Decades of research have demonstrated that normal aging is accompanied by cognitive change. Much of this change has been conceptualized as a decline in function. However, age-related changes are not universal, and decrements in older adult performance may be moderated by experience, genetics, and environmental factors. Cognitive aging research to date has also largely emphasized biological changes in the brain, with less evaluation of the range of external contributors to behavioral manifestations of age-related decrements in performance. This handbook provides a comprehensive overview of cutting-edge cognitive aging research through the lens of a life course perspective that takes into account both behavioral and neural changes. Focusing on the fundamental principles that characterize a life course approach - genetics, early life experiences, motivation, emotion, social contexts, and lifestyle interventions - this handbook is an essential resource for researchers in cognition, aging, and gerontology.