Is Déjà Vu Connected to Your Dreams?

You walk into a place for the first time, yet you know you have been here. The person across from you says something you seem to have heard before. For a second you even feel oddly sure of what will happen next. Then the thought arrives: hang on, I dreamed this.

It resembles déjà vu, and moments like this make you wonder whether a dream really came before the event, or whether memory somehow persuaded you that it did.

Déjà rêvé, the sense that you already dreamed this

Déjà vu is French for "already seen", the feeling that a place or a conversation you are meeting for the first time is one you have been through before. It has a close relative with a name of its own, déjà rêvé, or "already dreamed". The person is sure they lived this exact minute, or one very like it, in a dream. The feeling can be strong enough that you seem to know what the next few seconds will bring, though it stays a feeling and carries no real knowledge of what is coming.

Ordinary déjà vu is common in healthy people, although certain forms of it also occur in temporal lobe epilepsy. Most people know the sense of "I dreamed this", and it comes more often to younger people than older ones, and more often to people who remember their dreams well than to those who rarely do.

How the brain mistakes the familiar for the lived

In a moment like that, you usually can't recall when you saw the place. Perhaps something really did bring back a forgotten dream, since dreams are built from the same material as your days and the sleeping brain replays the day. Or perhaps the familiarity came without any particular memory behind it, and the brain is trying to explain it after the fact. The strangest thing about the feeling is how strong the certainty can be even when you can't name a single event you are comparing the moment to.

Prophetic dreams and a memory that rewrites

Say you dreamed about a plane a week ago. The dream was odd, but by morning you had almost forgotten it. Then a plane crash comes up on the news, and suddenly the dream returns with alarming clarity.

Now it seems the dream was a warning. But what was it actually like? Was the plane at the heart of it, or did it just flash past in the background? Did you dream of a crash, or only of a flight? A week after waking, these questions are much harder to answer than they seem.

When we recall a dream after an event, we can change its details without meaning to and give them a new meaning. And the dream that matched comes to mind because something gave it a reason to, while hundreds that matched nothing stay forgotten.

So one dream ends up with two versions. The first is the one you recalled after the fact, once the match had already happened. The second was written down that morning, before anything occurred, and only that one is worth comparing with what took place.

To have something to compare against, write your dreams down as soon as you wake, while they are still intact, and when waking life hits you with "I dreamed this" again, open your notes and compare without bending anything to fit. If your dreams live in Alisie, searching past dreams finds the right night from a single word such as "plane" or "flight".

Déjà vu inside a dream

Dreams keep bringing you back to the school you left long ago, the house you grew up in, the streets of a city that does not exist yet somehow feels known. Now and then, in the middle of a dream, you step into a room or meet someone and are hit by sharp recognition, as if you know what is behind the next door.

For people learning to become aware that they are dreaming, that recognition can be a hint that something about the scene is off. Asking how you know this city when you have never been here becomes a reason to check whether you are dreaming. If that odd recognition keeps returning in your dreams, you can make it a personal marker and practise noticing it.

Check instead of guessing

Memory doesn't always keep a dream the way you remembered it that morning. If one day it seems that what is happening was already in a dream, go back to the entry and compare the details. You may find a resemblance you hadn't noticed before. Or you may realise that what felt familiar was the feeling itself rather than any particular dream.