This chapter revisits Tinbergen’s four types of explanation. Features of motivation include arousal and activation, flexibility, layers of control, the opponent-process theory, excitation transfer, and the sensitization of particular stimulus–response connections. Similarities between motivations are discussed; for example, the dopaminergic pathway from the VTA to the NAcc underlies each motivation and wanting versus liking. The chapter describes interactions and competition between different motivations. Inadequacies of drive are noted. Evolutionary mismatch also applies to contemporary fears. The topic of need is revisited in the context of examples of where it arises in various chapters (e.g. the need for heat). The opponent process theory of motivation is described in terms of imprinting and withdrawal from drugs. The distinction between regulation and control, introduced in the context of temperature regulation, is revisited. Liking/pleasure often correlates with positive reinforcement but not always. The motor act involved in behaviour has a reinforcement value.