漢語族語言的低元音抬升現象：是同化、縮減，抑是兩者兼具？

Low Vowel Raising in Sinitic Languages: Assimilation, Reduction, or Both?

許多漢語族語言裡的低元音 /a/ 在介音 /j/ 與舌尖韻尾之間會變為 /e/ 元音（亦即「低元音抬升」）。藉由爬梳跨語言的語料，本文首先指出此現象與韻核元音音長、韻首的種類乃至於捲舌音之有無皆息息相關，因此將其視為純然協同構音之結果難免有以偏概全之虞。本文更進一步論證低元音抬升的動因應係輔音與元音間舌位前後同化作用加上音長縮減所誘發之舌位高低不到位現象的總合結果。兩者缺一不可。理論分析則採用 Flemming (2003)所提倡之將元音的舌位前後與輔音的舌尖性分開標註、且以共存制約連結兩者的處理模式，並佐以以語音為本的優選理論制約。本研究結果顯示低元音抬升（典型的「音韻」現象）其實應源自於種種協同構音（典型的「語音」現象）「加總」後所致，也讓我們對標準漢語音段層面音韻現象裡的標準分析進行了一些反思。

Many Sinitic languages respect low vowel raising (LVR) whereby the low vowel /a/ is raised to /e/ only when flanked by a palatal glide and a coronal coda. In this article, I show that LVR in Sinitic languages is a genuine process of grammar because low-level phonetic coarticulatory effects alone cannot account for crosslinguistic/ dialectal variation. Specifically, my survey reveals that vowel duration, onset consonants and/or the presence of retroflexes may have a direct bearing on LVR, thus calling for a phonological analysis. I argue that the phenomenon in question is better treated as additive effects of (i) target undershoot in the wake of impoverished vowel duration (i.e. vowel reduction) and (ii) contextual influences (i.e. backness assimilation). Phonological vowel quality change (LVR here) is motivated only when the benefit of contextual neutralization exceeds that of the sum of the “cost” of implementing the above coarticulatory patterns. Analytically, Flemming’s (2003) feature co-occurrence constraints, together with phonetically driven constraints, provide a straightforward account of the relationship between coronal place and vowel backness attested in LVR. Finally, implications for Mandarin segmental phonology are also discussed.