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19 Jul Why Do We Get Deja Vu? Part 2: Deja Vu Studies & Deja Vu Explanations
Having discussed the definition of deja vu and both examples & types of deja vu in part 1, here, as promised are some of the deja vu studies and deja vu explanations I discovered while trying to answer the question “Why do we get deja vu?”.
Deja Vu Studies & Theories
While Boirac first used the phrase deja vu to describe this feeling of having ‘been there before’ in his book, he did, however, not research the subject in depth – and for the best part of the 20th Century, researchers used Sigmund Freud’s theory that such experiences were caused by repressed memories or desires related to stressful events no longer accessible as regular memory (known as paramnesia) to explain deja vu.
Frequent association with alien abductions, ESP and past life experiences soon attached somewhat of a stigma to the study of deja vu, resulting in scientists completely ignoring it for many years.
Thankfully, researchers have recently started setting some of these associations aside and using brain imaging technology to study the phenomenon – placing it firmly within their study of memory in the hope to learn more about the formation, storage and retrieval of memory.
It has since been discovered that the brain’s medial temporal lobe, which includes the amygdala, the rhinal cortex and the Para hippocampal gyrus, plays a role in conscious memory.
In 1997, neuroscientist John D.E. Gabrieli (Stanford University) discovered that the:
* Hippocampus facilitates conscious memory recall
*Para hippocampal gyrus facilitates determination of what is and isn’t familiar (without having to retrieve memories to do it)
Research also appears to have shown that deja vu experiences:
* Seem to be most common in individuals aged between 15 and 25
* Decrease with age (although the ‘upper age limit’ differs among researchers)
*Seem to occur more often in people who travel a lot, can recall dreams and/or have:
*Higher incomes
*Higher levels of education
*Active imaginations
There is no definitive answer as to the impact of people’s state of mind (i.e. feeling tired & stressed or relaxed & refreshed) on their likelihood to experience deja vu yet, as researchers have evidence of both.
One study seemingly suggested that the more politically liberally and open-minded a person is, the more they are likely to experience this phenomenon – although this could, of course, simply mean open-minded people are more likely to ‘admit’ to having experiences that could be regarded as ‘weird’…
Deja Vu Explanations
So, how do these researchers use their findings to explain deja vu? As I mentioned earlier, they have come up with many different (40+) theories. I couldn’t possibly go into all of these, so here are four of the most ‘popular’ ones, which are the:
* Hologram Theory,
* Divided Attention Theory,
* Delayed Vision or Dual Processing Theory,
* Theory of “Memories” Derived from Other Sources, and the
* Theory of Precognitive Dreams Causing Deja Vu
Let’s look at these theories one by one…
The Hologram Theory
Psychiatrist Herman Sno (Netherlands) proposed that memories resemble holograms in that we can recreate an entire 3D image from a single fragment of a whole. The smaller this fragment is, however, the blurrier, ill-defined the final picture will be.
Sno says deja vu occurs when some little detail (a sight, smell, sound, etc.) within our current environment is like a remnant of a past memory and the brain uses this fragment to recreate a complete scene.
In other words, he believes that some small element of familiarity could be the seed of deja vu feelings (as do many other researchers).
An example of this would, for instance, be someone who experiences strong deja vu feelings while riding in a friend’s classic Morris Minor – without realising (or remembering) that their grandfather had a car like this and that he used to take them for rides in it when they were very young.
The look, feel and/or smell of the seats, dashboard, etc. could be bringing back childhood memories they didn’t know they had.
The Divided Attention Theory
Conducting related studies at SMU (Southern Methodist University) and Duke University, Dr Alan Brown and his colleague Elisabeth Marsh tried to recreate a deja vu-like process and test their theory of subliminal suggestion.
The plan was to show students photos of various locations and ask them which, if any, of these locations were familiar to them. Ensuring none of the students in the study group had ever been to any of these locations, they did, however, flash some of these photos onto the screen for between 10 and 20 milliseconds (subliminal speed; long enough to be registered by the brain but not long enough to be consciously recognised/remembered) before showing them to the group.
The findings of these experiments showed much higher rates of familiarity for the subliminally shown images than for the ones that were not flashed onto the screen.
A similar experiment (using word lists) conducted by Kevin Whitehouse & Larry Jacoby at Washington University revealed similar results.
Basing his divided attention or cell phone (i.e. when you’re talking on the phone while driving/doing something else, your attention is divided) theory on these findings, proposed that when people are distracted by something, they may subliminally take in their surroundings but not truly, consciously register them.
Once they focus on their environment/what they are doing, surroundings/activities that should not be familiar appear to be so.
Bearing this in mind, you may, for instance, experience a feeling of deja vu after walking into a new shop while talking on the phone or to a friend simply because your brain processed its sights, smells, sounds etc. before you actually looked around – and due to this, things seem familiar when you do look around properly,.
The Delayed Vision or Dual Processing Theory
Based on how new information is processed by the brain and how short- & long-term memories are stored, this theory was tested by Robert Efron (Boston Veterans Hospital) in 1963.
Efron proposed deja vu may be caused by a delay in neurological responses due to information entering the brain’s processing centres via multiple paths, which could cause blending of information being synchronised incorrectly.
He based his proposal on his findings that:
* The left hemisphere of the brain is responsible for the sorting of incoming information, and that
*Incoming information is received twice by the temporal lobe – first directly and then again following a detour via the brain’s right hemisphere
This ‘delayed transmission’ is typically received within a matter of milli-seconds. If it is, however, delayed a little longer for some reason, they brain may “timestamp” that specific delayed bit of information wrong and, as it was already processed, register it as previous memory – which could, of course, explain a sense of familiarity in unfamiliar places/situations.
The Theory of “Memories” Derived from Other Sources
The memories stored within our brains do not come exclusively via direct experiences but also from watching movies, reading books and looking at photographs. As such, we can have strong memories of something we’ve seen, watched or looked at without ever having experienced it.
This theory proposes that these memories, which are often pushed far into the back of our minds, can trigger feelings of deja vu when we experience/see something resembling those ‘long forgotten’ memories.
You may, for example, have seen a picture of a well-know landmark when you were a child. When visiting this landmark for the first time as an adult without remembering that you have seen the picture, it may appear unexpectedly familiar.
The Theory of Precognitive Dreams Causing Deja Vu
Entertained by, among others, A. Funkhouser, C Ríos & Ian Wilson (“Déjà Rêvé” & “Theory of Precognitive Dreams”) and Kazuhiko Fukuda, this theory proposes that deja vu experiences are caused by memories of precognitive dreams.
You may, for example, have had a precognitive dream about finding your ‘dream home’ and walking through various rooms within it.
When you finally find your perfect house, the rooms inside it may seem extremely familiar. If you don’t remember your dream, this could be interpreted as deja vu.
Researchers have linked evidence of deja vu experiences to precognitive dreams that occurred anywhere between a single day and up to eight years prior to the experience.
One of the questions raised by sceptics of this theory is why many of these experiences involve every day, mundane things. According to Funkhouser, one of the explanations for this is that people would be far more likely to remember less mundane, more “exciting” dreams – and would therefore be less likely to have subsequent deja vu experiences.
So, Why Do We Get Deja Vu?
All said and done, while this odd phenomenon has been studied for more than a century and researchers have developed dozens of theories about why and how it happens, no simple explanation has been discovered yet.
As time goes by and technological advances help us to further our knowledge of how the brain & memory work, we will hopefully also gain a better understanding of deja vu and why we get it.
In the meantime, what we do know for sure is that they are not precognitive experiences but brief moments of ‘unexpected recognition’. Have you had moments like this? I’d love to hear about them…
Further Sources/Reading:
“Déjà vu”, Robert Todd Carroll
“Déjà vu as…”, Kornelia Kozovska
“Déjà vu – A Glitch…”, Lynne Malcolm
“The Various Manifestations…”, Pacific Neuropsychiatric Institute
