Why Do We Get Déjà Vu?

You walk into a room you’ve never been in before. You are certain you’ve been here before.

Not a general feeling of familiarity — specific familiarity. The window is in the right wall, isn’t it? You knew it would be there. You can almost see what’s around the corner.

Then someone moves and breaks the moment. The certainty disappears. You’re left with that hollow, slightly embarrassing feeling: What just happened?

That’s déjà vu. From the French: “already seen.” About 70% of people experience it, most frequently between the ages of 15 and 25. And despite being one of the most reported neurological experiences on earth, scientists still genuinely disagree about where it comes from.

The Brain’s Two Memory Systems

Your brain doesn’t run one memory system — it runs several. Two of the most important are familiarity and recollection.

Familiarity is fast. It’s the quick “I’ve seen this before” signal that fires before your slower, deliberate memory can retrieve the specifics. Recollection is slower — it’s the system that pulls up context, time, place, details.

Usually these two fire in sync. You recognize a face, and the context arrives right alongside the recognition.

But what if familiarity fires first, before recollection can keep up?

You feel: I know this place. Then recollection scrambles to find the record and comes up empty: I have no memory of this place.

That mismatch — the certainty without the content — might be what we call déjà vu.

The Glitch Hypothesis

One popular theory: déjà vu is a processing error. Your brain’s memory storage and retrieval systems occasionally misfire, briefly stamping a new experience with the “previously stored” tag before the system realizes it hasn’t actually stored it yet.

Think of it like a filing error. Your brain accidentally files the present moment in the “past” folder a half-second too early, then corrects itself. The correction is what you notice — that uncanny recognition dissolving into confusion.

This would explain why déjà vu is common in young people (neural systems still calibrating) and why it spikes in people with temporal lobe epilepsy — the part of the brain most involved in memory processing.

The Divided Attention Theory

Another theory: déjà vu happens when your attention briefly splits.

You walk into a room. For a fraction of a second, part of your brain processes the space while you’re momentarily distracted. That subconscious first-look gets filed. Then, when you consciously attend to the room a moment later, your brain retrieves what it filed half a second ago and calls it memory.

The room seems familiar because, technically, it is. You saw it a half-second ago. Your brain just can’t tell the difference in time.

This would explain why déjà vu tends to happen when you’re tired, distracted, or dissociated — states where your attention is prone to brief splits.

The Simulation Hypothesis (the one people overthink)

Some people feel déjà vu and immediately think: past life, precognition, parallel universe. Pop culture loves this framing.

The honest answer: there’s no evidence for any of it.

That doesn’t mean the experience isn’t real. It very much is. But the feeling of mystical significance is almost certainly part of the experience, not evidence of something beyond it. Your brain, briefly misfiring, throws the “this matters” signal alongside the “this is familiar” signal. That’s why déjà vu feels important. The importance is a byproduct of the glitch.

Why It Matters

Déjà vu is interesting not because it might be supernatural, but because of what it reveals about ordinary consciousness.

Your sense of “now” is constructed — assembled from overlapping processes, some fast, some slow, some running slightly out of sync. Most of the time they converge cleanly and you experience smooth, continuous reality. Occasionally they don’t, and you get a seam.

Déjà vu is that seam. It’s your brain showing its work.

The “you” that experiences continuity is itself a construction — assembled moment to moment from overlapping systems that usually agree on what’s happening.

When they disagree, just for a second, you feel it.