[glup]

Various syntactic theories (HPSG, GPSG, minimalism, construction grammars) from linguistics are certainly derived constructs, but most researchers would agree that they all reflect real abstractions that humans make. I think the NLP community has good a job of harvesting the substantive aspects (which tend to be fairly conventionalized upon across theories) without overfitting on specific cases. "Alice drove down the street in her car" is easy for people to process, "The horse raced past the barn fell" is not, because it requires a pretty drastic reinterpretation of the structure when you get to the last word.

That said, there is some interesting work on "good-enough" language processing, which suggests that people maintain some fuzziness and don't fully resolve the structure when they don't need to. [1]

[1] http://csjarchive.cogsci.rpi.edu/proceedings/2009/papers/75/...

[microtonal]

but most researchers would agree that they all reflect real abstractions that humans make

They reflect a particular language in its well-written form. However, humans are extremely robust against syntax errors. I am not a linguist, but I think this speaks in favor of lexicalist approaches: we can be very free in word order, as long as our brain can match up e.g. verbs with their expected arguments.