Enhancing Iranian EFL Learners’ Vocabulary Depth and Breadth by Integrating of Extensive Reading and Writing: A Mixed Methods Study

Although vocabulary instruction has received considerable attention in EFL contexts, limited research has examined how combining receptive and productive modes of language learning may affect different dimensions of vocabulary development. Understanding how instructional modes influence these dimensions is crucial for effective teaching. The aim of this explanatory mixed-methods study was to examine the effect of integrating extensive reading and writing on the development of vocabulary depth and breadth. To this end, three groups of Iranian elementary EFL learners, selected through convenience sampling, practiced three different modes of instruction: extensive reading only (RO), writing only (WO), and extensive reading plus writing (RW). The data were collected through the word associates test (WAT), vocabulary levels test (VLT), and semi-structured interviews to capture both quantitative performance and qualitative experiences. Results indicated that both the RO and RW groups outperformed the WO group in vocabulary depth and breadth, with the RW instruction proving most effective. Furthermore, linear regression analyses revealed substantial shared variance between WAT and VLT scores across all groups. This highlights a strong relationship between vocabulary depth and breadth. Additionally, thematic analysis of the semi-structured interviews identified three key themes: enhanced vocabulary knowledge, increased engagement in language use, and the development of self-regulated learning. These results suggest that vocabulary depth and breadth are two interconnected aspects of vocabulary knowledge that mutually support one another. This study has important implications for syllabus designers, teachers, and learners in EFL settings.