Whatever else it is, hunger is a motivated state of mind. Psychologists have been studying such states for at least a century. We all feel hungry before dinner and full after a banquet, but those moments are the tip of the iceberg. Hunger is a process that’s always present, always running in the background, only occasionally rising into consciousness. It’s more like a mood. When it slowly rises or eases back down, even when it’s beneath consciousness, it alters our decisions. It warps our priorities and our emotional investment in long-term goals. It even changes our sensory perceptions – often quite profoundly.