Vocabulary Knowledge as a Predictor of Performance in Writing and Speaking: A Case of Turkish EFL Learners

This paper reports on empirical research that endeavors to investigate the role of vocabulary knowledge in the writing and speaking performance of 54 B2 level Turkish learners of English as a foreign language (EFL). The measured aspects of vocabulary knowledge (productive vocabulary size, receptive vocabulary size, and depth of vocabulary knowledge) were all found to correlate significantly with performance in writing and speaking (measured through the writing and speaking components of a proficiency test). Multiple regression analyses showed that vocabulary knowledge accounts for 26% of variance in writing performance and 17% of variance in speaking performance. Therefore, the study offers evidence that vocabulary knowledge is a significant predictor of performance in productive language skills. Suggestions for further research and pedagogical implications are given based on the findings of the research.