Xu Chen’s careful experimental study of wh-island effects in Chinese is a major contribution to Chinese and general linguistics. It is a rich and very significant development of James Huang’s pioneering work on Chinese 40 years ago, which opened new questions concerning the syntactic marking of the 'Duality of Semantics' that appears to be a fundamental property of human language. Xu Chen has approached this array of issues in a novel way: by carrying out careful experimental studies making use of the work of Jon Sprouse and others in developing the now-flourishing field of experimental linguistics. His results resolve many of the controversies about the properties of in-situ languages, and provide strong support for the optimal thesis: that human languages are uniform in basic properties, with surface variety traceable to options in the behavior of a small set of functional categories.

- Noam Chomsky, Massachusetts Institute of Technology & University of Arizona,