HOWs as Syntactic Predicates : Evidence from Tsou and Saisiyat

This paper reexamines the cross-linguistic generalization that interrogative HOW words function primarily as adverbs by demonstrating that in two Formosan languages—Tsou and Saisiyat—HOWs operate as full lexical verbs with predicative capabilities. By systematically applying five syntactic diagnostics (primary predication eligibility, theta-role assignment, object topic licensing, clause embedding, and complementation with control/causative verbs), we establish that HOWs in these languages are lexical predicates rather than adjuncts or light verbs. Furthermore, we identify an interrogative split: Measure/Resultative HOWs consistently employ structures of subject-predication in both languages, while Manner/Method HOWs exhibit complementation with obligatory control and voice concord of Saisiyat but either coordination or complementation in Tsou. This structural divergence suggests a grammaticalization pathway from coordination to complementation, with Tsou preserving the conservative pattern, while Saisiyat represents an innovative development. Our findings contribute to the cross-linguistic typology of interrogative words, control theory, voice restructuring phenomena in Austronesian languages, and clause union hierarchies.