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Introduction
There are two fundamental types of behavior: appetitive (preparatory) behavior, which is acquired by reinforcement learning, and instinctive behavior patterns, which are largely innate (Lorenz and Tinbergen, 1938; Lorenz, 1952). Appetitive behavior consists of orienting and locomotor actions; an orienting response to a complex cue is the simplest form of appetitive behavior. The purpose of appetitive behavior is to bring the animal into contact with a simple stimulus constellation that can release an innate, instinctive motor pattern, such as consummatory behavior (Lorenz and Tinbergen, 1938; Lorenz, 1952). Exposure to a releasing stimulus constellation or the release of an instinctive behavior pattern can act as a reward (or punisher) that reinforces (or weakens) appetitive behavior (reinforcement learning). From this perspective, we can distinguish between two types of appetitive behavior. First, exploratory or emotional (non-goal-directed) behavior is used when rewards (or punishers) are unpredictable (in uncertain situations); it consists of more or less random locomotor and orienting actions. Secondly, instrumental or voluntary (goal-directed) behavior is used when rewards (or punishers) are highly predictable (in certain situations). Either type of appetitive behavior comes to a close when the animal is in contact with a stimulus constellation that releases an instinctive behavior pattern (feeding, grooming, mating, etc.). Either type of appetitive behavior mode 'drives' the animal towards a particular physiologically significant outcome. While emotional appetitive behavior is accompanied by emotional arousal and a conscious emotional feeling of a certain kind, instrumental or goal-directed or voluntary behavior (in the sense of affectively neutral behavior) can be accompanied by a conscious experience of expectancy, volition, or intention.
We know that discrete (Pavlovian) stimuli can induce a general-purpose (emotional) mode of appetitive behavior (such as in the form of incentive arousal). The same can be said about complex contextual stimuli. The type of location or situation that an animal occupies is a contextual stimulus to which, as a result of reinforcement learning, affective or incentive value can be attributed. Animals learn where and when, that is, in which location or situation, to generate which behavior in order to maximize the probability of reward exposure and ensure the absence of punishment. In uncertain or less familiar locations, the animal may employ a general-purpose behavior mode (emotional behavior mode or incentive motivational state)...