Cedric Boeckx replies to some remarks by Hornstein on Berwick and Chomsky's "Why Only Us"

Norbert Hornstein commented on my "quite negative" review of Berwick and Chomsky's book _Why Only Us_ published in Inference (http://inference-review.com/article/not-only-us). Here is the link to his comments, posted here on the Faculty of Language blog: http://facultyoflanguage.blogspot.com.es/2017/04/inference-to-some-great-provocations.html

I want to begin by thanking him for reading the review and sharing his thoughts. The gist of his remarks is, if I read him right, that he is "not sure" what I find wrong with _Why Only Us_. He concludes by saying that "Why [Boeckx] doesn’t like (or doesn’t appear to like) this kind of story escapes me." I found the paragraphs he devotes to my review extremely useful, as they articulate, with greater clarity than what I could find in _Why Only Us_, some of the intuitions that animate the kind of evolutionary narrative advocated in the book I reviewed: The "All you need is Merge" approach. Hornstein's points give me the opportunity to stress some of the reasons why I think this kind of approach is misguided. This is what I want to express here.

In so far as I can see, Hornstein makes the following claims (which are, indeed, at the heart of _Why Only Us_) [the claims appear in roughly the order found on Hornstein's original post]

1. Hornstein seems to endorse Tattersall's oft-repeated claim, used in Why Only Us, that there is a link between linguistic abilities and the sort of symbolic activities that have been claimed to be specific to humans. This is important because the fossil evidence for these activities is used to date the emergence of the modern linguistic mind; specifically, to argue for a very recent emergence of the modern language faculty. Here is the relevant passage:

"in contrast to CB [Boeckx], IT [Tattersall] thinks it pretty clear that this “symbolic activity” is of “rather recent origin” and that, “as far as can be told, it was only our lineage that achieved symbolic intelligence with all of its (unintended) consequences” (1). If we read “symbolic” here to mean “linguistic” (which I think is a fair reading), it appears that IT is asking for exactly the kind of inquiry that CB thinks misconceived."

Perhaps it is too strong to say that Hornstein endorses it, but clearly he does not buy my skepticism towards this kind of argument, expressed in my review (and backed up with references to works questioning Tattersall that unfortunately Hornstein does not discuss, delegating to Tattersall as the unique expert.)

2. Hornstein grants me "several worthwhile points"; specifically, my claims that "there is more to language evolution than the emergence of the Basic Property (i.e. Merge and discretely infinite hierarchically structured objects) and that there may be more time available for selection to work its magic than is presupposed". Hornstein writes that "many would be happy to agree that though BP is a distinctive property of human language it may not be the only distinctive linguistic property." He continues "CB is right to observe that if there are others (sometimes grouped together as FLW vs FLN) then these need to be biologically fixed and that, to date, MP has had little to say about these. One might go further; to date it is not clear that we have identified many properties of FLW at all. Are there any?" Later on, he writes "CB is quite right that it behooves us to start identifying distinctive linguistic properties beyond the Basic Property and asking how they might have become fixed. And CB is also right that this is a domain in which comparative cognition/biology would be very useful", but stresses that "It is less clear that any of this applies to explaining the evolution of the Basic Property itself."

3. Hornstein seems to think that my problem is that I "think that B[erwick]&C[homsky] are too obsessed with" recursion (or Merge). He goes on: "But this seems to me an odd criticism. Why? Because B&C’s way into the ling-evo issues is exactly the right way to study the evolution of any trait: First identify the trait of interest. Second, explain how it could have emerged.  B&C identify the trait (viz. hierarchical recursion) and explain that it arose via the one time (non-gradual) emergence of a recursive operation like Merge. The problem with lots of evo of lang work is that it fails to take the first step of identifying the trait at issue. ... If one concedes that a basic feature of FL is the Basic Property, then obsessing about how it could have emerged is exactly the right way to proceed"

4. He thinks that my "discussion is off the mark" (specifically, my insistence on descent with modification and bottom-up approaches in the review) because Merge "is not going to be all that amenable to any thing but a “top-down, all-or-nothing” account". "What I mean", Hornstein says, "is that recursion is not something that takes place in steps"; "there is no such thing as “half recursion” and so there will be no very interesting “descent with modification” account of this property. Something special happened in humans. Among other things this led to hierarchical recursion. And this thing, whatever it was, likely came in one fell swoop. This might not be all there is to say about language, but this is one big thing about it and I don’t see why CB is resistant to this point."

5. Hornstein stresses that he "doubt[s] that hierarchical recursion is the whole story (and have even suggested that something other than Merge is the secret sauce that got things going), I do think that it is a big part of it and that downplaying its distinctiveness is not useful." He goes on: we "can agree that evolution involves descent with modification. The question is how big a role to attribute to descent and how much to modification (as well as how much modification is permitted). The MP idea can be seen as saying that much of FL is there before Merge got added. Merge is the “modification” all else the “descent.” "No mystery about the outline of such an analysis, though the details can be very hard to develop"... "it is hard for me to see what would go wrong if one assumed that Merge (like the third color neuron involved in trichromatic vision (thx Bill for this)) is a novel circuit and that FL does what it does by combining the powers of this new operation with those cognitive/computational powers inherited from our ancestors. That would be descent with modification"

6. He sums up: "The view Chomsky (and Berwick and Dawkins and Tattersall) favor is that there is something qualitatively different between language capable brains and ones that are not. This does not mean that they don’t also greatly overlap. It just means that they are not capacity congruent. But if there is a qualitative difference (e.g. a novel kind of circuit) then the emphasis will be on the modifications, not the descent in accounting for the distinctiveness. B&C is happy enough with the idea that FL properties are largely shared with our ancestors. But there is something different, and that difference is a big deal. And we have a pretty good idea about (some of) the fine structure of that difference and that is what Minimalist linguistics should aim to explain"

All of these are interesting points, although I think they miss the target, for reasons worth making explicit (again), if only because that way we can know what is likely to be productive and what is not. After all, I could be wrong, and Hornstein (and Berwick/Chomsky in Why Only Us) could be wrong. I'll tackle Hornstein's points in a somewhat different order from the one he used, but I don't think that doing so introduces any misrepresentation.

Let's begin with points of (apparent) agreement: Hornstein is willing to concede that we need a bit more than Merge, although if I read him well, he is not as clear about it as I would like. Why do I say so? On the one hand, he writes that "many would be happy to agree that though BP is a distinctive property of human language it may not be the only distinctive linguistic property. CB is right to observe that if there are others (sometimes grouped together as FLW vs FLN) then these need to be biologically fixed and that, to date, MP has had little to say about these. One might go further; to date it is not clear that we have identified many properties of FLW at all. Are there any?" On the other hand, he writes  "CB is also right that this is a domain in which comparative cognition/biology would be very useful (and has already been started [FN:There has been quite a lot of interesting comparative work done, most prominently by Berwick, on relating human phonology with bird song").

I won't comment much on the references provided by Hornstein in that footnote, but I must say that I think it reveals too much of a bias towards work done by linguists. In my opinion, the great comparative work that exists has not been done by linguists (in the narrow sense of the term). Hornstein's is not a lovely bias to display in the context of interdisciplinarity (indeed, it's not good to show this bias on a blog that likes to stress so much that people in other disciplines ignores the work of linguists. Don't do unto others ...) In the case of birdsong, this kind of work goes several decades back, and detailed studies like Jarvis 2004(!), or Samuels 2011 (cited in my review) hardly justify the "has already been started" claim about comparative cognition. But let's get to the main point: we can't just ask "are there any? (shared features)" and at the same time cite work that shows that there is a lot of it. But there is something worse, in light of my review: Hornstein seems to have no problem with the usefulness of comparative cognition ("a domain in which comparative cognition/biology would be very useful") so long as it applies to everything except Merge ("there will be no very interesting “descent with modification” account of this property"; "It is less clear that any of this applies to explaining the evolution of the Basic Property itself." "this property is not going to be all that amenable to any thing but a “top-down, all-or-nothing” account") This is one of the issues I intended to bring up in the review, and what I called "exceptional nativism". I'll return to this below, but for now, let me stress that even if Hornstein grants me that there is more than Merge, Merge is still special, in a way that is different from "other distinctive linguistic properties".

It's not the case that I object to _Why Only Us_ because I think Berwick and Chomsky are "too obsessed with Merge". I object to it because I think they obsess about it in the wrong way: they (and Hornstein) are obsessed in making it not only special, but distinct-in-a-way-that-other-distinct-things-are-not: it takes it out of the Darwinian domain of descent with modification.

Hornstein discusses Descent With Modification, but his prose reveals that he and I understand it differently. Indeed, he appears to understand it in a way that I warned against in my review. Here is the key passage: "the MP idea can be seen as saying that much of FL is there before Merge got added. Merge is the “modification” all else the “descent.” " I think this is wrong. It takes the phrase descent with modification pretty much like most linguists understood the FLN/FLB distinction of Hauser, Chomsky and Fitch 2002: there is FLN and there is FLB. There is descent and there is modification. But I don't think this is the core of the Darwinian logic: "Descent with modification" ought to be understood as "modified descent" (tinkering), not as "descent" put side by side with/distinct from modification. Because modification is modification of something shared; it's inextricably linked to descent. Descent with modification is not "this is shared" and "this is different" and when you put these 2 things you get "descent and modification", because the different is to be rooted in the shared. We can't just say Merge is the 'modification' bit unless we say what it is a modification of. (Needless to say, if, as Hornstein writes, we replace Merge by some other "secret sauce that got things going", my point still applies. The problem is with thinking in terms of some secret sauce, unless we break it down in no so secret ingredients, ingredients that can be studied, in isolation, in other species. That's the message in my review.)

The Darwinian logic is basically that the apple can only fall so far from the tree. The apple is not the tree. But it is to be traced back to the tree. As I put it in the review: there's got to be a way from there (them) to here (us). And Merge should not be any exception to this. I'll put it this way: if the way we define Merge makes it look like an exception to this kind of thinking, then we are looking (obsessing?) at Merge in the wrong way. If we find Merge interesting (and I do!), then we've got to find a way (or better, several ways, that we can then test) to make it amenable to "descent with modification"/"Bottom-up (as opposed to all-or-nothing/top-down) approaches. Of course, we could say, well, tough luck: we can't choose what nature gave us. It gave us Merge/recursion, and you can't understand this gradually. It's there or not. It's discontinuous but in a way different from the kind of discontinuity that biologists understand (significantly modified descent). But if we do so, then, tough luck indeed: we are confining Darwin's problem to a mystery. A fact, but a mysterious one ("Innate knowledge is a mystery, though a fact", as McGinn once put it.) It's fine by me, but then I can't understand how people can write about how "All you need is Merge" accounts shedding light on Darwin's problem. They must mean Darwin's mystery. To use Hume's phrase, such accounts restore Merge to that obscurity, in which it ever did and ever will remain”.

Don't get me wrong. It's a perfectly coherent position. Indeed, in a slightly different context, referenced in my review, David Poeppel talks about the "incommensurability problem" of linking mind and brain. Maybe we can't link both, just like we can't understand the evolution of Merge. Note here that I say the evolution of Merge. At times, Hornstein, like Berwick and Chomsky, gives me the impression that he thinks Merge is the solution. But it's the problem. It's that which needs to be explained. And I think that one way to proceed is to understand its neural basis and trace back the evolution of that (that is, engage with Poeppel's granularity mismatch problem, not endorse his incommensurability problem), because perhaps Merge described at the computational level (in Marr's sense) is mysterious from a descent-with-modification perspective, but not so at the algorithmic and implementational levels. And I think  it's the task of linguists too to get down to those levels (jointly with others), as opposed to lecturing to biologists about how Merge is the solution, and it's their problem if they don't get it. (Incidentally, it's a bit ironic that Hornstein praises Lobina's discussion of recursion in his blog post, but does not mention the fact that Lobina took issue with Hornstein's take on recursion in some of his publications.)

Hornstein writes that "The problem with lots of evo of lang work is that it fails to take the first step of identifying the trait at issue". He does not give references, so I cannot judge what he means by "lots". I like to think I read a lot, and my assessment doesn't match Hornstein's at all. I think a lot of work in evo of lang promotes a Darwinian feeling for the phenotype. This is quite different from, say, a Darcy-Thompsonian feeling for the phenotype. I see in lots of evo of lang work a desire to make talk about evo of language amenable to conventional evolutionary discourse. Why Only Us ("this property is not going to be all that amenable to any thing but a “top-down, all-or-nothing” account") is the exact opposite.

Perhaps a bit of an empirical discussion would help (I always find it helpful, but I don't know if Hornstein would agree here). Let's take the example of vocal learning, a key component of our language-faculty-mosaic. Not a cool as Merge for some, but still pretty neat. In fact, the way many talks and papers about vocal learning begin is quite like the way linguists like to talk about Merge. Let me spell this out. It's often pointed out that vocal learning  (the ability to control one's vocal apparatus to reproduce sounds one can hear, typically from con-specifics) is a fairly sparsely distributed trait in the animal kingdom. It may not be as unique as Merge ("Only us"), but it's close: it's "only" for a selected few. (I stress that I am talking about the classic presentation of this trait; ideas of a vocal learning continuum, which I like, would only make the point I am about to make stronger. See work by Petkov and Jarvis on this.) Like Merge, Vocal learning is an all or nothing affair. You have it, or you don't. It looks like an all or nothing thing. But unlike Merge, people have been able to gain insight into its neural structure, and break it down to component pieces. Among these, there is a critical cortico-laryngeal connection that appears to qualify for the "new circuit" that underlies vocal learning (see Fitch's book on evolution of language for references). And people have been able to get down to the molecular details for birds (Erich Jarvis, Constance Scharff, Stephanie White, and many others), bats (Sonja Vernes), and link it to language/speech (Simon Fisher and lots of people working on FOXP2). Erich Jarvis in particular has been able to show that most likely this new circuit has a motor origin, and "proto" aspects of it may be found in non-vocal learning birds (suboscines). All of this is quite rich in terms of insight. And this richness (testability, use of comparative method, etc.) makes the Merge solution to Darwin's problem pale in comparison. It's true, as Hornstein points out,  linguists know a lot about Merge, but they only know it from one perspective (the "Cartesian" perspective, the one that leads to "Why Only Us"), and this may not be the most useful perspective from a Darwinian point of view. The main message of my review  of Why Only Us was that.

Final point, on timing, and Hornstein's appeal to Tattersal's review of the fossil evidence for the emergence of symbolic behavior. No one can know everything (where would one put it?, as they say), but in my experience it's always good to rely on more than one expert (I cite some in the review). My main point about this in the review was not so much to question the dating of said emergence, but rather to ask for an account of how symbolic behavior is linked to linguistic behavior. I can see why it's plausible to think these are linked. But if the argument concerning the timing of the emergence of the language faculty rests on very few things, and it's one of them, we want more than a plausibility argument. (Norbert's blog loves to say "show me the money" when non-generativists make claims about language acquisition based on what strikes them as plausible. I guess, it's only fair to say "show me the money", or else I'll start selling Hornstein bridges.) It's plausible to think "how could they have done it without language". So, symbol, ergo language. But then again, I can't remember how I lived without my iphone. Poverty of Imagination arguments can be very weak. I know of very few attempts to mechanistically link symbolic and linguistic behavior. One attempt, by Juan Uriagereka, was about "knots" and the Chomsky hierarchy. David Lobina showed how this failed in a paper entitled "much ado about knotting". Victor Longa tried to link blombos style marks to crossing dependencies in language, but it's fair to say the argument for crossing dependencies there is nowhere near as neat as what Chomsky did in Syntactic Structures. Apart from that, I am not aware of any explanatory attempt. I once asked Tattersal after a talk he gave, and he told me something that amounted to "ask Chomsky". When I ask linguists, they tell me ask the experts like Tattersall. And so I begin to be suspicious...

But there is something more I could say about the timing issue that came to my mind when reading Hornstein's comments: if Merge is such an all-or-nothing thing, not subject to the logic of descent, then why should we care if it's recent or not? It could have emerged, in one fell swoop, millions of years ago, and remain "unattached" to "speech devices" until recently. And so why do we want to insist about a very recent origin? The timing issue is only very important if issues about gradual evolution matters. But if we stress that gradual evolution is out of the question, then, the timing issue is a red herring. So, why does Hornstein insist on it?

Let me close by thanking Norbert again for his comments. They led to this long post. But they often made me feel like Alice when she tells the Red Queen that one can't believe impossible things. Hornstein, like the Red Queen, disagrees. But it's not Wonderland, it's Darwinland.