Wednesday, September 12, 2018

The neural autonomy of syntax

Nothing does language like humans do language. This is not a hypothesis. It is a simple fact. Nonetheless, it is often either questioned or only reluctantly conceded. Therefore, I urge you to repeat the first sentence of this post three times before moving forward. It is both true and a truism. 

Let’s go further. The truth of this observation suggests the following non-trivial inference: there is something biologically special about humans that enables them (us) to be linguistically proficient andthis special mental power is linguistically specific. In other words, humans are uniquely cognitively endowed as a matter of biology when it comes to language and this biological gift is tailored to track some specific cognitive feature of language rather than (for example) being (just!) a general increase in (say)generalbrain power. On this view, the traditional GG conception stemming from Chomsky takes FL to be both species specific and domain specific. 

Before proceeding, let me at once note that these are independent specificity theses. I do this because every time I make this point, others insist in warning me that the fact mentioned in the first sentence does not imply the inference I just drew in the second paragraph. Quite right. In fact: 

It is logically possible that linguistic competence supervenes on no domain specific capacities but is still species specific in that only humans have (for example) sufficiently powerful general brains to be linguistically proficient. Say, for example, linguistic competence requires at least 500 units of cognitive power (CP) and only human brains can generate this much CP. However, modulo the extra CPs, the mental “programs” the CPs drive are the same as those that (at least some) other cognitive creatures enjoy, they just cannot drive them as fast or as far because of mileage restrictions imposed by low CP brains.

Similarly, it is logically possible that animals other than humans have domain specific linguistic powers. It is conceivable that apes, corvids, platypuses, manatees, and Portuguese water dogs all have brains that include FLs just like ours that are linguistically specific (e.g. syntax focused and not exercised in other cognitive endeavors). Were this so, then both they and we would have brains with specific linguistic sensitivities in virtue of having brains with linguistically bespoke wiring/circuitry or whatever specially tailored brain ware makes FL brains special. Of course, were I one of them I would keep this to myself as humans have the unfortunate tendency of dismembering anything that might yield scientific insight (or just might be tasty). If these other animals actually had an FL I am pretty sure some NIH scientist would be trying to figure out how to slice and dice their brains in order to figure out how its FL ticks.

So, both options are logically possible, but, the GG tradition stemming from Chomsky (and this includes yours truly, a fully paid up member of this tribe) has doubted that these logical options are live and that when it comes to language onlywe humans are built for it and what makes our cognitive profile special is a set of linguistically specific cognitive functions built into FL and dedicated to linguistic cognition. Or, to put this another way, FL has some special cognitive sauce that allows us to be as linguistically adept as we evidently are and we alone have minds/brains with this FL.

Nor do the exciting leaps of inference stop here. GG has gone even further out on the empirical limb and suggested that the bespoke property of FL that makes us linguistically special involves an autonomous SYNTAX (i.e. a syntax irreducible to either semantics or phonology and with its own special combinatoric properties). That’s right readers, syntax makes the linguistic world go round and only we got it and that’s why we are so linguistically special![1]Indeed, if a modern linguistic Ms or Mr Hillel were asked to sum up GG while standing on one foot s/he could do worse than say, only humans have syntax, all the rest is commentary.

This line of reasoning has been (and still is) considered very contentious. However, I recently ran across a paper by Campbell and Tyler (here, henceforth C&T) that argues for roughly this point (thx to Johan Bolhuis and William Matchin for sending it along). The paper has several interesting features, but perhaps the most intriguing (to me) is that Tyler is one of the authors. If memory serves, when I was growing up, Tyler was one of those who were very skeptical that there was anything cognitively special about language. Happily, it seems that times have changed.

C&T argues that brain localizes syntactic processing in the left frontotemporal lobe and “makes a strong case for the domain specificity of the frontotemporal syntax system and its autonomy from domain-general networks” (132). So, the paper argues for a neural version of the autonomy of syntax thesis. Let me say a few more words about it.

First, C&T notes that (of course) the syntax dedicated part of the brain regularly interacts with the non-syntactic domain general parts of the brain. However, the paper rightly notes that this does not argue against the claim that there is an autonomous syntactic system encoded in the brain. It merely means that finding it will be hard as this independence will often be obscured.  More particularly C&T says the activation of the domain general systems only arise “during task based language comprehension” (133). Tasks include having to make an acceptability judgment. When we focus on pure comprehension, however, without requiring any further “task” we find that “only the left-laterilized frontotemporal syntax system and auditory networks are activated” (133). Thus, the syntax system only links to the domain general ones during “overt task performance” and otherwise activates alone. C&T note that this implies that the syntactic system alone is sufficient for syntactic analysis during language comprehension.

Second, C&T argue that arguments against the neural autonomy of syntax rest on bad definitions of domain specificity. More particularly, according to C&T the benchmarks for autonomy in other studies beg the autonomy question by embedding a “task” in the measure and so “lead to the activation of additional domain-general regions” (133). As C&T notes, when such “tasks” are controlled for, we only find activation in the syntax region.

Third, the relevant notion of syntax is the one GGers know and love. For C&T takes syntax to be prime species specific feature of the brain and understands syntax in GGish terms to be implicated in “the construction of hierarchical syntactic structures.” C&T contrasts hierarchical relations with “adjacency relationships” which it claims “both human and non-human primates are sensitive to” (134). This is pretty much the conventional GG view and C&T endorses it.

And there is more. C&T endorses the Hauser, Chomsky, Fitch distinction between FLN and FLB. This is not surprising for once one adopts an autonomy of syntax thesis and appreciates the uniqueness of syntax in human minds/brains the distinction follows pretty quickly. Let me quote C&T (135):

In this brief overview, we have suggested that it is necessary to take a more nuanced view to differentiating domain-general and domain-specific components involved in language. While syntax seems to meet the criteria for domain-specificity….there are other key components in the wider language system which are domain-general in that they are also involved in a number of cognitive functions which do not involve language.

C&T has one last intriguing feature, at least for a GGer like me. The name ‘Chomsky’ or the terms ‘generative grammar’ are never mentioned, not even once (shades of Voldemort!). Quite clearly, the set of ideas that the paper explores presupposes the basic correctness of the Chomskyan generative enterprise. C&T arugues for a neural autonomy of syntax thesis and, in doing so, it relies on the main contours of the Chomsky/GG conception of FL. Yes, if C&T is correct it adds to this body of thought. But it clearly relies on it’s main claims and presupposes their essential correctness. A word to this effect would have been nice to see. That said, read the paper. Contrary to the assumptions of many, it argues that for a cog-neuro conception of the Chomsky conception of language. Even if it dares not speak his name.

[1]I suspect that waggle dancing bees and dead reckoning insects also non verbally advance a cognitive exceptionalism thesis and preen accordingly.

1 comment:

  1. I notice that the Campbell and Tyler article is published together with 30 others in a special issue on the evolution of language, with papers from such familiar names as Fitch, Friederici, Hurford, Marslen-Wilson, Levelt, Hagoort, Levinson, and Christiansen & Chater -- the latest round of arguments for and against saltation versus gradualism, and more.