The efficacy of lexical stress diacritics in the English comprehensibility and accentedness of Korean speakers




Kim, Keun

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In the field of second language (L2) pronunciation research and teaching, relatively less research has been conducted on the efficacy of suprasegmental features (e.g., stress and intonation) than that of segmentals (individual sounds) (Thomson & Derwing, 2015). However, previous studies reported that suprasegmental errors are as much or more responsible for accentedness and comprehensibility ratings than are segmentals (Munro & Derwing, 1995a; Kang, Rubin, & Pickering, 2010). English stress, a suprasegmental feature, can be very challenging for native Korean speakers to acquire due to the different prosodic systems of the two languages. While English has stress at the lexical level, Korean has tone patterns at the phrasal level known as the Accentual Phrase (Jun 1996). It is common that Korean speakers of English place stress on the wrong syllable or do not give sufficient auditory prominence to a stressed syllable in a word like sápphire. Korean learners of English are often frustrated by not knowing which syllable gets prominence because the English writing system does not provide this information. This point calls for enhanced input that can make stressed syllable salient for L2 learners. The purpose of the current study, therefore, was to investigate 30 native Korean subjects to examine the efficacy of providing enhanced input (lexical stress diacritics) on the accentedness and comprehensibility of their L2 English. In the pretest, the participants read aloud 15 English sentences without diacritics. Then, the subjects were given explicit treatment instructions on the production of increased pitch and extended duration as a marker of English stress with musical notation presented. The participants were invited to read aloud novel sentences written with diacritics to mark stress placement. In the treatment task (immediately following the treatment instructions on the same day), the participants read aloud the same sentences from the pretest but with correct stress placement indicated by diacritics. In the posttest, which took place two days after the pretest and the treatment task, participants read 15 sentences without diacritics again to see if the effects of the treatment were retained. Speech samples from three measurement points were rated by three native speakers of English in terms of comprehensibility and accentedness. Four main findings are reported. First, significant improvement was found between the pretest and treatment task in both comprehensibility and accentedness ratings. This result indicates that the participants gained immediate benefit from utilizing diacritics with stress correctly placed. Second, significant improvement was observed in the pretest vs. the posttest in both accentedness and comprehensibility ratings, demonstrating the effects of the treatment. Third, there was no significant difference between the treatment task and the posttest, suggesting that the participants retained what they learned from the treatment when diacritics were removed. Fourth, the significant improvement in the pretest vs. the posttest was observed across the participants’ level of English proficiency and gender, showing promise as a more generally applicable pronunciation teaching technique. Pedagogical and empirical implications along with limitations of the current study are discussed.



Comprehensibility, Accentedness, English pronunciation, Lexical stress, Lexical Stress Diacritics, Enhanced input, Korean Speakers