Déjà Vu
Animals, who doesn’t enjoy them. From filling a household, to teaching children about responsibility, to even encouraging emotional development.
Sounds familiar? That’s right, this was the first sentence of the last blogpost. But what about those times that you experienced the feeling of having seen or heard something before, but were sure that this was the first time you experienced it? That phenomenon is called déjà vu, French for ‘seen before’. This blogpost dives deeper into the history of déjà vu and explores possible (scientific) reasoning behind it
History
Déjà vu has been around for a long time but never really given attention to. A French man named Emile Boirac was the first to name this phenomenon in 1876. He studied psychic phenomena and thought the thing he called déjà vu was supernatural. He never continued investigating it further, as everyone either thought it was either a ‘side effect’ of reincarnation, or had something to do with aliens who probed people and wiped their brain…
Only in the 1950s psychologists started to scientifically study déjà vu. They used direct stimulation of the frontal cortex to evoke déjà vu, which they could then measure. Through this and similar experiments, a division arose. There was pathological déjà vu, caused by for example temporal lobe epilepsy, and regular déjà vu without a pathological origin. Besides the pathological difference, the length of the feeling differs as well. The pathological déjà vu’s can last entire parts of a day whereas regular déjà vu’s last seconds usually.
Still to this day, the phenomenon is not studied often. In 2006 a study was conducted where scientists tried to elicit déjà vu through hypnosis, which did not work as well as expected. The main issue with studying déjà vu is that it is incredibly difficult to elicit, making it the perfect blend between science and mystery.
Individual differences
As we know, each person is different. Around 60 to 80 percent of people experience déjà vu, the rest never does. Of the people who do experience déjà vu’s, some experience them on a regular basis (i.e. once a year), while others might have only experienced a handful in their lives. In general, déjà vu’s seem to occur more in young children and gradually occur less frequently as people get older. The intensity of the recall is also highly dependent on the individual and the situation. From a faint feeling of ‘hey, this is somewhat familiar?’ to a minute-long existential crisis where one tries to remember why the situation is so familiar, and sometimes even ‘knows’ what will happen next. Interestingly, frequent travellers are thought to experience deja vu more, as they have more varying experiences.
Personally, I have déjà vu’s quite often and sometimes they are pretty intense. They have always fascinated me and, next to dreams, are one of the things I find most wonderful about the human brain. So, how has humanity tried to explain the unexplainable?
Neurological theories
We start with the scientific explanation, after all we are scientists who seek for clear and logical explanations. Multiple potential explanations can be found in neurology.
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Divided attention. In new situations your attention is split in order to orient yourself properly. For example, when walking into a pub and talking to a friend, your main focus is on the conversation, but subliminary you still take in your surroundings. When you then consciously take in the rest of the pub, it could feel familiar even though you have never been there.
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Dual processing. Sensory information always enters the brain in the left hemisphere directly from your senses, but also through the right hemisphere. This process occurs almost instantaneously and your brain registers this as the same input. However, if for some reason the information flowing from the right hemisphere to the left hemisphere is delayed even a little bit, your brain registers this as new input. Because it is then also registered from the left hemisphere directly, the ‘new’ input from the right hemisphere feels vaguely familiar.
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Forgotten memory. Simply put, it could just be that you forgot that you experienced the situation at hand before and that moment brings back part of those earlier memories, giving you the feeling that you indeed have been there before but just don’t remember.
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Repressed memories. Similar to forgotten memories, our big friend Sigmund Freud suggested that déjà vu’s originate from short periods where repressed desires and trauma are triggered. In true Freud fashion, he figures out a way to link this theory on déjà vu to genitals.
Dream theory
Dreams can be about anything, which increases the chances that something you experience in real life for the first time is similar to something you have dreamed about before. People have reported that a déjà vu indeed corresponds to their dreams.
Reincarnation theory
According to the theory of reincarnation, people have lived multiple lifetimes before the current one. Memories of these lives are almost always forgotten, but slip through sometimes. This results in the feeling of déjà vu. A trigger in the environment allows a person to get access to these other consciousnesses.
Collective unconscious
We end this exploration with the most controversial theory (besides Freud’s theory of course). Carl Jung explained déjà vu with his theory that all people share the same knowledge. This collective unconscious is not readily available for people, hence it being unconscious. However, sometimes a person has short access to this pool of knowledge, resulting in the feeling of déjà vu. A slightly different take on this is that déjà vu is not proof of a shared unconscious, but of a shared consciousness. This is referred to as the glitch in reality theory. If this is true, whenever humans get a glimpse of this glitch in reality, damages are done to the foundations of time and the universe as we know it, allowing us to open a bridge between different realities (for example the one of aliens).
Other related concept
There are other forms of déjà vu as well. Jamais vu is the exact opposite of déjà vu and means ‘never seen before’. It is a weird and, I assume, scary feeling of knowing you have experienced something before but still feeling strongly that this is the first time. The most common example is when a certain word does not sound familiar at all, even though you know the word. More intense cases of jamais vu are related to conditions like amnesia and aphasia.
To conclude, it seems that scientists have not yet come to a common explanation for the phenomenon of déjà vu. The speculation continues as more research is conducted, leaving it a mix of science and mystery for now. Until there is an answer, I enjoy the magical feeling and sense of wonder that déjà vu’s give me.
