The standard reinforcement learning view of the involvement of neuromodulatory systems in instrumental conditioning in(cid:173) cludes a rather straightforward conception of motivation as prediction of sum future reward. Competition between actions is based on the motivating characteristics of their consequent states in this sense. Substantial, careful, experiments reviewed in Dickinson & Balleine, 12,13 into the neurobiology and psychol(cid:173) ogy of motivation shows that this view is incomplete. In many cases, animals are faced with the choice not between many dif(cid:173) ferent actions at a given state, but rather whether a single re(cid:173) sponse is worth executing at all. Evidence suggests that the motivational process underlying this choice has different psy(cid:173) chological and neural properties from that underlying action choice. We describe and model these motivational systems, and consider the way they interact.