Why are some ideas so sticky? A hypothesis

Anyone who has tried to articulate a new idea or criticize old ones may have noticed that some ideas are washed away relatively easily, while others seem to actively resist even the strongest challenges—some ideas are stickier than others. In some cases, there’s an obvious reason for this stickiness—in some cases there’s even a good reason for it. Some ideas are sticky because they’ve never really been interrogated. Some are sticky because there are powerful parts of society that depend on them. Some are sticky because they’re true, or close to true. But I’ve started to think there’s another reason an idea can be sticky—the amount of mental effort people put into understanding the idea as students.

Take, for instance, X-bar theory. I don’t think there’s some powerful cabal propping it up, it’s not old enough to just be taken for granted, and Chomsky’s Problems of Projection papers showed that it was not really tenable. Yet X-bar persists. Not just in how syntacticians draw trees, or how they informally talk about them, but I remember commentary on my definition of minimal search here involved puzzlement about why I didn’t simply formalize the idea that specifiers were invisible to search followed by more puzzlement when I explained that the notion of specifier was unformulable.

In my experience, the stickiness of X-bar theory—and syntactic projection/labels more broadly—doesn’t manifest itself in an attempt to rebut arguments against it, but in attempts to save it—to reconstitute it in a theory that doesn’t include it.[1]My reading of Zeijstra’s chapter in this volume is as one such attempt This is very strange behaviour—X-bar is a theoretical construct, it’s valid insofar as it is coherent and empirically useful. Why are syntacticians fighting for it? I wondered about this for a while and then I remembered my experience learning X-bar and teaching it—it’s a real challenge. It’s probably the first challenging theoretical construct that syntax students are exposed to. It tends to be presented as a fait accompli, so students just have to learn how it functions. As a result, those students who do manage to figure it out are proud of it and defend it like someone protecting their cherished possessions.[2]I think I may be describing “effort justification,” but I’m basing this just on the Wikipedia article

Of course, it’s a bit dangerous to speculate about the psychological motivations of others, but I’m certain I’ve had this reaction in the past when someone’s challenged an idea that I at one point struggled to learn. And I’ve heard students complain about the fact that every successive level of learning syntax starts with “everything you learned last year is wrong”—or at least that’s the sense they get. So, I have a feeling there’s at least a kernel of truth to my hypothesis. Now, how do I go about testing it?


As I was writing this, I remembered something I frequently think when I’m preparing tests and exams that I’ve thus far only formulated as a somewhat snarky question:

How much of our current linguistic theory depends on how well it lends itself to constructing problem sets and exam questions?


1 My reading of Zeijstra’s chapter in this volume is as one such attempt
2 I think I may be describing “effort justification,” but I’m basing this just on the Wikipedia article
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1) Of course specifier is “formulable” in the literal sense: X-bar is a fully formulable theory. Wrong, perhaps, but fully formulable.
2) Even if we go past the snarky objection in 1 and accept that you mean “unformulable under Merge-based theory”, “the object A standing in the following relation to a terminal node B: it is Merged to a projection of B which is not B itself and the result is a projection of B – is called specifier of B” is perfectly formulable, provided “projection of B” is formulable, which it is: “either B or a syntactic object derived by Merge with a projection of B such that B is the head of this Merge” – and head of Merge is defined in Merge itself, Chomsky is simply patently wrong here – to put it in shortened terms, “because A-over-A exists”, or, more generally, because the original arguments for endocentricity were never refuted – and see also below.
3) Problems of Projection (Chomsky 2013) is a bad paper that proves nothing it claims to prove. Chomsky jumps from “children follow structural relation not linear order” – by which, obviously, surface linear order is meant – to “[objects] appear in Z unordered, the latter a plausible assumption for reasons already discussed”, thus defining Merge as producing an unordered pair, which simply does not follow, in many ways. Even if Merge(A,B)=Merge(B,A) – that is, if it’s symmetric in the set theory sense – it doesn’t mean either that the result is {A,B} not <A,B> OR, perhaps even more importantly, that, even if the result looks like {A,B}, syntax doesn’t care for the properties of such pairs in a way that effectively makes them still A-headed (I mean, that’s how I chose the letters, of course for some A and B it’s actually B-headed but you know what I mean). Either means endocentricity aka head is definable – which means projection is definable – which means specifier is definable.
4) Moreover, even if that were overridden and Merge(A,B) were, indeed, just {A,B} without any way to always uniquely determine who’s the head of {A,B}, we would just need a notion of terminal node – aka the other understanding of the word “head”, obviously definable even then (object which was taken out from lexicon not built by Merge), I’ll use M0 to say that M is a terminal and MP to say that M isn’t – and some thinking to get to some notion that’s fairly close, although not identical. Let’s assume we have a structure of {X {A0 B}}. The special case of both A and B being terminals ({X {A0 B0}}) obviously arises at least once at first Merge, which is actually a further problem for Chomsky 2013 who promises to return to {H, H} but never does; but it is actually empirically true in the standard, asymmetric theory that roots may have complements but not specifiers – aka that {X {A0 B0}} is always an XP in standard terms – so X is not a specifier in {X {A0 B0}} (and it is always X0 – that is, {XP {A0 B0}} is, for whatever reason, un-Merge-able, that’s an empirical fact perhaps related to the “problems of projection” but meaning we can safely disregard this case for specifiers). Thus we are left with {X {A0 BP}}. If X is a terminal node (aka {X0 {A0 BP}}), we also stipulate it not to be a specifier (we look to establish the statement “you can’t look inside a specifier”, so we don’t need to bother with those things where there’s nothing to look inside). If it isn’t, it consists of {C D} (so the whole structure is {{C D} {A0 BP}}). If neither C nor D are terminal ({{CP DP} {A0 BP}}), X is a classic, X-bar-ish specifier. This only leaves the situations where C and/or D are terminals. If both are ({{C0 D0} {A0 BP}} then neither is a specifier – from the discussion above we can recall that such structures never happen but we can still spell this out. Finally, a symmetric {{C0 DP} {A0 BP}} (and equivalent {{D0 CP} {A0 BP}}) remains. If it’s symmetric, neither is a specifier of the other, which predicts both are permeable to search (and, if subextractions indeed exist, they support this prediction – the standard theory treats that via their moving through X’s specifier, so in our notation via an intermediate {{E {D0 CP}} {A0 BP}}, where E is contained in CP, but you needn’t). So we remain with a cut-down version of specifiers (namely, {CP DP} in {{CP DP} {A0 BP}} but not a useless one. (For specificity, I should mention that this presupposes that non-reprojecting head movement (Raising, see Harizanov & Gribanova 2018) and Lowering happens postsyntactically, by a different mechanism – which is supported by its seemingly not leaving copies.)
5)Nothing of what I said above means I believe that we necessarily need specifiers – just that calling something unformulable is both a risky proposition unless you have all your math written out and sometimes even then – and Chomsky has never done this in full since the 1980-ies – and not necessarily forcing discarding of that thing even if technically true (because you can then go “hm, I can’t define this exact thing but what happens if I try to come close and thus capture the original ideas with a slightly different notion?”).

6)Apart from all that, I don’t see how endocentricity (as opposed to X-bar schema specifically, as you casually conflate the two) is a challenging thing to learn. Endocentricity is the necessary and sufficient condition for equivalence between dependency-based trees and constituents-based trees, and dependency-based trees are quite intuitive. Aka “if you combine a verb and a noun phrase describing its patient you get a thing that behaves akin to a verb that never required such an addition of noun phrase in the first place” (see “run(s)” vs. “kill(s) Gary”) is a basic statement that’s pretty easy to grasp.

Points 1-5, I think, are orthogonal to the point I’m trying to make, but I’ll say this about them:

  1. The X-bar definition of specifier (daughter of a maximal projection, sister of an intermediate projection) is unformulable in a simplest Merge theory of syntax
  2. Any attempt to reformulate specifier for simplest Merge that I’ve seen either: (a) is not extensionally equivalent to the X-bar definition (e.g. they would say that in an {XP, YP} structure, XP is [Spec, Y] and YP is [Spec, X]) or,(b) depends on some ill-defined notion like selection to recapture the X-bar notion
  3. I can’t assess your critiques of the PoP papers in this forum. Are there published critiques you can point to?

As for point 6, I don’t know why X-bar or endocentricity would be difficult to learn, but my experience teaching undergraduates and reports from colleagues suggests that it is a difficult thing for undergraduates to learn. Similar remarks, I think, apply to the typed lambda calculus used by Heim & Kratzer—it’s actually an exceedingly simple system, but many, if not most, undergraduates and some grad students struggle to master it.