 Thus, reward is a mechanism that evolved to help increase the adaptive fitness of animals.In neuroscience, the reward system is a collection of brain structures and neural pathways that are responsible for reward-related cognition, including associative learning (primarily classical conditioning and operant reinforcement), incentive salience (i.e., motivation and "wanting", desire, or craving for a reward), and positively-valenced emotions, particularly emotions that involve pleasure (i.e., hedonic "liking").Terms that are commonly used to describe behavior related to the "wanting" or desire component of reward include appetitive behavior, approach behavior, preparatory behavior, instrumental behavior, anticipatory behavior, and seeking.