The formal structure of the construction formed by a numeral (Num), a sortal classifier (C) or mensural classifier (M), and a noun (N), is controversial, as both left-branching [[Num C/M] N] and right-branching [Num [C/M N]] structures have been argued for in the literature. In this paper we report two psycholinguistic experiments on speech production and perception in Mandarin to investigate this branching issue. First, we applied the syntax-phonology interface of tone 3 (T3) sandhi and performed a phonological analysis of native speakers' tone sandhi patterns of [Num C/M N] phrases composed of T3 monosyllabic words. Second, we conducted a click-detection experiment to see how native speakers would perceive a click inserted in a C/M phrase composed of monosyllabic words, as compared to when it is inserted in other syntactic structures with attested left or right-branching. Results from both experiments supported the leftbranching structure of classifier phrases.