Author: Kalash Pandey
Edited by: Nadia Hall
Have you ever, for a split second, felt that you were in the same situation or place before, but in reality, it was your first time ever visiting this place or approaching this situation? If you did, that is déjà vu, a French phrase that means “already seen,” and here is why you might have experienced it (Raypole, 2020).
Déjà vu is a complex memory phenomenon that is difficult to study because it usually occurs in people without underlying health concerns (Raypole, 2020). However, there are various theories about what causes déjà vu, such as:
Split perception
As the Healthline article “What Causes Déjà vu?” explains, the split perception theory states that when you do not “give [an] experience your full attention the first time it enter[s] your perception, it feels like two different events. But it’s really just one continued perception of the same event” (Raypole, 2020).
Minor brain circuit malfunctions
One theorized brain circuit malfunction is that, like an epileptic seizure, déjà vu can occur due to a glitch. This glitch happens when the region of the brain which is responsible for tracking present memories and the one which recalls stored memories are active at the same time. As a result, your brain thinks that the current event is actually a memory (Raypole, 2020).
A second brain circuit malfunction theory is related to short and long-term memory. According to this theory, a short-term memory takes a shortcut to long-term memory storage, and thus you perceive this short-term memory as a long-term memory (Raypole, 2020).
Memory recall
Psychology professor Anne Cleary's theory suggests that déjà vu is felt when the present events bring out similar past stored memories. But, you do not explicitly recall the memory, so this event leaves you with only some sense of familiarity (Raypole, 2020).
Neural transmission delay
The neural transmission delay theory explains that déjà vu occurs when information from two different neurological pathways arrives from the eyes to higher brain centers at different times, which makes the brain view the second message as an old one (Newman, 2017).
There is no simple explanation for the mechanism of déjà vu just yet, but with further research, the reason behind this tangled phenomenon may be uncovered in the future.
As mentioned before, déjà vu is quite normal to experience. Around 60% of people in good health experience some form of déjà vu in their lifetime (Brown, 2003). But in some cases, déjà vu can be a sign of dementia. Furthermore, some people with dementia mistake their experiences of déjà vu for genuine memories (Raypole, 2020).
Déjà vu has also been linked with seizures, specifically epileptic seizures. According to a Penn Medicine article, focal seizures, which initially affect only one part of the brain, occur in approximately 60% of people with epilepsy. A focal seizure can be difficult to identify as a seizure because it is brief and individuals suffering from a focal seizure may appear to be daydreaming. During a focal seizure, a person with epilepsy may experience déjà vu alongside hallucinations, sudden feelings that are hard to explain, mood swings, feelings of nausea, unusual sensations, and repetitive behaviors such as rocking back and forth. They also may not be able to control their own body movements (“Feel Like You’ve Been Here Before?”, 2019).
Although déjà vu is normally not a cause for concern, you should see a doctor if you experience the above symptoms or déjà vu more than once a month (Raypole, 2020).
References:
Brown, A. S. (2003). A review of the déjà vu experience. Psychological bulletin, 129(3), 394–413. https://doi.org/10.1037/0033-2909.129.3.394
Feel Like You’ve Been Here Before? It Might Be Déjà Vu. (2019, July 2). Penn Medicine. https://www.pennmedicine.org/updates/blogs/health-and-wellness/2019/july/deja-vu.
Newman, T. (2017, June 14). Déjà Vu: Re-experiencing the Unexperienced. Medical News Today. https://www.medicalnewstoday.com/articles/317895.
Raypole, C. (2020, March 30). What Causes Déjà Vu? Common Theories, Symptoms To Watch For, And More. Healthline. https://www.healthline.com/health/mental-health/what-causes-deja-vu#causes.