Spaced-Repetition Mobile Applications for Second-Language Vocabulary Acquisition: An Eight-Week Experimental Study with EFL Undergraduates

Abstract

Vocabulary size is among the strongest predictors of second-language proficiency, yet deliberate vocabulary study is poorly served by conventional classroom time and quickly abandoned wordlist self-study. Mobile-assisted language learning (MALL) applications promise to solve the practice problem through spaced-repetition scheduling and multimedia glossing, but experimental evidence with objective usage data and delayed testing remains limited. This study randomly assigned 96 B1-level EFL undergraduates to learn the same 240 target words over eight weeks either through a spaced-repetition mobile application with multimedia glosses (n = 48) or through structured paper wordlists with notebook practice (n = 48). Vocabulary knowledge was measured with a 50-item test at pre-test, post-test, and four-week delayed post-test; motivation was surveyed with an IMMS-based instrument; and app-group practice was logged automatically. Controlling for pre-test scores, the application group significantly outperformed the wordlist group at post-test (34.2 vs 28.9 of 50; d = 0.71) and retained the advantage at delayed testing (31.8 vs 25.7; d = 0.66), with absolute forgetting between post and delayed tests smaller in the app condition (−2.4 vs −3.2 points). Logged use averaged 11.4 minutes per day, and time-on-app predicted learning gains (r = 0.54), a dose–response relation consistent with the spacing mechanism. The application group also reported significantly higher attention and satisfaction. Results support spaced-repetition MALL as an effective, low-cost complement to classroom instruction for deliberate vocabulary learning, while analysis of usage decay across weeks cautions that engagement design, not initial adoption, is the binding constraint.