Examining EFL learners’ comprehension of derivational forms: The role of overlap with base word knowledge, word frequency, and contextual support

This study examines the degree to which low and high proficiency English as a foreign language (EFL) learners’ knowledge of base words (e.g. develop) overlaps with knowledge of their derivational forms (e.g. developer, redevelop) when reading. Low and high proficiency learners’ comprehension of derivational forms is also explored in relation to the frequency of occurrence of derivational forms and whether the derivational forms are presented with or without semantic context. A battery of meaning-recall tests measuring knowledge of base words and their derivational forms of varying frequencies of occurrence (high, mid, and low) in semantically contextualized and non-contextualized conditions were administered to 150 Japanese EFL learners. Results showed that learner knowledge of base words was not strongly indicative of equivalent knowledge of those base word’s derivational forms (i.e. low knowledge overlap). The analysis of knowledge overlap (Jaccard’s Index) showed that when participants knew a base word, they were likely to know its derivational form on average a little over 50% of the time. Mixed-effects ANOVA indicated that derivational forms’ frequency of occurrence in a written corpus strongly moderated their meaning recall. Learners’ lexical knowledge, however, only provided a negligible effect. Further, for both low and high proficiency learners, test items containing semantic context did not enhance learners’ meaning recall of derivational forms when reading.