On the locality of left branch extraction and the structure of NP

The paper considers several accounts of crosslinguistic variation regarding left branch extraction (LBE), focusing on adjectival LBE, and explores consequences of a proper analysis of LBE for the internal structure of NP. Two lines of research are pursued, both of which are based on the claim that languages that allow adjectival LBE do not have DP. One is based on the phase-based locality system, extending the phase system from clauses to NPs, and the other one is based on the existence of crosslinguistic variation regarding the position of adjectives in the traditional NP, with some languages having the traditional NP-over-AP structure, others having Abney's AP-over-NP structure. Which structure a language has is argued to depend on the presence/absence of DP in the language, the lack of DP leading to the NP-over-AP structure. Under this analysis, the ban on AP LBE in English-type languages follows from the ban on movement of non-constituents, a problem that does not arise in languages that allow AP LBE. The impossibility of LBE of AP in the presence of another AP in languages that in principle allow such extraction is argued to provide evidence that adjectives are located in multiple specifiers of the same head.