Breakthrough, Overload, or Stability: Evidence-Based Mixed-Methods Analysis of the Think-Aloud Protocol on L2 Japanese Writing

Developing Japanese writing ability as a second language (L2) requires learners to simultaneously manage linguistic, cognitive, and metacognitive resources. Although the Think Aloud Protocol (TAP) has been widely employed to access writers’ cognitive processes, its pedagogical impact on L2 Japanese writing remains underexplored. This study investigates the effects of TAP on the writing performance of Indonesian learners of Japanese at the A2–B1 proficiency levels, as defined by the Japan Foundation Standard (JF Standard), by examining both group-level performance changes and individual developmental trajectories. Using a convergent mixed-methods case study design, data were collected from 30 university students across three writing sessions (90 compositions): Pre-TAP, TAP-1, and TAP-2. Quantitative analysis revealed a gradual increase of 12.7% in mean scores from Pre-TAP to TAP-2. However, the overall difference across the three sessions did not reach statistical significance (Friedman χ2(2) = 5.447, p = 0.066). The mean improvement from Pre-TAP to TAP-2 was 1.37 points (95% CI [0.33, 2.43]), although the difference was not significant after Holm correction (adjusted p = 0.100). Nonetheless, individual-level analysis demonstrated divergent performance trajectories, including improvement, stability, and decline. These findings suggest that TAP functions differently across learners, serving as cognitive scaffolding for some, while imposing cognitive pressure and providing diagnostic value by revealing vulnerabilities in L2 writing skills for others.