高齡學習是提升個人知能與生活品質的關鍵，亦是活化高齡人力、促進社會貢獻的重要教育途徑。在高齡化趨勢下，長青學苑等終身學習場域在促進學員社會參與與人力活化中愈顯關鍵。本研究以計畫行為理論為基礎，並整合生命歷程理論與社會情緒選擇理論，建構「分齡化計畫行為理論延伸模型」，探討課程參與意願對中高齡與高齡學習者其生產性投入意圖的直接與間接關聯。研究對象為113年度上半年個案長青學苑課程之學員，共回收有效問卷925份，包含214位中高齡與711位高齡學員。結果顯示，知覺行為控制是兩組學員在生產性投入意圖的共同主要因素。值得注意的是，課程參與意願對高齡學員的生產性投入意圖具有直接正向效果，而對於中高齡學員，其關聯則須透過態度、主觀規範與知覺行為控制等間接作用。本研究成果不僅深化計畫行為理論在高齡學習行為研究中的應用與解釋力，更具體突顯了課程參與意願在高齡學員持續社會貢獻及強化其生產性角色上的獨特且關鍵功能。

Senior adult learning is not only crucial for enhancing individual knowledge and quality of life but is also regarded as an important educational approach for revitalizing senior human resources and fostering their sustained contributions to society. Amid the accelerating trend of population aging, lifelong learning institutions such as Evergreen Academies play an increasingly vital role in promoting older adults’ social participation and human capital activation. This study examines how senior adults’ willingness to participate in courses influences their productive engagement intention through psychological mechanisms, including attitude, subjective norm, and perceived behavioral control. Grounded in the Theory of Planned Behavior (TPB) and integrating Life Course Theory with Socioemotional Selectivity Theory, this research develops an “Age-Differentiated Extended Theory of Planned Behavior Model” to examine the direct and indirect effects of course participation willingness on the productive engagement intentions of middle-aged and older learners. Data were collected from 925 valid questionnaires administered to learners at an Evergreen Academy in the first half of 2024, including 214 middle-aged and 711 older learners. The results show that perceived behavioral control is the primary common factor influencing productive engagement intention in both groups. Notably, course participation willingness exerts a direct positive effect on seniors’ productive engagement intention, whereas for middle-aged and older learners, the effect operates indirectly through attitude, subjective norm, and perceived behavioral control. These findings enhance the application and explanatory power of TPB in senior adult learning research and underscore the unique role of course participation willingness in sustaining seniors’ social contributions and reinforcing their productive roles.