Yuka Akiyama, Sachiko Nakamura, Takumi Uchihara, Kazuya Saito
Abstract Despite growing interest in task engagement, few studies have examined how it contributes to L2 development. This longitudinal study examined how task engagement related to gains in L2 Japanese comprehensibility among nine UK‐based university students participating in a semester‐long, video‐mediated eTandem exchange with Japanese partners. Using 17 engagement indicators, we first provided a descriptive overview of associations between engagement and development. The strongest association was observed for Japanese partners' use of cultural questions . Guided by these results, we then employed interactional sociolinguistics concepts to understand how cultural questions facilitated comprehensibility development. The discourse analysis revealed that cultural questions shifted interactional frames and footings (Goffman, 1974, 1981), prompting L2 learners to take extended turns and practice making their speech comprehensible. The findings highlight the value of qualitative perspectives in task engagement research, showing that L2 comprehensibility development emerges not only from learners' own engagement but also through their partners' interactive behaviors.