Public service motivation may be understood as an individual's predisposition to respond to motives grounded primarily or uniquely in public institutions and organizations. The term "motives" is used here to mean psycho- logical deficiencies or needs that an individual feels some compulsion to eliminate. Following Knoke and Wright Isak, this discussion recognizes that these motives may fall into three analytically distinct categories: rational, norm- based, and affective. Rational motives involve actions grounded in individual utility maximization. Norm-based motives refer to actions generated by efforts to conform to norms. Affective motives refer to triggers of behavior that are grounded in emotional responses to various social con- texts