Why do people experience déjà vu?

People experience déjà vu when their brain thinks it’s seeing something new, but actually remembers it from before, like when you think you're playing a brand-new game, but it feels just like one you’ve played before.

Imagine you're eating your favorite snack, maybe chocolate chips, and suddenly you feel like you've eaten this exact same snack exactly this way before. That's déjà vu! It happens because your brain gets confused between what it sees and what it remembers. Sometimes the memory comes in a little late, so your brain says, “Wait… I think I’ve seen this before!”

Think of your brain as having two teams: one that looks at things (the "seeing" team) and one that remembers (the "memory" team). When you see something new, the seeing team sends a message. But sometimes the memory team gets it first, before the seeing team finishes its job, so your brain thinks, “Oh! I’ve seen this already!” That’s why it feels like you've been somewhere or done something before, even though you haven’t.

It's like getting two clues at once in a mystery game, one says "new," and the other says "old." Your brain doesn't know which to trust, so it says, “Wait… I think I’ve seen this before!”