Intradisciplinary heterogeneity of academic writing: A diachronic probe into interactional metadiscourse in medical research articles

While disciplinary variation of academic writing has been extensively documented, intradisciplinary investigations which promise to uncover rhetorical complexity within a discipline are relatively limited, especially from a diachronic perspective. This study examines intradisciplinary variation regarding interactional metadiscourse in medical research articles over the past 60 years. Based on a self-built corpus of 1530 research articles from 18 subdisciplines of medicine, this study revealed divergences between subdisciplines and the overall medical discipline in the use of interactional metadiscourse. Intradisciplinary variations were found in both the distribution of interactional metadiscourse across the 18 subdisciplines and the changes of these resources across the subdisciplines. The variations may be attributed to the nature of evidence, research methods, development stages, and realistic environments of subdisciplines. These findings offer diachronic evidence of intradisciplinary heterogeneity in academic writing and contribute to our understanding of changing writing practices and rhetorical complexity within a discipline.