The brain doesn’t just keep tabs on how much sugar enters the mouth or how much sugar winds up in the stomach. It even keeps track of what happens to that sugar. In another mind-bending experiment—he has a reputation for them—Araujo gave mice a drug that blocked sugar from being turned into energy. The mice tasted the sugar and it was sensed in the stomach, but if it couldn’t be used as fuel, sugar it lost its magnetic pull. What the brain ultimately cares about isn’t how food tastes. It cares whether food is useful.
