||Kang, Seokhan. (2020). A study of vowel variations in the adverb reduplication of Jeju Korean. The Linguistic Association of Korea Journal, 28(4), 1-28. In the emphatic reduplication of Jeju Korean which implies emphatic meanings, a vowel change takes place as a form of total reduplication. It is argued that vowel variations in the reduplication occur through both changes in vowel quantity and quality, using the extended duration of nuclear syllables and wider formant differences between F1 and F2. To provide the morphological evidence, 512 reduplicative adverbs have been checked and then divided into two forms: basic and emphatic. The forms are classified into two groups depending on the direction of vowel change: height and frontness. To demonstrate the direction of the phonological change, speech experiments have been carried out for ten native speakers of Jeju Korean over 60 years old. The analysis focuses on the principal features of acoustic/phonetic signals, namely, the fundamental frequency (Hz), intensity (dB), formant structure of F1 and F2, the duration of vowels, and the syllable nucleus. Out of six acoustic cues, formant structure (F1 and F2) and duration of the syllable-nucleus show statistical differences between the basic and emphatic reduplicants. The results imply that adverb reduplication, in the case of Jeju Korean, uses the perceptual effects through mora extension for acoustic quantity and rhythmic realization for vowel quality.