Does spaced repetition increase retention of phrasal verbs in adult L2 learners?

Abstract

This quasi-experimental study investigates whether spaced repetition and chunk-based instruction enhance adult EFL learners’ sensitivity to the syntactic constraints governing inseparable phrasal verbs. A total of 83 English undergraduate students at B1 proficiency level were recruited from universities in Brazil and Colombia for the study. The experimental group received a six-week intervention with flashcard activities and Kahoot-based spaced repetition of separable and inseparable phrasal verbs. The control group did not participate in the intervention and followed the standard English curriculum. Participants’ performance was assessed using an offline acceptability judgment task (AJT) before the intervention and online reading-time measures administered via PsychoPy after the intervention. However, the two groups were not equivalent at baseline, with the control group demonstrating moderate effect size for pre-test AJT accuracy (Cohen’s d = 0.73). A mixed-effects logistic regression incorporating pre-test accuracy as a covariate found no significant Group effect at post-test (p = .216), indicating that the apparent post-test advantage of the control group was largely attributable to pre-existing ability differences rather than the instructional intervention. The only robust fixed effect was Condition: the ungrammatical word order (INSEPvop) was significantly harder to evaluate correctly than the grammatical order (INSEPvpo) for all participants regardless of group. These findings highlight the importance of baseline equivalence and covariate-adjusted analyses in quasi-experimental SLA research, and identify methodological factors—including task-format differences between assessments and participant attrition—that should be addressed in future investigations of chunk-based instruction for phrasal verb acquisition in adult EFL learners.