The Case for Subject-Verb Dependency Distance as a Measure of Complexity and Readability

Complexity is a core concept in academic language, central to the development of both writing proficiency and readability. The measurement of complexity and readability is evolving, with large-grained measures like sentence length being supplemented with more fine-grained measures. Complexity in academic texts has increased, particularly with the use of noun phrases with complex postmodification. However, postmodification of noun phrases is a locus of complexity that has been overlooked. 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 paper argues for incorporating subject-verb dependency distance in measures of complexity and readability in academic writing. The study analysed subject-verb dependency distance in a 110,633-word corpus of published scientific writing from generalist and specialist journals, comparing journal types and highlighting how noun phrase postmodification influences this measure of complexity. This paper also discusses pedagogical implications and presents sentence transformations to illustrate how writing instructors can raise awareness of subject-verb dependency distance in the context of phrasal complexity.