This paper presents a summary of behavior concepts that together provide the outline of a possible developmental theory of prosocial motivation. These concepts, based on human role-taking capacities, include empathic distress, sympathetic distress, personal guilt, and existential guild. At first, a child cannot discriminate between himself and others in emphatic distress. Then he learns to discriminate and can feel sympathy for others through four developmental stages: (1) the child's assumption of the other's feelings are first based on the projection of his own feelings, even though his objective is to relieve the other's distress; (2) the child becomes aware that the other's perspective is different from his own, and guesses what his feedback should be, (3) the child synthesizes his empathic distress reaction to the other's feelings in a situation with a cognitive construction of the other's general misfortune, and (4) the child can comprehend the plight of entire groups of people. The concept of personal guilt is described as a synthesis of sympathetic distress and an awareness of being the cause of the other's distress. Existential guilt, which is the last concept, is described as coming from a realization that a person is enjoying what others cannot enjoy, or is not suffering what others suffer. Anecdotal examples of each prosocial behavior concept are given. (SET)