An emerging number of empirical studies have found vocabulary size is closely related to L2 learner’s general speaking ability. However, few studies are conducted to investigate the extent to which vocabulary size can explain L2 learners’ speaking ability in academic/formal contexts. This study, therefore, is aiming to examine the relationship between L2 learners’ receptive vocabulary size (general and academic) and their academic speaking ability reflected from lexical proficiency and fluency of the spoken discourse. Forty-two intermediate L2 learners’ spontaneous speech were collected via a monologue-type task in a formal class setting. X_Lex was used to measure general vocabulary size and AVST to measure academic vocabulary size. The results revealed: firstly, the academic vocabulary size can predict 20% (r = .450) of the speech length and 15% to 19% of the lexical proficiency in academic speech production; secondly, academic vocabulary size heavily loaded with K2 and K3 words works better in predicting L2 learners’ academic speaking ability than general vocabulary size resembling words from general corpora; finally, no meaningful association is found between vocabulary size and influence L2 learners’ speaking speed, but knowing more academic words help learners to produce longer spontaneous speech.
Yixin Wang-Taylor, Nankai University, China