Which NP does "all" associate with in e.g. "The pandas, the children all saw"--the pandas, the children, or both? The intuition of adult Mandarin Chinese native speakers regarding the interpretation of the adverbial quantifier "dou" 'all' remains unclear and controversial, and various incommensurate theories of domain selection have been proposed. These studies may have failed to yield clear results because they used testing materials in which the interpretation of "dou" is confounded with other principles of NP interpretation (e.g. "zhexie xiaohai" 'these children' is truth-functionally synonymous with 'all these children'). To address these concerns, we present the first set of experimental studies on adult knowledge and use of syntactic constraints on the quantifier domain of "dou." The results support the hypothesis that "dou" can take one and only one c-commanding NP as its domain, but falsify interesting theoretical accounts that assume a strict locality constraint on "dou" quantification.