 2004), implying that core grammatical
properties are not organized in a “syntacto-topic” fashion in the cortex
·
The neuroimaging profile of “language areas”
indicates that while these areas are sensitive to grammatical properties, their
functions are not tied to particular grammatical operations but rather with the
processing ramifications of them (Rogalsky & Hickok, 2011; Stowe et al.,
2005; Matchin et al., 2014; Santi & Grodzinsky, 2012; Santi et al., 2015)
As I explain in more detail later in this post, a language
faculty that makes prominent use of stored linguistic structures and a memory
retrieval system operating over them allows us to make coherent sense out of
these kinds of findings.
At any rate, it seems painfully true to me that the
‘syntacto-topic conjecture’ (Grodzinsky, 2006; Grodzinsky & Friederici,
2006), the attempt to neurally localize the modules of syntactic theories of GG
(e.g., Move alpha, Binding principles, fundamental syntactic operations, etc.),
has completely failed. Let me underscore that – there are no big chunks of
dedicated “grammatical” cortex to be found in the brain, if grammatical is to
be defined in these sorts of categories. At any rate, did we want to abandon
the Minimalist program and re-adopt Government and Binding (GB) theory in order
to localize its syntactic modules? One of the virtues of the Minimalist
program, in my view, is that it seeks a more fundamental explanation for the
theoretical postulates of GB (Norbert’s numerous blog discussions of this
issue), which we didn’t want as the primitive foundations of language for
reasons such as Darwin’s problem – the problem of how language emerged in the
species during evolution. Incidentally, the lack of correspondence between GB
and the brain is another reason to pursue something like the Minimalist
program, which possesses a much slimmer grammatical processing profile that
wouldn’t necessarily take up a huge swath of cortex. Positing a rich lexicon
with a slim syntactic operation seems to me to be a very plausible way to
connect up with what we know about the brain.
Except for the fact that I know of no linking theory between
grammar and behavior for a Minimalist grammar aside from Phillips (1996). And
even that linking theory really only addresses one issue listed above, the
issue of derivational order – it did not answer a whole host of questions
concerning the system writ large. Namely, it did not provide what I believe to
be the critical level of representation for online sentence processing – stored
structures. So I have no way of explaining the results of neuroimaging and
neuropsychology experiments in Minimalist terms, meaning that the only options
are: (1) adopt a lexicalist grammatical theory a la Culicover & Jackendoff (2005; 2006) and eschew many of the
insights of modern generative grammar (2) develop a satisfactory linking theory
for Minimalism (which I argue should incorporate stored structures, etc.).
It may be the case that syntacticians don’t care, because
these concerns are not relevant to providing a theory of language as they’ve
defined it. And I actually agree with this point – I don’t necessarily think
that syntacticians ought to change the way they do business to accommodate these
concerns. Here I strongly disagree with Jackendoff – I think there are good
reasons to maintain the competence/performance distinction in pursuing a good
description of the knowledge of language, because it allows them to focus and
develop theories, whereas I think if they were to start incorporating all of
this then they’d be paralyzed, because there is just too much going on in the
world of behavior (modulo experimental syntax approaches, e.g. Sprouse, 2015,
that are well-targeted within the domains of syntactic theory). I do recall a
talk by Chomsky at CUNY 2012 where he pretty much said “hey guys stop looking
at behavior there’s too much going on and you’ll get confused and go nowhere” –
it doesn’t seem like patently bad advice.
However, I don’t think our studies of behavior and the brain
have done nothing, and maybe it’s the right time for syntacticians,
psycholinguists, and neuroscientists to start connecting everything up
together.
There are also some very important reasons to care. If you
want your theories to be taken seriously by psycholinguists and neurolinguists,
you need to give them plausible ways in which your theoretical postulates can
be used during online processing. The days of Friederici and Grodzinsky are
numbered – Grodzinsky has already pretty much renounced the syntacto-topic
conjecture (finally – Santi et al., 2015), and Friederici clings to what I
think is a very hopeless position regarding Broca’s area and Merge (Zaccarella & Friederici,
2015). These were the only people that seriously engage with syntactic theory
in generative grammar who have any clout in cognitive neuroscience. Everyone
else seems to be pretty much ignoring mainstream Generative Grammar. Is that
what we want? I can imagine that this sort of stuff is important for intra- and
inter-departmental collaboration, funding, etc.
There seems to be a decline in the purchase of generative
grammar in the scientific community, which may only hasten with time and the
eventual death of Chomsky. A good way to forestall or reverse this is by
opening up a channel of communication with psychologists and neuroscientists
through these specific linking
theories (at least a sketch of one), not merely the promise of some possible linking theories (which appears to be what
Norbert is telling me in our conversations). We need to actually make at least
a rough sketch of a real linking theory in order to get this enterprise off the
ground.
Secondly, it might be the case that introducing a plausible
linking theory has ramifications for how you think about language and syntactic
theory. There could be some very useful insights into syntactic theory to be
gained once greater channels of communication are open and running.
I am worried that I cannot successfully combine my work in
neuroscience with syntactic theory and generative grammar. The conference that
I attend every year, the “Society for the Neurobiology of Language”, ought to be the most sympathetic place
you’d find for GG to talk to neurobiology. In reality, there is hardly ever a
peep about GG at these conferences. This ought to be a very disturbing state of
affairs for you – it certainly is to me. The sometimes latent, sometimes
explicit message that I keep receiving from my field is to stop caring about GG
because it bears no relation to what we do. I reject this message, but in order
to do meaningful work, I need to be armed with a good (sketch of a) linking
theory. A big goal of this post is to solicit reactions and suggestions from
syntacticians in developing this theory.
