Lexical complexity in academic lectures: Comparative analysis of EMI and Non-EMI settings and influential factors

Despite the substantial body of research on vocabulary in English Medium Instruction (EMI), there is a noticeable dearth of corpus-based studies examining lexical complexity of EMI lectures, particularly in specific disciplines. To fill this gap, this study developed an EMI spoken academic corpus in Business (EMIB) with 120 lectures collected from 54 lecturers with nine different first languages (L1), reaching 1.12 million tokens. The study compared the lexical complexity of EMI Business lectures in China with academic lectures in Anglophone and non-Anglophone settings, represented by teachers’ speech in the British Academic Spoken English Corpus (BASE) and the Corpus of English as a Lingua Franca in Academic Settings (ELFA), respectively. Lexical complexity was conceptualised by lexical sophistication (operationalised by lexical frequency profile and mean frequency band score) and lexical diversity (operationalised by the VOCD-D). Results show that ELFA has significantly higher lexical sophistication than BASE, and significantly lower lexical diversity than BASE and EMIB. This study further explored whether speaker L1, speaker gender, and discipline contributed to the lexical complexity of lectures using multiple linear regression with interaction terms. Results show that speaker L1 and discipline significantly impacted the lexical complexity of lectures. Pedagogical implications are discussed.