Researchers have agreed that motivation is an important factor in learning, but its influences are more nuanced than indicated by the current literature. In this talk, I will present a summary of my research program examining the roles of motivation in learning, highlighting their complicated nature. The topics include (but not limited to) 1) the effects of extrinsic incentives on motivation, 2) motivation and long-term learning consolidation, and 3) effects of competitive motivation on task performance. I underscore the importance of using multiple methodologies (e.g., behavioral experiments, longitudinal surveys, neuroimaging, meta-analysis, etc.) to provide a fine-grained and clear picture on these topics.