Islands -

"Who did you see [a picture of ___]?" (The phrase is the object).

Modern theories suggest certain phrases are "phases" that become invisible to the rest of the sentence once completed. 2. The Information Structure View Islands

Linguists debate whether these "walls" are built into our mental grammar or caused by how we process information. 1. The Architectural View "Who did you see [a picture of ___]

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". In English, you can usually extract a word

The second gap is inside an "island," but the first "licit" gap makes the whole sentence feel okay to a native speaker.

Many generative grammarians argue that islands are a result of the of human language.