This study examines effects of short, medium, and extended second language (L2) experience (3 months, 3 years, and 10 years of United States residence, respectively) on the production of five suprasegmentals (stress timing, peak alignment, speech rate, pause frequency, and pause duration) in six English declarative sentences by 30 adult Korean learners of English and 10 adult native English speakers. Acoustic analyses and listener judgments were used to determine how accurately the suprasegmentals were produced and to what extent they contributed to foreign accent. Results revealed that amount of experience influenced the production of one suprasegmental (stress timing), whereas adult learners' age at the time of first extensive exposure to the L2 (indexed as age of arrival in the United States) influenced the production of others (speech rate, pause frequency, pause duration). Moreover, it was found that suprasegmentals contributed to foreign accent at all levels of experience and that some suprasegmentals (pause duration, speech rate) were more likely to do so than others (stress timing, peak alignment). Overall, results revealed similarities between L2 segmental and suprasegmental learning.This research was partially supported by research grants from the University of Illinois and Brigham Young University. Many thanks are extended to Youngju Hong for her help in testing the Korean participants and to Molly Mack and James E. Flege for their advice throughout this research project. The authors gratefully acknowledge Randall Halter, Elizabeth Gatbonton, and five anonymous SSLA reviewers for their helpful suggestions on earlier drafts of this paper as well as Randall Halter for his invaluable statistical assistance.

The goal of this study was to determine which linguistic aspects of second language speech are related to accent and which to comprehensibility. To address this goal, 19 different speech measures in the oral productions of 40 native French speakers of English were examined in relation to accent and comprehensibility, as rated by 60 novice raters and three experienced teachers. Results showed that both constructs were associated with many speech measures, but that accent was uniquely related to aspects of phonology, including rhythm and segmental and syllable structure accuracy, while comprehensibility was chiefly linked to grammatical accuracy and lexical richness.

Comprehensibility, a major concept in second language (L2) pronunciation research that denotes listeners’ perceptions of how easily they understand L2 speech, is central to interlocutors’ communicative success in real-world contexts. Although comprehensibility has been modeled in several L2 oral proficiency scales—for example, the Test of English as a Foreign Language (TOEFL) or the International English Language Testing System (IELTS)—shortcomings of existing scales (e.g., vague descriptors) reflect limited empirical evidence as to which linguistic aspects influence listeners’ judgments of L2 comprehensibility at different ability levels. To address this gap, a mixed-methods approach was used in the present study to gain a deeper understanding of the linguistic aspects underlying listeners’ L2 comprehensibility ratings. First, speech samples of 40 native French learners of English were analyzed using 19 quantitative speech measures, including segmental, suprasegmental, fluency, lexical, grammatical, and discourse-level variables. These measures were then correlated with 60 native English listeners’ scalar judgments of the speakers’ comprehensibility. Next, three English as a second language (ESL) teachers provided introspective reports on the linguistic aspects of speech that they attended to when judging L2 comprehensibility. Following data triangulation, five speech measures were identified that clearly distinguished between L2 learners at different comprehensibility levels. Lexical richness and fluency measures differentiated between low-level learners; grammatical and discourse-level measures differentiated between high-level learners; and word stress errors discriminated between learners of all levels.

This study investigated how listener experience (extent of previous exposure to non-native speech) and semantic context (degree and type of semantic information available) influence measures of intelligibility, comprehensibility, and accentedness of non-native (L2) speech. Participants were 24 native English-speaking listeners, half experienced and half inexperienced with L2 speech, who transcribed and rated 90 English utterances spoken by six English and six Mandarin speakers. The utterances varied along two dimensions: real-world expectations (true vs. false utterances) and semantic meaningfulness (meaningful vs. meaningless utterances). Listeners with more experience understood more speech from the L1 and L2 speakers than listeners with less experience but did not rate it differently in comprehensibility and accentedness. All listeners understood and rated the utterances from L2 speakers based on the semantic context available: true–false utterances were understood and rated best, meaningless utterances least. These findings have implications for evaluating learner pronunciation and for training learners in successful L2 communication strategies.

The objective of this study was to determine how bilinguals' age at the time of language acquisition influenced the organization of their phonetic system(s). The productions of six English and five Korean vowels by English and Korean monolinguals were compared to the productions of the same vowels by early and late Korean-English bilinguals varying in amount of exposure to their second language. Results indicated that bilinguals' age profoundly influenced both the degree and the direction of the interaction between the phonetic systems of their native (L1) and second (L2) languages. In particular, early bilinguals manifested a bidirectional L1-L2 influence and produced distinct acoustic realizations of L1 and L2 vowels. Late bilinguals, however, showed evidence of a unidirectional influence of the L1 on the L2 and produced L2 vowels that were “colored” by acoustic properties of their L1. The degree and direction of L1-L2 influences in early and late bilinguals appeared to depend on the degree of acoustic similarity between L1 and L2 vowels and the length of their exposure to the L2. Overall, the findings underscored the complex nature of the restructuring of the L1-L2 phonetic system(s) in bilinguals.

The current project aimed to investigate the potentially different linguistic correlates of comprehensibility (i.e., ease of understanding) and accentedness (i.e., linguistic nativelikeness) in adult second language (L2) learners’ extemporaneous speech production. Timed picture descriptions from 120 beginner, intermediate, and advanced Japanese learners of English were analyzed using native speaker global judgments based on learners’ comprehensibility and accentedness, and then submitted to segmental, prosodic, temporal, lexical, and grammatical analyses. Results showed that comprehensibility was related to all linguistic domains, and accentedness was strongly tied with pronunciation (specifically segmentals) rather than lexical and grammatical domains. In particular, linguistic correlates of L2 comprehensibility and accentedness were found to vary by learners’ proficiency levels. In terms of comprehensibility, optimal rate of speech, appropriate and rich vocabulary use, and adequate and varied prosody were important for beginner to intermediate levels, whereas segmental accuracy, good prosody, and correct grammar featured strongly for intermediate to advanced levels. For accentedness, grammatical complexity was a feature of intermediate to high-level performance, whereas segmental and prosodic variables were essential to accentedness across all levels. These findings suggest that syllabi tailored to learners’ proficiency level (beginner, intermediate, or advanced) and learning goal (comprehensibility or nativelike accent) would be advantageous for the teaching of L2 speaking.