In a number of wh-in-situ languages, only causal wh-adverbs corresponding to ‘why’ exhibit island effects. The widely adopted explanation for this by Tsai (On economizing the theory of A-bar dependencies, 1994a, Nat Lang Linguist Theory 12(1):121–175, 1994b, in: Del Gobbo, Hoshi (eds) UCI working papers in linguistics, University of California, Irvine, 1999, J East Asian Linguist 17(2):83–115, 200...... hiện toàn bộ