Think about catching a ball. Your brain does not wait to see where it lands. It predicts the path before the ball arrives and moves your hand to the spot.
It does this with everything, all the time. Sounds, faces, words, danger. It guesses first, then checks the guess against what actually comes in.
A fridge hums in the corner. Within a minute you cannot hear it. Your brain predicted the sound would continue, so it stopped reporting it to you.
Then the motor cuts off, and suddenly you notice the silence. Nothing arrived. The silence broke the prediction, and a broken prediction is the only mail the brain bothers to send upstairs.
The brain is about 2 percent of your body weight, yet it burns roughly 20 percent of your fuel. Thinking is expensive. Processing every sound and color fresh, every instant, would cost more than a body can pay.
So it does the cheap thing. It runs on predictions and pays real attention only when something surprises it. Surprise is the brain saying: my model was wrong, update it.
Read a text and you can hear the wrong tone in it, cold or angry, because your brain supplied a voice the sender never used. Walk down stairs, expect one more step that is not there, and your whole body lurches.
That guess was not built by this moment. It was built by everything that happened to you before now. Two people can stand in the same room and live in two different rooms.
The color of this page, the smell of the room, the feel of your feet on the floor. All of it is reconstructed inside your skull. None of it is the raw thing.
You are not experiencing the world. You are experiencing your brain's best guess about the world. The guess is usually good enough that you can go a whole life without noticing it is a guess.