[Music] on a hot summer day in 2008 a professor leaves his campus building and heads across a parking lot toward his car ordinarily this would be a routine experience and not something at all memorable but this day is memorable to him it's memorable to him because on his way across the parking lot something stopped him in his tracks he remembers the heat emanating from the pavement as he stood there what stopped him in his tracks was an overwhelming sense that he had been through this exact situation before and this was not the kind of familiarity that you might have simply from having been through that parking lot before nor was it the kind of familiarity that you might have with a face that you couldn't place this was an intense feeling that everything that he was experiencing at this moment he had lived through before the precise lineup of the cars around him the clothes he was wearing the feel of the bag on his shoulder the sounds coming at him from different directions the heat from the pavement he felt as if he knew what was going to happen in the near future a bike would be coming by from his left from a place where bikes shouldn't even be riding the woman would be wearing a white shirt and riding a 10-speed this experience happened to a professor that i know named matthew and there are two noteworthy aspects to this story one is that it illustrates deja vu which is an overwhelming sense of familiarity with this situation that seems like it shouldn't be at all familiar because it's actually new the other is that it illustrates a phenomenon that many refer to as precognition which is for knowledge of an event especially of a paranormal kind if there's a really strange relationship between deja vu and precognition which is apparent in this story it's also apparent if you do an internet search on the term precognition which will turn up websites like one entitled top 10 signs your pre-cog number four on this list is you have deja vu another website is entitled 13 signs you have psychic abilities number two on this list is you've experienced deja vu countless times it goes on to say deja vu is a sure sign that you have some sort of psychic ability but this connection between deja vu and precognition is not just the stuff of psychic websites researchers who have surveyed people about their past experiences with deja vu have encountered reports of precognition for example one survey participant said everything that she said i knew she was going to say another survey participant said it almost feels like i'm having a premonition and yet another said it's like an old memory that i'm in the middle of living out then there is this peculiar case from 1959 a neurosurgeon named wilder penfield induced a deja vu in a patient through brain stimulation dr penfield was famous for stimulating the brains of consciously awake patients during brain surgery and having them report on their subjective experience the idea was to try to understand how brain activity relates to subjective experience it's not surprising that he was able to induce deja vu by stimulating a region known as the medial temporal lobe region right about here and this is not surprising because we now know that this area is involved in deja vu we know this because patients who have seizures that originate in this part of the brain tend to have chronic deja vu as a symptom so it's not surprising that he was able to induce deja vu by stimulating this part of the brain what is surprising is that he also seems to have induced a feeling of seeing into the future upon stimulation the patient reported just a tiny flash of familiarity and a feeling that i knew everything that was going to happen in the near future as though i had been through all this before and i thought i knew exactly what you were going to do next so can deja vu really lead to precognition as a scientist i was skeptical but i also wondered if there might be a logical explanation here that's not rooted in the paranormal after all there are many phenomena throughout history that people have attributed to paranormal causes prior to understanding them for example prior to understanding microorganisms people often attributed paranormal causes to the reason behind contagious disease and prior to understanding epilepsy people often thought that seizures were a sign of demon possession so i wondered if perhaps there was a logical explanation to the connection between deja vu and precognition as well as a scientist i really wanted to find a way to study this in the laboratory i just needed to find a way to induce the experience of deja vu in the lab what we would need is some sort of deja vu generator and while this might sound like the stuff of science fiction it's actually not that far-fetched an idea as one of my former students went on to post on twitter at one point professor cleary once asked me to help build a deja vu generator in vr you say yes to a thing like that vr here refers to virtual reality and what we had done using virtual reality was we attempted to create that seemingly inexplicable juxtaposition between intense familiarity and newness that is characteristic of deja vu if you think back to the definition of deja vu it's an overwhelming sense of familiarity in a situation that feels like it shouldn't be familiar because it's actually new well our deja vu generator was based on a theory about how deja vu works the theory is that if you're in the midst of a current experience and there happens to be a highly similar prior experience somewhere in your memory that prior memory can produce a feeling of familiarity with the current situation if you happen to be able to call to mind that prior experience by consciously recollecting it then you won't have deja vu because that feeling of familiarity will be explainable however if you fail to consciously recollect that prior experience that is sending you those feelings of familiarity that is when you're likely to have deja vu because now you're faced with this feeling of familiarity that's not easy to explain in a situation that seems new the more intense the feeling of familiarity the more likely deja vu is so we attempted to create this type of experience using virtual reality and the way that we did this was to create high similarity between otherwise distinct scenes by creating uh identical spatial layouts between them this is a bird's eye view of how we achieve this on the left is a bird's eye view of the spatial layout of an aquarium on the right is a bird's eye view of a spatial layout of a reception area so we would place participants within a scene like the aquarium and then sometime later on in the study we would place them in the identically configured scene like the reception area here's another example this time of a bedroom and here is its identically configured scene a clothing store we developed dozens of these types of identically configured scenes for use in our study and the idea was that when a person is immersed in a scene like this clothing store if they fail to recall the spatially similar scene from memory in this case the bedroom will that juxtaposition of familiarity and novelty lead them to be more likely to report deja vu in this case than in a spatially unique and new scene and sure enough that is exactly what we found people were more likely to report deja vu among scenes that spatially resembled earlier but forgotten scenes than among completely uh spatially unique scenes now it's important to note that spatial similarity is not the only factor that can contribute to deja vu it's likely only one we've did another study where we were able to show that the more similar a current situation is to a forgotten situation in memory the more likely deja vu actually is so if you think back to matthew walking across that parking lot it was likely more than just the lineup of the cars it was the clothes he was wearing the heat from the pavement the feel of the bag on his shoulder the different sounds coming from different directions all of these things likely combined to produce his feeling of deja vu that day so we have a deja vu generator and now i've told you a little bit about how it works so the question is can we use this deja vu generator to examine the question of whether deja vu can lead to precognition if you think back to one of the survey participants from earlier who'd stated it's like an old memory that i'm in the middle of living out what we really needed to do was find a way to put people in the middle of a memory we wanted to see if we could put people in the middle of a memory that they forgot could they then predict what happens next on the basis of that unretrieved memory if so we might have the first scientific explanation for how people can have precognition during deja vu so what we did was we took the same scenes that we had used in our previous virtual reality research and we turned them into virtual tours so that they would unfold over time much like a real life experience might and so a person might be exploring a virtual tour like the aquarium and that tour would follow a particular navigational path through the scene maybe it would end in a leftward turn then sometime later on in the study the person would be viewing a virtual tour of an identically configured scene like the reception area in this case that tour would follow the exact same navigational path as the earlier similar scene but only up to a point it would stop short of that final leftward turn this was our method of putting people in the middle of a memory so to speak we wanted to see if this would enable actual prediction so if a person is stopped at that turn in the reception area and they can't recall that earlier tour with the aquarium can they predict that the turn should be left without knowing why well our deja vu generator worked as planned deja vu was indeed more likely among virtual tours that were highly similar to earlier viewed but forgotten tours however there was no predictive ability whatsoever people showed no precognition i was very disappointed and i actually threw in the towel at one point and let this study sit untouched and unpublished for many years because i deemed it a huge failure and then years later it occurred to me well wait a minute we never actually asked people if they felt like they could predict if you think back to the patient from 1959 in the brain stimulation study presumably he didn't actually predict what the doctor was going to do next presumably that was an illusion and so we ran this study again and this time we added the question do you feel like you know the direction of the next term and sure enough people were more likely to feel like they knew what the direction of the next turn should be when they were experiencing deja vu than when they were not so there really is something to this link between deja vu and precognition it just turns out to be illusory now i know what some of you are probably thinking some of you are probably sitting there thinking no that's not my experience with deja vu when i have it i really do predict what happens next i was talking about these results at a conference once and a scientist approached me afterward and he kind of looked both ways to make sure nobody was around and he lowered his voice and he asked well how do you explain when you really do predict and so i thought about this for a long while and i began to wonder if perhaps our brains have a way of tricking us into thinking that we predicted after the fact when perhaps we hadn't and so the idea goes like this perhaps when we're in the midst of a deja vu state it feels to us like we're right on the verge of retrieving from memory this entire situation around us including how it unfolds this might be somewhat similar to when you have an experience of a word on the tip of your tongue you feel like it's right there you don't quite have it yet but you're going to have it any moment we might call it in the case of deja vu being on the tip of an experience if you're on the tip of an experience it might feel like you're right about to retrieve exactly what happens next and this might give rise to a feeling of precognition then as the situation continues to unfold before your eyes it continues to feel intensely familiar well perhaps that intense familiarity is taken to be a signal of having correctly predicted maybe it makes us feel like we knew it all along when we really didn't so to test this in the lab we used our virtual tour approach again so we had people view virtual tours where they would stop short of a turn and they were asked are you experiencing deja vu and do you feel like you know the direction of the next turn but then what we did differently this time is we then let it continue into the next turn now we had set this up so that it would essentially be like trying to predict a coin flip for every participant there was a 50 chance that the turn would be last and a 50 chance that the turn would be right in this case the turn went left but the participant was then asked did that unfold as you had expected and sure enough what we found was that people were more likely to feel like they knew it all along following deja vu we ran a slightly different variant of this study where we additionally asked people to rate how intense their feeling of familiarity with the scene was and what we found was that high familiarity intensity is the common thread to all of this when you're faced with that juxtaposition of familiarity and novelty that's difficult to explain if that familiarity is really intense it can lead to an illusion of precognition like you're right about to predict and then after the scene does unfold it can lead to an illusion of having known it all along so in short deja vu doesn't lead to precognition it leads to illusory precognition thank you