Motivated to exhaustion? Public service motivation, curvilinear strain, and the buffer of collaborative culture

Public service motivation (PSM) is widely treated as a resource that strengthens engagement, yet excessive motivation may yield diminishing returns. Integrating the job demands-resources model, conservation of resources theory, and the too-much-of-a-good-thing logic, this study tests a curvilinear relationship between PSM and job exhaustion, and the moderating role of collaborative culture. Using a two-wave survey of 408 Korean public servants with a one-month lag, hierarchical regressions identify a U-shaped pattern: exhaustion declines at low-to-moderate PSM but rises beyond a threshold. Collaborative culture significantly flattens this curve, indicating that supportive, collective norms mitigate PSM-related strain at very high levels of PSM. The findings challenge the assumption that PSM is uniformly beneficial, recasting PSM as a conditional resource that can operate as a demand at high levels. The study clarifies when PSM is sustainable and positions collaboration as an actionable boundary condition, yielding implications for motivation theory and for the collaborative organization of public service.