This experimentally-oriented book provides a critical examination of research and theory with a topical approach. It covers a broad range of motivational concepts from both human and animal theory and research, with an emphasis on the biological bases of motivation. Chapter topics include the nature of motivation theory; species-specific behaviors; eating and taste; thirst, temperature regulation, addiction, and reproduction; drive and activation; rewards as both reinforcers and incentives; escape, fear, avoidance, and punishment; frustration, anxiety, stress, and coping; aggression and altruism; personality and individual differences; attitudes and cognitive consistency; interpersonal attraction; and applications of motivation theory. For individuals interested in the motivation of humans and animals.