If I had ever been here before on another time around the wheel
I would probably know just how to deal
With all of you.
– David Crosby
You’re walking down an unfamiliar street, visiting a new city, or hiking a new trail you’ve never hiked, and you’re suddenly overwhelmed with the sense that you’ve been there, in that exact spot, having experienced that exact same situation before – despite knowing that you never have.
Then it’s gone as quickly as it came and you carry on, maybe a little puzzled, but no worse for wear.
Déjà vu is that singular and striking feeling of familiarity when something is unfamiliar, of “knowing” someone you’ve never met, of being somewhere before you’ve never been. It can be disorienting and disconcerting. It can feel mysterious and spiritual, a feeling outside of time and place. Theories attempting to explain why we experience déjà vu have ranged from parallel universes to precognition, and it wasn’t until recently that researchers had an idea of what it was, or what it meant.
Historically, communities linked déjà vu to past life resonance or spiritual awakenings, witchcraft and the devil. Others have acknowledged it as a mysterious and quirky thing that happens, but is of no real consequence. According to the Spiritual Research Foundation, at least 50% of déjà vu instances are caused by something called “the tuning fork phenomenon” which occurs when one person’s frequency resonates with another person’s (or non-corporeal body’s) frequency. On their website, the result of this frequency resonance is described as “a notion that they have witnessed or experienced a new situation previously, when in actuality it is someone else’s experience.”
One of the coolest, and most scientifically likely, explanations for déjà vu is the parallel universe or alternate reality theory: the Multiverse. According to Really Complicated Physics, the idea that there are infinite universes where we all exist in different realities is not only not ridiculous, it’s actually kinda likely. Therefore, some folks believe that déjà vu occurs when the you in this universe is doing something similar to the you in a parallel universe that just happens to be close to this one.
Or, it could just be a glitch in The Matrix.
Alas, the truth is a little less fantastical, a little more mundane, and makes a lot of sense. There’s really nothing mysterious or glitchy about déjà vu at all. It’s just your brain, doing brain things.
According to Dr. James Giordano, Professor of Neurology and Biochemistry at Georgetown University Medical Center in Washington, DC, déjà vu is no big mystery: “Déjà vu appears to occur because the processes for perceiving current situations and events relies on the brain's ability to match new things to those we have experienced before, so as to make sense of the world.” He says, “In a simplified way, brain mechanisms are engaged to compare current sensory input to prior information, so that we can evaluate a situation and make decisions about our actions.”
So, we unconsciously compare what we’re experiencing now to what we have experienced in the past to figure out where to put it in our brain. It may seem creepy when it happens, but it’s a normal function of memory, and it helps us to decide not just what’s happening now, but what happens next and how to respond.
Dr. Giordano explains the nuts and bolts of it, “Déjà vu involves a number of brain networks, including those that function in sensory processes, memory, emotion, and decision-making.” Even though these processes occur in different parts of the brain, “this happens very quickly, and in most cases, information reaches the frontal cortex in a simultaneous, harmonized way.”
Between 60-70% of humans experience déjà vu, and data suggests that those who experience it have the bulk of their experiences between the ages of 15 and 25, with it slowly tapering off as you age. This stands to reason. As we grow older, as with other parts of our bodies, the brain begins to function less efficiently, so researchers believe that the decrease in déjà vu experiences is due to age-related changes.
So is it a glitch in a still-developing brain? Nope. It’s actually a sign of a functioning and healthy memory. In an interview with Scientific American, researcher and cognitive psychologist Anne Cleary at Colorado State University in Fort Collins said, "One reason for the jarring sense that accompanies déjà vu may be the contrast between the sense of newness and the simultaneous sense of oldness — something unfamiliar should not also feel familiar."
A sense of familiarity in an unfamiliar place may be striking and discordant, but rest assured, it’s not your brain misfiring. It’s not the devil and it’s not a memory from a past life – it’s just your brain doing its thing.
Did You Know?
Between 60-70% of humans experience déjà vu
Déjà vu is most common among people between 15 and 25 years old
Déjà vu isn’t magic, but rather it is your brain trying to find patterns
Wanna Dig Deeper?
Listen: to the “How Déjà Vu Works” episode of the How Stuff Works podcast