Have you ever visited a new city, yet it felt like you’ve been there before? Or did you have a conversation that seemed familiar word by word? If the answer is yes, you have experienced déjà vu. This phenomenon happens randomly, lasts only a few seconds, and makes people question the nature of reality.
I’ve had déjà vu for as long as I can remember. I didn’t know what caused it, what it meant, but it felt like magic to my child self – something out of the fairy tales I liked so much.
For the most part, déjà vu is still that – a mystery. The term means already seen and was firstly used in 1876 by the French philosopher Émile Boirac. Modern researches have unveiled some of its characteristics, so here’s what we know up to the present time about it.
Over time, déjà vu has been treated as a sign of a past life, as a connection with supernatural entities, or as a manifestation of repressed desires. The development of neuroscience in the last few decades helped to shed some light on the phenomenon. Here are some possible scientific explanations for déjà vu.
A Trick of Memory
The consensus between scientists is that déjà vu is a consequence of a flaw in familiarity-based recognition. We tend to recognize stimuli that we feel we have encountered before, even if we can’t pinpoint where or when. Our mind connects current situations with pieces of previously acquired information based on a vaguely shared characteristic.
This trigger characteristic can be anything: a shape, color, or sound. I’ll give you a simple example. During an auditory-verbal memory test, the participants have to listen to a few sets of ten words. The experimenter asks them to forget them and to pay attention to another batch instead. The participants have to write down as many words from the last list as possible. Most of the participants tend to remember better the words from the latest list that had something in common with the words from earlier lists (for example, lady sounds similar to eighty).
For more interesting facts about memory, read this article.
From a neurological point of view, déjà vu manifests when there is a delay in neuronal transmission between the perceptual organs and higher-order processing centers in the brain. In other words, we process external information quicker than we assess if the information is new or not.
It happened to me when I saw pictures from old town squares from all over the world. My first impulse was to say I recognized some of them from my previous travels or from some documentaries I watched, but I was mistaken. The architectural style gave me a false sense of familiarity.
Stress favors déjà vu
When we are under stress, we don’t get enough sleep, we have problems prioritizing our work, our attention decreases and, you guessed it, we have trouble remembering information correctly. All these lead to glitches in the way we process reality, thus favoring déjà vu.
For more details regarding the causes of déjà vu, I recommend this material.
Socio-demographic factors influence how often we experience déjà vu
Up to 70% of the world’s population has at least one déjà vu episode during their lifetime. While it’s difficult to study the phenomenon due to its flashlight nature, there seem to be some general factors that shape the experience.
I used to have déjà vu a lot when I was a kid. Since I grew up, the phenomenon’s frequency decreased to maybe a few times a year. I don’t know if that’s objectively true or I don’t notice it as much because I am way busier with life now. But let’s see what the experts say.
It seems that déjà vu happens most frequently between ages 15 and 25 and the occurrence indeed decreases with age. One possible reason is neuroplasticity. Our brains are still developing until the mid-20s, therefore the neuronal circuits are more active in processing the information – sometimes, in a less accurate way. Another reason has to do with the fact that younger people expose themselves to a multitude of stimuli. The resulting experiences might lead to some momentary disruptions in neurotransmission, therefore in figuring out whether a place is familiar or not.
Social and educational status
It seems that highly educated and employed people aged between 20-35 years report a higher rate of déjà vu than their lesser-skilled counterparts. The explanation is unclear, but the intensive cognitive effort might cause over-excitation of specific brain regions that lead to déjà vu.
We are yet to understand this eerie phenomenon. Until then, I can’t help but rejoice when I experience déjà vu: the little thrill that accompanies it makes me more aware of my surroundings and of the magic that stems from my own brain.