Syntactic complexity features of science research article introductions: Rhetorical-functional and disciplinary variation perspectives

An increasing body of genre analysis research within English for Academic Purposes (EAP) has attended to the relationship between linguistic features and their rhetorical functions in academic writing. Previous studies along this line have focused primarily on lexical or phraseological features and less on syntactic complexity features, with few exceptions. This study contributes to this body of research by investigating the rhetorical functions of syntactically complex sentences in science research article (RA) introductions, using a corpus containing the introduction sections of 300 published RAs in six science disciplines. The corpus samples were annotated for rhetorical move-steps using an adapted version of the Create a Research Space model (Swales, 2004) and analyzed using five indices tapping into different aspects of syntactic complexity. Results showed that the syntactic complexity indices varied significantly among the rhetorical move-steps but remained stable across hard-pure and hard-applied disciplines. Furthermore, science RA writers employed different types of syntactic complexity features more often for achieving different rhetorical functions. The implications of our findings for academic writing research and pedagogy are discussed.