Task Modality and Vocabulary Development in Content-Based EFL Tasks: A Mixed-Methods Study of Oral and Written Performance

Abstract

This mixed-methods study investigates the impact of task modality, oral versus written, on vocabulary performance in content-based, task-driven activities among intermediate EFL learners. Forty participants completed two problem-solving tasks, describing a science experiment and analyzing an environmental scenario, in both oral and written forms. The study addressed four research questions examining lexical richness, lexical accuracy, lexical appropriateness, and the vocabulary-related strategies learners employ when performing oral and written versions of the same tasks. Vocabulary output was analyzed using quantitative measures of lexical performance alongside qualitative analysis of learners’ modality-specific strategies. Results indicate that written tasks elicited significantly higher lexical richness and more precise, contextually appropriate vocabulary, whereas oral tasks favored fluency and greater reliance on high-frequency, familiar items. Qualitative findings further reveal that learners tended to use repetition and retrieval-based strategies during oral production but engaged in lexical experimentation and strategic refinement in writing. Interpreted through cognitive SLA and task-based learning frameworks, these findings highlight the role of cognitive load and attentional allocation in shaping modality-dependent vocabulary use. The study provides empirical support for integrating both oral and written content-based tasks in EFL instruction and offers practical implications for designing task-based assessments that promote vocabulary development.