Once a subject moves to its final position, its internal structure is "frozen" and cannot be accessed.
Subjects usually provide "old" information (the background). Trying to pull a "new" focus out of a backgrounded subject creates a mental clash.
"*Who did [a picture of ___] hang on the wall?" (The phrase is the subject). Why Do Islands Exist? Islands
Extracting from a subject might simply be too mentally taxing for the brain to process in real-time. Exceptions and "Parasitic" Gaps
Some researchers suggest the problem isn't grammar, but . Once a subject moves to its final position,
The second gap is inside an "island," but the first "licit" gap makes the whole sentence feel okay to a native speaker.
Linguists debate whether these "walls" are built into our mental grammar or caused by how we process information. 1. The Architectural View "*Who did [a picture of ___] hang on the wall
Not all subject islands are equally strong. Some violations become acceptable if they are "saved" by a second gap in the sentence, known as a .