Comparing Written and Spoken Complexity, Accuracy, and Fluency Among Advanced Korean Learners

ABSTRACT

This study examined how modality shapes complexity, accuracy, and fluency (CAF) among advanced second language (L2) Korean learners under parallel narrative tasks. A total of 102 learners completed matched written and spoken tasks with fixed time limits and no pre-task planning. To enhance comparability, we aligned the segmentation units (Terminable units for writing and Analysis of Speech units for speech) and applied clause- and unit-level metrics alongside syllables-per-second fluency. The results indicate robust modality effects under these conditions: Writing exhibited greater unit-level complexity (higher clauses per unit and subordinated clauses per unit), whereas speech exhibited greater clause-level complexity and faster rates (syllables per second). Further, writing demonstrated lower unit-level accuracy. Proficiency correlated with overall CAF; however, macro-level gains plateaued at advanced levels; development was most evident in micro-level fluency control (e.g., strategic pausing and reduced repetitions). Modality–proficiency interactions were limited, except for a minimal additional decline in written clause-based accuracy among lower-proficiency learners. These findings suggest that modality reliably shapes L2 production under time-constrained narratives and underscore the value of typology-aware clause–unit disaggregation when comparing modalities. In terms of pedagogy, the results highlight modality-sensitive instruction that prioritizes fine-grained operational control over further increases in global length or speed.