When people talk about “the psychological reality of syntax”, there are (at least) two importantly different types of psychological state that they might have in mind. One of them is what I call mental phrase markers (MPMs)—representations of the syntactic structure of incoming linguistic stimuli, constructed in the course of on-line comprehension, and also whatever states play an analogous role in language production. MPMs are relatively transient states; their “lifespan” is typically measured in milliseconds. The other type of state is what I’ll call mental syntactic principles (MSPs)—representations of the general rules, principles, or constraints that jointly constitute a grammar for a language. MSPs are standing structures, architectural features of the human parsing mechanism. When the language faculty is inactive, i.e., when no comprehension or production processes are taking place, these structures are, so to speak, dormant. In the jargon of contemporary metaphysics, we can say that they are dispositional, rather than occurrent.In principle, MPMs can be psychologically real while MSPs are not. Alternatively, as I shall argue, both can be useful psychological constructs, but MPMs are best seen as explicit (subpersonal) representations, whereas there is little or no evidence that MSPs are psychologically real in that sense.
On the psychological reality of MPMS:
1. Neurolinguistics: EEG studies using the violation paradigm have found that early left anterior negativity is elicited by, and only by, syntactically ill-formed phrases. [...] These and other studies show that the human sentence-processing mechanism constructs distinctly syntactic representations.2. Structural priming: In producing language, people tend to employ the syntactic structures that they recently produced or comprehended. [...]ermine their content to a degree of precision that ERP studies cannot yet achieve.3. “Garden-path” processing: Linguistic input is rife with ambiguity. The language processing system is remarkably effective in selecting the correct resolution of such ambiguities. When it fails to do so, the anomaly shows up in behavior—e.g., extended fixations on a crucial part of a sentence, in eye-tracking studies (Rayner, Carlson, and Frazier, 1983), or a modulation of reaction times in cross-modal priming studies (Nicol and Swinney, 1989). Three principles of ambiguity resolution, Minimal Attachment, Late Closure, and the Minimal Chain Principle, form the foundation of many psychologically plausible parsing models (Frazier, 1979; DeVincenzi, 1991). [...]A fourth argument for the psychological reality of MPMs is indirect: I claim that no known model of language processing can explain the available data concerning human parsing preferences without positing MPMs.
Now things get tricky:
Having argued for the psychological reality of MPMs, I claim that their construction and manipulation can only be accomplished by a mechanism that either explicitly represents a grammar or embodies it. A system that “embodies” a grammar does not store a set of rules and principles in an explicit data structure (Stabler, 1983) and does not “access” or “read” them during real-time operations. Rather, the rules of the grammar are “hardwired” into the causal structure of the system, in such a way as to guide the construction of MPMs. In order to be an instance of embodiment, in the sense that I intend here, this hardwiring must also meet a condition that is stronger than the mere ability to process inputs of a certain type—i.e., stronger than mere “conformity” to a rule. For every rule or principle of the grammar, the hardwired system must have a unique causal mechanism that mediates the computation of all the syntactic representations that are in the domain and range of that rule or principle (Davies, 1995). A language-processing system can conform to a particular grammar without embodying it in this sense. Embodiment is weaker than representation, but stronger than conformity, in ways that are open to empirical test.The embodiment/representation distinction is important, but making progress on the psychological reality issue requires being as clear as possible about the relationships between it and five other distinctions: conscious/nonconscious, personal/subpersonal, implicit/explicit, declarative/procedural, and occurrent/dispositional.
And with that, I leave you to puzzle through this most interesting post. I would underscore the importance of Pereplyotchik's distinction between representation and embodiement and his later assertion, "At present, I argue, there are no decisive reasons for thinking that grammars are declaratively represented as data structures in the mind/brain, rather than embodied as hardwired procedural dispositions." Whew!