What Exactly Causes Déjà Vu? Scientists May Finally Know the Answer Thanks to Virtual Reality

Déjà Vu is a common yet still mysterious phenomenon where we experience the feeling that we've been somewhere or done something before actually doing it.
Déjà vu

If you’ve ever had déjà vu — a phenomenon where you believe you’ve been in a particular circumstance before (even though it’s not possible), then you know how disorienting it can be. Déjà vu, which translates as “already seen” in French, can give you the impression that you know someone or have been somewhere before.

Philosophers, neurologists, and writers have struggled with the déjà vu phenomenon for many years. While scientists can explain what it is, déjà vu has remained a mystery as they are yet to phantom why it occurs.

Since the late 1800s, several theories began to emerge concerning what might trigger déjà vu. While some believe it’s a sign to remember an experience from a previous life, others think it may have stemmed from a brain or mental dysfunction.

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Or perhaps it was only a brief blip in the otherwise regular operation of human memory. But it wasn’t until recently that the phenomenon began to get dissected by the science community.

Moving from the supernatural to the scientific

Dr. Akira O’Connor explained that déjà vu is a feeling of familiarity and the metacognitive realization that these feelings are unwarranted. He’s a senior psychology lecturer at the University of St Andrews. 

He states, “Déjà vu is fundamentally a conflict between the perception of familiarity and the understanding that familiarity is false.” 


And what separates it from other memory occurrences “is the awareness that you’re being misled.” 

Dozens of theories attempt to explain why our memories might malfunction this way

Some claim there is a similar short in our brain circuits leading to long-term and short-term memories, thereby causing new information to go directly into our long-term memory instead of stopping briefly in the short-term memory bank. Others blame the rhinal cortex—the part of the brain that signals when something feels familiar, even though no memories are present to support it.

Another theory explains that déjà vu is connected with memories that feel real but aren’t. This form of déjà vu can be compared to the feeling you get when you can’t tell if something happened in a dream or is a reality. However, researchers are beginning to contest this notion.


In a different study, 21 volunteers were given a lab-induced déjà vu experience while scanning their brains with fMRI – functional magnetic resonance imaging. Interestingly, the memory-related brain regions, like the hippocampus, were not triggered as we might expect if the feeling were connected to a false memory. Instead, the researchers discovered that the brain regions involved in decision-making were the most engaged. Their interpretation of these findings implies that it may actually be due to our brains trying to resolve a dispute. In other words, the human brain searches through our memories like a phone book for discrepancies between what we believe has happened to us and what actually happened. 

190603 Functional magnetic resonance imaging at the Imperial Centre for Psychedelic Research
Functional magnetic resonance imaging by Thomas Angus under CC BY-SA 4.0

Alan Brown research

Alan Brown decided to investigate or look into the different previous research published on déjà vu. Much of what he could gather had a paranormal quality – that is, having to do with the supernatural, like psychic abilities or past lives. 

Brown found that about two-thirds of people usually experience déjà vu. He explained that the most typical triggers of it include a scene, place, and conversation.


He also cited references from the medical literature on a possible connection between déjà vu and some types of brain seizure activity. A 2014 article in Scientific American explained that small seizures in the brain region responsible for forming and retrieving memories might be why some things feel familiar despite never having encountered them before. 

Brown’s analysis brought the notion of déjà vu into the mainstream – both in a book geared toward scientists and a scientific journal that scientists who study cognition frequently read. His research also provided a blueprint for scientists who wanted to design experiments to investigate déjà vu.

An investigative study of the déjà vu phenomenon

Prompted by Brown’s work, many researchers have begun to conduct experiments to test hypotheses about possible déjà Vu triggers.


To investigate this idea in the laboratory, a research team tested a near-century-old assumption that déjà vu can occur when there’s a spatial resemblance between a current scene and an unrecalled scene in the memory. Psychologists called this the “Gestalt familiarity hypothesis.”

Gestalt Principles Composition
Gestalt Principles Composition by Akermariano under CC BY-SA 3.0

Imagine passing through a place, and you wonder, “have I been here before? Have we ever discussed this exact spot before? Is it possible I’ve already seen this catwalk by this hallway?”

The scene’s layout, including positioning particular objects within the area, may cause this déjà vu feeling. Its layout may be identical to that of another scene you have already witnessed in the past.


A “glitch in the Matrix” – Carrie-Anne Moss

Déjà vu is a “glitch in the Matrix,” according to Carrie-Anne Moss: a simulated reality that prevents people from realizing that intelligent machines have taken over the world. While the explanation is ideal for cyberpunk science fiction, it provides no scientific insight into the phenomenon. 

The déjà vu feeling is brief and often expected, which is why it’s equated with being a mystery. Déjà vu intrigues us for the exact same reasons that make studying difficult.

Other scientists have tried using tricks like hypnosis and virtual reality

Cleary and her team applied virtual reality (VR) to place people within scenes to manipulate the environments people were placed in. Some scenes had the same spatial configuration, despite being different. After reviewing the results, they found that the déjà vu phenomenon was more likely to occur when people were in a scene having a similar spatial layout to a previous scenario they had seen but couldn’t remember. 


“The spatial similarity of a new scene to one in memory that isn’t being consciously recalled at the moment, according to this research, may be one of the contributing factors to déjà vu,” Cleary said.

“But it doesn’t imply that spatial resemblance is the only reason for déjà vu,” she continued.

“It’s likely many factors contribute to what makes a scene or a situation feels familiar. Hence, further research is underway to investigate additional possible factors in this mysterious phenomenon.”


Déjà vu may be a memory phenomenon

Due to these experiments, scientists now believe that déjà vu is a memory phenomenon. We come across scenery that reminds us of something, yet we cannot correctly recall that memory. Therefore, our brain detects connections between our current experience and a previous one. However, we’re left with an unidentified feeling of familiarity.