Science explains that weird déjà vu feeling

The brain’s familiarity trick, Déjà vu vs. delusions, How illusions shape déjà vu, The origin of déjà vu, The fatigue factor, How age shapes déjà vu experiences, The brain’s role in déjà vu, Memory glitches, A healthy brain, Déjà vu’s mysterious opposite, When letters and words stop making sense, Common words, strange feelings

Ever had that eerie feeling you’ve lived a moment before—like reality is on a strange loop? That’s déjà vu, French for “already seen.” And it’s not just a quirky brain glitch; it’s actually a fascinating clash between a false sense of familiarity and what you know to be true. Surprisingly common, as studies show about two-thirds of people have experienced it at least once, scientists have been trying to crack its mystery for years, and for good reason.

The brain’s familiarity trick

The brain’s familiarity trick, Déjà vu vs. delusions, How illusions shape déjà vu, The origin of déjà vu, The fatigue factor, How age shapes déjà vu experiences, The brain’s role in déjà vu, Memory glitches, A healthy brain, Déjà vu’s mysterious opposite, When letters and words stop making sense, Common words, strange feelings

In an interview with Psychology Today, Akira O’Connor of the University of St Andrews explains déjà vu as a clash between feeling something is familiar and knowing it shouldn’t be. It’s that tricky awareness—realizing your brain is playing a clever trick—that makes déjà vu so unique.

Déjà vu vs. delusions

The brain’s familiarity trick, Déjà vu vs. delusions, How illusions shape déjà vu, The origin of déjà vu, The fatigue factor, How age shapes déjà vu experiences, The brain’s role in déjà vu, Memory glitches, A healthy brain, Déjà vu’s mysterious opposite, When letters and words stop making sense, Common words, strange feelings

Déjà vu shares traits with delusions, as both involve a false belief. But while delusions are fixed beliefs held despite evidence, déjà vu is a fleeting trick of the mind, where familiarity clashes with reality for a moment.

How illusions shape déjà vu

The brain’s familiarity trick, Déjà vu vs. delusions, How illusions shape déjà vu, The origin of déjà vu, The fatigue factor, How age shapes déjà vu experiences, The brain’s role in déjà vu, Memory glitches, A healthy brain, Déjà vu’s mysterious opposite, When letters and words stop making sense, Common words, strange feelings

An illusion distorts our senses by twisting reality, which is a common experience during déjà vu. In simple words, it often involves our senses playing tricks, making the moment feel even more surreal.

The origin of déjà vu

The brain’s familiarity trick, Déjà vu vs. delusions, How illusions shape déjà vu, The origin of déjà vu, The fatigue factor, How age shapes déjà vu experiences, The brain’s role in déjà vu, Memory glitches, A healthy brain, Déjà vu’s mysterious opposite, When letters and words stop making sense, Common words, strange feelings

The term déjà vu likely originated in the 1870s, coined by French philosopher Émile Boirac in his book 'The Psychology of the Future'. Since then, it’s captured curiosity across psychology and neuroscience.

The fatigue factor

The brain’s familiarity trick, Déjà vu vs. delusions, How illusions shape déjà vu, The origin of déjà vu, The fatigue factor, How age shapes déjà vu experiences, The brain’s role in déjà vu, Memory glitches, A healthy brain, Déjà vu’s mysterious opposite, When letters and words stop making sense, Common words, strange feelings

Various factors can trigger déjà vu, especially fatigue and stress. When the brain is tired, its neurons may misfire more easily, causing that familiar-but-not-quite-right feeling we know as déjà vu.

How age shapes déjà vu experiences

The brain’s familiarity trick, Déjà vu vs. delusions, How illusions shape déjà vu, The origin of déjà vu, The fatigue factor, How age shapes déjà vu experiences, The brain’s role in déjà vu, Memory glitches, A healthy brain, Déjà vu’s mysterious opposite, When letters and words stop making sense, Common words, strange feelings

O’Connor says déjà vu reports usually begin around age five, increase through childhood, and peak in the early to mid-twenties.

The brain’s familiarity trick, Déjà vu vs. delusions, How illusions shape déjà vu, The origin of déjà vu, The fatigue factor, How age shapes déjà vu experiences, The brain’s role in déjà vu, Memory glitches, A healthy brain, Déjà vu’s mysterious opposite, When letters and words stop making sense, Common words, strange feelings

As we age, our brain’s error-spotting ability, including catching déjà vu moments, can decline. O’Connor finds it fascinating that younger people experience more déjà vu, even though older adults often have more memory quirks.

The brain’s role in déjà vu

The brain’s familiarity trick, Déjà vu vs. delusions, How illusions shape déjà vu, The origin of déjà vu, The fatigue factor, How age shapes déjà vu experiences, The brain’s role in déjà vu, Memory glitches, A healthy brain, Déjà vu’s mysterious opposite, When letters and words stop making sense, Common words, strange feelings

“There’s a part of the brain in the medial temporal lobe, near your cheekbones and ears, that helps form memories and gives you the feeling of remembering. This area plays a key role in the déjà vu experience,” explains O’Connor.

Memory glitches

The brain’s familiarity trick, Déjà vu vs. delusions, How illusions shape déjà vu, The origin of déjà vu, The fatigue factor, How age shapes déjà vu experiences, The brain’s role in déjà vu, Memory glitches, A healthy brain, Déjà vu’s mysterious opposite, When letters and words stop making sense, Common words, strange feelings

Déjà vu might happen when the medial temporal lobe misfires, triggering a false sense of familiarity: a memory sensation that makes you feel like you’ve experienced the moment before, even if you haven’t.

A healthy brain

The brain’s familiarity trick, Déjà vu vs. delusions, How illusions shape déjà vu, The origin of déjà vu, The fatigue factor, How age shapes déjà vu experiences, The brain’s role in déjà vu, Memory glitches, A healthy brain, Déjà vu’s mysterious opposite, When letters and words stop making sense, Common words, strange feelings

Déjà vu can actually be a good sign, as it shows that your brain’s fact-checking system is working properly, helping you recognize when something feels familiar—even if it isn’t real.

Déjà vu’s mysterious opposite

The brain’s familiarity trick, Déjà vu vs. delusions, How illusions shape déjà vu, The origin of déjà vu, The fatigue factor, How age shapes déjà vu experiences, The brain’s role in déjà vu, Memory glitches, A healthy brain, Déjà vu’s mysterious opposite, When letters and words stop making sense, Common words, strange feelings

Déjà vu isn’t the only memory glitch out there. Its opposite, jamais vu—French for “never seen”—is when something you know well suddenly feels completely unfamiliar, like seeing it for the first time.

When letters and words stop making sense

The brain’s familiarity trick, Déjà vu vs. delusions, How illusions shape déjà vu, The origin of déjà vu, The fatigue factor, How age shapes déjà vu experiences, The brain’s role in déjà vu, Memory glitches, A healthy brain, Déjà vu’s mysterious opposite, When letters and words stop making sense, Common words, strange feelings

O’Connor notes that most people have likely stared at a word so long it suddenly looks misspelled—or starts to feel like it’s not a real word at all!

Common words, strange feelings

The brain’s familiarity trick, Déjà vu vs. delusions, How illusions shape déjà vu, The origin of déjà vu, The fatigue factor, How age shapes déjà vu experiences, The brain’s role in déjà vu, Memory glitches, A healthy brain, Déjà vu’s mysterious opposite, When letters and words stop making sense, Common words, strange feelings

They found that the most commonly used words, like "the," were the most likely to trigger jamais vu. The more often a word was repeated, the more likely it was to suddenly feel unfamiliar to participants.

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