We have all had that eerie feeling when we experience a situation and we know we've been there before. We have no idea how but there's this strong feeling of familiarity. So what exactly goes on when we feel deja vu?
Deja vu is french for 'already seen'.
It's a feeling when you see or experience something for the first time and you feel like you've seen or experienced it before.
Often, people are tempted to relate this to some exotic, fantasy rich experience like past life or unravelling of some prophesy.
If you're a matrix (movie) fan and believe that you and everything you see is a computer simulation, you may have strong feelings about deja vu being a glitch in the matrix.
While the simulation bit sounds very fascinating, we might be arriving to a conclusion that deja vu isn't quite a glitch in the matrix.
In reality, deja vu is everything to do with our brain.
Sorry Matrix fans and fantasy lovers!
So what causes deja vu?
Well, scientists haven't quite confirmed yet that they absolutely understand what causes deja vu.
Because there's no reliable and predictable way for us to cause deja vu to happen. And because of that, it's hard to reproduce in a lab and studied.
Most theories explaining deja vu are thought to be caused by the brain making false memories and can be described by one of the following explanations -
1. Dual Processing :
Theories related to dual processing suggest that if our brain normally performs task A before task B, sometimes due to some delay in task A, it may perform task B before task A and that could cause deja vu.
Scientifically speaking, it's when two coordinated cognitive processes go out of sync.
For example - When you see a new table, your brain would look for an existing memory of that table and if it exists, induce a feeling of familiarity. But in some cases, it could induce the feeling of familiarity before fetching the memory. Now since you already feel familiar about the table and there is no existing memory of it, you'll experience deja vu.
2. Your nervous system not functioning properly :
These theories suggest that deja vu occurs when neurons in your brain are fired spontaneously or delayed in transmission.
Example - If you're seeing a new table, usually the information (in this case, image of the table) enters both your eyes and reaches your visual cortex where it get's registered as a memory. But in times of deja vu, perhaps the information entering from your left eye reaches your frontal cortex before the one entering from your right eye and both get registered twice - making you feel familiar about the table.
3. Not paying attention to details :
There are some theories which suggest that when we have a false sense of familiarity with a situation, some (but not all) parts of it are familiar.
For example - If you visit a friends house and find a table similar to that in your great aunt's house, you might not remember the later and be mislead to believe you've been in that room (or even situation) before.
The closest we've gotten to understanding deja vu
In 2016, a group of researchers lead by Akira O'Connor did succeed in inducing a feeling of deja vu in some subjects and studied their neurological pattern.
So what did they find?
Since almost every other theory about deja vu relates to false memory, they expected a part of the brain involved in memories - called 'hippocampus' - to light up.
But instead, the team found that frontal areas of the brain which are involved in decision making became active.
What does this mean?
All we know is - if these findings are confirmed, it may suggest that during deja vu, there may be some conflict resolution going on in the brain. It also may be a sign that your brain’s memory checking system is working well, and that you’re less likely to misremember events
Didn't we hear deja vu had something to do with parallel universes?
Very unlikely so - since we are already close to establishing that it's everything to do with stuff going on in our brains. But who knows?
Physicists and string theorists widely believe in the idea of a multiverse - where an infinite number of parallel universes exist.
And so, we have a fringe theory explaining deja vu. It says that since universe behave like waves (on different wavelengths), deja vu might occur when two universes, normally on a separate wavelength or frequency, are temporarily in sync.
Dr. Michio Kaku explains this very elegantly in this short video -