The phonetic evolution of reduplicated expressions: reduplication, lexical tones and prosody

In Na, a Sino-Tibetan language with lexical tones, some reduplication schemes involve tone change, whereas others consist in full reduplication without tone change. The synchronic coexistence of these two sets allows for an experimental comparison, which leads to a simple explanation. Both sets appear to originate in total reduplication, without tone change, the schemes which now involve tone change resulting from a later evolution: the phonologisation of the effect of intonational boundaries on pitch. A High tone in final position within the reduplicated compound is lowered to Mid; an initial Low tone is raised, also to Mid. A reflection is set out concerning the historical conditions under which the allophonic variation of lexical tones could be reinterpreted as a difference of tonal categories