Exploring the Nexus Between Psychological Capital, Perceived Organisational Support, and Sustainable Employee Performance in Nigerian Federal Civil Service

This doctoral study examines the nexus between psychological capital (PsyCap), perceived organisational support (POS), and sustainable employee performance in the Nigerian Federal Civil Service, contributing original theoretical and empirical insights to positive organizational behaviour literature in a public sector context. Conventional performance improvement strategies in the Nigerian public sector have focused on structural and motivational interventions, largely neglecting the psychological capital resources of individual civil servants as performance determinants. Grounded in Luthans' Psychological Capital Theory, Conservation of Resources Theory, and the Sustainable HRM Framework, this study employs a two-wave longitudinal quantitative design with 420 civil servants across five federal ministries in Abuja, Kano, and Lagos over a 12-month period. Latent growth curve modelling and cross-lagged panel analysis are applied to establish temporal causal ordering. The study makes three original contributions. First, it provides the first longitudinal test of the PsyCap-performance relationship in a Nigerian public sector context, departing from cross-sectional designs that dominate the existing African PsyCap literature. Second, it introduces sustainable performance, defined as performance that is maintained without depleting employee well-being, as the dependent variable, extending PsyCap scholarship beyond traditional output measures. Third, it tests a POS-as-moderator model, finding that high POS environments amplify PsyCap's longitudinal effect on sustainable performance. Recommendations include PsyCap development programs integrated into civil service training curricula, POS-enhancing supervisory management training, and incorporation of sustainable performance metrics in the IPPIS appraisal module. Keywords: psychological capital, perceived organisational support, sustainable performance, federal civil service, longitudinal study