Why do we check the fridge again when we already know what's in it?
The Real Answer
There is no established brain rule that stores what was in the fridge but forgets when you last checked it. Reopening the fridge is better understood as a mix of ordinary motives such as habit, hunger, boredom, uncertainty, and the very low cost of checking again. The door takes seconds to open, so even a small hope that you overlooked something can be enough to trigger another look without requiring a special memory mechanism.
You open the fridge, stare at the same three containers for five seconds, close it, then open it again like something new appeared while the door was shut. You've isolated the one appliance in your house that rewards disappointment with repetition.
The Dunce Dynamics Institute Examines Why People Ask This
The behavior is funny because you often know the inventory before you open the door. The question appears when you catch yourself checking again anyway and realize that a tiny possibility of a better option was enough to make you look.