Gratitude, like other positive emotions, has inspired many theological and philosophical writings, but it has inspired very little vigorous, empirical research. In an effort to remedy this oversight, this volume brings together prominent scientists from various disciplines to examine what has become known as the most-neglected emotion. The volume begins with the historical, philosophical, and theoretical foundations of gratitude, then presents the current research perspectives from social, personality, and developmental psychology, as well as from primatology, anthropology, and biology. The volume also includes a comprehensive, annotated bibliography of research on gratitude. This work contributes a great deal to the growing positive psychology initiative and to the scientific investigation of positive human emotions. It will be an invaluable resource for researchers and students in social, personality, and developmental, clinical, and health psychology, as well as to sociologists and cultural anthropologists.