I’ve been railing on for a while about this issue, but have just finished a brief paper which I’ve Lingbuzzed, so thought it deserved a blogette. My fundamental concern is about the relationship between restrictiveness and simplicity in syntactic theory. An easy means of restricting the yield of a generative system is to place extra conditions on its operation with the result that the system as a whole becomes more complex. Simplifying a system typically involves reducing or removing these extra conditions, potentially leading to a loss of restrictiveness.

Chomsky’s  introduction of the operation Merge, and the unification of displacement and structure building operations that it accomplishes, was a marked step forward in terms of simplifying the  structure building component of generative grammar. But the simplicity of the standard inductive definition of syntactic objects that incorporates Merge has opened up a vast range of novel derivational types. Recent years have seen for example, derivations that involve rollup head movement, head-movement to specifier followed by morphological merger (Matushansky), rollup phrasal movement (Koopman, Sportiche, Cinque, Svenonius and many others), undermerge (Pesetsky. Yuan), countercyclic tucking-in movements (Richards), countercyclic late Merge (Takahashi, Hulsey, and the MIT crowd in general), and, the topic of this brief paper, sidewards movement, or, equivalently, Parallel Merge (Nunes, Hornstein, Citko, Johnson).

An alternative to adding conditions to a generative system as a means of restricting its outputs is to build the architecture of the system in such a way that it allows only a restricted range of derivational types, that is, to aim for an architecture that embodies the constraints rather than representing them explicitly (cf. Pylyshyn’s Razor). This opens up the possibility of both restricting a system and simplifying it. In my Syntax of Substance book for example, I argued for a system that does not project functional categories as heads, following Brody’s Telescoped Trees idea. This immediately removes derivational types involving certain kinds of head movement from the computational system. Apparent head movement effects have to be, rather, a kind of direct morphologization of syntactic units in certain configurations. No heads means no rollup head movement, no head to specifier movement followed by morphological merger, no `undermerge’ and no parallel merge derivations for head movement (a la Bobaljik and Brown). That same system (Adger 2013) also rules out roll-up phrasal movements via an interaction between the structure building and labelling components of the grammar (essentially, roll-up configurations lead to structures with two complements). It follows that the kinds of roll-up remnant derivations argued for by Kayne and Cinque are ungenerable and the empirical effects they handle must be dealt with otherwise. In all of these cases the concern was to reduce the range of derivational types by constructing a system whose architecture simply does not allow them. Adger 2013 makes the argument that the system presented there is at least no more complex than standard Bare Phrase Structure architectures.

In the draft paper I just posted, I’ve tried to tackle the issue of Sidewards Movement/Parallel Merge derivations, by attributing a memory architecture to Merge. The basic idea, which I presented in my Baggett lectures last year, is to split the workspace into two, mimicking a kind of cache/register structure that we see in the architecture of many computers. One workspace contains the resources for the derivation (I call it the Resource Space) and the other is a smaller (indeed binary) space that is where Merge applies, which I call the Operating Space. So a syntactic derivation essentially involves reading and writing things to and from the Operating Space, where the actual combination takes place.

This architecture makes Parallel Merge derivations impossible, as there is just not enough space/memory in the Operating Space to have the three elements that are needed for such a derivation. This is really just a way of formally making good on Chomsky’s observation that Parallel Merge/Sideways Movement derivations are in some sense ternary.

In the paper I define the formal system that has this result, and argue that it makes sense of the fact that the two gaps in a parasitic gap construction do not behave interpretively identical, extending some old observations of Alan Munn’s. But the main point is really to try to reduce the range of derivational types, and hence the restrictiveness of the system, without explicitly constraining the computational operations themselves. The extra complexity, such as it is, is actually a means of simplifying or economising memory in the computational system.

The paper is here.