Longitudinal Development of German Discourse Coherence Among Nigerian PhD Students: A Case Study Approach

This study investigates the longitudinal development of discourse coherence in written German academic texts produced by Nigerian doctoral students, tracking changes in cohesive device use, thematic progression, and rhetorical organisation over a three-year period of doctoral study. Discourse coherence, the capacity to create semantically and rhetorically unified texts through the strategic deployment of cohesive resources, represents a key marker of advanced academic literacy in German that has received limited attention in African doctoral research training contexts. The study adopts an embedded multiple case study design, following eight Nigerian PhD students enrolled in German-medium or German-language-intensive doctoral programmes at the University of Göttingen and the Humboldt University of Berlin. Participants were recruited from Nigeria's South West, North Central, and South East zones and represent diverse disciplinary backgrounds. Written texts including research proposals, chapter drafts, and journal manuscripts are collected at six-monthly intervals and analysed using a validated German academic discourse coherence framework. Individual developmental trajectories are mapped and compared. Findings reveal substantial variation in coherence development trajectories, with disciplinary socialisation, supervisory feedback quality, and social integration in German academic networks as the most influential factors. The study contributes to doctoral academic literacy theory and to the design of pre-doctoral German language writing preparation programmes. Keywords: discourse coherence, German academic writing, doctoral students, Nigeria, longitudinal development.