The potential influence of cross-linguistic lexical similarity on lexical diversity in L2 English writing

We examined the potential influence of L1-L2 lexical similarity on L2 lexical diversity, to determine whether the robust facilitative effect of lexical similarity that is found in processing and broad learning outcomes extends to this measure of L2 production. Our sample included two matching learner sub-corpora, containing 8,500 and 6,390 English texts, written in response to 95 and 71 writing tasks, by speakers of 9 typologically diverse L1s, in the A1–B2 CEFR range of L2 English proficiency. We found that lexical similarity did not influence L2 lexical diversity, at any proficiency level. This finding suggests that the facilitative effect of similarity does not necessarily extend to L2 production, at least in the case of certain global measures, like lexical diversity, and certain task-based settings, like the present educational one, where lexical choices are driven primarily by the constrained communicative needs of the tasks. This is supported by the strong task effects that we found, which we quantified using mixed-effects models, while also shedding light on the use of lexical diversity as an indicator of L2 proficiency.