Déjà vu
Déjà vu, which translates to "already seen" in French, is a common psychological phenomenon characterized by a feeling of familiarity when encountering a new person, place, or event, often leading individuals to believe they have experienced the situation before. This sensation occurs in approximately 60 to 90 percent of people at least once in their lives and is typically sudden and fleeting, making it challenging to study. Various theories have emerged over time to explain déjà vu, ranging from spiritual interpretations, like previous lives, to scientific hypotheses focused on memory processing in the brain.
In the context of memory, déjà vu is linked to how our brain encodes, stores, and recalls different types of memories, notably episodic and semantic memories. Researchers have found that memories are stored in different parts of the brain, similar to ingredients in a recipe, which can lead to glitches that result in memories being mistakenly perceived as familiar. Some scientists have also observed that individuals with certain types of epilepsy may experience déjà vu prior to seizures, indicating a potential neurological basis for the phenomenon. Additionally, there is a related condition known as déjà vécu, where individuals consistently feel as though they have already lived their current experiences, often due to malfunctions in memory storage. This intricate interplay of memory processes and perceptions invites ongoing exploration into the nature of human recollection and familiarity.
On this Page
Déjà vu
Déjà vu is a feeling of familiarity experienced when a person meets someone new or encounters a location or an event for the first time. A person with déjà vu might say, "I've been here before," or "I've met you before," even when these options are not possible. Ninety percent of people experience this sensation at least once in their lives. Dozens of different explanations have been proposed for why déjà vu occurs. These range from spiritual/supernatural explanations such as previous lives or out-of-body experiences to simple mistakes of memory. In the twenty-first century, scientists have been exploring the possibility that déjà vu is the result of how the brain processes and recalls memories.
Background
Memories are stored records of what a person has experienced or learned. To be fully useable, a memory has to be encoded, stored, and then recalled by the brain. Scientists have determined that there are different types of memories and the brain stores them in different ways.
Working memory is a kind of short-term memory. It is the kind of memory that is activated when a person is told someone's address or phone number and is writing it down. Implicit and explicit are two types of long-term memory. Implicit memories are motor memories, or memories that allow parts of the body to function without conscious thought. Walking, talking, and eating are examples of motor memories and are stored in the parts of the brain known as the basal ganglia and cerebellum. Explicit memories are episodic (memories of an experience) or semantic (memories of information and facts) and are stored in three parts of the brain: the hippocampus, the neocortex, and the amygdala. Explicit memories are the kind of memories associated with déjà vu.
Scientists have determined that episodic memories of experiences are not stored together in one place in the brain—instead of being in one unit, bits of the memory are stored in separate parts of the brain. The visual memories are in one location, recollections of sounds and smells are in other areas, and feelings and other sensations are also stored separately.
Overview
The term "déjà vu" means "already seen" in French. It was first used by French philosopher Émile Boirac (1851–1917) in 1876 and refers to a sudden and often fleeting sensation that a person has already seen, done, or experienced something that the person is in the process of encountering. For example, a person may walk into a room of a home being visited for the first time and experience a sense that they have been there before. Sometimes, the sensation comes from a combination of circumstances, such as seeing a certain billboard on the roadside while hearing a particular song on the car radio.
People have been aware of the sensation of déjà vu for centuries and have developed many theories to explain it. Ancient Greeks saw the experience as proof that souls could move from one body to another. St. Augustine (354–430 CE) wrote about false memories to describe the feeling of déjà vu. However, the phenomenon has proven difficult to study. Although it is estimated that 60 to 90 percent of all people experience it, the sensation is sudden, unpredictable, and generally cannot be deliberately provoked.
However, in the twenty-first century, scientists found several ways to study aspects of déjà vu. They determined that some epileptics experience déjà vu just prior to the onset of a seizure. The consistent nature of these experiences allowed scientists to study brain function and identify an electrical discharge in areas of the brain known as the rhinal cortices as a possible source of the experience.
Other scientists devised experiments to simulate a false memory similar to a déjà vu experience. They read lists of related words to test subjects, leaving out the word that linked them. For example, the words might be pillow, bed, and dream, which are all linked to sleep, though that word was not mentioned. They then tested the subjects' memories to see if they had heard the linking word by asking if they heard any words that started with "s." Finally, they asked the subjects to list the words they heard. Many subjects mentioned the word "sleep," an indication that false memories can be created by association. From this, researchers hypothesized that déjà vu is the result of the brain processing similar memories.
Tests by other researchers showed that if people were exposed to images of rooms with objects in a certain place, an image of a room with different but similar objects would be seen as familiar. For example, suppose a person was shown a room in a historic home with a bed to the left, a table and lamp directly ahead, and two antique chairs to the right. If, later, the person was shown an image of a hotel room with modern furniture in a similar configuration, the person was likely to say that the room looked familiar.
Some scientists believe that the complicated nature of episodic memories and the fact that they are stored as separate "ingredients" of a complete memory may cause memory mistakes that register as déjà vu experiences. Usually, a person can tell the difference between something that is being imagined and something that actually happened. However, when a person is experiencing something that bears some similarity to something experienced previously, scientists believe the brain may mix past information with new information in a way that seems like a legitimate memory, resulting in the sensation of déjà vu.
Researchers have also identified a condition in which people seem to experience déjà vu on a regular basis. The sensation is so constant that some people stop reading the paper or watching television because it seems to them that they have seen and read it all multiple times before. Scientists believe it is caused by a malfunction in the memory storage process, where the new experience is immediately interpreted as a past memory. This generally happens to older people and has been studied as another example of a memory glitch. The phenomenon is called déjà vécu," or "already lived."
Bibliography
Blanchfield, Theodora. "Deja Vu: Its Meaning and Why We Experience It." Verywell Mind, 20 May 2024, www.verywellmind.com/what-is-deja-vu-why-do-we-experience-it-5272526. Accessed 16 Jan. 2025.
Choi, Charles Q. "Been There, Done That—Or Did I? Déjà Vu Found to Originate in Similar Scenes." Scientific American, 6 June 2012, www.scientificamerican.com/article/deja-vu-found-originate-similar-scenes/. Accessed 24 Oct. 2017.
Draaisma, Douwe. Why Life Speeds Up As You Get Older: How Memory Shapes Our Past. Cambridge UP, 2012, pp. 131-171.
"Explainer: What is Déjà Vu and Why Does It Happen?" The Conversation, 9 Jan. 2013, theconversation.com/explainer-what-is-deja-vu-and-why-does-it-happen-11355. Accessed 24 Oct. 2017.
Hamzelou, Jessica. "Mystery of Déjà Vu Explained: It's How We Check Our Memories." New Scientist, 16 Aug. 2016, www.newscientist.com/article/2101089-mystery-of-deja-vu-explained-its-how-we-check-our-memories/. Accessed 24 Oct. 2017.
"Memory." Queensland Brain Institute, University of Queensland, qbi.uq.edu.au/brain-basics/memory. Accessed 16 Jan. 2025.
Neppe, Vernon M. "An Overview Perspective on what Déjà Vu is (Part 1)." Journal of Psychology and Clinical Psychiatry, 26 May 2015, www.pni.org/neuropsychiatry/deja‗vu/JPCPY-02-0011‗deja‗vu1.pdf. Accessed 24 Oct. 2017.
Ratliff, Evan. "Déjà Vu, Again and Again." New York Times Magazine, 2 July 2006, www.nytimes.com/2006/07/02/magazine/02dejavu.html. Accessed 24 Oct. 2017.
Stanton, Dawn. "Probing Question: What Causes Déjà Vu?" Penn State News, 2 Feb. 2010, news.psu.edu/story/141215/2010/02/02/research/probing-question-what-causes-deja-vu. Accessed 24 Oct. 2017.
"What Is Déjà Vu and Can Science Explain It?" BBC Bitesize, Apr. 2024, www.bbc.co.uk/bitesize/articles/zdpbwsg. Accessed 16 Jan. 2025.