Deja vu is a strange feeling that you’ve experienced something before, even when you are sure it hasn’t.
It’s that feeling when you walk into a new place, and it feels oddly familiar, or when you meet someone new, and you feel like you’ve known them before.
It’s a problematic phenomenon for researchers and scientists to study due to its brief and unpredictable nature. However, a few models have been presented to explain what may be happening.
The “Crossed Circuits” Explanation
One theory suggests that deja vu is caused by a mixup in the neural circuits that process sensory information and memory.
Usually, our brains take in information through our senses. This information is then passed into different parts of the brain, following specific pathways from short-term to long-term memory storage.
If some “glitch” happens along this pathway, it may cause a current sensation to feel like a distant memory instead of an immediate experience.
The “Delayed Processing” Explanation
Another model of the deja vu phenomenon asserts that a change in processing speed may be to blame.
Our brains take in a lot of information every second, and it’s constantly sorting, organizing, and storing this information in different areas.
Sometimes, one piece of sensory information may be processed faster than another, meaning that bit of experience may have raced to your memory before you perceived it. Then by the time you perceive it (milliseconds later), it feels like a memory because it is already stored in your memory (milliseconds before).
The “Doubled Experience” Explanation
Another possibility is that there may be splitting or doubling of the sensory information, giving the impression that this one event is multiple happenings occurring at different times.
Like the ones described above, this explanation approaches deja vu from the understanding that it is a malfunction or misfiring of neural circuits in the brain. But it’s also possible that there may be a much more benign explanation.
The “Similar Situation” Explanation
It might feel familiar because it is familiar. Maybe not this same situation in precisely the same way, but something similar.
Perhaps you’ve been in a place, maybe a long time ago, that has similar features or inspires in you a similar feeling, and that’s why it feels like you’ve been here before.
Or maybe you’ve met someone with a similar appearance or personality, so this new person gives you the feeling of deja vu, even though you don’t consciously remember that other person.
The mystery of deja vu is not yet fully understood, but it’s typically harmless. Suppose you are experiencing it frequently (more than once a month) or have accompanying symptoms such as hallucinations or involuntary muscle movements. In that case, you should talk to your doctor, as deja vu can sometimes be associated with seizures, epilepsy, or dementia.