How many L2 word meanings can learners recall? A latent trait approach to vocabulary size estimation

This study investigated the size of meaning-recall vocabulary knowledge and its variations across word-frequency and second language (L2) proficiency levels. Despite the extensive research history in determining lexical coverage and thresholds for effective L2 use, much of the evidence is based on measures of meaning-recognition vocabulary knowledge. Using a latent-trait approach, we calculated the probability that learners could recall the meaning of each word in a vocabulary size test. Differences in vocabulary size between recognition and recall formats were analyzed across word-frequency bands and L2 proficiency levels. Results indicate that most learners struggle to recall the meanings of word families beyond the second-most frequent band. Moreover, the gap between meaning-recall and meaning-recognition vocabulary sizes was substantial and expanded as word-frequency and L2 proficiency levels decreased. These findings contribute to defining realistic L2 vocabulary teaching goals and selecting appropriate teaching methods. Construct-irrelevant measurements lead to a misunderstanding of L2 lexical proficiency, emphasizing the importance of test format selection according to the developmental stages of learners’ vocabulary knowledge.