Why do humans experience déjà vu, and what causes the sensation?

Humans experience déjà vu when their brain thinks it has seen something before, even though it hasn’t.

Imagine you’re playing with your favorite toy car, and suddenly it feels like you’ve driven this exact path before, but you haven’t. That’s déjà vu, like a little memory trick in your brain!

Your brain has two parts that help you remember things: one is fast and quick, like a sprinter; the other is slower, like a runner who takes time to think.

When you see something new, the fast part of your brain might say, “I know this!” before the slow part catches up. That’s why it feels like you’ve already seen that thing, even though you haven’t!

Sometimes, your brain gets confused when you're tired or busy. Like when you’re walking to school and suddenly feel like you've been there before. It’s just the brain playing a little trick on you, like when you mix up your socks in the morning!