Hong Kong Polytechnic University

Causality is integral to academic writing, and the use of causality markers can vary over time and across disciplines. While previous research has focused mainly on how linking adverbials connect causal clauses, few studies have explored verbs and nouns as causality markers. This study examines how the use of causality markers in research articles has evolved over 40 years and between two disciplinary divisions (hard vs. soft and applied vs. pure). Drawing on a corpus of 480 research articles collected from two periods (1981–1985 and 2016–2020) and four disciplines (physics, chemical engineering, sociology, and education), mixed three-way ANOVAs were conducted to examine diachronic and cross-disciplinary differences in the use of causality markers. The diachronic contrasts reveal an increasing use of linking adverbials to express causal explanations over time. Furthermore, in hard-discipline articles, result linking adverbials have been increasingly replaced by verbal expressions in signaling result relations. These diachronic patterns are interpreted in light of broader institutional and policy shifts toward research accountability and transparency, as well as the rise of interdisciplinarity in hard disciplines. The cross-disciplinary comparisons show a higher incidence of reason and result relations in the hard-discipline articles, reason relations in pure-discipline articles, and result relations in applied-discipline articles. These differences could be explained by the distinctive knowledge structures and epistemologies that define these disciplines. The findings underscore the need for current and discipline-specific pedagogical strategies for teaching the expression of scientific causality. • Articles published in 2016–2020 used more causality markers than those from 1981 to 1985. • Hard-discipline articles used causality markers more frequently than soft-discipline ones. • Pure-discipline articles used more reason expressions than applied-discipline ones. • Applied-discipline articles made more frequent use of result linking adverbials. • Diachronic trends in the linguistic realizations of causality varied across disciplines.