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.