pleasant and unpleasant feelings provoked by external stimuli arise from their ability to predict the alleviation of bodily imbalances. Stimuli that promote a return to homeostasis are routinely experienced as pleasurable
Panksepp defines hedonic valence as a direct function of homeostatic prediction, grounding pleasure and displeasure in the organism’s deviation from and return toward physiological equilibrium.
, Affective Neuroscience The Foundations of Human and Animal, 1998thesis