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What is Deja Vu?

Did you ever get that odd and unsettling feeling or sense that you’ve been in an exact situation before? Or you’ve already experienced something that you know for certain you are doing for the very first time? Have you ever felt that overwhelming sense of familiarity with something that you shouldn’t be familiar with at all?


This phenomenon is called “déjà vu,” which in French literally means “already seen.” Essentially, it is a sensation that something we’re experiencing at the moment has happened before, whether it’s just a single element such as a taste, a sight or a sound, or whether it’s an entire sequence of events. Déjà vu is a common intuitive feeling that has happened to around 60 to 70 percent of people, and it occurs more frequently to people between 15 and 25 years old compared to any other age group.

Déjà vu is a rather complex phenomenon, and like many unusual phenomena involving the brain, it has yet to be fully understood. There is much speculation as to how and why this phenomenon occurs in people. To many parapsychologists, this occurs when things and experience from our past lives merge with our present life. Several psychoanalysts, on the other hand, attribute the phenomenon to nothing more than simple fantasy and wish fulfillment of our desires and dreams.

Then, there’s the psychological standpoint, which generally considers déjà vu to be caused by a memory mismatch that in turn, causes people to feel that they’ve already experienced a specific event that they know is completely novel to them. Though not fully proven, some experts in the field generally agree that déjà vu occurs because of a communication issue between the short term and long term memory, a rare occurrence that functions like a circuit breaker.

Although the actual cause of déjà vu has yet to be confirmed by science, there are many different theories that attempt to explain how it happens, and they each have interesting implications for the mechanisms of the human brain. For those who are fascinated by this phenomenon and want to try to get to the bottom of this psychological mystery, here are three psychological theories that have been proposed to explain déjà vu!


One theory suggests that déjà vu is caused by memories failing to form correctly in the brain. This theory is called “dual processing,” and it is the most widely accepted take on this mysterious phenomenon among psychologists. The dual processing theory is based on the way the human brain processes new information and how it stores short-term and long-term memories. Essentially, the theory holds that déjà vu happens when two cognitive processes are momentarily out of sync.

In 1963, Robert Efron at the Veterans Hospital in Boston tested his proposed idea that a delayed neurological response is what causes déjà vu. According to him, because information enters the processing centers of the brain via more than a single path, it is likely that there are instances that the blending of information might not synchronize correctly.

In testing his theory, not only did he find the temporal lobe of the brain’s left hemisphere to be responsible for sorting incoming information, he also discovered that the temporal lobe receives this incoming information twice, but with a milliseconds-long delay between transmission. The information arrives once directly, and a second time after its detour through the right hemisphere of the brain. Should the second transmission get delayed by just slightly longer, then the brain might put a later timestamp on that information and consider it as a different memory from the previous memory already processed by the first transmission? This neurological delay is what could possibly explain the sudden sense of familiarity people feel on certain experiences or events.


Another theory suggests that déjà vu could be triggered by things that we have seen subliminally but we just haven’t registered on a conscious level yet. Called “divided attention,” this theory relies on the brain’s inability to focus on all things at once, which means it has the tendency to momentarily “forget” about other actions or events that are happening in real-time.

According to this theory, it is not necessary for people to actually have experienced an event or a stimulus in the past for déjà vu to occur. Instead, divided attention theory tells us that when we are first exposed to a situation and we are momentarily distracted by something else such as a thought or a sight, this causes us not to pay attention to what’s going on around us. While we may not have consciously taken note of what was happening to our surroundings at the time, we have, however, taken it in unconsciously. But as we regain awareness, the entire sequence of events rushes back to us as eerily familiar, as if our memory is convincing us that we’ve been there before – which we kind-of have, in a way.


The last theory that we will be discussing is the ‘hologram theory’. Dutch psychiatrist Herman Sno proposed the idea that memories are like holograms, which means that a person can recreate the entire three-dimensional image from any fragment of the whole.

Based on his reasoning, human memories are so interlinked with each other that experiencing just a single fragment is enough for a person’s brain to reconstruct an entire multi-sensory memory. However, there is a caveat to the brain’s automatic process of “filling in the blanks” – and that is, the smaller the fragment, the fuzzier the ultimate picture or scene will be.

According to Sno, déjà vu happens when certain details in the current environment we are in – be it sight, sound, smell or something else – resembles some remnant memory in our past, and our brain recreates a complete picture or an entire scene from that fragment alone. This could be particularly confusing if our memory of that past event is either vague or incomplete since the brain would just have to put in other bits of information to complete the picture, even if the added memory isn’t actually our own. This brings out a feeling of familiarity as well as the powerful sensation of reliving a forgotten memory which in turn could trigger the experience of déjà vu.

And so, based on this theory, you could experience déjà vu when picking up a can just because the feeling of the metal is the same as the bike handle that you once had, or when you go to a restaurant and saw a tablecloth without actually remembering that your grandmother also had the same one on her dining table when you were just a small child.

Although déjà vu has been extensively studied as a phenomenon for over a century, and researchers have come up with dozens of advanced theories about its cause, there is no specific theory that claims to be the 100% accurate answer to this mystery. Until now, we can honestly say that there is no simple explanation for how exactly how déjà vu works and why it happens.

Perhaps sometime in the near future – when our technology is advanced enough and we have learned more thoroughly about how the brain works – will we finally be able to unlock the compelling secrets behind this strange phenomenon.


  1. https://youtu.be/foVMwJtlR5s
  2. https://youtu.be/nFAvUkjba-Q
  3. http://www.healthguidance.org/entry/17131/1/What-Causes-Deja-Vu.html
  4. http://science.howstuffworks.com/science-vs-myth/extrasensory-perceptions/question657.htm
  5. http://www.brainfacts.org/about-neuroscience/ask-an-expert/articles/2014/what-causes-deja-vu/
  6. http://www.huffingtonpost.com.au/2016/03/15/why-we-get-deja-vu_n_9463818.html
  7. http://listverse.com/2016/06/19/10-fascinating-theories-to-explain-deja-vu/

Dual Processing Theory

  1. http://www.healthguidance.org/entry/17131/1/What-Causes-Deja-Vu.html
  2. https://www.psychologytoday.com/articles/200503/been-there-done
  3. http://science.howstuffworks.com/science-vs-myth/deja-vu4.htm
  4. http://www.medicaldaily.com/deja-vu-and-its-relatives-how-simple-mistakes-memory-could-signal-deeper-neurological-problems
  5. http://listverse.com/2016/06/19/10-fascinating-theories-to-explain-deja-vu/

‘Divided Attention’ Theory

  1. http://www.healthguidance.org/entry/17131/1/What-Causes-Deja-Vu.html
  2. http://www.medicaldaily.com/deja-vu-and-its-relatives-how-simple-mistakes-memory-could-signal-deeper-neurological-problems
  3. http://listverse.com/2016/06/19/10-fascinating-theories-to-explain-deja-vu/

Hologram Theory

  1. http://www.healthguidance.org/entry/17131/1/What-Causes-Deja-Vu.html
  2. http://science.howstuffworks.com/science-vs-myth/deja-vu4.htm
  3. http://www.medicaldaily.com/deja-vu-and-its-relatives-how-simple-mistakes-memory-could-signal-deeper-neurological-problems
  4. http://listverse.com/2016/06/19/10-fascinating-theories-to-explain-deja-vu/
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