SYSK TRENDING: Understanding Déjà Vu

Almost everyone has experienced déjà vu—that strange, fleeting feeling that what’s happening right now has somehow already happened before. It can be subtle or intensely vivid, sometimes even a little unsettling. For a moment, it feels like your brain is replaying reality. But is it just a glitch in memory… or something more? Scientists have been trying to understand déjà vu for decades, and the answers are more fascinating than you might expect. Is it a sign your brain is working correctly—or a sign something is off? Why does it tend to happen in certain situations and not others? And why can it feel so real, even when you know it isn’t? Anne Cleary, professor at Colorado State University and one of the leading researchers studying this phenomenon, joins me to explain what’s really going on inside your brain during a déjà vu experience. She is the author of The Déjà Vu Experience (https://amzn.to/3ErC6Fm), and in our conversation she breaks down the science behind this eerie sensation, why it happens, and what it reveals about how memory actually works. She also has a fascinating TED Talk on the subject you can watch here: https://www.youtube.com/watch?v=nFAvUkjba-Q If you’ve ever paused mid-moment and thought, “Wait… I’ve lived this before,” this is an explanation you won’t want to miss. PLEASE SUPPORT OUR SPONSORS DUTCH: If your pet is still scratching and you’ve tried everything at the pet store –it’s time to stop guessing and go prescription. Support us and use code SYSK for $40 off your membership at ⁠⁠⁠https://Dutch.com⁠⁠⁠ RULA: Thousands of people are already using Rula to get affordable, high-quality therapy that’s actually covered by insurance. Visit ⁠⁠⁠https://Rula.com/sysk⁠⁠⁠ to get started. QUINCE: Refresh your wardrobe with Quince! Go to ⁠⁠⁠⁠⁠⁠⁠⁠⁠https://Quince.dom/sysk ⁠⁠⁠⁠⁠⁠⁠⁠⁠for free shipping on your order and 365-day returns. Now available in Canada, too! SHOPIFY: See less carts go abandoned with Shopify and their Shop Pay button! Sign up for your $1 per month trail and start selling today at ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠https://Shopify.com/sysk⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ Learn more about your ad choices. Visit megaphone.fm/adchoices

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:02Mike Carruthers?

  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 déjà vu. Joining me is cognitive scientist Anne Cleary, who has spent years researching the science behind déjà vu.

• 0:46Mike Carruthers?

  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. Now, here's something that might be worth a minute of your time. How would you like $1,000 to spend on shopping? Especially with the holidays coming? Well, the people behind Shopify have a shopping site called shop.com. And to celebrate the new shop.com, they're giving away $1 million in Shop Cash. But not to one person. A thousand people will each win $1,000 in Shop Cash.

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• 2:28Mike Carruthers?

  There's a pretty good chance that you have experienced déjà 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.

• 3:12Mike Carruthers?

  Hi Anne, welcome to Something You Should Know.

• 3:15Speaker 01

  Thanks.

• 3:16Mike Carruthers?

  So you've been studying this phenomenon of déjà 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?

• 3:28Speaker 01

  Well, the definition of déjà 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. And so you're unable to recall the source of the familiarity that you're experiencing with it.

• 4:08Mike Carruthers?

  What is the history of déjà vu? In the sense of, you know, when was it first identified? How long has it been studied?

• 4:17Speaker 01

  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 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 the single use phrase in English for describing the experience itself.

• 5:01Mike Carruthers?

  Well, we use it in English, but it is a it is a French word. So why do we continue to use a French word?

• 5:08Speaker 01

  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.

• 5:50Mike Carruthers?

  What do we know about the experience of déjà 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?

• 6:08Speaker 01

  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 déjà vu at some point in their life. Now, an interesting aspect and a complete mystery regarding déjà 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 twenties

• 6:48Speaker 01

  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.

• 7:19Mike Carruthers?

  Does it normally happen in the morning, in the evening? It doesn't matter?

• 7:25Speaker 01

  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.

• 7:48Mike Carruthers?

  So here's the thing that I really don't understand about déjà 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.

• 8:13Mike Carruthers?

  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 déjà vu because I know I've been there before. But when I have déjà vu, it's a very kind of mystical wow. So what's the difference?

• 8:41Speaker 01

  Yes, and this is exactly why I am so interested in déjà 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 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

• 9:26Speaker 01

  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 déjà 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.

• 10:08Speaker 01

  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 déjà vu.

• 10:40Mike Carruthers?

  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.

• 10:48Speaker 01

  Yes.

• 10:50Mike Carruthers?

  And the the experience of déjà vu, I know you talk in your TED Talk that 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 what they know what's going to happen next.

• 11:10Speaker 01

  Yes, this is one of the most interesting aspects of déjà vu from my perspective. So I I've been studying déjà vu for over a decade now from the perspective that it is probably a window on to how our memory systems work. And in the process of studying it, I have come to the realization that for many, many people, déjà 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 déjà vu experience.

• 11:56Speaker 01

  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 déjà vu actually is and people's associating it with the paranormal. But enough people kept coming forward and contacting me or telling me their déjà vu stories that with this element involved, this feeling of prediction or knowing what's happened, what's going to happen next, that I began to wonder if if there might be something to this and something that might be able to be studied scientifically.

• 12:37Speaker 01

  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 déjà 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.

• 13:08Mike Carruthers?

  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.

• 13:30Speaker 01

  It's interesting that you mention that, because there is an auditory form of déjà vu. The phrase for that is déjà entendu. 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 Adolf, 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

• 14:14Speaker 01

  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 déjà entendu. And interestingly, over the years, in some of our research, taking this approach to examining the feeling of déjà entendu, so the feeling of having heard something before,

• 14:57Speaker 01

  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, 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?

• 15:43Mike Carruthers?

  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?

• 16:15Speaker 01

  So there are a number of non-scientific explanations of déjà 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 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 déjà vu.

• 16:59Speaker 01

  We have an inherent need to explain to ourselves why we're experiencing certain things. And when, when we have a sensation like that, like déjà vu, that's, 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...

• 17:22Speaker 01

  Explanation that has come up in various literatures over the past hundred years is the idea that déjà 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 you're psychic. Very often, one of the factors that will come up in a list on a number of different websites is déjà vu, or the idea that you experience déjà vu very often, that that may be a sign that you're psychic. And I suspect that one of the reasons why déjà vu tends to be associated with with

• 18:02Speaker 01

  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 déjà vu and the sensation of being able to predict what's going to happen next.

• 18:26Mike Carruthers?

  Another question I wanted to ask is, so when you experience déjà vu and you realize it's déjà 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 when you're in déjà vu, does the same thing happen?

• 18:44Speaker 01

  That's a very interesting question. I haven't thought about that before, but I can say that when I personally experienced déjà vu, which is 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 déjà 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 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.

• 19:22Mike Carruthers?

  You mentioned that that most of the experiences that people have with déjà vu are places. When you look at the experiences, are there any other common threads in terms of the people not being in them or in them, they're negative, perceived as negative experiences, or benign experiences, or positive experiences, or they remind you of positive? Is there any, are there any common threads?

• 19:50Speaker 01

  The most common seems to be places with followed by next common elicitor of déjà 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 in frequency of people's reports across survey studies, the 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.

• 20:33Mike Carruthers?

  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, when I felt like I knew what was going to happen. It was just a like a fleeting, I've been here before, I've done this before, I've said this before, and then it's gone.

• 20:55Speaker 01

  And I, I share your experience. I, I don't think that I have ever had the feeling of prediction before myself. And, 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, in trying to study it. It definitely happens to a lot of people.

• 21:22Mike Carruthers?

  How would you categorize, I mean, is this a flaw in the brain? Is this just a like a misfire? Is this just, is there any sense of what causes it?

• 21:34Speaker 01

  So I think that for most people, what probably causes déjà vu is, 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.

• 22:18Speaker 01

  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 for most people, it's this rare environmental situation that's eliciting it. And it's probably just indicating the normal operation of 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 déjà vu can be an indicator of certain types of seizure activity.

• 23:00Speaker 01

  And that has been known in the medical community for some time now. So if if you're experiencing déjà vu, say, four times a week, or maybe even more than that, there are people who will experience déjà 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.

• 23:24Mike Carruthers?

  So why do you study it? What's the hope? What's the the potential outcome of understanding déjà vu better?

• 23:32Speaker 01

  So I think that if we understood déjà vu better, it would give us a good glimpse into more fully understanding human memory as a whole. So I I suspect that when déjà vu happens, it's it's 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 déjà vu. One hypothesis that I have is that perhaps familiarity detection,

• 24:14Speaker 01

  this ability of our minds to process whether something's familiar versus novel, is usually something that's just rapidly occurring sort of underneath the surface, and it's not really grabbing our attention.

• 24:28Mike Carruthers?

  Do people in all cultures report déjà vu?

• 24:32Speaker 01

  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 déjà 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 déjà vu and asking if these colleagues were familiar with what I was talking about.

• 25:13Speaker 01

  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.

• 25:42Mike Carruthers?

  Well, I have always liked that experience of déjà 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 déjà 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.

• 26:19Speaker 01

  Thanks, Mike. This was fun.

• 26:21Mike Carruthers?

  And that's it for this S Y S K Trending episode. I'm Mike Carruthers. Thank you for listening to Something You Should Know.