Deja Vu: A Mental Mystery

Written by Emir Taha Macit

Picture this: you’re going about your day, engaging in an activity. Then, suddenly, a feeling of familiarity hits you, and you feel like you’ve been here or done this before. But also, at the same time, you know that you haven’t. This feeling is actually a well-researched psychological phenomenon called “Déjà Vu.” Being French for “already seen,” déjà vu is a fascinating occurrence whose reason remains mostly unknown, but it can still teach us a lot about human psychology.

There have been many theories about what causes déjà vu, ranging from spiritual to scientific to medical. While some have believed it to be a recollection of a memory in a past life, others have thought it to be ‘a glitch in the Matrix.’ Although theories like these are exciting, they are most likely not true, and it is a good idea to consider the possible scientific reasons instead. Some of the most credible scientific theories include miscommunications in the brain concerning either dual processing or memory. Besides that, the medical reasons include disorders such as epilepsy, which may lead to more instances of déjà vu.

Let’s start by going over the dual processing theory. According to this theory, déjà vu is caused by some processes of the brain losing their regular synchronization for just a moment, and these processes could be 3 pairs of things. The first pair includes familiarity and retrieving. If the part of your brain that helps give familiarity to things goes out of sync with the part that helps recall where the familiarity comes from, déjà vu may occur. The second pair is encoding and again, retrieving. Encoding is the process by which the brain designates something as a memory, and if a time mismatch happens between it and the retrieval process, you may mistake a new experience for an old memory. The final pair is two different consciousnesses in the brain. Some scientists believe our brains have two types of consciousness: one that processes information gathered from the world outside, and one that operates on the inside—things like imagination and mental state. This theory suggests that déjà vu may occur if, in a certain mental state, you mistake information gathered from the outside as one that was a product of the consciousness inside. However, this theory should be approached with caution, as it is the most speculative of the three.

The other scientific theory involves your memory. In a 2006 study conducted by the Leeds Memory Group, patients were given a simple memory that included looking at a word printed in a specific color while under hypnosis. Some of the patients, who were later told to either forget or remember the memory, reported feeling a sensation resembling déjà vu when they saw the word again. The study may suggest that déjà vu happens when we experience something that reminds us of a memory that we can’t fully recall. Another theory about déjà vu being a phenomenon derived from memory is that it results from a miscommunication between the part of the brain responsible for memories and the one responsible for processing new information. According to neurologist Dr. Jean Khoury, if the part of the brain that takes in new information has a problem in the way it interacts with its surroundings, it may create a false memory, leading to déjà vu. This means that the mistake that happens between these parts of the brain may be the result of miscommunication.

There are also several medical reasons as to why déjà vu may happen. First, déjà vu can be caused by seizures, such as epileptic episodes. This is because of the misfires that may happen in the brain during a seizure. Second, lack of sleep may cause déjà vu, as being tired may disrupt certain processes in the brain. Déjà vu may even be caused by stress, resulting from the changes in cognitive function in times of anxiety.

In conclusion, déjà vu is a fascinating and, at times, concerning phenomenon that displays just how much goes on in the human brain subconsciously, and how complex the human mind is. It has been a popular topic to study, especially in recent years. Even though we still do not know what exactly the cause of déjà vu is, we can for sure do our best to research and conduct experiments.

References:

1. “Neurotransmitters: What They Are, Functions”, Cleveland Clinic, 2022 https://my.clevelandclinic.org/health/articles/22513-neurotransmitters

2. Jana Vasković, “Neurotransmitters”, Ken Hub, 2023, https://www.kenhub.com/en/library/physiology/neurotransmitters

3. “Neurotransmitters”, Paris Brain Institute, 2025, 

4. https://parisbraininstitute.org/glossary/neurotransmitters