Rethinking reinforcement learning: The interoceptive origin of reward

Rewards play a crucial role in sculpting all motivated behavior. Traditionally, research on reinforcement learning has centered on how rewards guide learning and decision-making. Here, we examine the origins of rewards themselves. Specifically, it is now well-recognized that the critical reinforcing signal for food is generated internally and subliminally during the process of digestion. As such, a shift in our understanding of rewards as an immediate sensory gratification to a state-dependent evaluation of an action's impact on vital physiological processes is called for. We integrate this perspective into a revised reinforcement learning framework that recognizes the subliminal nature of biological rewards and their dependency on internal states and goals.