兒向語（infant-directed speech)是兒童語言習得早期最重要的語言輸入，然而兒向語舒入聲調對比的議題一直未獲相關文獻關注，因 此本研究將透過客語對這個問題進行探討。本研究收集了六位客籍 母親與婴兒及實驗者的言語互動所發出的客語去聲調（舒）與陽入 調（入）語音樣本，並利用PRAAT語音分析軟體進行基頻分析，包 含均值（F。mean)、輪廓（F。contour)、斜率（F。slope)及時長（F。 duration)。研究結果顯示，與成人語相比，兒向語聲調的基頻均值、 基頻輪廓、基頻斜率及基頻時長均有顯著的擴張與延長。更重要的 是，本研究發現兒向語中的舒入調分離現象，入聲調的基頻輪廓及基 頻均值明顯高於舒聲調。本文認為這種語音現象與[p, t, k]韻尾在語流 中因快速發音所形成的喉塞化有關。最後，本文進一步利用研究結果 檢視「母婴語音互動模式」的適切性。

This study contrasted checked and non-checked tones in Hakka infant-directed speech (IDS). Six mothers participated in speech recordings. Tonal samples were gathered from mothers' natural verbal interaction in connected speech with their infants and the experimenter, and were analyzed by PRAAT for fundamental frequency (F0). Results displayed that F0 mean, F0 contour, F0 slope and F0 duration were all phonetically expanded and lengthened in IDS, as compared with adult-directed speech (ADS). Most important of all, checked and non-checked tones in IDS displayed tonal separability, with checked tones higher in F0 contour and F0 mean than nonchecked tones. It was further argued that such tonal separability resulted from glottalization phonetically reduced from the [p, t, k] codas in the rapid production of connected speech. Finally, this study examined the appropriateness of Mother-Infant Phonetic Interaction (MIPhI) Model in terms of current research results.