Humans benefit greatly from living in groups by exchanging goods and services, coordinating efforts to obtain food, sharing childcare duties, and so forth. As such, we rely and thrive on committed, cooperative relationships with others. Thus, when such relationships are damaged, it is of utmost importance to repair them and to thereby restore their benevolent, compassionate, and cooperative goals. Key to this repair is forgiveness. We know a great deal about forgiveness and its social functions in adults, but almost nothing about its development in childhood. This gap is astonishing considering it is in childhood that we form our first – and some of our most meaningful - relationships. This is the gap that the project aims to fill. Specifically, we draw from theories of human cooperation to pose questions about foundational forgiveness in childhood. We will study preschool-age children using well-controlled, age-appropriate experiments and simple, child-friendly measures of forgiveness to answer the following Big Questions: 1) When does forgiveness emerge? This Big Question has two (more concrete) sub-components: 1A) Does remorse elicit forgiveness in children? 1B) Do children more readily forgive their cooperation partners? The project also seeks to answer a second Big Question that is novel in the forgiveness literature: 2) Do we value forgiveness in others? That is, if forgiveness sustains cooperation, do we, even as young children, value forgiving more than unforgiving individuals? The deliverables of the project will be three empirical articles and one theoretical article. The project will offer fresh and much-needed insight into the development of forgiveness. Moreover, by establishing simple, child-friendly measures of forgiveness, it will open up the study of forgiveness to developmental researchers. Together, this project will significantly advance our understanding of the origins of forgiveness and thus of human sociality and cooperation.