Surely most of us have been in a situation where you genuinely feel like you've already seen where you are and what you're doing.
This, my friends, is called déjà vu.
Even the briefest of flashes of déjà vu is enough to throw most people off their stride completely and leave them wondering who they are and whether there's been a glitch in the Matrix.
It affects somewhere between two thirds and four-fifths of all people and has fascinated scientists over the years. Despite the fascination, it is a topic on which science is far from able to explain.
Some experts believe it originates in the medial temporal lobes of the brain, which control long-term memory - however they are unable to study the phenomenon deeply as déjà vu, by its nature, is fleeting and brief.
It cannot be recorded or tracked, as it just happens and then goes away almost immediately. You'd have to be hooked up to a set of instruments that monitor brain signals for a long time and hope they would be able to register what's going on upstairs when déjà vu strikes.
Scientists are having a look at epileptics to see whether they hold the key to déjà vu.
Seizures also begin in the medial temporal lobe, meaning some researchers, according to The Conversation, reckon that they could somehow be linked. It is possible to study the growth of seizures - which are essentially electrical overloads in the brain - and track them as they pass through the brain.
Through this theory, these academics believe that déjà vu is also an electrical overload, stimulated in the rhinal cortices portion of the brain and then impacted upon the medial temporal lobe. This would mean that a false signal is sent, implying that the brain has seen something before, even when it hasn't.
Another theory holds that déjà vu occurs due to a failure of memory.
Essentially, the brain bypasses the short-term memory section of the brain, in which new experiences should be categorised, and goes straight to the long-term memory section, with the result being that you think that what you are experiencing is something that you have experienced before.
Once your memory realises that it hasn't seen this new information previously, it sends it back to the short-term section, hence the fleeting feeling of déjà vu.
Of course, there are plenty of paranormal explanations as well. Everything from past lives - having experienced an event in a different life - to alien events and even dream recognition, where you have dreamed something and then experienced it for real, are cited.
The uncanny comes into play too: our memory takes in things that we have thought rather than actually experienced, and even films that we have seen or books that we have read can be converted into versions in our mind.
But until someone can actually explain what happens, it looks like the strongest theory is a glitch in the Matrix.