On the Effects of Spaced Versus Massed Practice on Deliberate Learning of English Idioms across L2 Proficiency Levels

This study investigated the effects of spaced versus massed practice on the deliberate learning of English opaque idioms across different second language (L2) proficiency levels. A total of 199 Iranian EFL learners at different proficiency levels were taught 40 opaque idioms under either spaced (distributed over 5 days) or massed (concentrated in two sessions) conditions. Learning outcomes were measured through immediate, short-delayed (12 days), and long-delayed (100 days) cued-form and meaning-recall posttests. Results showed that while massed practice led to better immediate recall for the low-proficiency learners, spaced practice resulted in superior long-term retention for mid- and high-proficiency learners. These findings underscore proficiency as a critical boundary condition of the spacing effect within a memory-scheduling framework, suggesting that while massed practice supports initial encoding for learners with limited L2 resources, spaced practice facilitates durable retention for those with established proficiency. The study findings extend spacing effect to multiword expressions and offer pedagogical insights into adaptive vocabulary instruction tailored to learner proficiency.