The study of emotion has largely focused on negative affects, such as fear, inhibition, and rage, with relatively little attention paid to positive affects, such as affiliation and love. As a result, although various models of the development of negative emotion have been advanced in the literature, very little is known about the development of positive, approach-related behaviors. Moreover, an understanding of positive affect is of vital importance to further understanding disorders of engagement and cognition, such as autism. This book will be the first to bring together some of the leading thinkers on the development of positive affect, creating a new focus for affective neuroscience. The contributors will present their research on the development of positive affect in child, nonhuman, and clinical population.