Science Explains Deja Vu…Or Not
October 4th, 2007
This month's issue of Popular Science magazine includes a sizeable section about current brain/mind research, including an article devoted to what they call "eerie mysteries of perception" — synesthesia, out-of-body experiences, the sense of being watched, and deja vu. For the sake of this article, I'm going to focus on deja vu because I believe the research mentioned in the magazine does little to further an understanding of the phenomenon.
Deja vu, a French term for "already seen", is the feeling of having previously experienced a current situation. It often provokes a strong sense of familiarity because the subject feels with near certainty that he/she has already been through the same experience once before.
Deja vu comes in different forms. There is situational deja vu, referred to as deja vecu ("already lived" or "already experienced"), in which a person feels he has already experienced an entire event exactly as it is currently being experienced, in the same surroundings at the same time of day with the same people, the same conversation, the same clothing and objects, etc.
There is also location-specific deja vu, referred to as deja visite, ("already visited"), in which a person arrives at a place for the first time and experiences a feeling that he has already visited the place at least once before. This form of deja vu is sometimes accompanied by extensive knowledge of the location, such as a familiarity with the layout of a town or building — details that would not be known by someone who had never visited the place.
The article in Popular Science describes research by Susuma Tonegawa, a biologist at MIT. Tonegawa was able to identify specific receptors in the hippocampus in mice that allow the mice to differentiate between places that are similar in appearance. Mice that did not have the appropriate receptors in the brain responded the same way to new rooms as they had responded to slightly different rooms they had seen often.
The theory proposed in the article (it's unclear if this theory was originally proposed by Tonegawa or is instead speculation on the part of Veronique Greenwood, the article's author) suggests that a similar effect occurs in humans as a result of disorientation experienced when the brain confuses a new location with the memory of a similar known location.
This theory doesn't seem comprehensive enough to explain many of the aspects of my own experiences of deja vu. It doesn't explain why I can be in the midst of a conversation with friends or family members and suddenly be struck by the sense that I've experienced all this before, not just in this location but with the same people, with each of them wearing the same clothing and standing in the same positions and saying precisely the same thing and gesturing in the same way. It doesn't explain why, when this type of deja vu occurs, I can sometimes anticipate the next comment or gesture.
There are several other scientific theories about deja vu, most having to do with conflicts in the brain's handling of short-term and long-term memory, which may explain more thoroughly the many facets of the deja vu experience. One possible explanation is a tiny malfunction in the brain's long-term and short-term memory, in which the person believes information is coming from long-term memory when in actuality it is coming from the short-term memory being created in the present moment. A similar explanation blames deja vu on very brief delays in perception and cognitive processing. This theory proposes that an occasional hiccup in the routing of sensory information from the current experience into memory storage causes the sensation of experiencing something and remembering it at the same time.
Another explanation is that the brain, in trying to combine the information from all the senses to create a complete picture of the current experience, brings forward similar or related details from past experiences — such as the same smell, sight or sound — by retrieving them from long-term memory. These sensory impressions from past memories overlap with the impressions from the new experience and give it the appearance of having come from long-term memory. (This theory seems somewhat similar to Tonegawa's theory.)
There are also many spirituality-based theories regarding deja vu, but most of them are very far-fetched and they all lack the evidence necessary to support them. I'm open-minded and don't discount the possibility of one of these theories eventually being proven true, but I can't commit to any of these explanations since at present there is not enough evidence for them:
Dreams
Various cultures throughout history have explored the possibility of precognitive dreams, and many people believe dreams of the future are the source of deja vu. Scientists are also exploring dreams as a source for the memories experienced during incidents of deja vu. It has been suggested that our dreams, which often are filled with trivial information about day-to-day events, provide enough of a basis for "memories" that trigger deja vu in waking life.
Clairvoyance/Precognition
Clairvoyance refers to the ability to see the future. Supporters of this idea propose that deja vu is the result of having already seen the current situation in a precognitive vision.
Reincarnation
Believers in reincarnation suggest deja vu is the result of past-life memories coming to the surface when a person arrives at a place she visited in a previous life or sees a person she knew in a previous life. This suggestion is usually dismissed by scientists because it does not explain deja vu experiences involving recent events or objects only invented within the person's current lifetime.
Soul Markers
Some people believe when we die our soul travels to another level of existence and plans our next lifetime, including who our parents will be, whether we will be male or female, and the major events that will set the course for our life. In this school of belief, experiences of deja vu are considered markers set by our Higher Self to remind us to pay attention to this moment, a way to alert us that there is something important we need to learn from this experience or from an upcoming experience. I don't subscribe to the beliefs underlying this idea, but I find the concept inspiring and try to use my own deja vu experiences as reminders to live in the moment.
Parallel Universes
Proponents of the theory of parallel universes suggest that deja vu occurs when the same event occurs in two or more parallel universes, causing an overlap, or when a person experiences something in this universe that his/her counterpart has already experienced in a parallel universe.
As you can see, there are many different theories about the cause of deja vu. Some of them are more plausible than others, but all of them are intriguing.
Robert says:
I've had 2 specific 'deja vu' moments… or I suppose they would fall more into the category of 'dreamed ahead of time'. While still living in Massachusetts, I dreamed of being in a large, open room with wood floor — standing and talking with five people. A year after, I moved to Washington state (a place I had never lived before) — and a year after that, I was suddenly 'in' the dream — where my mind said "Hey, I've seen this and know what's going to be said next, etc."
Again, had a 'dream' of a corridor with a metal 'stripe' with red on each side of it bisecting the long corridor. 18 months later, I was in basic training (another state and place I'd never been before), and stood at the intersection of two corridors. Looking down 'mine' — was the metal and red (fire break in the structure).
Neither really falls into the 'mistaking similar places/circumstances' since they were 'seen' long prior to moves to new states/cities/situations that were not 'familiar'.
I suppose 'precognition' is the closest match — though there is one idea not really mentioned. Since it is 'my' mind and vision and memory, am I 'just' receiving my own transmissions — sort of out of the normal temporal 'chain of event's — guess that sort of goes into the idea of the akashic record …. more hand wavey metatheory than most scientists want to deal with.
Oct 5th, 2007 at 3:40 pm
Jesse says:
Interesting article, I've already read much of the information from misc. places but still well written.
I decided to post on this article because for about two years I have experienced something that seems very similar to "déjà vecu".
Actually, I've experienced it to the point of questioning whether I was having seizures.
The best way to explain it will sound a bit absurd, so bare with me.. It is a very similar feeling to dejavu, except for the experience is that of, remembering the current situation from the future-tense, as if I've experienced not only the current moment I'm in, but as if that moment is just a small speck of memory on a timeline I've already lived through, and I even have glimpses of future moments of having these dejavu experiences. It seems progressive also, Like the experience leads somewhere, to an end of some kind. This leaves me with a feeling of awe and amazement, but it's a bit scary too so.. I'd like to know if anyone has experienced something similar to this before before I sucker out the big bucks for an MRI.
Oct 22nd, 2007 at 7:25 am
Bert Johnson says:
I get it all the time. There are two forms for me, one is a dream realization, the other is simply "remembering" rather than "experiencing". It's disconcerting, since it makes me question the validity of my memory. I wonder if my subconscious isn't tailoring past memories and experiences to heighten a sense of self-importance by convincing myself I somehow am "remember future events". For example: I broke up with a girlfriend two years ago - she was two months pregnant with someone else's child. I told her that I saw her taking a dusty haired girl to see her father - the girl had a boy's haircut and was often mistaken for a boy. Three months ago, we started writing again, and now live together in Austin, TX. She has a dusty haired daughter whose father lives in L.A. and demands that she comes to see him rather than him come to Texas. It's frustrating - did I really "know" this situation several years ago? Is it self-fulfilling prophecies coupled with a lucky guess on her child's gender? When I meet someone for the first time, yet I believe I know them already, am I projecting a preformed idea of a personality I've decided onto someone who doesn't fill that role, and therefore never witness the true person through my delusions, or is there a possibility that somehow my brain becomes, as Vonnegut would say, occasionally "unstuck in time"?
B.Johnson
Mar 22nd, 2008 at 11:29 am