Proceedings of the Annual Meeting of the Cognitive Science Society

Lexical diversity, the proportion of unique lemmas in a text, is known to vary across first language and second language production. It has been used by researchers as a proxy for language proficiency, particularly for classroom language learners. Lexical diversity has been found to vary by language background, potentially at least partly due to cross-linguistic influence. We investigated whether or how lexical diversity differs across groups with varied language backgrounds, namely monolinguals, bilinguals, adult language learners, and post-attrition speakers. We expected that these groups would show differing mean lexical diversity scores due to their different backgrounds with varying combinations of languages and levels of proficiency. Data from 114 participants were stratified and showed substantial between-group overlap in their lexical diversity scores. However, some significant by-group differences in lexical diversity were found. We discuss the implications of these results.