Have you ever had that strange feeling that what's happening right now has already happened before?
Like you've lived this exact moment, same place, same conversation, same everything.
Well, that eerie sensation is called déjà vu, and it's more common and more fascinating than you might think.
Since it happens so often, we're diving into what's really going on in your brain when you experience it.
Is it a memory glitch, a prediction error, or something else entirely?
And that's why today's SYSK trending topic is Understanding Deja Vu.
Joining me is cognitive scientist Anne Cleary, who has spent years researching the science behind déjà vu.
She'll explain why your brain creates this illusion of familiarity and what it reveals about how memory actually works.
So why does the present sometimes feel like the past?
We'll find out right after this. of the Regency era.
You might know it as the time when Bridgerton takes place or as the time when Jane Austen wrote her books.
The Regency era was also an explosive time of social change, sex scandals and maybe the worst king in British history.
Vulgar History's new season is all about the Regency era, the balls, the gowns, and all the scandal.
Listen to Vulgar History, Regency era, wherever you get podcasts.
There's a pretty good chance that you have experienced deja vu.
That feeling that you've been here before, or that you've said this before, or that you're experiencing something now that has already happened in the past.
So what is that?
Some say it's paranormal or it's a clue to your psychic abilities and others say that's nonsense.
Anne Cleary is someone who studies déjà vu.
She is a professor at Colorado State University and she has a great TED Talk on this subject that you can see online.
There's a link to it in the show notes.
And she is author of a book called The Déjà Vu Experience.
Hi, Anne.
Welcome to Something You Should Know.
Thanks.
So you've been studying this phenomenon of deja vu.
What do you think is going on?
What is it that gives us that sense that I've done this before or I've been here before?
Well, the definition of deja vu is the experience of having experienced something before, while simultaneously also feeling that that's impossible because this is the first time that you're experiencing it.
From my perspective, what causes it is likely memory.
It's likely that you have experienced something either this situation or something very much like it at some point in your past and you have simply forgotten that prior experience.
You're unable to recall the source of the familiarity that you're experiencing with it.
What is the history of deja vu in the sense of when was it first identified?
How long has it been studied?
So déjà vu began to appear in literature in around the late 1800s or so.
Philosophers and thinkers began writing about it and speculating as to its cause.
There's currently still some debate about over when the phrase déjà vu first began appearing in the literature and in intellectual circles.
But it's clear that by about the mid 20th century or so the phrase had caught on and that became the single use phrase in English for describing the experience itself.
Well, we use it in English, but it is a French word.
So why do we continue to use a French word?
It first started in France among intellectuals and philosophers.
I believe that the reason we're still using the French phrase in English is because there simply isn't a better term in English.
And interestingly, some colleagues and I have been examining well, are there words in other languages for this same experience?
And in some other languages, it's actually the French phrase as well.
So I believe in Spanish, for example, people also use the French phrase déjà vu.
And it's an interesting question.
Does every language have a phrase for this?
Because it's such an odd, unusual experience.
What do we know about the experience of deja vu in terms of who's had it?
When does it happen in life, and during the day and time of year?
And are there any similarities or it just pops up whenever?
Yeah, it's hard to pinpoint when exactly it's going to occur for someone in daily life.
But most people have had the experience at some point or other.
So, according to survey research, about two thirds of the population reports having had deja vu at some point in their life.
Now, an interesting aspect and a complete mystery regarding deja vu's incidence is that it tends to decrease with age.
And so it peaks in young adulthood, the frequency with which people report experiencing it, that is.
It peaks in around the early 20s or so and then starts to decline from there, becoming lesser and lesser as people grow older.
Another interesting aspect is that, if you look at survey, research regarding what people feel prompts it when it does happen to them.
It seems that the most common elicitor is scenes.
So places tend to be the most common elicitor of the experience, followed by conversations with people.
Does it normally happen in the morning, in the evening?
It doesn't matter?
Yeah, there have been some survey studies about that.
I'm not sure I would make too much of it other than it tends to be correlated with fatigue.
And so, from that perspective, it may have a slightly greater likelihood of occurring later in the day, when people are more likely to be tired.
And also later in the week for some reason.
So here's the thing that I really don't understand about deja vu, because you had said that you know it's probably related to memory.
You're having an experience of something that you've never experienced before, but seems like you have.
I have a lot of experiences that I have experienced before.
I don't get that magical feeling anymore.
When I remember things I've experienced before and I'm experiencing them again.
So there's something else going on.
It isn't just a memory.
Even a memory that I haven't experienced for years.
I can walk into an old house and go, oh, I've been here before.
It's not deja vu because I know I've been there before.
But when I have deja vu, it's a very kind of mystical, wow.
So what's the difference?
Yes, and this is exactly why I am so interested in Deja Vu as a memory researcher, because I think it is providing us with a unique window into how our memory systems might operate.
So, as you describe, Most of the time our experiences are familiar to us and we have experienced something related to the situation, but it doesn't elicit this very mysterious sensation of fear, simultaneously feeling like it's intensely familiar, but yet that's impossible.
And so the key question is what is going on in those situations?
And it seems as if it's likely that something in memory's normal operation is is being disrupted or has gone awry in some way.
And it's now drawing our attention to that.
But to really get at your question, this is something that we've been aiming to investigate in our laboratory.
And one of the key hypotheses that we have had for what might cause that very unique type of experience that is deja vu is when there's a juxtaposition between an intense sense of familiarity on the one hand, and yet a recognition of novelty or newness on the other hand.
And so it may be that, when you have this juxtaposition, that that is what really leads to this strange sensation.
And it may be that that juxtaposition doesn't happen very often.
Usually, things either are very obviously familiar and they're not novel, or they're very obviously new and they're not familiar.
And it's when you have this juxtaposition of both at the same time that perhaps you have this strange, eerie sensation that we call deja vu.
So it's a feeling of I've never been here before, but it seems like I've been here before versus oh, I remember this.
Yes.
And the experience of deja vu.
I know you talk in your TED Talk that a lot of people report that not only do they experience something that they think they've experienced before, that they don't remember having ever done that, but that they also think they know what's going to happen next.
Yes, this is one of the most interesting aspects of deja vu from my perspective.
So I've been studying deja vu for over a decade now, from the perspective that it is probably a window onto how our memory systems work.
And in the process of studying it, I have come to the realization that for many, many people, deja vu doesn't just feel like a strong sense of familiarity juxtaposed with newness.
It doesn't just feel like a memory.
Many, many people have the experience of feeling as if they know exactly what is going to happen next when they're in the midst of a deja vu experience.
And years ago, I was kind of dismissive about this as a scientist.
I thought, oh, you know, that there can't possibly be anything to that.
That must just be people's beliefs about what deja vu actually is and people's associating it with the paranormal.
But enough people kept coming forward and contacting me or telling me their deja vu stories with this element involved, this feeling of prediction or knowing what's going to happen next, that I began to wonder if there might be something to this and something that might be able to be studied scientifically.
So years ago I came up with the hypothesis that perhaps there is a memory explanation for the feeling of prediction.
That is, maybe.
If it is the case that deja vu can be driven by an unrecalled memory for something very similar to the current situation, then perhaps that unrecalled memory could also lead a person to have a sense of knowing what's going to happen next, based on how the situation happened in the past.
I'm not sure why, but you know what this kind of reminds me of?
If you ask somebody, what are the lyrics to a specific song?
They'll often have trouble remembering the lyrics off the top of their head.
But if you play the song, if they're kind of singing along with the song, the lyrics just come.
They just, you know them, but you need that prompt.
It's interesting that you mentioned that because there is an auditory form of deja vu.
The phrase for that is deja entendue.
And we have actually used music in our lab to try to investigate that.
And what we did in that study was to try to create an auditory analog to the spatial type of scene.
Similarity that I mentioned was to use what are called piano puzzlers.
So there's a musical composer named Bruce Adolph who every week, for a radio show, produces what he calls a piano puzzler, which is a unique combination of the genre of a particular musician.
And some popular sort of nursery rhyme or pop song.
He combines them in a unique way that has this tendency to elicit a feeling of familiarity.
So when you hear a piano puzzler, very often it feels familiar and you can't pinpoint why.
Yet it's also recognizably new at the same time, because it doesn't sound like a piece that you've exactly heard before.
And so we've used these in the past, these piano puzzlers, to examine...
Deja Entendu.
And interestingly, over the years, in some of our research, taking this approach to examining the feeling of Deja Entendu.
So the feeling of having heard something before, even though you're pretty sure this is also a new song that you've never exactly heard before.
People also have feelings of prediction during déjà entendu.
So if we ask people if they feel like they can predict whether the next note upon stopping the musical piece is going to be high or low, people feel very strongly that they can make that prediction, even when they can't.
And when we ask people if they feel like they can predict whether the next sound is going to come from the left or from the right, And they feel very strongly when they have that sense of déjà entendu for a musical piece.
They feel very strongly that they can predict where the next song is, where the next note is going to come from.
Is it going to be from the left or the right?
We're talking about déjà vu, and my guest is Anne Cleary, who researches déjà vu.
She is a professor at Colorado State University and author of the book, The Déjà Vu Experience.
So Anne, I imagine the history of déjà vu is filled with explanations of the paranormal, that this must mean all kinds of things and who knows what.
What are some of the other non-scientific explanations for déjà vu that you find intriguing?
So there are a number of non-scientific explanations of deja vu that fall into the paranormal realm.
And one of them concerns past lives.
So one explanation that has existed in the paranormal literature for centuries probably over 100 years or so is that the explanation might be that when you have this sensation, it is because it's alerting you to a very similar experience that you lived through in a past life.
Now I suspect that this is just a way that people have come up with for trying to explain the bizarre experience.
That is deja vu.
We have an inherent need to explain to ourselves why we're experiencing certain things.
When we have a sensation like that, like deja vu, that's jarring and maybe even a little bit eerie or alarming, it can be comforting to come up with an explanation, to kind of explain it away.
Another paranormal explanation that has come up in various literatures over the past hundred years is is the idea that deja vu is somehow a psychic phenomenon.
And in fact, you'll see that explanation even today.
If you were to type into a search engine, signs your psychic.
Very often.
One of the factors that will come up in a list on a number of different websites is deja vu, or the idea that you experience deja vu very often, but that may be a sign that you're psychic.
And I suspect that one of the reasons why deja vu tends to be associated with this idea of being psychic or able to predict the future is its very association with the sense of prediction.
So we've now been able to document in a scientific way that there actually is a subjective association.
It's illusory, but there is a subjective association between the sensation of deja vu and the sensation of being able to predict what's going to happen next.
Another question I wanted to ask is so when you experience deja vu and you realize it's deja vu, is it kind of like when you're dreaming and you realize you're dreaming, you kind of pop out of it, you wake up?
When you're in deja vu, does the same thing happen?
That's a very interesting question.
I haven't thought about that before, but I can say that when I personally experienced deja vu which is quite rare these days, it seems to be a brief, fleeting experience.
And so you know I, as a memory researcher who studies deja vu, I love having the experience and would like to be able to analyze it when it happens to me.
And I do feel, as you describe, that when it happens it's so brief and fleeting that uh, By the time I start to analyze it, it's gone.
And maybe it's because I'm trying to analyze it, now it's gone and I can't analyze it in real time.
You mentioned that most of the experiences that people have with deja vu are places.
When you look at the experiences, are there any other common threads in terms of...
People not being in them, or in them they're perceived as negative experiences or benign experiences, or positive experiences, or they remind you of positive.
Are there any common threads?
The most common seems to be places followed by next common elicitor of deja vu.
If you look across people's survey reports, conversations with people.
So things that other people said.
So, when you're in the midst of a conversation, something someone is saying to you can be a common elicitor.
And then followed by infrequency of people's reports across survey studies.
And the feeling of you having said something to someone else before.
So the feeling that you have said this exact thing before, that you're saying right now in the midst of a conversation.
Yeah, I've had all of that.
But you know what I've never really felt I've had is the...
Where I felt like I knew what was going to happen next.
I can't, I don't think I've ever.
I can't remember a time when I felt like I knew what was going to happen.
It was just like a fleeting.
I've been here before, I've done this before, I've said this before, and then it's gone.
And I share your experience.
I don't think that I have ever had the feeling of prediction before myself.
And like you, for me, it's very fleeting.
And I kind of wish I could have that experience so I could try to analyze it.
But I don't think that I ever have.
I hear it from many, many people though, which is what has piqued my interest in trying to study it.
It definitely happens to a lot of people.
How would you categorize?
I mean, is this a flaw in the brain?
Is this just like a misfire?
Is there any sense of what causes it?
So I think that for most people, what probably causes deja vu is an environmental circumstance, where something in the environment is highly similar to something that you've experienced in your past.
And you're failing to recall the source of that familiarity.
But yet, at the same time, you're also noticing the newness of the situation that you're in and that it's probably that rare occurrence in the environment around you of newness and oldness, which probably doesn't happen very often, and so it causes this sort of brief hang-up of wait.
Is this new?
Is this old?
What is driving this and it it captures your attention and prompts you to really try to search your memory.
I think what most of us do when we're in the midst of that type of experience is search our memory.
We start looking in our memory for what's relevant here.
Is there something that this is reminding me of?
Why is this feeling so familiar?
And so I think for most people, it's this rare environmental situation that's eliciting it.
And it's probably just indicating the normal operation of our memories.
There are some cases though, where it really can be indicative of a glitch in the system, if you will.
So very frequent deja vu can be an indicator of certain types of seizure activity.
And that has been known in the medical community for some time now.
So if you're experiencing deja vu say, four times a week, Or maybe even more than that, there are people who will experience deja vu several times a day.
If it's happening that often, it could be an indication that there are some minor seizures taking place in the brain.
So why do you study it?
What's the hope?
What's the potential outcome of understanding deja vu better?
So I think that if we understood deja vu better, it would give us a good glimpse into more fully understanding human memory as a whole.
So I suspect that when deja vu happens, it's providing us this window into how our cognitive processes are working, in a way that they're probably usually working under the surface.
So you had mentioned earlier that in most situations Things are familiar and yet we don't have this striking sensation of deja vu.
One hypothesis that I have is that perhaps familiarity detection, this ability of our minds to process whether something's familiar versus novel, It's usually something that's just rapidly occurring, sort of underneath the surface and it's not really grabbing our attention.
Do people in all cultures report deja vu?
That is a big question that I currently have.
And in fact I have been collaborating with some colleagues to try to answer that question because it's unknown.
I can say that there are a number of research papers in different cultures and languages on the topic of deja vu.
And so it's not limited to say English speaking or French speaking Western types of cultures.
When I was visiting some colleagues in China several years ago, I began speaking about some of my research on deja vu and asking if these colleagues were familiar with what I was talking about.
And they began arguing with one another in Mandarin. about what the appropriate term would be.
And so they all knew what I was talking about, but it wasn't clear that there was a single term that would be used in Mandarin to describe the experience.
So I think there's reason to suspect that it may be a culturally universal experience, But there has not been a good research study yet that has fully explored that.
Well, I have always liked that experience of deja vu.
And I know that there will always be people like you who you know try to explain it scientifically and understand what it is from a scientific point of view.
But I like the magical and mystical sense that I have of deja vu.
And I think most people do.
Anne Cleary has been my guest.
She's a professor at Colorado State University.
She researches déjà vu, and she is author of the book, The Déjà Vu Experience.
And there's a link to that book in the show notes.
Thank you, Anne.
Thanks, Mike.
This was fun.
And that's it for this SYSK Trending episode.
I'm Mike Carruthers.
Thank you for listening to Something You Should Know.
