Extracting from a subject might simply be too mentally taxing for the brain to process in real-time. Exceptions and "Parasitic" Gaps
Once a subject moves to its final position, its internal structure is "frozen" and cannot be accessed.
Linguists debate whether these "walls" are built into our mental grammar or caused by how we process information. 1. The Architectural View Islands
A occurs when the grammatical subject of a sentence acts as one of these barriers. In English, you can usually extract a word from the object of a sentence, but doing the same to the subject results in an ill-formed "island violation".
"Which book did you file ___ [without reading ___]?" Extracting from a subject might simply be too
Some researchers suggest the problem isn't grammar, but .
Many generative grammarians argue that islands are a result of the of human language. "Which book did you file ___ [without reading ___]
The second gap is inside an "island," but the first "licit" gap makes the whole sentence feel okay to a native speaker.