How much receptive affix knowledge do L1 speakers and L2 learners have?

Abstract Although there is a growing interest in assessing how much L2 receptive affix knowledge learners have, research testing this knowledge using an extensive, standardized measure is relatively scarce. This study tested 21 L1 and 107 L2 learners of English to assess receptive knowledge of forms, meanings, and grammatical functions of 118 derivational affixes. Participants’ responses on the Word Part Levels Test were analyzed in mixed effects logistic regression models that examined the effects of affix difficulty, affix knowledge aspect, and vocabulary levels in predicting response accuracy. Results indicated that L1 and L2 affix knowledge differed depending on affix difficulty and knowledge aspect, L2 affix knowledge increased as a function of L2 vocabulary levels, and there was a clear difference between learners that had not mastered the first 1,000 frequency level and the rest of the learners. This suggests that developing the knowledge of the highest frequency vocabulary is critical to improve affix knowledge. The importance of using standardized measures of vocabulary in teaching and researching vocabulary knowledge is also discussed.