LexJP: A test to efficiently assess vocabulary knowledge of Japanese

With a pressing need for consistent, efficient measures of language proficiency across studies on second language learners and bilingual speakers (Park et al., 2022), vocabulary tests in languages like French, Spanish, Chinese, Dutch, and Portuguese have been developed and utilized as objective measures of general language proficiency (Lee et al., 2023). However, there remains a gap in effective tools for assessing Japanese proficiency. To address this, our study introduces a Lexical Test for Japanese Speakers (LexJP), a quick test offering researchers an easy method for evaluating lexical proficiency in Japanese. This study has two parts: Study 1, with 25 native Japanese speakers and 60 Japanese learners, selected items for the final version of the LexJP. Study 2 validated the LexJP with 77 Japanese learners by comparing their LexJP scores to language proficiency levels based on the Japanese-Language Proficiency Test scores, demonstrating LexJP as an efficient and reliable tool for measuring Japanese proficiency.