What causes déjà vu and why does it feel so strong?

You’ve had déjà vu when you feel like you've been somewhere or done something before, even though it's actually new to you.

Imagine you're eating your favorite snack, maybe chocolate cookies, and suddenly, you feel like you've already eaten these exact same cookies in the exact same spot. That’s déjà vu!

Your brain has two parts that help you remember things: one is fast, and the other is slower. The fast part thinks it knows what's happening, but the slow part hasn’t caught up yet.

It’s like when you’re playing a game with your friend, and you both say the same word at the same time, “I knew it!”, even though neither of you was sure who would say it first. Your brain gets confused, and that confusion feels like déjà vu.

Your brain thinks something special is happening because both parts are trying to remember the same thing at once. It’s a little bit like when your favorite toy breaks, you feel surprised and maybe even a little sad, but it's all because of how important that toy was to you. Your brain feels important things are going on, so déjà vu feels super strong!