This study examined the effect of app-based grammar instruction on the development of second language (L2) grammar knowledge and compared its effectiveness to traditional form-focused instruction in a classroom environment. Additionally, the study investigated how learners’ intrinsic motivation, extrinsic motivation, and enjoyment were associated with L2 grammar development over time. A total of 217 Korean middle school students participated and were assigned to either an experimental group (app-based instruction) or a control group (traditional instruction).
Over a six-week instructional period, both groups received lessons on the same target grammar structure as part of the regular curriculum. Grammar achievement was measured through a pre-test, an immediate post-test, and a delayed post-test, while affective variables were assessed using survey instruments. Data were analyzed using linear mixed-effects modeling to accommodate repeated measures and individual variability. The findings revealed no statistically significant main effect of instructional method; however, a significant effect of time was noted, with learners in both groups showing sustained improvement in grammar performance. Among the affective variables, enjoyment was positively associated with grammar development, followed by extrinsic motivation, whereas intrinsic motivation exhibited a positive but non-significant association.