在前人的研究中，已透過音韻規則的角度分析梅縣客語 (Meixian Hakka) 和曼谷客語 (Bangkok Hakka)， 但仍有部分疑問未獲得合理解釋。諸如：部分聲調不會受變調規則(Tone sandhi)的影響、變調的觸發條件以及本調 (Citation tone) 和變調間結構上的關係等。 有鑒於此，本研究透過優選理論 (Optimality theory, OT) 重新分析梅縣客語和曼谷客語。 上述兩個方言有兩種變調的方式 : 同化(assimilation)和異化(dissimilation)。在此基礎上，為了更準確的描述變調現象，本研究在分析上主要採用必要性起伏原則 (obligatory contour principle) 和避免起伏原則 (no-jumping principle)，並應用聯合制約 (Constraint Conjunction approach) 的概念。採取此分析方式的理由在於分析對象的變調具有相當有標(marked)且受限於中心詞(head)右端音節的聲調。此外，本研究也採用一部分比聲調結構性制約(tonal markedness constraint)更高排序的信實性制約(faithfulness constraint)。這些制約會導致部分聲調或變調結構不受變調規則影響，例如：調域 (register) 和聲調的起點 (initial target) 將保留原始樣貌。 研究結果指出，聲調結構性制約和數個排序最高的聲調信實性制約能更準確地呈現梅縣客語和曼谷客語在變調時，輸入值與輸出值之間的對應關係 (input-output correspondence)。在論文結尾，筆者將綜覽本研究並提出未來可繼續延伸的相關議題。 / The grammar of Meixian and Bangkok Hakka tone sandhi has been analyzed from a rule based approach. Nevertheless, there are some questions and details that could not be solved by the analysis, such as the status of tones that do not undergo sandhi, triggers of the tone sandhi, and the structural relation between citation tones and their sandhi counterparts. Thus, the purpose of this study is to re-analyze the tone sandhi in Meixian and Bangkok Hakka under the constraint based framework, Optimality Theory (OT). There are two mechanisms of tonal alternations in the two dialects’ tone sandhi: assimilation, and dissimilation. So in order to capture the tonal alternations, the current analysis applies the concepts of the Obligatory Contour Principle, and the No-Jumping Principle. The constraints generated according to these principles work well with the application of the Constraint Conjunction approach. The conjoined constraints are needed since the tone alternations are highly marked, and depend a lot on the head/right syllable tone. Furthermore, this thesis also posits several faithfulness constraints that rank higher than the tone sandhi markedness constraint. The high ranked faithfulness constraints govern the preservation of several tones from any alternation, and preservation of some structures of the citation tones when they become sandhi tones (i.e. register and initial target). In conclusion, the positing of tone sandhi markedness constraints and undominated identity constraints presents a better input-output correspondence relation of the tone sandhi phenomena in Meixian and Bangkok Hakka. To conclude the thesis, a brief summary of the study and possible further issues are presented.

本論文以優選理論分析六家饒平客語和寧都田頭客語雙音節詞之連讀變調，並藉由聲調內部結構說明變調的動機。在六家饒平客語方面，主要是呈現位置變調(positional tone sandhi)，較有標(more marked)的聲調位於前字時發生變調。另外，此方言的陽平和陽去因歷史演變，兩者的本調(citation tone)同為HH，但兩者因不同的變調形式而產生不同的變調(sandhi tone)。陽去的變調形式為位置變調，而陽平的變調形式為環境變調(contextual tone sandhi)。本文採用聯合制約(Local Constraint Conjunction)捕捉環境變調制約運作的環境。另外，運用「詞素特定音韻」(morpheme-specific phonology)標記聯合制約，解釋陽平和陽去不同的變調規則。在寧都田頭客語方面，變調受詞法結構影響，且兩個音節皆有可能發生變調。本文利用標記制約理論(indexed constraints approach)解釋不同結構的變調情形。另藉由位置信實制約不同的排序，嘗試說明聲調的保留屬於類型差異(typological differences)。而此方言的變調類型包含位置變調和環境變調，同樣要求較有標的聲調改變，並使用聯合制約說明在環境變調的情況下制約運作的環境。 / This thesis investigates the tone sandhi in Liujia Raoping Hakka and Ningdu Tiantou Hakka under the framework of Optimality Theory. The internal structure of the tone reveals the motivation and the mechanism of tone sandhi. In terms of the tone sandhi in Liujia Raoping Hakka, the universal tonal markedness tendency could be regarded as the motivation triggering the positional tone sandhi in the left syllable. Moreover, the morpheme-specific phonology is adapted to account for the tone sandhi of historical merged tones, Yangping and Yangqu. Yangping and Yangqu are both high level tones; however, they display different tone sandhi patterns. Yangping displays the contextual tone sandhi whereas Yangqu displays the positional tone sandhi. Local conjunction constraints are posited to restrict markedness constraints to specific contexts in order to account for the mechanism of contextual tone sandhi. On the other hand, in terms of the tone sandhi in Ningdu Tiantou Hakka, the tone sandhi is construction sensitive and takes place in both syllables. The indexed constraint approach is adopted to explain the tone sandhi in different constructions. In addition, the preservation of tone is argued to be the typological difference according to different rankings of the positional faithfulness constraints. Finally, the tonal markedness tendency motivates the positional tone sandhi and the conjoined constraints are posited to govern the contextual tone sandhi in this dialect.