Minding the complexity gap? A corpus-based analysis of subject-verb

Scientific English writing proficiency is vital for Chinese biomedical PhD candidates. In scientific writing, complexity is central to writing proficiency development and readability, with its measurement including both large-grained and fine-grained metrics. Scientific texts have grown more complex, especially in specialist journals, partly due to the increased use of noun phrases with elaborate postmodification. However, postmodification of noun phrases is a locus of complexity and readability that has been overlooked in scientific writing. In noun phrases where the head is the subject of a verb, postmodification will necessarily intervene between that subject and verb. Longer distances between syntactically dependent words increase complexity and reading difficulty. This study hypothesises that generalist journal texts are less complex than specialist journal texts in respect to subject-verb dependency distance. To inform the study, a 190,000-word corpus of generalist and specialist scientific writing was collected from published research articles in 1960 and 2020. A coding system was used to measure both the length and complexity of material intervening between subjects and verbs. Results generally support the above hypothesis and show that subject-verb complexity has generally declined over time. The data also confirm the central role of NP prepositional postmodification in subject-verb dependency distance and demonstrate a proliferation in the use of these structures. The implications of the study’s findings are discussed with reference to theory and pedagogy, including writing development frameworks which posit that the use of complex noun phrase postmodification marks advanced levels of proficiency. It is argued that this study supports the inclusion of subject-verb dependency distance in the suite of fine-grained measures of complexity and readability.