Measuring L1 and L2 Productive Derivational Knowledge: How Many Derivatives Can L1 and L2 Learners with Differing Vocabulary Levels Produce?

Derivational knowledge, the ability to understand and produce derivatives of a word, is essential for vocabulary learners to expand their lexical knowledge. Earlier research (e.g., Schmitt & Zimmerman, 2002) has shown that L2 learners may have limited ability to produce derivatives compared to L1 speakers. However, the degree to which productive derivational knowledge differs between L1 and L2 learners, and among learners at different levels of vocabulary knowledge has yet to be examined. The present study investigated the extent to which L1 English speakers (n = 23) and L2 English learners (n = 107) at varying vocabulary levels (1000-5000) could produce the derivatives of 90 headwords in a decontextualized derivative recall test. A generalized linear mixed model indicated that L1 and L2 productive derivational knowledge significantly differed, and L2 productive derivational knowledge differed among learners with different vocabulary levels. However, the results revealed that the L1 speakers and the learners who had mastered the higher vocabulary levels (3000-5000) produced a similar number of derivatives in the decontextualized recall test. The findings suggest that learners' vocabulary levels could be indicative of L2 productive derivational knowledge to some degree. Lastly, the results are discussed to provide pedagogical implications for teaching and assessing L2 productive derivational knowledge.