WEBVTT - Déjà vu, Anxiety and Dreams, Part 2 0:00:03.040 --> 0:00:05.360 Welcome to Stuff to Blow Your Mind production of My 0:00:05.480 --> 0:00:14.480 Heart Radio. Hey, welcome to Stuff to Blow Your Mind. 0:00:14.520 --> 0:00:17.200 My name is Robert Lamb and I'm Joe McCormick, and 0:00:17.239 --> 0:00:20.239 we're back with part two of our talk about deja vu. 0:00:20.680 --> 0:00:22.960 That's right, if you didn't listen to part one, go 0:00:23.000 --> 0:00:25.239 back and listen to part one, because this is this 0:00:25.320 --> 0:00:28.319 is definitely one of those, uh pair of episodes where 0:00:28.360 --> 0:00:31.600 you need to experience them in order. But we we 0:00:31.680 --> 0:00:35.480 kicked off by talking about some personal experiences with deja vu, 0:00:36.159 --> 0:00:39.840 uh and also getting into some of the rich variety 0:00:39.960 --> 0:00:44.120 that is to be found under the broad categorization of 0:00:44.200 --> 0:00:48.480 deja vu experiences. In this episode, we're going to kick 0:00:48.520 --> 0:00:51.120 off by really getting into some of the major theories 0:00:51.120 --> 0:00:55.360 and explanations for this thing called deja vu. Right, So, 0:00:55.520 --> 0:00:59.360 last time I cited there's a major paper on the 0:00:59.360 --> 0:01:01.640 research on deja vu that was published in two thousand 0:01:01.760 --> 0:01:05.560 three by a researcher named Alan S. Brown, was published 0:01:05.600 --> 0:01:08.479 in Psychological Bulletin, and we cited it last time, talking 0:01:08.480 --> 0:01:11.880 about a lot of the common findings about deja vu, 0:01:11.959 --> 0:01:15.039 including the fact that it appears to be very strongly 0:01:15.080 --> 0:01:18.600 associated with stress and fatigue. The more tired and stressed 0:01:18.600 --> 0:01:20.440 out you are, the more likely you are to have 0:01:20.440 --> 0:01:23.880 a deja vu experience. The studies that show it associated 0:01:23.880 --> 0:01:27.240 with travel, people who travel are more likely to experience 0:01:27.280 --> 0:01:30.960 deja vu. Um, the studies that show that that certain 0:01:31.040 --> 0:01:34.400 drugs can apparently cause lots of deja vu. And then 0:01:34.520 --> 0:01:38.360 especially the fact that deja vu appears to decrease with age, 0:01:38.480 --> 0:01:40.600 that as you get older in life, you you on 0:01:40.720 --> 0:01:44.600 average have fewer deja vu experiences, which I'm still finding 0:01:44.600 --> 0:01:47.560 interesting and I'm coming back to that one a lot. 0:01:47.600 --> 0:01:50.160 But yeah, So now we want to dive into, uh, 0:01:50.200 --> 0:01:53.120 the major theories and explanations, and my main guide on 0:01:53.160 --> 0:01:57.160 this is Brown's paper from two thousand three where he 0:01:57.160 --> 0:01:59.560 he reviews most of the existing research. There's been a 0:01:59.560 --> 0:02:01.880 few develop elements since then, and we'll talk about those 0:02:02.680 --> 0:02:06.400 later on, but they're they're basically several. They're like four 0:02:06.440 --> 0:02:11.440 main categories that Brown outlines about what the explanations for 0:02:11.520 --> 0:02:14.280 deja vu could be. And the categories are going to 0:02:14.360 --> 0:02:16.520 be the following. So first, you've got some kind of 0:02:16.680 --> 0:02:22.000 dual processing. Second, you've got neurological dysfunction, Third, you have 0:02:22.520 --> 0:02:28.760 memory issues, and then fourth you have attentional catch up. Um. Now, 0:02:28.800 --> 0:02:30.480 one of the first things I think we should mention 0:02:30.600 --> 0:02:33.200 is that it can be kind of difficult to understand 0:02:33.240 --> 0:02:36.280 the causes of deja vu because deja vu is inherently 0:02:36.440 --> 0:02:40.280 a little bit difficult to study. It's not super easy 0:02:40.360 --> 0:02:44.760 to trigger episodes of deja vu in a laboratory or 0:02:44.840 --> 0:02:48.360 brain imaging context. There's some techniques we can mention, but 0:02:48.720 --> 0:02:50.679 you can't just like start up an f M R 0:02:50.720 --> 0:02:53.520 I and then run it and hope somebody has an 0:02:53.520 --> 0:02:56.880 experience of deja vu while it's running. Remember, like, deja 0:02:56.960 --> 0:03:00.440 vu is relatively rare. Most people experience it at some 0:03:00.480 --> 0:03:02.560 point in their life. But I think you know, an 0:03:02.560 --> 0:03:04.960 average figure figure is that a lot of people say 0:03:05.000 --> 0:03:07.760 they have a deja vu experience something like once a year. 0:03:08.280 --> 0:03:11.040 So you couldn't expect for it to just happen while 0:03:11.040 --> 0:03:13.680 you're looking for it. Yeah, deja vu is not really 0:03:13.680 --> 0:03:16.200 the sort of thing you can just have on command. 0:03:16.280 --> 0:03:19.360 Nobody can say, all right, have some deja vu. And likewise, 0:03:19.880 --> 0:03:21.920 it's not that I haven't seen I don't think I've 0:03:21.960 --> 0:03:24.640 seen any evidence or any claims of anybody who could 0:03:24.680 --> 0:03:27.960 produce a feeling of deja vu. Just by willing it 0:03:28.160 --> 0:03:32.399 that we will get into some unique cases a little later, right. Uh. 0:03:32.720 --> 0:03:36.520 That would be an interesting uh skill if one had it. Now. 0:03:36.560 --> 0:03:39.480 There are some cases where it appears that deja vu 0:03:39.600 --> 0:03:43.440 can be triggered by certain clinical interventions. We mentioned a 0:03:43.480 --> 0:03:46.480 couple of cases of it being associated with certain combinations 0:03:46.480 --> 0:03:48.880 of drugs in the last episode, like a couple of 0:03:48.960 --> 0:03:53.600 drugs used to treat the flu um. But also by 0:03:53.840 --> 0:03:58.080 no big surprise here, electrical stimulation of the brain. Uh. 0:03:58.120 --> 0:04:01.240 In his big review, Brown described abs findings about deja 0:04:01.280 --> 0:04:04.920 vu and brain stimulation and patients with temporal lobe epilepsy. Again, 0:04:05.040 --> 0:04:09.040 remember um from last time that deja vu is one 0:04:09.320 --> 0:04:12.080 of the symptoms that has been described as part of 0:04:12.120 --> 0:04:16.320 the aura preceding and epileptic seizure in people with temporal 0:04:16.360 --> 0:04:20.359 lobe epilepsy. But another thing about temporal lobe epilepsy is 0:04:20.400 --> 0:04:24.200 that in some cases in history, electrical stimulation of the 0:04:24.240 --> 0:04:28.400 brain has been used in the treatment and diagnosis of 0:04:28.520 --> 0:04:32.320 temporal lobe epilepsy. UM. And so I want to read 0:04:32.360 --> 0:04:35.240 a section from Brown here writing about this. Brown writes, 0:04:35.320 --> 0:04:38.680 quote with surface stimulation of the cortex, and that's electrical 0:04:38.720 --> 0:04:43.560 stimulation Mullen and Penfield elicited deja vu experiences in ten 0:04:43.720 --> 0:04:47.760 out of two hundred and seventeen people with temporal lobe epilepsy. 0:04:47.960 --> 0:04:52.440 Recent procedures involving deep electrode brain implantation have shown that 0:04:52.520 --> 0:04:56.200 deja vu, similar to one that occurs in the aura, 0:04:56.360 --> 0:05:00.400 can be elicited with stimulation of the amygdala and hippocampus, 0:05:00.440 --> 0:05:03.640 Although these experiences were not reported in detail. The deja 0:05:03.760 --> 0:05:08.039 vu generally consisted of a sudden feeling of unfamiliarity in 0:05:08.040 --> 0:05:12.520 the hospital environment and was often accompanied by epigastric phenomena 0:05:12.600 --> 0:05:17.280 and fear and uh. Epigastric phenomena refers to strange feelings 0:05:17.279 --> 0:05:19.560 in the abdomen, especially I think the upper part of 0:05:19.640 --> 0:05:22.760 the abdomen. I've read it described as um getting a 0:05:22.760 --> 0:05:25.599 feeling sort of above the stomach and right below the chest, 0:05:26.080 --> 0:05:28.400 like this weird feeling, kind of like when you're on 0:05:28.400 --> 0:05:31.440 a roller coaster and you're you're plummeting down on the 0:05:31.480 --> 0:05:34.400 other side, you know that rising in the gut. Yeah, yeah, 0:05:34.440 --> 0:05:35.960 I believe we discussed that a little bit in the 0:05:36.000 --> 0:05:39.600 last episode. Brown writes quote. The elicitation of deja vou 0:05:39.720 --> 0:05:44.040 through electrical stimulation may not be reliable hal grin at all. 0:05:44.080 --> 0:05:47.360 In nineteen seventy eight, stimulated several dozen brain locations in 0:05:47.400 --> 0:05:50.600 a group of people with temporal lobe epilepsy on two 0:05:50.640 --> 0:05:53.839 different occasions, two weeks apart, and found that a number 0:05:53.880 --> 0:05:56.960 of sites that elicited a deja vu on one session 0:05:57.080 --> 0:06:00.640 did not do so on the other. Deja vu experiences 0:06:00.680 --> 0:06:05.599 also resulted from stimulating the non diseased hemisphere, suggesting that 0:06:05.640 --> 0:06:09.080 the experience is not necessarily specific to the tissue where 0:06:09.080 --> 0:06:12.280 the seizure originates. So that's interesting. You've got deja vu 0:06:12.360 --> 0:06:16.360 associated in some cases with people with temporal lobe epilepsy, 0:06:16.480 --> 0:06:20.800 but that it appears like if you you stimulate one 0:06:20.839 --> 0:06:22.920 part of the brain one week and it gives you 0:06:22.960 --> 0:06:25.479 deja vu, but a different part of the brain the 0:06:25.520 --> 0:06:27.719 next week that might give you deja vu, and maybe 0:06:27.720 --> 0:06:30.120 the original place that gave you deja vu last week 0:06:30.160 --> 0:06:33.000 doesn't give it to you anymore. So, uh yeah, there's 0:06:33.000 --> 0:06:37.599 some kind of discontinuity here about how exactly stimulating different 0:06:37.640 --> 0:06:41.480 parts of the brain contribute to the deja vu experience subjectively. 0:06:42.000 --> 0:06:44.400 But there have been some other interesting things that I 0:06:44.440 --> 0:06:47.480 know we'll get too later in the episode of trying 0:06:47.520 --> 0:06:52.359 to trigger deja vu and otherwise neurologically typical people, for example, 0:06:52.480 --> 0:06:56.640 using using certain types of virtual reality stimulation. That, yeah, 0:06:56.680 --> 0:06:58.279 I think we're we'll get to that maybe in the 0:06:58.279 --> 0:07:00.960 third part of today's episode, But I guess we got 0:07:00.960 --> 0:07:04.760 to get directly to these four main theories explaining what 0:07:04.839 --> 0:07:06.760 could be going on in the brain when you're having 0:07:06.800 --> 0:07:10.960 deja vu. Um, assuming it's not like a supernatural phenomenon, 0:07:11.000 --> 0:07:12.920 which we don't think it is, that there's a good 0:07:12.960 --> 0:07:16.400 amount of evidence that it is a function of the brain. 0:07:17.240 --> 0:07:21.280 So the ghost hypothesis is really not not not highly 0:07:21.320 --> 0:07:24.720 valued scientific circles here. Yeah, so we won't be picking 0:07:24.800 --> 0:07:27.120 up on that one today. But so again, these are 0:07:27.280 --> 0:07:31.960 the four main branches that brown outlines are dual processing, 0:07:32.560 --> 0:07:37.280 neurological dysfunction, memory error, and attentional catch up. And I'll 0:07:37.320 --> 0:07:39.640 go ahead and say that I think the main two 0:07:39.840 --> 0:07:43.400 branches that have explanatory power going for them today, at 0:07:43.480 --> 0:07:45.480 least as far as I can tell, are the last 0:07:45.520 --> 0:07:49.160 two I mentioned, like the memory ones and the attentional ones. 0:07:49.720 --> 0:07:51.840 But since the other two have been very important in 0:07:51.920 --> 0:07:54.320 the history of studying deja view, we should at least 0:07:54.320 --> 0:07:56.800 talk about them for a bit. Um. So the first 0:07:56.840 --> 0:07:59.480 one is this idea of dual processing. There are these 0:07:59.560 --> 0:08:03.000 multiple hypotheses that fall into this category, but they all 0:08:03.040 --> 0:08:05.360 basically amount to the same thing. They say, you know, 0:08:05.400 --> 0:08:08.640 there are two different processes in the brain that usually 0:08:08.680 --> 0:08:13.120 occur simultaneously. They happen at the same time, but occasionally 0:08:13.200 --> 0:08:17.720 they become a synchronous, they get detached in time and 0:08:17.760 --> 0:08:22.040 suddenly there's a lag between them. And these types of 0:08:22.080 --> 0:08:25.800 explanations tend to be the oldest and least scientifically justified, 0:08:26.320 --> 0:08:28.720 but they are kind of interesting to think about. So, 0:08:28.960 --> 0:08:31.960 for example, one that Brown sites is the idea of 0:08:32.640 --> 0:08:36.480 this old theory of dual consciousness. Uh. The idea is 0:08:36.559 --> 0:08:39.360 that there there are two separate types of consciousness in 0:08:39.400 --> 0:08:42.720 the brain. There's one normal type of consciousness, and what 0:08:42.800 --> 0:08:46.280 that does is monitor everything that happens in the outside world. It's, 0:08:46.360 --> 0:08:49.160 you know, your regular brain that's looking out through your 0:08:49.160 --> 0:08:52.400 eyes and sees what's going on. And then the other 0:08:52.600 --> 0:08:56.880 version is the parasitic consciousness, which we might refer to 0:08:56.960 --> 0:09:01.679 as metacognition. It monitors the internal state of the brain itself. 0:09:02.160 --> 0:09:05.520 And under this old hypothesis, deja VU is created when 0:09:05.600 --> 0:09:09.840 normal consciousness is impaired by something like fatigue or stress, 0:09:10.440 --> 0:09:14.319 and it's left up to the parasitic consciousness to evaluate 0:09:14.400 --> 0:09:18.440 incoming information. And because the parasitic consciousness is not well 0:09:18.480 --> 0:09:22.920 adapted to evaluating incoming information, it gets confused, and it 0:09:23.000 --> 0:09:26.000 confuses what it's looking at now for a memory of 0:09:26.040 --> 0:09:29.800 the past. Uh. While I like this idea, this one 0:09:29.840 --> 0:09:33.080 appears to be entirely speculative. It's mostly based on like 0:09:33.200 --> 0:09:35.839 nineteenth century conceptions of the mind and brain. So I 0:09:35.880 --> 0:09:38.880 don't think this one is very likely a good explanation today. 0:09:39.320 --> 0:09:42.200 Now another one, uh in this branch is would be 0:09:42.240 --> 0:09:45.920 like encoding and retrieval. Brown says, this was proposed by 0:09:45.960 --> 0:09:49.400 Denayer in nineteen seventy nine, and basically it takes the 0:09:49.440 --> 0:09:52.600 form of a metaphor of the brain is a combination 0:09:52.760 --> 0:09:56.240 tape recorder and player. Uh did you did you have 0:09:56.240 --> 0:09:58.400 one of those when you're a kid? Robert? Oh? Yeah, 0:09:58.440 --> 0:10:01.160 of course, but yeah, okay, So the metaphor here by 0:10:01.200 --> 0:10:03.880 Dena Air is that your brain has a combination tape 0:10:03.880 --> 0:10:06.560 recorder and player. And and Brown explains this well, so 0:10:06.559 --> 0:10:09.880 I'm going to quote from him quote under normal conditions 0:10:10.000 --> 0:10:14.240 memory encoding and retrieval operate in a manner similar to 0:10:14.360 --> 0:10:18.000 the record and play heads respectively. On a tape recorder. 0:10:18.280 --> 0:10:22.360 Either the record in code or the play retrieve head 0:10:22.440 --> 0:10:26.800 can be on, but not both at once. On rare occasions, 0:10:26.840 --> 0:10:29.920 the tape machine and a person's memory has both record 0:10:30.080 --> 0:10:34.959 and play heads active simultaneously during a new experience, creating 0:10:34.960 --> 0:10:38.520 a false sense of familiarity for the newly encoded experience. 0:10:39.320 --> 0:10:43.280 So basically, the idea is that you are experiencing the 0:10:43.400 --> 0:10:48.680 memory as it is happening, um, which sounds paradoxical, but 0:10:49.160 --> 0:10:52.080 but the idea of encoding and retrieving happening at the 0:10:52.080 --> 0:10:55.760 same time. Yeah, and so this never Brown says, this 0:10:55.840 --> 0:10:59.840 hypothesis never really got developed beyond just this metaphorical stage. 0:10:59.840 --> 0:11:02.120 Like he never you know, got into the nitty gritty 0:11:02.160 --> 0:11:04.520 of like what parts of the brain this would exactly 0:11:04.559 --> 0:11:07.360 be involving and how it would work. Um. But I 0:11:07.360 --> 0:11:11.160 would say, while it is still at this metaphorical stage, 0:11:11.240 --> 0:11:16.040 this is kind of close to some later, later explanations 0:11:16.040 --> 0:11:19.160 that are backed up by more empirical research. I think 0:11:19.200 --> 0:11:21.319 it's not quite on the money, but it's it's getting 0:11:21.360 --> 0:11:24.400 part of the way there, especially I think, especially with 0:11:24.400 --> 0:11:26.320 with some of the ones that we'll talk about with 0:11:26.320 --> 0:11:29.400 with attention later on. Yeah, and also like how it 0:11:29.480 --> 0:11:33.720 kind of helps to further breakdown the nature of of 0:11:33.760 --> 0:11:36.360 something that is novel and something that is familiar and 0:11:36.400 --> 0:11:40.600 how it basically works, you know, in our experience of 0:11:40.720 --> 0:11:45.040 cognitive data. Yeah. Well, and it makes me think about how, um, 0:11:45.080 --> 0:11:50.080 in a way, there's almost no real objective thing that 0:11:50.200 --> 0:11:53.800 is novelty. You know that, Like every time you're looking 0:11:53.800 --> 0:11:56.200 at anything in the world, in a way, it's sort 0:11:56.240 --> 0:11:59.440 of novel because like your heads in a different position, 0:11:59.559 --> 0:12:01.680 and you'll even if you're looking at something you've looked 0:12:01.679 --> 0:12:04.160 at a thousand times before, the lights kind of different, 0:12:04.240 --> 0:12:07.000 you're looking at it from a slightly different angle. The 0:12:07.080 --> 0:12:10.600 brain just does a does a very good job taking 0:12:10.679 --> 0:12:13.760 things that are you know, different data sets coming in 0:12:13.840 --> 0:12:15.840 through the eyes or the ears or whatever it is, 0:12:16.080 --> 0:12:18.120 and saying like, Okay, you know what that is. That's 0:12:18.160 --> 0:12:20.440 the same coffee cup you've looked at a thousand times, 0:12:20.480 --> 0:12:24.679 even though it's not a photo exact copy of how 0:12:24.720 --> 0:12:26.640 it looked the last time you looked at it. Yeah, 0:12:26.640 --> 0:12:29.480 I mean, as since data goes the details of the 0:12:29.480 --> 0:12:31.839 coffee cup are not that important, And the brain does 0:12:32.160 --> 0:12:35.320 a pretty good job in in UM working with the 0:12:35.320 --> 0:12:37.600 senses of letting that kind of fade into the background. 0:12:38.160 --> 0:12:40.200 But then you know, any day you're able to pick 0:12:40.280 --> 0:12:42.839 up that coffee cup and really focus on it and 0:12:43.120 --> 0:12:45.480 kind of see it for the first time. And that's 0:12:45.480 --> 0:12:48.440 one of the the crazy things about the the close 0:12:48.480 --> 0:12:53.720 relationship between the novel and the familiar. Yeah, and that 0:12:53.800 --> 0:12:57.239 emphasizes that like the novel and familiar, they're not objective 0:12:57.280 --> 0:13:01.199 features of the world. They're like subjective simulation sans yeah. 0:13:01.440 --> 0:13:03.640 This is this is almost an example of this, but 0:13:03.679 --> 0:13:06.840 not quite. Um. I I don't I've had an Xbox 0:13:07.320 --> 0:13:09.920 one controller for so long and I just discovered you 0:13:09.920 --> 0:13:15.480 can plug headphones into the controller itself to get sound. Totally. 0:13:15.840 --> 0:13:19.800 It's changed my life here in um. You know, self isolation. Oh, 0:13:19.840 --> 0:13:22.200 now late in the night, your house is not filled 0:13:22.200 --> 0:13:26.959 with tiny screams that right, right? Yeah, I want to Yeah, 0:13:27.000 --> 0:13:29.400 if I want to play Doom Eternal at a at 0:13:29.400 --> 0:13:31.200 a weird hour, I can. I can be the only 0:13:31.200 --> 0:13:33.920 one to hear it. Likewise, my son is trying out 0:13:33.960 --> 0:13:36.480 Minecraft for the first time, and we can plug him 0:13:36.520 --> 0:13:39.080 into the the controller and then if he jerks the 0:13:39.080 --> 0:13:42.320 controller around, he's not pulling things off of the you know, 0:13:42.360 --> 0:13:45.920 the TV tray or something. So uh so yeah, but 0:13:45.920 --> 0:13:47.440 but you know, there's an example. I don't know how 0:13:47.480 --> 0:13:49.360 many times I've looked at this device, but I've never 0:13:49.400 --> 0:13:52.880 seen this detail. And uh uh. You know a lot 0:13:52.960 --> 0:13:54.520 of things in life are like that. You know, when 0:13:54.520 --> 0:13:57.160 you really really stop to look at at it, you 0:13:57.200 --> 0:14:00.360 can you can uncover the novel wrinkles and the thing. 0:14:00.760 --> 0:14:02.800 I might want to come back to this example later 0:14:02.840 --> 0:14:06.080 in the episode. Uh and maybe when we talk about 0:14:06.120 --> 0:14:09.360 the memory and intentional branches. Okay, two more examples of 0:14:09.440 --> 0:14:12.880 dual processing hypotheses. So another one Brown sites is. The 0:14:12.920 --> 0:14:16.240 idea of perception and memory seems kind of similar to 0:14:16.280 --> 0:14:20.200 the last one. It was proposed by a researcher named Bergson. Basically, 0:14:20.200 --> 0:14:23.760 it supposes that perception and memory formation happened at the 0:14:23.800 --> 0:14:26.680 same time. Like, you know, I I look at Gritty, 0:14:26.720 --> 0:14:29.880 the Philadelphia Flyers mascot for the first time, my brain 0:14:29.960 --> 0:14:33.800 sees him creates the memory of having seen him simultaneously. 0:14:34.360 --> 0:14:38.360 Bergson suggests that sometimes stress or fatigue can cause the 0:14:38.400 --> 0:14:42.400 newly formed memory to bump into perception, so that I 0:14:42.440 --> 0:14:45.920 get the feeling that I have seen Gritty before. Again, 0:14:45.960 --> 0:14:48.560 this one is kind of fuzzy and speculative as far 0:14:48.560 --> 0:14:52.120 as hypotheses go. Well, you know, we all feel that 0:14:52.160 --> 0:14:54.360 we've seen Gritty before because Gritty was with us in 0:14:54.400 --> 0:14:59.000 the womb. Gritty is primordial. Yeah, Gritty was there before 0:14:59.040 --> 0:15:01.360 we were born. You know that's going to happen one day, 0:15:01.400 --> 0:15:05.080 like they they a big block of shale shares away 0:15:05.120 --> 0:15:08.080 from a Cambrian formation and then just just the outline 0:15:08.080 --> 0:15:11.160 of Gritty there among the trial bites. He was waiting 0:15:11.200 --> 0:15:14.120 the whole time. Okay, But then the fourth one of 0:15:14.160 --> 0:15:18.000 these dual processing hypotheses potheses. Sorry, this is the only 0:15:18.000 --> 0:15:20.680 one of the four that really seemed all that plausible 0:15:20.720 --> 0:15:24.480 to me. So this one is called familiarity and retrieval. 0:15:24.960 --> 0:15:28.080 And this was proposed by a researcher named Glure in 0:15:28.200 --> 0:15:32.520 nineteen nine. And Glore suggested that when we encounter an 0:15:32.560 --> 0:15:35.760 image or an object or scenario or whatever it is 0:15:35.800 --> 0:15:39.240 that we've seen before, there are two separate things that happen. 0:15:39.920 --> 0:15:43.280 One is the retrieval of the past memories about that thing. 0:15:43.360 --> 0:15:45.800 So I see Gritty, I have seen him before, and 0:15:45.840 --> 0:15:48.200 I remember the other times I saw Gritty and had 0:15:48.240 --> 0:15:52.120 thoughts about him. But the other thing is the emotion 0:15:52.240 --> 0:15:56.680 of familiarity that accompanies the recall. So I see Gritty, 0:15:56.720 --> 0:15:59.720 I have memories, but also I have a feeling. It's 0:15:59.760 --> 0:16:02.320 this emotional feeling that, oh, I know who that is. 0:16:03.080 --> 0:16:06.160 Uh that you know that is Gritty. I feel familiar 0:16:06.200 --> 0:16:08.480 with what's going on right now. And from what I 0:16:08.520 --> 0:16:12.920 can tell, there's not really any direct evidence for this hypothesis, 0:16:12.920 --> 0:16:14.920 but this one does seem kind of plausible to me 0:16:15.000 --> 0:16:19.280 because we've talked about other cases of mismatch between recognition 0:16:19.280 --> 0:16:22.960 and familiarity. For example, in talking about cap Graw delusion, 0:16:23.000 --> 0:16:25.400 I think we mentioned in Part one, which is this 0:16:25.440 --> 0:16:28.480 delusion often caused by brain injury, in which a person 0:16:28.560 --> 0:16:32.560 believes that their loved ones have been replaced by lookalikes 0:16:32.640 --> 0:16:36.960 or doppelgangers. And it's believed that cap Graw delusion stems 0:16:37.040 --> 0:16:40.840 from a malfunction in the brain where recognition is triggered. 0:16:41.000 --> 0:16:43.480 So you see a person and you know who you're 0:16:43.480 --> 0:16:46.440 looking at, like, yes, you know that that is Jeff, 0:16:46.920 --> 0:16:50.880 but the normally accompanying feeling of familiarity is not there. 0:16:50.920 --> 0:16:54.480 It doesn't get triggered. So you see somebody recognize as Jeff, 0:16:54.520 --> 0:16:57.400 but he does not feel familiar. It doesn't feel like 0:16:57.480 --> 0:17:00.560 your old friend, so you say, oh, he's and replaced 0:17:00.600 --> 0:17:03.400 by a look alike. What's normally a case of dual 0:17:03.440 --> 0:17:07.199 processing here has been severed. So if a dual processing 0:17:07.240 --> 0:17:10.400 failure like this we're actually an explanation for deja vu, 0:17:11.160 --> 0:17:13.160 I think it would have to go the opposite way, right, 0:17:13.160 --> 0:17:15.400 It would have to go the opposite of cap Graw delusion, 0:17:15.440 --> 0:17:19.399 where a feeling of familiarity is triggered while actual retrieval 0:17:19.440 --> 0:17:23.000 of associated memories is not. And along these lines of 0:17:23.080 --> 0:17:26.320 cap Graw delusion would would actually be more analogous to 0:17:26.359 --> 0:17:28.920 the inverse of deja vu that we mentioned last time, 0:17:29.000 --> 0:17:34.040 jama vu, in which a familiar object suddenly feels unfamiliar. 0:17:34.680 --> 0:17:37.400 But again, from what I can tell, this kind of explanation, 0:17:37.440 --> 0:17:40.479 I think it's perfectly possible, but I can't find direct 0:17:40.520 --> 0:17:43.199 experimental evidence for it, so I think it might just 0:17:43.400 --> 0:17:46.679 remain right now in the realm of like, yeah, maybe 0:17:46.720 --> 0:17:49.520 something like this could explain some cases of deja vu, 0:17:49.640 --> 0:17:52.800 but we we don't have strong evidence that these explanations 0:17:52.840 --> 0:17:55.399 are the right ones yet. Alright, Well, on that note, 0:17:55.480 --> 0:17:57.359 let's take a quick break, but when we come back, 0:17:57.400 --> 0:18:00.840 we will continue to explore some of the explanations for 0:18:00.880 --> 0:18:06.800 what may be going on with deja vus. Thank thank alright, 0:18:06.800 --> 0:18:09.080 we're back, all right. So we just talked about the 0:18:09.119 --> 0:18:13.240 first branch of possible explanations for deja vu. Uh, probably 0:18:13.280 --> 0:18:15.760 the oldest branch of explanations, which was the idea of 0:18:15.840 --> 0:18:19.399 dual processing that when you experienced deja vu, it's because 0:18:19.400 --> 0:18:21.840 two different things that normally happened in the at the 0:18:21.880 --> 0:18:25.560 same time in the brain get severed and one happens 0:18:25.600 --> 0:18:27.800 after the other one, or they get you know, one 0:18:27.840 --> 0:18:31.040 happens without the other one, and this causes this this 0:18:31.200 --> 0:18:35.200 disconnect um. The next branch of explanations that Alan S. 0:18:35.240 --> 0:18:39.920 Brown offers in his two thousand three paper are neurological explanations. Now, 0:18:40.040 --> 0:18:43.440 the first one is seizures. We know that deja vu 0:18:43.720 --> 0:18:47.000 is a you're not not super common, but a recognized 0:18:47.040 --> 0:18:51.720 experience in the aura of people who have temporal lobe epilepsy. 0:18:51.800 --> 0:18:54.560 So what if normal deja vu do you that happens 0:18:54.560 --> 0:18:56.879 in you know, sixty percent of people at some point 0:18:57.880 --> 0:19:02.320 it's actually just a kind of mild seizure. A lot 0:19:02.359 --> 0:19:04.960 of people have proposed this over the years, but Brown 0:19:05.000 --> 0:19:07.240 says that the evidence for this does not appear to 0:19:07.240 --> 0:19:10.080 be very good. Though deja vu is a feature of 0:19:10.080 --> 0:19:13.679 seizures for people with t l E, people with epilepsy 0:19:13.720 --> 0:19:16.840 in general are not more prone to every day deja 0:19:16.920 --> 0:19:20.920 vu than people without epilepsy, and people who experience more 0:19:20.960 --> 0:19:24.000 episodes of deja vu than average are not any more 0:19:24.040 --> 0:19:27.240 prone to seizures than anybody else. So again, we can't 0:19:27.240 --> 0:19:31.000 actually look at deja vu as it's happening and compare 0:19:31.040 --> 0:19:33.320 it to say, what's happening in the brain during a seizure, 0:19:33.600 --> 0:19:37.520 but we can look at frequency, uh, between these two 0:19:37.800 --> 0:19:41.439 sets of of individuals. Yeah, and so it just doesn't 0:19:41.520 --> 0:19:44.560 look like seizures are going to be a good explanation 0:19:44.680 --> 0:19:47.200 for deja vu. Generally, it looks more like there might 0:19:47.280 --> 0:19:50.560 you know, deja vu just happens to be one of 0:19:50.680 --> 0:19:53.399 the things that sometimes happens in the brain of somebody 0:19:53.440 --> 0:19:55.720 about to have a seizure, but it's not overall a 0:19:55.800 --> 0:20:00.040 generalized seizure phenomenon um. Now, the other major near a 0:20:00.080 --> 0:20:04.800 logical explanation that Brown sites is neural transmission delay, and 0:20:04.840 --> 0:20:08.040 this refers to a set of explanations where information traveling 0:20:08.119 --> 0:20:12.120 from the perceptual organs such as the eye. Uh, it's 0:20:12.119 --> 0:20:14.560 traveling to different parts of the brain, and it gets 0:20:14.720 --> 0:20:18.639 delayed along one of those pathways by neuronal misfiring or 0:20:18.680 --> 0:20:21.560 some of their malfunction. And one example that's given is 0:20:22.119 --> 0:20:26.040 the two different hemispheres of the brain usually receive information 0:20:26.080 --> 0:20:29.359 at the same time. But what if one hemisphere realizes 0:20:29.440 --> 0:20:32.800 that you're looking at gritty slightly after the other one does, 0:20:33.720 --> 0:20:37.400 And under this hypothesis, the delay causes a freshly perceived 0:20:37.440 --> 0:20:41.120 stimulus to be interpreted as old information because one part 0:20:41.119 --> 0:20:43.960 of the brain has already experienced it by by the 0:20:44.000 --> 0:20:46.160 time it gets to the other part. Well, this seems 0:20:46.160 --> 0:20:48.080 like a good place to move on to some of 0:20:48.119 --> 0:20:51.720 the additional explanations, because we're talking about old information. What 0:20:51.880 --> 0:20:55.000 he's old information but a memory. Yeah, exactly. So now 0:20:55.040 --> 0:20:58.080 we're getting into those were the two older branches. Now 0:20:58.080 --> 0:21:00.000 we're getting into the branches that I think are more 0:21:00.000 --> 0:21:04.359 were favored among researchers today, the memory based explanations, especially 0:21:04.440 --> 0:21:09.439 implicit memories and attentional explanations. Uh. Now, Robert, if we 0:21:09.480 --> 0:21:11.439 if we go to memory based I think you're going 0:21:11.480 --> 0:21:13.760 to get into this branch of explanations a little bit 0:21:13.760 --> 0:21:15.679 more when you talk about the research by and M 0:21:15.680 --> 0:21:18.840 cleary and Alexander B. Claxton. Later on, I saw you 0:21:18.840 --> 0:21:21.280 had something about that, So maybe we can talk more 0:21:21.280 --> 0:21:24.000 in depth about the memory based explanations then, but just 0:21:24.040 --> 0:21:27.160 do a short version now. The gist here is that 0:21:27.440 --> 0:21:30.520 desha vou is perhaps uh maybe it has something to 0:21:30.560 --> 0:21:34.720 do with the way that memories are encoded and retrieved. 0:21:35.200 --> 0:21:38.120 So imagine you're in one of these deja vu scenarios. 0:21:38.160 --> 0:21:41.760 Maybe you're you're going down a staircase into a basement 0:21:41.880 --> 0:21:44.919 in a house, and you suddenly get this flash like, oh, 0:21:44.960 --> 0:21:47.720 I've been here before, but you haven't been here before. 0:21:48.400 --> 0:21:51.200 What if when you're experiencing deja vu on that staircase, 0:21:51.440 --> 0:21:55.240 you are remembering something you've seen before. It's just not 0:21:55.400 --> 0:21:59.040 this house. It's not the same thing you're looking at now. 0:21:59.240 --> 0:22:03.720 You're feeling familiarity because of some vague features of similarity 0:22:04.080 --> 0:22:08.159 that overlap with your current experience and some other memory 0:22:08.280 --> 0:22:11.960 that you are not directly accessing in full. Maybe when 0:22:12.000 --> 0:22:14.600 I experienced the deja vu of like running into a 0:22:14.640 --> 0:22:17.679 tree branch while playing in the yard. The feeling of 0:22:17.720 --> 0:22:20.480 familiarity with the scene comes from the fact that there 0:22:20.600 --> 0:22:23.719 was some other time I was playing in maybe a 0:22:23.760 --> 0:22:27.680 similar looking place or a place with similar spatial arrangements 0:22:27.680 --> 0:22:30.760 of objects, and my friends were standing around me in 0:22:30.800 --> 0:22:34.560 a similar kind of orientation, and maybe I was injured 0:22:34.920 --> 0:22:37.879