Deconstructing comprehensibility: identifying the linguistic influences on listeners' L2 comprehensibility ratings

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

Disentangling accent from comprehensibility

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

Second language pronunciation assessment: A look at the present and the future

Over three decades ago, Michael Canale summarized what he considered to be the challenges facing language assessment in the era of communicative language learning and teaching: Just as the shift in emphasis from language form to language use has placed new demands on language teaching, so too has it placed new demands on language testing. Evaluation within a communicative approach must address, for example, new content areas such as sociolin- guistic appropriateness rules, new testing formats to permit and encour- age creative, open-ended language use, new test administration procedures to emphasize interpersonal interaction in authentic situa- tions, and new scoring procedures of a manual and judgemental nature. (Canale, 1984: 79) Applied to second language (L2) pronunciation assessment, this descrip- tion remains highly relevant today, raising a number of important issues, such as: broadening the scope of pronunciation assessment beyond the focus on a single aspect of pronunciation (e.g. segmental accuracy) or a single standard (e.g. absence of a discernible nonnative accent); targeting pronunciation assess- ment for various interlocutors in interactive settings, for instance, outside a typical focus on academic performance by students in Western societies; as well as developing and fine-tuning novel assessment instruments and proce- dures. Above all, Canale’s description aptly summarizes an ongoing quest in language assessment to capture the authenticity and interactiveness of language use (e.g. Bachman, 1990; Bachman & Palmer, 2010). The contribu- tions to this edited volume address some of the challenges identified by Canale in innovative ways. Before summarizing these contributions, we hasten to add that no edited volume, including this one, can provide an exhaustive overview of all possible issues in L2 pronunciation assessment; most chapters in this volume are focused on testing or informal evaluative judgements of speech in real-world settings and not on classroom-based assessment, including diagnostic assessment or feedback on test takers’ per- formance. However, the range of topics, the variety of research methodologies and paradigms, and the scope of implications featured here make this volume a timely addition to the growing area of L2 pronunciation assessment

Linguistic dimensions of l2 accentedness and comprehensibility vary across speaking tasks

This study critically examined the previously reported partial independence between second language (L2) accentedness (degree to which L2 speech differs from the target variety) and comprehensibility (ease of understanding). In prior work, comprehensibility was linked to multiple linguistic dimensions of L2 speech (phonology, fluency, lexis, grammar) whereas accentedness was narrowly associated with L2 phonology. However, these findings stemmed from a single task (picture narrative), suggesting that task type could affect the particular linguistic measures distinguishing comprehensibility from accentedness. To address this limitation, speech ratings of 10 native listeners assessing 60 speakers of L2 English in three tasks (picture narrative, IELTS, TOEFL) were analyzed, targeting two global ratings (accentedness, comprehensibility) and 10 linguistic measures (segmental and word stress accuracy, intonation, rhythm, speech rate, grammatical accuracy and complexity, lexical richness and complexity, discourse richness). Linguistic distinctions between accentedness and comprehensibility were less pronounced in the cognitively complex task (TOEFL), with overlapping sets of phonology, lexis, and grammar variables contributing to listener ratings of accentedness and comprehensibility. This finding points to multifaceted, task-specific relationships between these two constructs

The Effects of Talker Variability and Frequency of Exposure on the Acquisition of Spoken Word Knowledge

Eighty Japanese learners of English as a foreign language encountered 40 target words in one of four experimental conditions (three encounters, six encounters, three encounters with talker variability, and six encounters with talker variability). A picture-naming test was conducted three times (pretest, immediate posttest, and delayed posttest) and elicited speech samples were scored in terms of form-meaning connection (spoken form recall) and word stress accuracy (stress placement accuracy and vowel duration ratio). Results suggested that frequency of exposure consistently promoted the recall of spoken forms, whereas talker variability was more closely related to the enhancement of word stress accuracy. These findings shed light on how input quantity (frequency) and quality (variability) affect different stages of lexical development and provide implications for vocabulary teaching

Lexical aspects of comprehensibility and nativeness from the perspective of native-speaking English raters

This study analyzed the contribution of lexical factors to native-speaking raters’ assessments of comprehensibility and nativeness in second language (L2) speech. Using transcribed samples to reduce non-lexical sources of bias, 10 naïve L1 English raters evaluated speech samples from 97 L2 English learners across two tasks (picture description and TOEFL integrated). Subsequently, the 194 transcripts were analyzed through statistical software (e.g., Coh-metrix, VocabProfile) for 29 variables spanning various lexical dimensions. For the picture description task, separation in lexical correlates of the two constructs was found, with distinct lexical measures tied to comprehensibility and nativeness. In the TOEFL integrated task, comprehensibility and nativeness were largely indistinguishable, with identical sets of lexical variables, covering dimensions of diversity and range. Findings are discussed in relation to the acquisition, assessment, and teaching of lexical properties in L2 speech

Shielding of a moving test charge in a quantum plasma

The linearized potential of a moving test charge in a one-component fully degenerate fermion plasma is studied using the Lindhard dielectric function. The motion is found to greatly enhance the Friedel oscillations behind the charge, especially for velocities larger than a half of the Fermi velocity, in which case the asymptotic behavior of their amplitude changes from 1/r^3 to 1/r^2.5. In the absence of the quantum recoil (tunneling) the potential reduces to a form similar to that in a classical Maxwellian plasma, with a difference being that the plasma oscillations behind the charge at velocities larger than the Fermi velocity are not Landau-damped.Comment: 9 pages, 11 figures. v3: Fixed typo, updated abstrac