Dimensions of L2 Oral Language Performance: A Study of Complexity, Accuracy, and Fluency Development Over Time

Miho Tomita,

Graduate School of Languages and Linguistics, Sophia University, Japan


This study examined the developmental patterns of second language (L2) oral language performance as measured by complexity, accuracy, and fluency (CAF) and the relationship between these three variables over time. A total of 31 Japanese-L1 university students, grouped into two proficiency levels (lower and intermediate), participated in a semester-long task-based speaking course. Speaking tests involving impromptu speech tasks were administered four times over the 15-week semester, and learners’ oral data were analyzed to measure CAF. The results indicated that syntactic complexity had mild growth over time, with some fluctuations. Lexical complexity showed a mild U-shaped curve with slight changes in growth. Accuracy showed U-shaped trajectories, showing a decline followed by a steeper increase over time, and fluency exhibited steady growth over time. Regarding correlations between CAF, trade-off effects were evident between lexical complexity and syntactic complexity and between lexical complexity and accuracy. We observed a positive correlation between accuracy and syntactic complexity and between fluency and syntactic complexity. Regarding the relation between fluency and accuracy, the results were mixed, and there was an observed trend towards significance between fluency and lexical complexity. The findings also indicated that lower- and intermediate-proficiency learners had similar change trajectories except for one syntactic complexity measure.

Keywords: CAF, Complexity, Accuracy, Fluency, Speaking


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