Interrogatives of reason in Tibeto-Burman languages of Sichuan

This is a typological study of the why-interrogative expressions in Tibeto-Burman languages, or the non-Chinese Sino-Tibetan languages, in Sichuan, southwest China. After examining 22 languages/dialects, the interrogative category of reason is grouped into three types, viz. the distinct why-type, the how-type, and the what-type, according to the interrogative categories from which they are derived. It is discovered that the what-type is the dominant strategy for languages in Sichuan to derive the reason category. It is also common for Tibeto-Burman languages to use verbal interrogatives, namely interrogative verb phrases and interrogative words with verbal origins, dominantly in the sense of ‘to do what’ and ‘to become what’, to ask for reason. After a focused investigation of the verbal interrogatives, it is found that Tibeto-Burman languages in Sichuan distinguish purpose from cause via word/phrase distinction, sentential positions and semantic differences. A path of grammaticalization of the verbal interrogatives is thus proposed and analyzed. Finally, the derivation maps of interrogatives in Cysouw (2005) and Hölzl (2018) are complemented with a refined distinction between purpose and cause.