Déjà Vu, Jamais Vu and 5 More Strange Experiences of the Mind

Seven Experiences of the Mind: Familiarity, Memory and Perception

Déjà vu is the sudden, strong feeling that you have lived the present moment before, even though you know you cannot have. Around two thirds of people say they have experienced it at least once. Researchers today mostly see it as a harmless memory glitch: a flash of familiarity without the memory that should explain it.

Déjà vu has several lesser-known relatives with equally poetic French names. Some describe the opposite feeling, when something familiar suddenly seems strange. Others describe a memory that is almost, but not quite, within reach, or the perfect reply that arrives only after the conversation is over. Here are seven of these experiences, what each one feels like, and what science can and cannot say about them.

Déjà vu: "already seen"

The term was first used in 1876 by the French philosopher Émile Boirac. An episode usually lasts a few seconds. You walk into a room or hear a phrase and feel certain that this exact moment has happened before, yet you cannot say when, and the feeling fades as quickly as it came.

What causes it?

There is no single agreed explanation, but the leading ideas all involve memory:

Familiarity without recall. Psychologists distinguish between recognising that something feels familiar and recalling where you met it. Déjà vu may happen when the first system fires without the second. Anne Cleary and colleagues used virtual-reality scenes in 2012 to show that a new place laid out like a forgotten one can trigger the feeling.
Forgotten experiences. We repeat routines, conversations and journeys constantly. Part of a current scene may genuinely match something you saw, read or dreamed and have since forgotten.
A timing hiccup. In the 1960s the neurologist Robert Efron proposed that if signals reach the brain's processing centres slightly out of step, one experience could register twice, the second feeling like a repeat.

Surveys suggest déjà vu is more common in younger people, in those who travel often and in people who remember their dreams well. A 2018 brain-imaging study by Urquhart and colleagues linked induced déjà vu to brain areas involved in checking memories for conflict, which may explain why we know the feeling is false even as we have it.

Déjà vécu: "already lived"

Popular articles often describe déjà vécu as a more vivid déjà vu, with sounds, smells and emotions included. In the scientific literature it means something more serious. It is a persistent false conviction of having already lived through the present situation, so strong that people may change their behaviour because of it, for example refusing to watch the news because they believe they have seen it already.

Researchers such as Chris Moulin have described it in people with memory disorders, including some forms of dementia. Unlike ordinary déjà vu, it does not pass in a few seconds, and the person may not recognise that the feeling is mistaken. Anyone who notices this in themselves or a relative should talk to a doctor.

Déjà visité and déjà senti

Déjà visité: "already visited"

Déjà visité is the feeling of knowing a place you have never been, such as a street in a new city or a path in an unfamiliar forest. Some people find it deeply moving, as if they had come home somewhere they had never lived. Spiritual explanations circulate online, but the virtual-reality research above offers a simpler one: the layout of a new place can echo somewhere you once saw in person, in a film or in a photograph, and the familiarity arrives without the source.

Déjà senti: "already felt"

7 Strange Phenomena Of The Mind - Déjà Senti

Déjà senti is a feeling of having already felt or thought something, without the strong visual sense of déjà vu. A common everyday version is believing you have just said something out loud, only to realise you only thought it, often while daydreaming. In neurology, a sudden "already felt" sensation is also described as one of the auras that can come before a seizure in temporal lobe epilepsy. For most people, though, occasional episodes are a normal quirk of a wandering mind.

Jamais vu: "never seen"

Jamais vu is the reverse of déjà vu: something you know well suddenly feels strange and new. The easiest way to trigger it is to repeat or write a word over and over until it looks or sounds like nonsense. Many people remember doing this as children with a simple word and feeling slightly spooked when it seemed to lose its meaning.

Chris Moulin and colleagues at the University of Leeds tested this by asking 95 volunteers to write the word "door" 30 times in 60 seconds. About 68% reported a jamais-vu-like feeling, and some began to doubt that "door" was a real word. The related effect of words losing meaning when repeated is called semantic satiation, a term coined by Leon Jakobovits James at McGill University in 1962. One theory is that the brain tunes down its response to a signal it keeps receiving, a kind of fatigue in the circuits that link the word to its meaning.

Presque vu: "almost seen"

Presque vu is the feeling of being on the verge of a thought, insight or memory that never quite arrives. Its most familiar form is the tip-of-the-tongue state: you know the word, you can almost hear it, but it will not come.

This is one of the best-studied experiences in this list. In a classic 1966 study at Harvard, Roger Brown and David McNeill read definitions of rare words to volunteers. People stuck on the tip of the tongue could often name the first letter or the number of syllables, showing that part of the memory really was available. Tip-of-the-tongue moments become more frequent with age, happen more to bilingual people in their less-used language and often resolve when someone offers the first letter. Occasional episodes are normal at any age; they only become a medical concern when they interfere with daily life.

L'esprit de l'escalier: "staircase wit"

Almost everyone knows this one: the clever comeback that only occurs to you on the way home. The phrase comes from the French writer Denis Diderot, who described in his Paradox of the Actor (written in 1773 and revised in 1778) being left speechless at a dinner at the home of the statesman Jacques Necker. He thought of his reply only when he reached the bottom of the stairs, by which point the gathering was behind him.

Other languages have their own names for it. German speakers say Treppenwitz, Yiddish has trepverter ("staircase words"), and an old English equivalent is "afterwit". It is not a disorder at all, just a reminder that the brain often works better once the pressure is off.

When a strange feeling is worth checking

All seven of these experiences are common, and a sense of familiarity or strangeness on its own does not mean anything is wrong. A useful way to think about them is as descriptions rather than explanations: feeling that an event has happened before is not proof that it has, and a short list of names is not a diagnosis.

It is worth talking to a doctor if episodes become very frequent or long-lasting, if they come with confusion, blank spells, unusual smells or tastes, or jerking movements, or if someone stops recognising that the feeling is false. These can occasionally point to a neurological condition such as epilepsy or a memory disorder, and they are best checked properly.

For most of us, though, déjà vu and its relatives are a small window into how memory works, showing that "I know this" and "I remember this" are two separate things. For more on the brain, see The Lamp Dream: A Circulated Account of an Imagined Life.

Sources: Déjà vu (Wikipedia); Tip of the tongue (Wikipedia); Semantic satiation (Wikipedia); L'esprit de l'escalier (Wikipedia). Topic originally inspired by The Spirit Science. Final illustration: Relativity (1953) by M. C. Escher.

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