1 00:00:04,760 --> 00:00:09,000 Speaker 1: Why do brains dream? And what's going on with the 2 00:00:09,039 --> 00:00:13,800 Speaker 1: bizarreness of dreams? Why doesn't your clock work in your dreams? 3 00:00:14,240 --> 00:00:16,080 Speaker 1: And even though you spend a lot of your day 4 00:00:16,160 --> 00:00:20,120 Speaker 1: working on cell phones and computers, why do those almost 5 00:00:20,320 --> 00:00:23,799 Speaker 1: never make appearances in your dream content? There are so 6 00:00:23,880 --> 00:00:27,080 Speaker 1: many cool questions that we're going to address today. Is 7 00:00:27,200 --> 00:00:31,320 Speaker 1: dream content the same across cultures and across time? Are 8 00:00:31,440 --> 00:00:35,280 Speaker 1: dreams experienced in black and white or in color? Why 9 00:00:35,280 --> 00:00:38,640 Speaker 1: do I think about dreams as this strange love child 10 00:00:38,760 --> 00:00:43,280 Speaker 1: between brain plasticity and the rotation of the planet. What 11 00:00:43,440 --> 00:00:47,559 Speaker 1: is the relationship between schizophrenia and dreaming? And in the 12 00:00:47,600 --> 00:00:50,800 Speaker 1: future will we be able to read out the content 13 00:00:51,200 --> 00:00:58,320 Speaker 1: of somebody's dream? Welcome to Inner Cosmos with me David Eagleman. 14 00:00:58,600 --> 00:01:01,960 Speaker 1: I'm a neuroscientist and author at Stanford and in these 15 00:01:02,000 --> 00:01:05,920 Speaker 1: episodes we sail deeply into our three pound universe to 16 00:01:06,000 --> 00:01:09,640 Speaker 1: understand why and how our lives look the way they 17 00:01:09,720 --> 00:01:19,320 Speaker 1: do and how we experience our life includes our nocturnal life. 18 00:01:19,400 --> 00:01:23,520 Speaker 1: We spend a third of our lives with our eyes closed, 19 00:01:24,000 --> 00:01:28,520 Speaker 1: lying still and horizontal, like a meat robot that's been 20 00:01:28,640 --> 00:01:33,080 Speaker 1: switched off. But why in the last episode, we talked 21 00:01:33,120 --> 00:01:36,960 Speaker 1: all about sleep, why brains do that, and why all 22 00:01:37,000 --> 00:01:40,080 Speaker 1: animals do that, and what is happening in the brain 23 00:01:40,240 --> 00:01:44,280 Speaker 1: during sleep. Today we're going to zoom in on one 24 00:01:44,319 --> 00:01:48,360 Speaker 1: of my favorite subjects, a very strange thing the brain does, 25 00:01:48,440 --> 00:01:52,560 Speaker 1: which we call dreaming. We spend a fraction of our 26 00:01:52,600 --> 00:01:57,320 Speaker 1: sleep time locked in a different reality, swimming around in 27 00:01:57,480 --> 00:02:01,400 Speaker 1: plots which aren't real, and they're often not even realistic, 28 00:02:02,000 --> 00:02:07,680 Speaker 1: but which nonetheless convince us entirely. And today we're going 29 00:02:07,760 --> 00:02:11,400 Speaker 1: to see what that's all about. Humans have been writing 30 00:02:11,440 --> 00:02:14,919 Speaker 1: about dreams and pondering about them for a long time, 31 00:02:15,080 --> 00:02:17,680 Speaker 1: and essentially we have evidence of this from the beginning 32 00:02:17,720 --> 00:02:23,160 Speaker 1: of writing. We see detailed dream reports from ancient Egyptians 33 00:02:23,240 --> 00:02:27,280 Speaker 1: and Romans and Chinese. The Bible is full of dreams. 34 00:02:27,360 --> 00:02:31,040 Speaker 1: Every culture in the world has been fascinated by these 35 00:02:31,080 --> 00:02:34,320 Speaker 1: strange nocturnal journeys that we go on. And as we'll 36 00:02:34,360 --> 00:02:38,960 Speaker 1: see shortly, there's an interesting surprise, which is that dream content, 37 00:02:39,120 --> 00:02:42,120 Speaker 1: in other words, the kind of things that people dream about, 38 00:02:42,560 --> 00:02:47,600 Speaker 1: is essentially the same across cultures and across time, and 39 00:02:47,639 --> 00:02:50,480 Speaker 1: that serves as a clue that will allow us to 40 00:02:50,680 --> 00:02:54,560 Speaker 1: unlock some mysteries about what otherwise feels like a deeply 41 00:02:54,720 --> 00:02:59,560 Speaker 1: mysterious experience that we enjoy or suffer every night of 42 00:02:59,600 --> 00:03:03,320 Speaker 1: our life lives. So strap in for an episode full 43 00:03:03,320 --> 00:03:06,760 Speaker 1: of surprises. So let's start with a poem that Lord 44 00:03:06,760 --> 00:03:11,120 Speaker 1: Byron wrote in eighteen sixteen called The Dream. He wrote, 45 00:03:11,520 --> 00:03:15,840 Speaker 1: sleep hath its own world and a wide realm of 46 00:03:16,040 --> 00:03:22,240 Speaker 1: wild reality. And dreams, in their development have breath and tears, 47 00:03:22,320 --> 00:03:26,000 Speaker 1: and tortures and the touch of joy. They leave a 48 00:03:26,080 --> 00:03:31,640 Speaker 1: weight upon our waking thoughts. So dreams are indeed a 49 00:03:32,200 --> 00:03:35,800 Speaker 1: wild reality. The thing we all find so amazing about 50 00:03:35,880 --> 00:03:40,720 Speaker 1: dreaming is its bizarreness. You're seeing new things, you hold 51 00:03:41,080 --> 00:03:45,080 Speaker 1: strange beliefs, and you fall for it all hook line 52 00:03:45,120 --> 00:03:48,680 Speaker 1: and sinker. Whatever your brain serves up to you, you 53 00:03:48,720 --> 00:03:52,040 Speaker 1: believe it entirely. So we'll talk about all this, But 54 00:03:52,120 --> 00:03:56,240 Speaker 1: let's first zoom in on what's happening inside the brain. 55 00:03:56,960 --> 00:04:02,360 Speaker 1: Dreaming occurs during rapid eye moos movement or rem sleep, 56 00:04:03,120 --> 00:04:05,720 Speaker 1: where your eyes are darting back and forth. There's nothing 57 00:04:05,800 --> 00:04:08,200 Speaker 1: coming in the eyes, of course, they're shut, so all 58 00:04:08,240 --> 00:04:13,160 Speaker 1: the activity is internally generated. For good housekeeping, all just 59 00:04:13,240 --> 00:04:17,680 Speaker 1: note that rem sleep isn't necessarily equivalent to dream sleep, 60 00:04:17,880 --> 00:04:21,040 Speaker 1: but that's when most dreaming occurs. Now, how do we 61 00:04:21,120 --> 00:04:24,480 Speaker 1: know that, Well, it's because if you wait until someone 62 00:04:24,720 --> 00:04:27,480 Speaker 1: enters rems sleep, their eyes are going back and forth, 63 00:04:27,680 --> 00:04:29,920 Speaker 1: and then you shake them awake and you say, hey, 64 00:04:30,400 --> 00:04:34,880 Speaker 1: what were you just experiencing? They'll tell you WHOA, I 65 00:04:35,040 --> 00:04:38,440 Speaker 1: was just panicking because I was at work but realized 66 00:04:38,480 --> 00:04:40,520 Speaker 1: I had forgotten to put on pants, and I was 67 00:04:40,600 --> 00:04:43,800 Speaker 1: hiding behind the plant pots and figuring out how to 68 00:04:44,000 --> 00:04:47,280 Speaker 1: escape before the meeting started. But if you wake them 69 00:04:47,360 --> 00:04:50,479 Speaker 1: up during the rest of the ninety minute sleep cycle, 70 00:04:50,920 --> 00:04:53,640 Speaker 1: during the stages that we call slow wave sleep, and 71 00:04:53,680 --> 00:04:57,240 Speaker 1: you say, hey, what were you just experiencing, they'll generally 72 00:04:57,279 --> 00:05:02,120 Speaker 1: say nothing, I wasn't there. Now, for completeness, I'll mention 73 00:05:02,279 --> 00:05:07,400 Speaker 1: that sometimes people report some form of mental activity during 74 00:05:07,560 --> 00:05:10,880 Speaker 1: slow wave sleep, but when they do, this is usually 75 00:05:10,920 --> 00:05:15,400 Speaker 1: just a thought or making a plan. But it lacks 76 00:05:15,440 --> 00:05:21,520 Speaker 1: the visual vividness and the hallucinatory components of typical dreams. 77 00:05:21,760 --> 00:05:25,440 Speaker 1: So dreaming of the sort we're interested in today happens 78 00:05:25,520 --> 00:05:32,280 Speaker 1: during rem sleep. Now, although dreams seem so untethered and ethereal, 79 00:05:32,760 --> 00:05:36,520 Speaker 1: there are specific things happening under the hood. Dreaming depends 80 00:05:36,560 --> 00:05:40,920 Speaker 1: on the normal functioning of a particular network of brain areas. 81 00:05:41,320 --> 00:05:45,200 Speaker 1: This is primarily in the limbic and paralymbic and association areas. 82 00:05:45,560 --> 00:05:48,200 Speaker 1: Now we know that from brain imaging, but also because 83 00:05:48,320 --> 00:05:53,200 Speaker 1: damage in this network can produce temporary or permanent dream 84 00:05:53,560 --> 00:05:59,440 Speaker 1: loss or impairment like loss of visual dream imagery. Now, 85 00:05:59,480 --> 00:06:01,880 Speaker 1: not all of those areas might sound familiar to you, 86 00:06:01,920 --> 00:06:04,960 Speaker 1: but you've probably heard of the limbic system, which sits 87 00:06:04,960 --> 00:06:08,880 Speaker 1: at the heart of your emotions. So presumably this is 88 00:06:08,920 --> 00:06:13,880 Speaker 1: why dreams are so overloaded with high emotion. And I 89 00:06:13,920 --> 00:06:16,960 Speaker 1: also want to mention a brain era that is suppressed 90 00:06:17,120 --> 00:06:20,560 Speaker 1: during rem sleep, and that is the hippocampus. This is 91 00:06:20,560 --> 00:06:24,440 Speaker 1: an area that's required to convert short term memory into 92 00:06:24,480 --> 00:06:27,080 Speaker 1: long term memory. And this is why when you wake 93 00:06:27,160 --> 00:06:31,200 Speaker 1: up from a dream, you can remember it so clearly, 94 00:06:31,279 --> 00:06:35,279 Speaker 1: but after about fifteen minutes it just slips away from you. 95 00:06:35,279 --> 00:06:38,560 Speaker 1: You just can't hold on to what happened. This is 96 00:06:38,560 --> 00:06:42,440 Speaker 1: because you have the short term memory just fine, but 97 00:06:42,560 --> 00:06:45,880 Speaker 1: you're not converting it into long term memory, and so 98 00:06:46,000 --> 00:06:50,000 Speaker 1: it simply fades before your eyes. And by the way, 99 00:06:50,040 --> 00:06:53,000 Speaker 1: I think this experience that we have every morning can 100 00:06:53,440 --> 00:06:56,520 Speaker 1: enhance our empathy about what it would be like to 101 00:06:56,560 --> 00:07:00,480 Speaker 1: have something like Alzheimer's disease, because a person with Allsheimers 102 00:07:00,880 --> 00:07:03,320 Speaker 1: says on the phone, Okay, I'll be right down there 103 00:07:03,360 --> 00:07:05,800 Speaker 1: in a moment, and they hang up, and then the 104 00:07:05,880 --> 00:07:09,600 Speaker 1: memory of that just slips away. So even though you 105 00:07:09,680 --> 00:07:13,000 Speaker 1: might tell a relative with Alzheimer's, come on, just try 106 00:07:13,080 --> 00:07:16,840 Speaker 1: harder to remember. Just think about somebody telling that to 107 00:07:16,880 --> 00:07:20,760 Speaker 1: you about your dreams in the morning. So back to 108 00:07:20,800 --> 00:07:23,560 Speaker 1: the Byron poem, the line that I thought was interesting 109 00:07:23,760 --> 00:07:28,600 Speaker 1: was they leave a weight upon our waking thoughts because 110 00:07:28,840 --> 00:07:32,040 Speaker 1: they don't directly interact with our waking thoughts, but instead 111 00:07:32,080 --> 00:07:36,040 Speaker 1: they can just put a spin on our mood, even 112 00:07:36,080 --> 00:07:39,840 Speaker 1: if we don't remember why. Okay, so what do we 113 00:07:39,960 --> 00:07:44,160 Speaker 1: see in the brain when dreaming begins, Well, just before 114 00:07:44,240 --> 00:07:48,000 Speaker 1: the onset of your eyes darting back and forth, you 115 00:07:48,080 --> 00:07:51,440 Speaker 1: have a group of neurons in the brain stem, specifically 116 00:07:51,480 --> 00:07:54,600 Speaker 1: in an area called the ponds, and these crank up, 117 00:07:54,920 --> 00:07:58,920 Speaker 1: and these trigger several consequences. The first is that your 118 00:07:59,160 --> 00:08:04,320 Speaker 1: major muscle groups get paralyzed. This is called atonia. So 119 00:08:04,560 --> 00:08:08,520 Speaker 1: you've got this elaborate neural circuitry that keeps the body 120 00:08:08,640 --> 00:08:13,040 Speaker 1: paralyzed during dreaming. And by the way, the very elaborateness 121 00:08:13,080 --> 00:08:18,720 Speaker 1: of this circuitry emphasizes the biological importance of dream sleep. 122 00:08:19,040 --> 00:08:22,600 Speaker 1: You don't get this kind of complexity by accident. Presumably, 123 00:08:23,040 --> 00:08:27,280 Speaker 1: dreaming would be unlikely to evolve and remain without an 124 00:08:27,320 --> 00:08:30,600 Speaker 1: important function behind it. So why do we get this 125 00:08:30,680 --> 00:08:34,640 Speaker 1: paralysis of the muscles. It allows the possibility for the 126 00:08:34,640 --> 00:08:40,080 Speaker 1: brain to experience things and simulate reality without actually moving 127 00:08:40,120 --> 00:08:43,560 Speaker 1: the body. The second consequence of these neurons in the 128 00:08:43,600 --> 00:08:47,040 Speaker 1: ponds is that they trigger these waves of activity known 129 00:08:47,040 --> 00:08:51,360 Speaker 1: as PGO waves, and these are key to the experience 130 00:08:51,600 --> 00:08:56,360 Speaker 1: of dreaming. These PGO waves travel to a tiny area 131 00:08:56,480 --> 00:08:59,760 Speaker 1: called the geniculate nucleus and from there these waves of 132 00:08:59,760 --> 00:09:03,440 Speaker 1: activity slam into the occipital cortex at the back of 133 00:09:03,480 --> 00:09:07,640 Speaker 1: your head. In other words, they drive activity into the 134 00:09:07,840 --> 00:09:11,280 Speaker 1: visual system. So that's why these are called PGO waves. 135 00:09:11,320 --> 00:09:14,520 Speaker 1: Because they start in the ponds, p move to the 136 00:09:14,600 --> 00:09:18,679 Speaker 1: geniculate g and go to the occipital cortex. Oh pgoh 137 00:09:18,960 --> 00:09:22,280 Speaker 1: I mention all this detail. Because PGO waves are the 138 00:09:22,440 --> 00:09:28,200 Speaker 1: neural correlate of dreaming, the visual areas become alive with 139 00:09:28,280 --> 00:09:33,280 Speaker 1: activity allowing us to see our dreams. You blast activity 140 00:09:33,280 --> 00:09:37,800 Speaker 1: into the visual cortex and you enjoy visual experience even 141 00:09:37,840 --> 00:09:42,560 Speaker 1: though your eyes are closed. Now, interestingly, when you measure 142 00:09:42,640 --> 00:09:47,040 Speaker 1: electrical activity across the brain with EEG, when you do 143 00:09:47,080 --> 00:09:50,040 Speaker 1: this during rem sleep, it looks really similar to that 144 00:09:50,160 --> 00:09:54,960 Speaker 1: during the waking state. You see similar patterns in both states, 145 00:09:55,240 --> 00:09:58,679 Speaker 1: for example, lots of gamma wave frequency, which is generally 146 00:09:58,720 --> 00:10:03,280 Speaker 1: thought to reflect something about cognitive processing, with the exception 147 00:10:03,640 --> 00:10:08,160 Speaker 1: of the paralyzed muscles and the lack of external visual 148 00:10:08,200 --> 00:10:11,520 Speaker 1: input because your eyes are closed, the states of rem 149 00:10:11,559 --> 00:10:15,120 Speaker 1: sleep and of wakefulness they kind of resemble one another. 150 00:10:15,400 --> 00:10:17,600 Speaker 1: And this is what we might expect from a state 151 00:10:17,679 --> 00:10:23,960 Speaker 1: of consciousness that's altered. But it's some sort of consciousness nonetheless. Okay, 152 00:10:24,080 --> 00:10:27,160 Speaker 1: so that's what's happening in the brain when we dream. 153 00:10:27,320 --> 00:10:31,199 Speaker 1: But why do we dream? Well, there are various hypotheses 154 00:10:31,240 --> 00:10:33,800 Speaker 1: about this, and I mentioned one last week, which is 155 00:10:33,800 --> 00:10:38,480 Speaker 1: that maybe dreams allow us to simulate rare situations. In 156 00:10:38,520 --> 00:10:44,760 Speaker 1: other words, these nocturnal neural simulations might allow us and 157 00:10:44,800 --> 00:10:49,240 Speaker 1: all animals to test out activities without the danger and 158 00:10:49,400 --> 00:10:51,440 Speaker 1: risk of doing so in the real world. So you 159 00:10:51,520 --> 00:10:56,240 Speaker 1: can practice through different scenarios with your muscles all shut down. 160 00:10:56,800 --> 00:11:00,920 Speaker 1: So people who advocate this theory suggest that the periodic 161 00:11:01,120 --> 00:11:05,080 Speaker 1: stimulation of the cortex in this semi random and non 162 00:11:05,120 --> 00:11:09,520 Speaker 1: specific manner this can maintain circuits that are really important 163 00:11:09,559 --> 00:11:13,480 Speaker 1: for survival, but they rarely get activated because you don't 164 00:11:13,520 --> 00:11:16,920 Speaker 1: run into emergencies that often. So the idea is that 165 00:11:16,960 --> 00:11:20,480 Speaker 1: you're just sending in random activity, keeping the engine oiled 166 00:11:20,880 --> 00:11:24,640 Speaker 1: in case you need one of these programs sometime, and 167 00:11:24,760 --> 00:11:27,800 Speaker 1: some researchers suggest that it's even more specific than that. 168 00:11:27,920 --> 00:11:32,679 Speaker 1: A version of this framework called threat simulation theory, suggests 169 00:11:32,720 --> 00:11:36,840 Speaker 1: that dreams exist to simulate threatening events and to rehearse 170 00:11:36,960 --> 00:11:39,720 Speaker 1: what to do in the face of threat, and that 171 00:11:39,800 --> 00:11:42,880 Speaker 1: seems on its surface at least consistent with the high 172 00:11:42,920 --> 00:11:47,800 Speaker 1: prevalence of violence and aggression in dreams. But I want 173 00:11:47,800 --> 00:11:51,080 Speaker 1: to note that there's no data that directly supports this idea, 174 00:11:51,160 --> 00:11:55,480 Speaker 1: and I mentioned last week that this theory suggests that 175 00:11:55,520 --> 00:11:59,200 Speaker 1: people exposed to more survival threats in waking life might 176 00:11:59,280 --> 00:12:02,800 Speaker 1: have a more common experience of threat dreams at night, 177 00:12:03,160 --> 00:12:06,600 Speaker 1: but the data do not support that. Also, the threat 178 00:12:06,640 --> 00:12:10,240 Speaker 1: perception theory doesn't explain the fact that most dreams are 179 00:12:10,280 --> 00:12:14,960 Speaker 1: totally meaningless and bizarre instead of involving any meaningful threat 180 00:12:15,000 --> 00:12:18,160 Speaker 1: perception or threat avoidance. So back to the question of 181 00:12:18,280 --> 00:12:21,640 Speaker 1: why we dream. A few years ago, my colleague Don 182 00:12:21,720 --> 00:12:25,200 Speaker 1: Vaughan and I proposed a new theory which is the 183 00:12:25,240 --> 00:12:30,200 Speaker 1: only one that makes quantitative predictions across species. And if 184 00:12:30,240 --> 00:12:33,440 Speaker 1: you heard episode eleven you may remember about this. That 185 00:12:33,480 --> 00:12:36,920 Speaker 1: theory has to do with brain plasticity. And here's the idea. 186 00:12:37,160 --> 00:12:40,320 Speaker 1: In a nutshell, we know that if a person goes blind, 187 00:12:40,960 --> 00:12:44,959 Speaker 1: other senses start to take over what was the visual cortex. 188 00:12:45,000 --> 00:12:47,840 Speaker 1: In other words, the territory of the visual system is 189 00:12:47,840 --> 00:12:51,760 Speaker 1: not fixed permanently, but instead the wiring of the brain 190 00:12:51,840 --> 00:12:55,600 Speaker 1: is quite fluid, and there's a takeover that happens. Okay, now, 191 00:12:55,640 --> 00:12:58,160 Speaker 1: it turns out that if you take a normally cited 192 00:12:58,200 --> 00:13:03,120 Speaker 1: person and you blindfold, you can start seeing the beginnings 193 00:13:03,240 --> 00:13:07,880 Speaker 1: of this takeover in neuroimaging starting in about one hour. 194 00:13:08,400 --> 00:13:12,120 Speaker 1: And that really surprised us because of how fast the 195 00:13:12,160 --> 00:13:16,240 Speaker 1: takeover starts to happen. So what does this rapidity of 196 00:13:16,360 --> 00:13:19,480 Speaker 1: the takeover of the cortex have to do with dreaming? 197 00:13:20,080 --> 00:13:23,439 Speaker 1: While in the incessant competition for territory in the brain, 198 00:13:23,960 --> 00:13:27,720 Speaker 1: the visual system has a special challenge because of the 199 00:13:27,760 --> 00:13:32,800 Speaker 1: planet's rotation, we experience darkness for about twelve out of 200 00:13:32,840 --> 00:13:36,040 Speaker 1: every twenty four hours. And obviously I'm talking about our 201 00:13:36,120 --> 00:13:42,280 Speaker 1: evolutionary history, not the recently electrically blessed times. In other words, 202 00:13:42,360 --> 00:13:47,200 Speaker 1: our ancestors all spent their lives as inadvertent participants in 203 00:13:47,240 --> 00:13:51,040 Speaker 1: a blindfold experiment every single night. So how did their 204 00:13:51,160 --> 00:13:55,679 Speaker 1: visual cortex defend its territory when you've got no data 205 00:13:55,720 --> 00:13:59,080 Speaker 1: coming in through the eyes. So our proposal is that 206 00:13:59,160 --> 00:14:03,160 Speaker 1: the visual corret tex preserves its territory by finding a 207 00:14:03,160 --> 00:14:05,640 Speaker 1: way to remain active at night. And we call this 208 00:14:05,720 --> 00:14:11,240 Speaker 1: the defensive activation theory. And the purpose of dreaming here 209 00:14:11,960 --> 00:14:15,560 Speaker 1: is to keep cells in the visual cortex active, and 210 00:14:15,600 --> 00:14:19,120 Speaker 1: that's how it resists conquest by the territories of the 211 00:14:19,480 --> 00:14:22,960 Speaker 1: other senses. Vision is the only one of the senses 212 00:14:23,040 --> 00:14:27,000 Speaker 1: that's disadvantaged by darkness. You can still touch and smell, 213 00:14:27,040 --> 00:14:29,200 Speaker 1: and taste and hear in the dark, and so it's 214 00:14:29,240 --> 00:14:33,960 Speaker 1: the only sense that needs internally generated activity to maintain 215 00:14:34,160 --> 00:14:37,960 Speaker 1: its borders during the long night. So, as a result, 216 00:14:38,000 --> 00:14:42,280 Speaker 1: about every ninety minutes you get this internally generated activity 217 00:14:42,280 --> 00:14:47,320 Speaker 1: that blasts exclusively into the visual cortex, and so dreams 218 00:14:47,360 --> 00:14:52,720 Speaker 1: are experienced as primarily visual. So several predictions immediately fall 219 00:14:52,760 --> 00:14:58,240 Speaker 1: out of the defensive activation theory. First, because brain plasticity 220 00:14:58,280 --> 00:15:01,440 Speaker 1: diminishes with age, this would suggest that the amount of 221 00:15:01,480 --> 00:15:05,200 Speaker 1: time spent in REM sleep should also decrease as one 222 00:15:05,320 --> 00:15:08,080 Speaker 1: moves through the lifespan, and that turns out to be 223 00:15:08,120 --> 00:15:12,840 Speaker 1: exactly what happens. REM sleep in humans accounts for half 224 00:15:13,000 --> 00:15:16,480 Speaker 1: of an infant's sleep time, but as a person grows older, 225 00:15:16,880 --> 00:15:21,800 Speaker 1: the percentage of remsleep decreases steadily. In other words, diminishing 226 00:15:21,880 --> 00:15:26,360 Speaker 1: plasticity of the brain correlates with less REM sleep. But 227 00:15:26,400 --> 00:15:30,360 Speaker 1: more importantly, we made a more quantified prediction. We said, hey, 228 00:15:30,760 --> 00:15:34,960 Speaker 1: maybe the more flexible and animal's brain is the more 229 00:15:35,160 --> 00:15:38,920 Speaker 1: REM sleep it requires to defend its visual cortex. So 230 00:15:39,040 --> 00:15:43,040 Speaker 1: Don and I studied the plasticity in twenty five species 231 00:15:43,080 --> 00:15:46,440 Speaker 1: of primates and we found that the species with more 232 00:15:46,480 --> 00:15:50,720 Speaker 1: plastic brains spend more time in REMS sleep every night. 233 00:15:51,000 --> 00:15:54,560 Speaker 1: So you'd think that these two measures REM sleep and 234 00:15:54,680 --> 00:15:58,200 Speaker 1: brain plasticity they would be totally unconnected, So it was 235 00:15:58,320 --> 00:16:02,080 Speaker 1: very surprising to find that they are tightly linked. So 236 00:16:02,280 --> 00:16:08,080 Speaker 1: dreaming defends the visual cortex. Now, the circuitry that underpins dreaming. 237 00:16:08,240 --> 00:16:12,240 Speaker 1: This is so ancient and deeply wired that even people 238 00:16:12,280 --> 00:16:15,240 Speaker 1: who are blind have it. But note that blind people 239 00:16:15,280 --> 00:16:20,480 Speaker 1: don't have visual dreams. Instead, their nighttime hallucinations involve the 240 00:16:20,600 --> 00:16:24,960 Speaker 1: other senses, like feeling their way around an oddly arranged 241 00:16:25,040 --> 00:16:30,440 Speaker 1: kitchen or hearing strangers speaking. Why because other sensory errors 242 00:16:30,520 --> 00:16:35,080 Speaker 1: have annexed the underused visual cortex. So think about it 243 00:16:35,120 --> 00:16:38,360 Speaker 1: this way. People who can see and those with visual impairments, 244 00:16:38,560 --> 00:16:42,600 Speaker 1: they both have activity shooting into their occipital lobe during dreaming, 245 00:16:42,960 --> 00:16:47,880 Speaker 1: but the senses processed by that territory are different. The 246 00:16:47,960 --> 00:16:52,720 Speaker 1: defensive activation theory also makes more general predictions. If dream 247 00:16:52,800 --> 00:16:56,000 Speaker 1: sleep is triggered by the absence of visual input during 248 00:16:56,000 --> 00:16:59,720 Speaker 1: the night, we might presume that a person deprived of 249 00:16:59,840 --> 00:17:05,359 Speaker 1: vision while awake could similarly experience dreamlike visual hallucinations. And 250 00:17:05,359 --> 00:17:09,560 Speaker 1: that is exactly what happens when people have degenerating vision, 251 00:17:09,840 --> 00:17:12,919 Speaker 1: or they end up in solitary confinement or even just 252 00:17:12,960 --> 00:17:16,480 Speaker 1: in a dark float tank. Any situation in which vision 253 00:17:16,520 --> 00:17:22,000 Speaker 1: gets deprived, the brain starts fighting back and having hallucinations. 254 00:17:22,480 --> 00:17:26,920 Speaker 1: So that's the idea. Dreams are a screensaver. The brain 255 00:17:26,960 --> 00:17:30,800 Speaker 1: puts activity into the visual cortex to prevent it from 256 00:17:30,800 --> 00:17:34,720 Speaker 1: getting ruined during the night. Okay, so you might say, fine, 257 00:17:34,800 --> 00:17:39,399 Speaker 1: your hypothesis seems plausible, But why do dreams seem to 258 00:17:39,440 --> 00:17:43,560 Speaker 1: be stories? After all, we don't just see random snow 259 00:17:43,760 --> 00:17:47,600 Speaker 1: like on an old television. We experience stories, and in fact, 260 00:17:47,960 --> 00:17:52,240 Speaker 1: there are various stories of someone discovering something in dreams, 261 00:17:52,359 --> 00:17:55,960 Speaker 1: like Kurkule thinking of the structure of the Benzene ring 262 00:17:56,080 --> 00:17:59,000 Speaker 1: based on a dream he had of two snakes biting 263 00:17:59,000 --> 00:18:02,679 Speaker 1: each other's tails, or Paul McCartney dreaming the melody for 264 00:18:02,720 --> 00:18:07,240 Speaker 1: the song Yesterday. So what's up with dream content? The 265 00:18:07,359 --> 00:18:12,200 Speaker 1: key is that the brain is a storytelling machine. Your 266 00:18:12,240 --> 00:18:17,840 Speaker 1: brain is deeply carved with roadways that represent your experience 267 00:18:17,880 --> 00:18:20,120 Speaker 1: in the world, and these are stored in what are 268 00:18:20,119 --> 00:18:24,520 Speaker 1: called associative neural networks, which means that everything connects to 269 00:18:24,560 --> 00:18:28,159 Speaker 1: other things based on how they relate. So if I 270 00:18:28,200 --> 00:18:31,560 Speaker 1: ask you to think of a mouse that's physically connected 271 00:18:31,600 --> 00:18:34,919 Speaker 1: in your brain's networks to your concept of cheese or 272 00:18:34,960 --> 00:18:38,919 Speaker 1: exterminators or mickey mouse or mazes, or running wheels, or 273 00:18:38,960 --> 00:18:43,240 Speaker 1: mouse traps or pet stores everything else you've ever associated 274 00:18:43,560 --> 00:18:48,360 Speaker 1: with a mouse. So all concepts are related and linked 275 00:18:48,400 --> 00:18:53,280 Speaker 1: physically to what happens during sleep and dreaming. Well, the 276 00:18:53,400 --> 00:18:57,199 Speaker 1: synapses that are used during the day tend to be 277 00:18:57,480 --> 00:19:01,560 Speaker 1: slightly more chemically active, say, they're more hot from the 278 00:19:01,600 --> 00:19:05,440 Speaker 1: activity of the day, and so your dreams usually involve 279 00:19:05,880 --> 00:19:08,200 Speaker 1: something from the day or something that's on your mind. 280 00:19:08,600 --> 00:19:13,000 Speaker 1: They often involve the memories and desires and fears and 281 00:19:13,119 --> 00:19:17,159 Speaker 1: hopes that are brewing in your inner life. But the 282 00:19:17,280 --> 00:19:21,359 Speaker 1: associations are much looser. So maybe you have something about 283 00:19:21,359 --> 00:19:23,840 Speaker 1: your boss or something that happened in a class or whatever, 284 00:19:24,160 --> 00:19:28,000 Speaker 1: but the dream quickly goes off in some weird direction. 285 00:19:28,240 --> 00:19:32,800 Speaker 1: The associations are looser, and so we end up dreaming 286 00:19:32,920 --> 00:19:37,840 Speaker 1: stories with looser associations, following paths along the associative neural 287 00:19:37,880 --> 00:19:41,960 Speaker 1: network that we might not otherwise take. But things make sense, 288 00:19:42,200 --> 00:19:46,359 Speaker 1: at least in the light of dream logic. So even 289 00:19:46,359 --> 00:19:50,520 Speaker 1: if the visual cortex is just getting volleys of random activity, 290 00:19:51,040 --> 00:19:53,920 Speaker 1: you get meaning out of it. You get some sort 291 00:19:53,960 --> 00:19:58,200 Speaker 1: of story. Now people often wake up and say, no, way, 292 00:19:58,240 --> 00:20:01,480 Speaker 1: that wasn't random, That was a metaphor. I'm trying to 293 00:20:01,520 --> 00:20:04,400 Speaker 1: decide if I should quit this job, and I had 294 00:20:04,440 --> 00:20:07,200 Speaker 1: a dream that I went into the office and the 295 00:20:07,240 --> 00:20:09,960 Speaker 1: floor was tilted at forty five degrees and no matter 296 00:20:10,000 --> 00:20:12,480 Speaker 1: what I did, I kept slipping back down. And that 297 00:20:12,640 --> 00:20:16,440 Speaker 1: was a metaphor about the impossibility of my advancement. There, 298 00:20:16,600 --> 00:20:20,960 Speaker 1: that was a sign from my unconscious. Okay, so maybe 299 00:20:21,359 --> 00:20:25,560 Speaker 1: the interesting thing about interpreting the content of dreams is 300 00:20:25,600 --> 00:20:28,840 Speaker 1: that they might be one hundred percent random, but they 301 00:20:28,880 --> 00:20:32,399 Speaker 1: act like a Rorshack blot, which is to say, you 302 00:20:32,440 --> 00:20:35,840 Speaker 1: can assign any sort of meaning to them. You remember 303 00:20:35,840 --> 00:20:38,440 Speaker 1: a Rorshack blot, which is where you squish some ink 304 00:20:38,520 --> 00:20:41,320 Speaker 1: between two pages, and then you pull the pages apart 305 00:20:41,520 --> 00:20:43,879 Speaker 1: and you get some random shape, and you ask people 306 00:20:43,920 --> 00:20:48,640 Speaker 1: to interpret what they're seeing to assign meaning to it. 307 00:20:48,760 --> 00:20:51,040 Speaker 1: And it's easy enough to say, yeah, that looks like 308 00:20:51,119 --> 00:20:53,520 Speaker 1: this thing in my life, maybe this issue that's been 309 00:20:53,600 --> 00:20:56,560 Speaker 1: chewing at me. And that's how doctor Rhorshak used this 310 00:20:56,760 --> 00:21:01,240 Speaker 1: to determine what had meaning in a person's mind. But 311 00:21:01,280 --> 00:21:04,639 Speaker 1: you would never say the blob of ink carried meaning. 312 00:21:04,760 --> 00:21:08,640 Speaker 1: It's all about the imposition of meaning by the viewer. 313 00:21:09,280 --> 00:21:12,720 Speaker 1: And this, I suggest could be what happens with dreams 314 00:21:12,840 --> 00:21:17,080 Speaker 1: as well. You interpret the ink blob, and that interpretation 315 00:21:17,680 --> 00:21:20,800 Speaker 1: might have significance to your life, but you imposed that 316 00:21:20,920 --> 00:21:24,960 Speaker 1: meaning instead of it being inherent in the dream. Here's 317 00:21:25,000 --> 00:21:29,560 Speaker 1: an interesting parallel. Pablo Picasso once said, we all know 318 00:21:29,920 --> 00:21:33,879 Speaker 1: that art is not truth. Art is a lie that 319 00:21:34,000 --> 00:21:36,840 Speaker 1: makes us realize the truth, and that could be the 320 00:21:36,840 --> 00:21:40,160 Speaker 1: same thing with dreams. They are a lie that makes 321 00:21:40,240 --> 00:21:43,240 Speaker 1: us realize the truth. So in this sense, it's the 322 00:21:43,240 --> 00:21:46,199 Speaker 1: same thing. If you're thinking about some problem and you 323 00:21:46,280 --> 00:21:48,920 Speaker 1: go to the bookshelf and you pull off any random 324 00:21:48,920 --> 00:21:51,080 Speaker 1: book and turn to a random page and you read 325 00:21:51,119 --> 00:21:55,560 Speaker 1: the sentence. Often it will very tangentially give you some 326 00:21:56,200 --> 00:21:58,800 Speaker 1: push to the thing that you're trying to solve. But 327 00:21:58,840 --> 00:22:01,920 Speaker 1: that doesn't mean the awe of the book cared about 328 00:22:01,960 --> 00:22:05,680 Speaker 1: you and wrote that sentence with that future moment in mind. 329 00:22:05,720 --> 00:22:07,879 Speaker 1: It simply tells us that lots of things in the 330 00:22:07,920 --> 00:22:11,440 Speaker 1: world are like lots of other things and can therefore 331 00:22:11,520 --> 00:22:14,680 Speaker 1: be interpreted. And I do just want to add one 332 00:22:14,720 --> 00:22:17,840 Speaker 1: more word of caution to the game of dream interpretation. 333 00:22:18,400 --> 00:22:20,840 Speaker 1: By the time you turn to the person next to 334 00:22:20,840 --> 00:22:22,679 Speaker 1: you and say, oh my gosh, I just had the 335 00:22:22,760 --> 00:22:26,840 Speaker 1: strangest dream and you tell them, you are forced to 336 00:22:26,880 --> 00:22:30,800 Speaker 1: add another layer of narrative scaffolding so that it makes 337 00:22:30,840 --> 00:22:34,640 Speaker 1: sense as a story that you're telling. So a narrative 338 00:22:34,680 --> 00:22:38,240 Speaker 1: that's very thin can seem to have more flesh after 339 00:22:38,320 --> 00:22:41,800 Speaker 1: you've pushed it through your storytelling machinery. In other words, 340 00:22:41,840 --> 00:22:45,399 Speaker 1: we layer on narrative structure to give our dreams a 341 00:22:45,520 --> 00:22:48,520 Speaker 1: shape that they didn't actually have. And so especially if 342 00:22:48,520 --> 00:22:51,320 Speaker 1: you've had a dream that you've told over and over, 343 00:22:51,720 --> 00:22:54,320 Speaker 1: it usually has more of a scaffolding than it actually 344 00:22:54,560 --> 00:22:59,679 Speaker 1: started with. Nonetheless, the content of dreams has always fascinated humans, 345 00:23:00,080 --> 00:23:05,080 Speaker 1: spurring societies to invent cultural uses for dreams in religious 346 00:23:05,080 --> 00:23:11,000 Speaker 1: ceremonies and medicinal practices, or doomed attempts to predict the future. 347 00:23:12,000 --> 00:23:15,359 Speaker 1: Sigmund Freud, who lived decades before modern brain science, he 348 00:23:15,400 --> 00:23:19,680 Speaker 1: thought that dreams provided an inroad into the underlying functions 349 00:23:19,720 --> 00:23:23,840 Speaker 1: of the brain and especially the subconscious. He suggested, as 350 00:23:23,920 --> 00:23:28,720 Speaker 1: had many before him, that dreams concealed hidden meanings that 351 00:23:28,840 --> 00:23:32,680 Speaker 1: were just at the threshold of breaking through the barrier 352 00:23:32,800 --> 00:23:37,520 Speaker 1: to consciousness. More specifically, he proposed that dreams constitute a 353 00:23:37,640 --> 00:23:43,040 Speaker 1: disguised attempt at wish fulfillment. Similarly, Carl Jung positive that 354 00:23:43,160 --> 00:23:48,760 Speaker 1: dreams may offset features of a character personality that you 355 00:23:48,880 --> 00:23:52,520 Speaker 1: might ignore while you're awake. In general, both those theories 356 00:23:52,560 --> 00:23:56,360 Speaker 1: have been criticized because they can't be proven wrong, and 357 00:23:56,520 --> 00:24:00,960 Speaker 1: critics have pointed out that the wish fulfillment interpretation seems 358 00:24:01,080 --> 00:24:06,320 Speaker 1: improbable in view of the recurring nightmares that attend post 359 00:24:06,359 --> 00:24:09,320 Speaker 1: traumatic stress disorder. So I am, of course not the 360 00:24:09,359 --> 00:24:13,080 Speaker 1: first to propose that dreams might have no inherent meaning. 361 00:24:13,359 --> 00:24:17,080 Speaker 1: The psychiatrists j al And Hobson and Robert McCarley suggest 362 00:24:17,160 --> 00:24:20,040 Speaker 1: that dreams may have no meaning at all, and they 363 00:24:20,080 --> 00:24:23,560 Speaker 1: have a model they call the activation synthesis model, which 364 00:24:23,560 --> 00:24:26,840 Speaker 1: proposes that random activity from the brain stem goes to 365 00:24:26,880 --> 00:24:30,120 Speaker 1: the cortex, which tries to turn it into motor output. 366 00:24:30,680 --> 00:24:34,040 Speaker 1: But given the paralysis of the major muscle groups, the 367 00:24:34,119 --> 00:24:39,560 Speaker 1: brain has to explain the paradox between outgoing motor signals 368 00:24:39,920 --> 00:24:44,879 Speaker 1: and a lack of expected sensory feedback. So in this situation, 369 00:24:45,280 --> 00:24:51,600 Speaker 1: the cortex synthesizes an explanation, essentially weaving a story from 370 00:24:51,600 --> 00:24:56,280 Speaker 1: the random inputs. Now Hobson and McCary faced criticism for 371 00:24:56,359 --> 00:24:59,600 Speaker 1: this aspect of their theory because dreams often do have 372 00:24:59,640 --> 00:25:02,920 Speaker 1: a relation relationship to life experience. So in that light, 373 00:25:02,960 --> 00:25:07,320 Speaker 1: they made modifications to allow that dream content relates to 374 00:25:07,440 --> 00:25:09,760 Speaker 1: memories and fears and desires and hopes and so on, 375 00:25:10,320 --> 00:25:13,879 Speaker 1: but that these provide the background context and not the 376 00:25:13,920 --> 00:25:19,120 Speaker 1: exact content of the cortexas interpretation of the random activity. 377 00:25:19,520 --> 00:25:22,359 Speaker 1: So which is it, Does dream content tell us anything 378 00:25:22,400 --> 00:25:25,440 Speaker 1: at all? Or nothing? Well, here's how we can approach 379 00:25:25,520 --> 00:25:29,199 Speaker 1: the problem. When you look at one person's dreams like 380 00:25:29,240 --> 00:25:31,359 Speaker 1: you think about your own dreams, you may not be 381 00:25:31,440 --> 00:25:34,560 Speaker 1: able to use the content as a key to unlock 382 00:25:34,720 --> 00:25:37,840 Speaker 1: much about the brain. But as you move from considering 383 00:25:38,000 --> 00:25:42,280 Speaker 1: one dreamer to doing the science and looking at thousands 384 00:25:42,280 --> 00:25:45,120 Speaker 1: of dream reports and hundreds of thousands from all over 385 00:25:45,160 --> 00:25:48,520 Speaker 1: the world, you can start to see the fence lines. 386 00:25:48,880 --> 00:25:53,119 Speaker 1: You see that dreams aren't a wild unleashing where anything 387 00:25:53,160 --> 00:25:58,000 Speaker 1: can happen. Instead, dreams have particular rules to the stories, 388 00:25:58,359 --> 00:26:01,680 Speaker 1: and that gives us hints. So what are those rules? Well, 389 00:26:01,720 --> 00:26:03,639 Speaker 1: I recently read a very cool new book by my 390 00:26:03,680 --> 00:26:07,240 Speaker 1: colleague Rahul John day Al called This Is Why You Dream, 391 00:26:07,359 --> 00:26:10,639 Speaker 1: and he outlines a series of studies that demonstrate a 392 00:26:10,760 --> 00:26:16,720 Speaker 1: remarkable consistency of themes. Across cultures and across decades, the 393 00:26:16,880 --> 00:26:21,920 Speaker 1: same kinds of dreams are reported, for example, being unable 394 00:26:22,000 --> 00:26:25,240 Speaker 1: to find one's way or being late for an important event. 395 00:26:25,600 --> 00:26:29,760 Speaker 1: In dreams, both men and women usually experience more aggression 396 00:26:29,840 --> 00:26:33,439 Speaker 1: than friendliness, although men in almost all societies have greater 397 00:26:33,520 --> 00:26:37,000 Speaker 1: physical aggression in their dreams than women do. Everyone experiences 398 00:26:37,040 --> 00:26:41,400 Speaker 1: more misfortune than good fortune. People experience more negative emotions 399 00:26:41,440 --> 00:26:45,520 Speaker 1: than positive emotions. So the cross cultural research suggests that 400 00:26:45,720 --> 00:26:49,159 Speaker 1: dreams are similar across a wide range of cultures in 401 00:26:49,200 --> 00:26:52,720 Speaker 1: terms of the subject matter, the level of aggression, familiarity 402 00:26:52,760 --> 00:26:55,040 Speaker 1: with the people in the dreams. For example, let me 403 00:26:55,119 --> 00:26:57,960 Speaker 1: zoom in on this. Jandeal points out that in the 404 00:26:58,040 --> 00:27:01,800 Speaker 1: nineteen fifties there were ques given to college students in 405 00:27:01,840 --> 00:27:05,399 Speaker 1: America and college students in Japan, and the questionnaire asked 406 00:27:05,440 --> 00:27:09,000 Speaker 1: them what they had dreamt about, like showing up somewhere 407 00:27:09,040 --> 00:27:11,680 Speaker 1: with no clothes or flying or trying to do something 408 00:27:11,680 --> 00:27:15,280 Speaker 1: again and again, or being buried alive, or something involving 409 00:27:15,359 --> 00:27:18,280 Speaker 1: school and their teachers or whatever. And as it turns out, 410 00:27:18,320 --> 00:27:22,360 Speaker 1: although American and Japanese students were living pretty different lives, 411 00:27:22,440 --> 00:27:26,400 Speaker 1: their answers were essentially the same. So for the Americans, 412 00:27:26,720 --> 00:27:31,840 Speaker 1: the top five dreams were falling, being attacked or pursued, 413 00:27:32,400 --> 00:27:35,960 Speaker 1: trying again and again to do something, a dream involving 414 00:27:36,200 --> 00:27:40,680 Speaker 1: school or teachers, or studying, and sexual experiences. And when 415 00:27:40,680 --> 00:27:43,280 Speaker 1: you compare this to the Japanese students, it was essentially 416 00:27:43,280 --> 00:27:47,880 Speaker 1: the same. Their dreams were ranked as being attacked or pursued, falling, 417 00:27:48,280 --> 00:27:51,560 Speaker 1: trying again and again to do something, dreams about school 418 00:27:51,640 --> 00:27:54,760 Speaker 1: or teachers or studying, and being frozen with fright, and 419 00:27:54,840 --> 00:27:58,720 Speaker 1: sexual experiences were number six. So halfway across the world, 420 00:27:58,880 --> 00:28:20,439 Speaker 1: very different cultures, same dream content. Now, fifty years after 421 00:28:20,480 --> 00:28:23,800 Speaker 1: that study, similar questions were given to students in China 422 00:28:23,960 --> 00:28:26,359 Speaker 1: and Germany, and they came up with the century the 423 00:28:26,400 --> 00:28:30,639 Speaker 1: same answers. Again, you find people dreaming of being chaste, 424 00:28:30,720 --> 00:28:33,800 Speaker 1: or pursued, or arriving too late, like missing an airplane 425 00:28:33,880 --> 00:28:36,080 Speaker 1: or a final exam. Now you might say, fine, but 426 00:28:36,119 --> 00:28:38,959 Speaker 1: these are all industrialized countries and maybe their lives are 427 00:28:39,000 --> 00:28:41,840 Speaker 1: sort of similar. But in fact people have also studied 428 00:28:41,960 --> 00:28:46,240 Speaker 1: indigenous societies in Brazil and Mexico and Australia and they 429 00:28:46,280 --> 00:28:51,160 Speaker 1: find extremely similar results. The cultures are quite different. But 430 00:28:51,320 --> 00:28:55,000 Speaker 1: the plots of the dreams are not. So there have 431 00:28:55,000 --> 00:28:56,920 Speaker 1: been lots of studies on this sort of thing now, 432 00:28:56,920 --> 00:28:59,880 Speaker 1: and they all conclude that dream content is a century 433 00:29:00,120 --> 00:29:04,320 Speaker 1: same across cultures and across time. As one example, wherever 434 00:29:04,360 --> 00:29:07,680 Speaker 1: you are in the world, men dream more about other men, 435 00:29:07,800 --> 00:29:11,400 Speaker 1: while women dream equally of men and women, and all 436 00:29:11,480 --> 00:29:14,920 Speaker 1: people across cultures are more likely to be victims of 437 00:29:15,040 --> 00:29:20,800 Speaker 1: violence rather than perpetrators. So dreams cover similar themes across 438 00:29:20,800 --> 00:29:24,120 Speaker 1: the world, irrespective of language and culture and time. It 439 00:29:24,200 --> 00:29:26,720 Speaker 1: doesn't seem to matter how rich you are, how poor 440 00:29:26,760 --> 00:29:29,080 Speaker 1: you are. So what does that mean? Well, what's the 441 00:29:29,080 --> 00:29:32,200 Speaker 1: one thing we all have in common? Our organs on 442 00:29:32,240 --> 00:29:35,440 Speaker 1: the inside and specifically the brain. As easy as it 443 00:29:35,560 --> 00:29:37,800 Speaker 1: is to look at different cultures around the world, with 444 00:29:37,880 --> 00:29:42,640 Speaker 1: different governments and different religions and different costumes, this variability 445 00:29:42,680 --> 00:29:46,000 Speaker 1: has cropped up in the last millisecond of human history. 446 00:29:46,320 --> 00:29:48,440 Speaker 1: And if you look just under the skin and the bone, 447 00:29:48,480 --> 00:29:51,400 Speaker 1: you find the same brain in us all. It's the 448 00:29:51,440 --> 00:29:55,160 Speaker 1: same engine under the hood. So whenever we find something 449 00:29:55,280 --> 00:29:59,640 Speaker 1: clear like oh, everyone dreams about the same thing, that 450 00:30:00,600 --> 00:30:05,120 Speaker 1: we are looking at something fundamental and ancient and universal, 451 00:30:05,440 --> 00:30:07,920 Speaker 1: and we find all sorts of other interesting answers by 452 00:30:07,920 --> 00:30:11,840 Speaker 1: looking across thousands of dreams. For example, what if dreams 453 00:30:11,880 --> 00:30:15,320 Speaker 1: are a way to live out fantasies like sexual fantasy. 454 00:30:15,600 --> 00:30:19,240 Speaker 1: That seems consistent with how we talk about dreams a 455 00:30:19,320 --> 00:30:23,320 Speaker 1: way of acting out our desires. But in studies across 456 00:30:23,320 --> 00:30:26,760 Speaker 1: all cultures, it turns out that fewer than ten percent 457 00:30:26,800 --> 00:30:29,840 Speaker 1: of dreams are sexual, which I find fascinating given the 458 00:30:29,840 --> 00:30:34,080 Speaker 1: way we talk about dreams. If a young single person 459 00:30:34,160 --> 00:30:36,720 Speaker 1: says to another single person, oh, I had a dream 460 00:30:36,760 --> 00:30:40,440 Speaker 1: about you last night, then everyone titters, makes assumptions about that, 461 00:30:40,800 --> 00:30:44,200 Speaker 1: and we have terms like dream girl or dream guide, 462 00:30:44,200 --> 00:30:47,760 Speaker 1: But in fact, ninety percent of our dreams have nothing 463 00:30:47,800 --> 00:30:51,240 Speaker 1: to do with that. So the content is remarkably similar 464 00:30:51,280 --> 00:30:54,440 Speaker 1: across the world. But where things get really interesting is 465 00:30:54,480 --> 00:30:58,320 Speaker 1: when we zoom in one more level and really examine 466 00:30:58,320 --> 00:31:01,760 Speaker 1: what dreamscapes look like like in detail. And I'm not 467 00:31:01,840 --> 00:31:05,239 Speaker 1: asking about what's in the dream script here, but if 468 00:31:05,240 --> 00:31:08,080 Speaker 1: you look very closely across thousands of dream reports, you 469 00:31:08,120 --> 00:31:11,760 Speaker 1: can ask what is not in the script. So I 470 00:31:11,800 --> 00:31:14,240 Speaker 1: want to return to a question I posed at the beginning, 471 00:31:14,320 --> 00:31:16,840 Speaker 1: which is that we live in a society where we 472 00:31:16,880 --> 00:31:20,680 Speaker 1: are constantly hunched over our cell phones and our laptops. 473 00:31:20,920 --> 00:31:24,360 Speaker 1: How come these essentially never show up in our dreams? 474 00:31:24,440 --> 00:31:27,840 Speaker 1: Isn't that weird? And even in the era before computers, 475 00:31:27,880 --> 00:31:30,240 Speaker 1: back when people read a lot more books, how come 476 00:31:30,320 --> 00:31:34,480 Speaker 1: no one sits around reading books in their dreams. Why 477 00:31:34,520 --> 00:31:37,600 Speaker 1: can't you even see any text in your dreams? Why 478 00:31:37,600 --> 00:31:41,040 Speaker 1: do you spend so much time writing stuff down in 479 00:31:41,080 --> 00:31:44,200 Speaker 1: real life but you never can write stuff down in 480 00:31:44,280 --> 00:31:47,280 Speaker 1: a dream. How come you never do math in a dream, 481 00:31:47,680 --> 00:31:50,800 Speaker 1: like calculating a tip for a restaurant bill, Even if 482 00:31:50,880 --> 00:31:53,200 Speaker 1: that comes up in a dream plot, it feels totally 483 00:31:53,200 --> 00:31:57,200 Speaker 1: impossible to get the right answer. Well, all of this 484 00:31:57,320 --> 00:32:00,880 Speaker 1: serves as a big clue into the networks that are 485 00:32:01,000 --> 00:32:04,120 Speaker 1: active during a dream, and this is pretty well worked 486 00:32:04,160 --> 00:32:07,280 Speaker 1: out with brain imaging now, although anyone who is being 487 00:32:07,400 --> 00:32:10,560 Speaker 1: very observant probably could have guessed this all even a 488 00:32:10,600 --> 00:32:14,160 Speaker 1: century ago. What reading and writing, and cell phones and 489 00:32:14,200 --> 00:32:17,320 Speaker 1: computers all have in common is that they require the 490 00:32:17,440 --> 00:32:20,200 Speaker 1: use of a network in the brain that we summarize 491 00:32:20,240 --> 00:32:24,160 Speaker 1: as the executive network, which involves a lot of activity 492 00:32:24,280 --> 00:32:27,640 Speaker 1: largely distributed in the frontal lobes and the parietal lobes, 493 00:32:27,960 --> 00:32:32,400 Speaker 1: and you need this for rule based problem solving and 494 00:32:32,720 --> 00:32:35,520 Speaker 1: for making decisions when you've got a particular goal in 495 00:32:35,560 --> 00:32:37,840 Speaker 1: front of you that you're trying to solve. And the 496 00:32:37,960 --> 00:32:42,280 Speaker 1: key is that activity in the executive network is reduced. 497 00:32:42,320 --> 00:32:46,640 Speaker 1: I'll just say it's shut down while you are dreaming, 498 00:32:46,960 --> 00:32:49,880 Speaker 1: so you're not able to read and write and launch 499 00:32:49,920 --> 00:32:51,800 Speaker 1: an app on your cell phone screen and so on, 500 00:32:51,880 --> 00:32:56,320 Speaker 1: because that work requires the executive network, and that network 501 00:32:56,480 --> 00:32:59,600 Speaker 1: is off duty for the night. But what is on 502 00:32:59,760 --> 00:33:04,320 Speaker 1: is an network we summarize as the default mode network, 503 00:33:04,640 --> 00:33:07,720 Speaker 1: which is what kindles to life when you shut your 504 00:33:07,760 --> 00:33:11,520 Speaker 1: eyes and you're not involved in gathering information and acting 505 00:33:11,560 --> 00:33:15,120 Speaker 1: on some other task. So this is called the default 506 00:33:15,200 --> 00:33:20,240 Speaker 1: mode network, but many scientists are renaming this the imagination 507 00:33:20,480 --> 00:33:25,520 Speaker 1: network because this is what lets your storehouse of experiences fly. 508 00:33:26,160 --> 00:33:29,360 Speaker 1: You can piece ideas together and come up with new 509 00:33:29,720 --> 00:33:34,000 Speaker 1: hypotheses and thoughts, and this is what's firing on all 510 00:33:34,240 --> 00:33:39,000 Speaker 1: cylinders when you dream. So the executive network has reduced, 511 00:33:39,160 --> 00:33:42,760 Speaker 1: the imagination network is enhanced, and this is what gives 512 00:33:42,880 --> 00:33:47,520 Speaker 1: dreams their very untethered character. There are other clues you 513 00:33:47,520 --> 00:33:51,720 Speaker 1: can also gather from looking at detailed dream reports, which 514 00:33:51,760 --> 00:33:55,440 Speaker 1: is that sometimes objects will turn into other objects, but 515 00:33:55,480 --> 00:33:58,800 Speaker 1: they're always related in some way. What I mean is 516 00:33:58,880 --> 00:34:02,800 Speaker 1: you might have your bicycle turn into a motorcycle, or 517 00:34:02,920 --> 00:34:07,880 Speaker 1: your small house becomes a mansion, or the cafeteria becomes 518 00:34:07,920 --> 00:34:11,759 Speaker 1: a restaurant, or the hammer becomes a screwdriver, but you 519 00:34:11,920 --> 00:34:16,160 Speaker 1: don't find the bicycle turning into a restaurant or your 520 00:34:16,239 --> 00:34:20,120 Speaker 1: house turning into a hammer. What does that tell us? Well, 521 00:34:20,200 --> 00:34:23,920 Speaker 1: under the hood, we have what are known as semantic maps, 522 00:34:24,480 --> 00:34:29,040 Speaker 1: and more than associations, which I mentioned before, semantic maps 523 00:34:29,120 --> 00:34:31,239 Speaker 1: refer to the way that all the stuff in your 524 00:34:31,280 --> 00:34:35,680 Speaker 1: brain is laid out in terms of relationships between concepts. 525 00:34:35,800 --> 00:34:39,560 Speaker 1: For example, in your semantic map, you have the concept 526 00:34:39,600 --> 00:34:43,920 Speaker 1: of an animal, which might include categories like mammals and 527 00:34:43,920 --> 00:34:46,759 Speaker 1: birds and reptiles and so on, and within one of 528 00:34:46,800 --> 00:34:50,600 Speaker 1: those categories you might have more specific concepts like dog 529 00:34:50,640 --> 00:34:53,719 Speaker 1: and cat and eagle and salmon and snake and frog 530 00:34:53,800 --> 00:34:56,000 Speaker 1: and so on. Things are laid out in your brain 531 00:34:56,080 --> 00:34:59,719 Speaker 1: based on their conceptual meaning. And what we find is 532 00:34:59,760 --> 00:35:04,120 Speaker 1: that dreams follow the semantic maps. In other words, they 533 00:35:04,120 --> 00:35:07,960 Speaker 1: stay local in the little clusters of the maps. So 534 00:35:08,080 --> 00:35:10,719 Speaker 1: this is why you see the bicycle turning into the 535 00:35:10,760 --> 00:35:14,840 Speaker 1: motorcycle because they're both forms of transportation, but not into 536 00:35:15,280 --> 00:35:18,080 Speaker 1: the screwdriver, which is a tool and in a totally 537 00:35:18,080 --> 00:35:22,960 Speaker 1: different category. These things live in different little neighborhoods of 538 00:35:23,000 --> 00:35:27,040 Speaker 1: the semantic map. So again, a careful look at dream 539 00:35:27,080 --> 00:35:30,680 Speaker 1: reports tells us important clues about what is going on 540 00:35:31,000 --> 00:35:33,799 Speaker 1: under the hood, and that tells us that while the 541 00:35:33,800 --> 00:35:37,759 Speaker 1: themes are universal strife and falling and attempting to do 542 00:35:37,800 --> 00:35:41,200 Speaker 1: something over and over, the details are filled in with 543 00:35:41,280 --> 00:35:45,360 Speaker 1: the specifics of your semantic maps. And this all brings 544 00:35:45,400 --> 00:35:47,920 Speaker 1: me back around to a question I had since I 545 00:35:48,000 --> 00:35:52,240 Speaker 1: was a kid about whether dreams are experienced in black 546 00:35:52,280 --> 00:35:55,000 Speaker 1: and white or in color. Now. When I was a child, 547 00:35:55,480 --> 00:35:57,799 Speaker 1: I remember at some point that my parents told me 548 00:35:58,280 --> 00:36:01,400 Speaker 1: that we dream in black and white, and I was 549 00:36:01,440 --> 00:36:03,920 Speaker 1: confused by this because I didn't seem to dream in 550 00:36:03,960 --> 00:36:06,319 Speaker 1: black and white. As far as I could tell, my 551 00:36:06,520 --> 00:36:09,160 Speaker 1: dreams were in color, so I thought I must be 552 00:36:09,239 --> 00:36:13,760 Speaker 1: somehow assessing that incorrectly. Because they were both very smart 553 00:36:13,800 --> 00:36:16,959 Speaker 1: and educated. My mother was a biology teacher, my father 554 00:36:17,040 --> 00:36:19,920 Speaker 1: was a medical doctor, and as I grew older, I 555 00:36:19,960 --> 00:36:22,720 Speaker 1: asked my friends about this, but I couldn't find anyone 556 00:36:22,719 --> 00:36:26,279 Speaker 1: who thought that their dreams were not in color. Now, 557 00:36:26,360 --> 00:36:29,239 Speaker 1: because I genuinely knew that my parents were brilliant, I 558 00:36:29,280 --> 00:36:32,920 Speaker 1: thought maybe there was something they knew that I didn't like. 559 00:36:33,040 --> 00:36:35,680 Speaker 1: Maybe we were dreaming in black and white but didn't 560 00:36:35,719 --> 00:36:39,280 Speaker 1: realize it. And then I found several large scale surveys 561 00:36:39,320 --> 00:36:43,000 Speaker 1: that reported what my parents had said, that most people 562 00:36:43,080 --> 00:36:46,240 Speaker 1: dream in black and white. One study was from nineteen 563 00:36:46,320 --> 00:36:48,840 Speaker 1: fifty eight and they said only nine percent of people 564 00:36:48,960 --> 00:36:52,000 Speaker 1: dream in color, and a paper in nineteen forty two 565 00:36:52,040 --> 00:36:55,960 Speaker 1: reported that only ten percent claimed to frequently or very 566 00:36:55,960 --> 00:36:59,000 Speaker 1: frequently dream in color, and a report in nineteen fifty 567 00:36:59,000 --> 00:37:02,120 Speaker 1: one had the highest percentage. They said that twenty nine 568 00:37:02,160 --> 00:37:05,359 Speaker 1: percent of dreams are in color. But even this didn't 569 00:37:05,400 --> 00:37:09,400 Speaker 1: make things clear what was going on, because dream reports 570 00:37:09,480 --> 00:37:13,760 Speaker 1: from earlier, like Freud's reports of dreams in nineteen hundred, 571 00:37:14,480 --> 00:37:19,120 Speaker 1: often had explicit color descriptions in them. So somehow it 572 00:37:19,280 --> 00:37:24,759 Speaker 1: seemed to be only my parents' generation that dreamed in 573 00:37:24,880 --> 00:37:27,560 Speaker 1: black and white. And it turns out if you run 574 00:37:27,560 --> 00:37:31,640 Speaker 1: the study now, almost everyone says they dream in color. 575 00:37:32,040 --> 00:37:34,799 Speaker 1: As you may have guessed by now. The hypothesis on 576 00:37:34,840 --> 00:37:39,000 Speaker 1: this is that people were influenced by watching black and 577 00:37:39,040 --> 00:37:42,120 Speaker 1: white television and black and white movies and black and 578 00:37:42,120 --> 00:37:47,319 Speaker 1: white photographs, and once the technology changed to color, then 579 00:37:47,440 --> 00:37:50,880 Speaker 1: so did dreams. I'm putting a very nice paper by 580 00:37:51,000 --> 00:37:54,520 Speaker 1: Eric Schwitzkeebel on my site that compiles all these studies 581 00:37:54,560 --> 00:37:58,120 Speaker 1: through the years and the change in the reports. Again, 582 00:37:58,160 --> 00:38:01,600 Speaker 1: this demonstrates that the content of our dreams has to 583 00:38:01,640 --> 00:38:05,359 Speaker 1: do with the experiences that we have now. I'll tell 584 00:38:05,360 --> 00:38:07,440 Speaker 1: you an interesting side note on this. I happened to 585 00:38:07,440 --> 00:38:11,120 Speaker 1: live in California and during COVID, everyone in my neighborhood 586 00:38:11,160 --> 00:38:13,480 Speaker 1: wore masks, and it was a very weird time, and 587 00:38:13,520 --> 00:38:16,279 Speaker 1: so we rarely saw other human beings for a couple 588 00:38:16,360 --> 00:38:19,360 Speaker 1: of years without everyone being in masks. And one of 589 00:38:19,440 --> 00:38:21,799 Speaker 1: the things I remember from that time was that we 590 00:38:21,800 --> 00:38:24,640 Speaker 1: would sometimes watch a movie on TV, and it was 591 00:38:24,680 --> 00:38:27,640 Speaker 1: so shocking that people in the movie would push their 592 00:38:27,680 --> 00:38:30,080 Speaker 1: way through a dense crowd and sit so close to 593 00:38:30,160 --> 00:38:32,880 Speaker 1: their friends and the people they were talking with, and 594 00:38:32,920 --> 00:38:36,600 Speaker 1: they were indoors with such density. And it became in 595 00:38:36,680 --> 00:38:39,839 Speaker 1: twenty twenty so noticeable and so shocking when we were 596 00:38:39,840 --> 00:38:42,839 Speaker 1: in the middle of COVID. Interestingly, it's a little hard 597 00:38:42,840 --> 00:38:45,160 Speaker 1: to remember that now, but I remember it well because 598 00:38:45,200 --> 00:38:47,399 Speaker 1: I was taking careful notes on what was going on 599 00:38:47,920 --> 00:38:52,080 Speaker 1: with my dreams during this time, and specifically, since my 600 00:38:52,320 --> 00:38:55,800 Speaker 1: real life involved the very thinned out crowds and everyone 601 00:38:55,840 --> 00:38:59,080 Speaker 1: in masks, did that show up in my dreams? And 602 00:38:59,120 --> 00:39:03,040 Speaker 1: the answer was is no. The thing that struck me 603 00:39:03,080 --> 00:39:06,640 Speaker 1: the entire time during lockdown is that my dreams were 604 00:39:06,719 --> 00:39:09,480 Speaker 1: totally normal. In my dreams, I was at a big 605 00:39:09,520 --> 00:39:11,440 Speaker 1: party and there were lots of people around, and no 606 00:39:11,440 --> 00:39:14,600 Speaker 1: one ever had masks in my dreams, which struck me 607 00:39:14,680 --> 00:39:16,799 Speaker 1: as weird when I would wake up. Why didn't my 608 00:39:16,920 --> 00:39:21,680 Speaker 1: dreams reflect my daily experience? Now, this is just a 609 00:39:21,719 --> 00:39:24,680 Speaker 1: single person's report, and I didn't think to study this 610 00:39:24,760 --> 00:39:27,160 Speaker 1: carefully at the time by doing a big online survey 611 00:39:27,200 --> 00:39:30,360 Speaker 1: of everyone. But if it's generally true that other people 612 00:39:30,360 --> 00:39:34,799 Speaker 1: were having these very salient daily experiences of lockdown and 613 00:39:34,880 --> 00:39:38,600 Speaker 1: masks and yet it wasn't appearing in their dreams, the 614 00:39:38,640 --> 00:39:41,839 Speaker 1: only interpretation I can make is that our dreams reflect 615 00:39:42,000 --> 00:39:46,800 Speaker 1: pathways that get laid down over our youth when we're young. 616 00:39:47,440 --> 00:39:50,200 Speaker 1: And if that's the case, then maybe we could still 617 00:39:50,320 --> 00:39:54,439 Speaker 1: find some black and white dreaming among older people. Now, 618 00:39:54,560 --> 00:39:57,799 Speaker 1: in other words, maybe you'd still see some of that now, 619 00:39:58,160 --> 00:40:01,799 Speaker 1: even though those people have been watching color television for 620 00:40:01,920 --> 00:40:04,439 Speaker 1: sixty years. Now, with all the things on my plate, 621 00:40:04,480 --> 00:40:06,560 Speaker 1: I'm not going to have time to pull off that study. 622 00:40:06,600 --> 00:40:09,279 Speaker 1: But I would love it if listeners could ask their 623 00:40:09,360 --> 00:40:13,360 Speaker 1: oldest living relatives they a parent, or grandparent or great grandparent, 624 00:40:13,800 --> 00:40:18,640 Speaker 1: how they dream and determine if anyone still dreams in 625 00:40:18,719 --> 00:40:36,960 Speaker 1: black and white and what their age is. Okay, so 626 00:40:37,040 --> 00:40:40,080 Speaker 1: that story of black and white dreaming correlated with black 627 00:40:40,120 --> 00:40:42,880 Speaker 1: and white television. That seems like a clean story, But 628 00:40:42,920 --> 00:40:45,600 Speaker 1: there's one thing that still bugs me about it. Although 629 00:40:45,840 --> 00:40:49,399 Speaker 1: television and movies were in black and white, obviously the 630 00:40:49,440 --> 00:40:53,240 Speaker 1: world wasn't. When my parents walked outside, they saw green 631 00:40:53,320 --> 00:40:56,960 Speaker 1: trees and blue skies and red cardinals and yellow sunflowers 632 00:40:57,000 --> 00:41:01,279 Speaker 1: and so on. So why didn't their dreams reflect that? Well, 633 00:41:01,320 --> 00:41:03,719 Speaker 1: there are two things to say here. First, not everyone 634 00:41:03,800 --> 00:41:06,480 Speaker 1: dreamed in black and white. Instead, it was between let's 635 00:41:06,520 --> 00:41:09,560 Speaker 1: say seventy to ninety percent. So had I been alive 636 00:41:09,560 --> 00:41:11,800 Speaker 1: in the nineteen fifties, I would have studied the issue 637 00:41:11,840 --> 00:41:15,400 Speaker 1: of how many hours of television people watched each day, 638 00:41:15,680 --> 00:41:17,839 Speaker 1: and perhaps some measure of how many black and white 639 00:41:17,840 --> 00:41:20,400 Speaker 1: movies they saw on how many newspapers with black and 640 00:41:20,400 --> 00:41:23,439 Speaker 1: white photos and so on, and correlated that to whether 641 00:41:23,560 --> 00:41:26,440 Speaker 1: or not they had black and white dreams. Second, I 642 00:41:26,480 --> 00:41:29,880 Speaker 1: have a totally speculative hypothesis. I don't have any evidence 643 00:41:29,920 --> 00:41:31,960 Speaker 1: for this, but I'm going to say it anyway. What 644 00:41:32,200 --> 00:41:35,760 Speaker 1: if some part of the brain knows, at least in part, 645 00:41:36,440 --> 00:41:40,279 Speaker 1: that dreams are like a fake movie, and in that 646 00:41:40,360 --> 00:41:43,799 Speaker 1: way it takes on the property of fiction, which in 647 00:41:43,840 --> 00:41:46,719 Speaker 1: those days was black and white. Because note that even 648 00:41:46,800 --> 00:41:49,359 Speaker 1: when you're in the middle of a movie, some part 649 00:41:49,360 --> 00:41:51,719 Speaker 1: of your brain still knows you're watching a movie. And 650 00:41:51,760 --> 00:41:54,560 Speaker 1: this is why when the train comes at the camera, 651 00:41:54,600 --> 00:41:57,839 Speaker 1: you don't actually duck and scream. So even though we're 652 00:41:57,880 --> 00:42:02,160 Speaker 1: compelled by fiction, we don't fall for it completely. Could 653 00:42:02,200 --> 00:42:06,000 Speaker 1: it be that to the brain, dreams are more like movies. 654 00:42:06,760 --> 00:42:09,279 Speaker 1: I don't know, because I missed that era, so the 655 00:42:09,320 --> 00:42:13,000 Speaker 1: opportunity seems gone to study that. But I'm wondering if 656 00:42:13,040 --> 00:42:16,120 Speaker 1: we're going to have another shot at studying this question 657 00:42:16,680 --> 00:42:21,080 Speaker 1: once virtual reality becomes ubiquitous and pervasive, and whether a 658 00:42:21,160 --> 00:42:24,719 Speaker 1: big chunk of the population will report dreams that are 659 00:42:24,760 --> 00:42:29,840 Speaker 1: more like synthesized virtual reality worlds than like our daily life. 660 00:42:29,880 --> 00:42:33,239 Speaker 1: To me, this would shed light on the mystery of 661 00:42:33,320 --> 00:42:36,399 Speaker 1: the black and white dreams and the details by which 662 00:42:36,440 --> 00:42:41,960 Speaker 1: your dreams are determined by your experiences in the world. Now, 663 00:42:42,000 --> 00:42:44,759 Speaker 1: there's still lots of stuff that I think we don't understand. 664 00:42:44,880 --> 00:42:49,719 Speaker 1: One is why we can have false, implanted memories inside 665 00:42:49,719 --> 00:42:52,280 Speaker 1: a dream. This is something I've wondered about for years. 666 00:42:52,640 --> 00:42:55,440 Speaker 1: For example, I had a dream many years ago about 667 00:42:55,480 --> 00:42:58,840 Speaker 1: my brother's wedding and he was yelling at me and saying, 668 00:42:59,160 --> 00:43:01,760 Speaker 1: I can't believe you said that to Jenny and ruined 669 00:43:01,800 --> 00:43:04,560 Speaker 1: my wedding, and I felt horrible. I felt as guilty 670 00:43:04,560 --> 00:43:06,759 Speaker 1: as I ever felt. Why did I do that? Why 671 00:43:06,880 --> 00:43:10,040 Speaker 1: was I so insensitive? And then I woke up. As 672 00:43:10,080 --> 00:43:12,080 Speaker 1: it turns out, my brother had a lovely wedding that 673 00:43:12,120 --> 00:43:14,760 Speaker 1: went just perfectly, and I of course never said anything 674 00:43:14,840 --> 00:43:18,399 Speaker 1: bad to his bride, my lovely sister in law Jenny. Ever, 675 00:43:18,520 --> 00:43:21,520 Speaker 1: there was never trouble of any sort there. So why 676 00:43:21,520 --> 00:43:24,600 Speaker 1: did I fall for the false memory? Why couldn't I 677 00:43:24,680 --> 00:43:27,799 Speaker 1: access my real memories of the wedding while I was 678 00:43:27,960 --> 00:43:32,080 Speaker 1: inside the dream? In other words, the issue is that 679 00:43:32,200 --> 00:43:35,360 Speaker 1: not only did I have a false memory. But also 680 00:43:35,400 --> 00:43:38,680 Speaker 1: I had no access to my real memory of the wedding. 681 00:43:39,400 --> 00:43:42,680 Speaker 1: One set of memories was replaced by another. And this 682 00:43:42,719 --> 00:43:45,839 Speaker 1: is what freaks me out, not just about dreams, but 683 00:43:45,920 --> 00:43:51,239 Speaker 1: about our sense of reality. We buy whatever our brains 684 00:43:51,480 --> 00:43:54,560 Speaker 1: serve up to us at every moment. We buy the 685 00:43:54,680 --> 00:43:58,080 Speaker 1: plot of a dream completely. And by the way, this 686 00:43:58,160 --> 00:44:02,000 Speaker 1: is one interpretation of what happened in schizophrenia. The way 687 00:44:02,040 --> 00:44:06,160 Speaker 1: psychiatrists used to describe this about a century ago is 688 00:44:06,160 --> 00:44:11,160 Speaker 1: that psychosis is essentially an intrusion of the dream state 689 00:44:11,360 --> 00:44:14,799 Speaker 1: into the waking state. So the next time you see 690 00:44:14,840 --> 00:44:17,640 Speaker 1: a man talking to himself on the street and having 691 00:44:17,719 --> 00:44:20,560 Speaker 1: an argument with someone who is not there in front 692 00:44:20,560 --> 00:44:24,400 Speaker 1: of him, interpret it through this lens that he is 693 00:44:24,480 --> 00:44:29,040 Speaker 1: having an awake dream, and you might understand what's happening 694 00:44:29,200 --> 00:44:31,759 Speaker 1: in a fresh way. So what we see here, and 695 00:44:31,800 --> 00:44:34,080 Speaker 1: what we've seen in many of these episodes, is that 696 00:44:34,120 --> 00:44:38,120 Speaker 1: we accept whatever reality is served up to us. And 697 00:44:38,160 --> 00:44:41,120 Speaker 1: by the way, I think this is why literature works 698 00:44:41,160 --> 00:44:44,880 Speaker 1: with our species, because we can so easily adopt a 699 00:44:44,960 --> 00:44:48,480 Speaker 1: different reality. We can read a book and we laugh 700 00:44:48,560 --> 00:44:54,040 Speaker 1: and we weep. We are effortlessly deluded. And to understand 701 00:44:54,040 --> 00:44:58,000 Speaker 1: this I think we shouldn't use the term suspension of disbeliefs. 702 00:44:58,000 --> 00:45:02,719 Speaker 1: It's the wrong term because an applies that disbelief is 703 00:45:02,840 --> 00:45:06,839 Speaker 1: the standard disbelief is the normal operating mode. In fact, 704 00:45:06,920 --> 00:45:10,320 Speaker 1: it might be just the opposite. Our brains are perfectly 705 00:45:10,440 --> 00:45:15,160 Speaker 1: willing to accept whatever they are fed. Now, I want 706 00:45:15,160 --> 00:45:17,560 Speaker 1: to hit one more question in today's episode, which is 707 00:45:17,680 --> 00:45:22,480 Speaker 1: where is dreaming headed? Would it be possible to read 708 00:45:22,680 --> 00:45:27,320 Speaker 1: out the content of somebody's dreams? Well, if you happen 709 00:45:27,360 --> 00:45:30,080 Speaker 1: to have heard my episode number twenty seven, you'll know 710 00:45:30,160 --> 00:45:33,880 Speaker 1: that the answer is already yes, at least to some degree. 711 00:45:34,360 --> 00:45:37,240 Speaker 1: Different research groups have been working since at least twenty 712 00:45:37,239 --> 00:45:40,160 Speaker 1: eleven to see if they can measure brain activity in 713 00:45:40,160 --> 00:45:44,200 Speaker 1: the visual cortex to assess what somebody is seeing in 714 00:45:44,239 --> 00:45:46,880 Speaker 1: front of their eyes. In other words, if you're looking 715 00:45:47,120 --> 00:45:50,280 Speaker 1: at a building, there's a different activity in your visual 716 00:45:50,320 --> 00:45:52,920 Speaker 1: cortex than if you're looking at a puppy or a 717 00:45:52,920 --> 00:45:55,240 Speaker 1: cup of coffee and so on, and so the research 718 00:45:55,400 --> 00:45:58,560 Speaker 1: question is can you tell what a person is seeing 719 00:45:58,880 --> 00:46:01,520 Speaker 1: just by measuring the pasterns in their visual cortex? And 720 00:46:01,560 --> 00:46:04,400 Speaker 1: the answer is that you can pretty well tell what 721 00:46:04,520 --> 00:46:07,799 Speaker 1: somebody is seeing this way. After that research came out, 722 00:46:08,320 --> 00:46:12,680 Speaker 1: people realized we might be able to measure dreams because 723 00:46:12,760 --> 00:46:16,919 Speaker 1: dreams are activity in the primary visual cortex. Dreams are 724 00:46:16,960 --> 00:46:22,040 Speaker 1: experienced as visual because it's activity in the visual cortex, 725 00:46:22,080 --> 00:46:26,560 Speaker 1: and your brain understands that as visual experience. So Yuki 726 00:46:26,680 --> 00:46:29,480 Speaker 1: also Comma Tani and his colleagues published a paper a 727 00:46:29,520 --> 00:46:32,920 Speaker 1: few years ago in which he took this same approach. 728 00:46:32,960 --> 00:46:35,200 Speaker 1: He had people look at a bunch of pictures and 729 00:46:35,239 --> 00:46:37,160 Speaker 1: watch a bunch of videos while they were in the 730 00:46:37,200 --> 00:46:41,000 Speaker 1: brain scanner, and then he used machine learning to decode 731 00:46:41,480 --> 00:46:45,160 Speaker 1: how the picture out there corresponds to the activity patterns 732 00:46:45,200 --> 00:46:48,640 Speaker 1: in the brain. And now you let people go to 733 00:46:48,840 --> 00:46:52,680 Speaker 1: sleep in the scanner, and you measure their visual cortex, 734 00:46:53,080 --> 00:46:56,040 Speaker 1: and you use the machine learning model to decode what 735 00:46:56,120 --> 00:46:59,680 Speaker 1: that activity would correspond to, in other words, what they 736 00:46:59,760 --> 00:47:04,880 Speaker 1: were presumably seeing in their dream. And once the machine 737 00:47:04,920 --> 00:47:07,400 Speaker 1: learning model gives an answer, then you can make a 738 00:47:07,440 --> 00:47:11,880 Speaker 1: little video reconstruction of their dream, and you can watch 739 00:47:11,960 --> 00:47:17,279 Speaker 1: what presumably was the experience for the dreamer, albeit with 740 00:47:17,440 --> 00:47:22,000 Speaker 1: very low resolution. Now, when you're decoding pictures or videos, 741 00:47:22,040 --> 00:47:24,319 Speaker 1: it's easier to know if you're getting it right. When 742 00:47:24,360 --> 00:47:28,400 Speaker 1: you're decoding dreaming, it's harder to know for sure that 743 00:47:28,440 --> 00:47:30,960 Speaker 1: you got the right answer. You have to wake up 744 00:47:31,000 --> 00:47:33,880 Speaker 1: your participants and say, hey, what do you remember, and 745 00:47:33,920 --> 00:47:36,439 Speaker 1: then you compare that to what you think you might 746 00:47:36,560 --> 00:47:39,880 Speaker 1: have decoded. But even with those caveats, this gives the 747 00:47:40,000 --> 00:47:44,719 Speaker 1: rough start to a dream decoder that could tell you 748 00:47:44,920 --> 00:47:48,120 Speaker 1: what you were dreaming about. And presumably this will only 749 00:47:48,160 --> 00:47:51,880 Speaker 1: become higher resolution with time. So it maybe that in 750 00:47:51,920 --> 00:47:56,120 Speaker 1: the future we are able to know what you dreamed 751 00:47:56,239 --> 00:47:58,799 Speaker 1: even if you can't remember it. You could keep a 752 00:47:59,080 --> 00:48:03,560 Speaker 1: digitized dream diary that way, or you could share your 753 00:48:03,640 --> 00:48:08,080 Speaker 1: dreams with a girlfriend or boyfriend, or less likely, a 754 00:48:08,239 --> 00:48:11,520 Speaker 1: dream could be used in a court of lossome day. 755 00:48:12,000 --> 00:48:13,839 Speaker 1: Who knows where this will all go, but we can 756 00:48:13,920 --> 00:48:17,600 Speaker 1: imagine that in two hundred years from now, dreams may 757 00:48:17,640 --> 00:48:21,600 Speaker 1: be a very different sort of thing than the entirely 758 00:48:21,800 --> 00:48:25,920 Speaker 1: private experience that we enjoy now. So let's wrap up. 759 00:48:26,239 --> 00:48:28,719 Speaker 1: To my mind, the biggest issue that freaks me out 760 00:48:28,760 --> 00:48:34,200 Speaker 1: about dreams is this issue that we believe patently impossible situations, 761 00:48:34,239 --> 00:48:38,680 Speaker 1: and we accept false memories even when they contradict events 762 00:48:38,719 --> 00:48:42,040 Speaker 1: that we know to be true in waking life. This 763 00:48:42,120 --> 00:48:44,880 Speaker 1: represents a deeper question about why we can be so 764 00:48:45,239 --> 00:48:50,320 Speaker 1: easily fooled, but many other questions about dreams can be answered. 765 00:48:50,400 --> 00:48:53,600 Speaker 1: In the meantime, we're in a moment of using the 766 00:48:53,640 --> 00:48:57,360 Speaker 1: tools of neuroscience to tie specific details of the biology 767 00:48:57,640 --> 00:48:59,960 Speaker 1: to the experience of dreaming. We still have a lot 768 00:49:00,080 --> 00:49:03,439 Speaker 1: long way to go, but some promising leads can come 769 00:49:03,480 --> 00:49:08,040 Speaker 1: from the way that dream content changes with drugs. For example, 770 00:49:08,400 --> 00:49:11,800 Speaker 1: dreams can be made more vivid and frightening by drugs 771 00:49:11,800 --> 00:49:16,759 Speaker 1: that affect the dopamine system or by alkaloids. Antidepressants tend 772 00:49:16,800 --> 00:49:21,480 Speaker 1: to reduce the amount of dream sleep. Medications to reduce 773 00:49:21,520 --> 00:49:25,960 Speaker 1: epileptic seizures also seem to reduce nightmares. So we can 774 00:49:26,000 --> 00:49:29,840 Speaker 1: imagine in the near future having systematic studies to work 775 00:49:29,880 --> 00:49:33,759 Speaker 1: out the effects of different drugs on dream content, and 776 00:49:33,840 --> 00:49:36,799 Speaker 1: to do this in conjunction with brain imaging, and we 777 00:49:36,880 --> 00:49:40,840 Speaker 1: might be able to further nail down the relationships between 778 00:49:41,480 --> 00:49:46,480 Speaker 1: dream content and specific bits of the dream generation network. 779 00:49:47,040 --> 00:49:50,600 Speaker 1: And beyond drugs, we can also look to disease because 780 00:49:50,640 --> 00:49:55,120 Speaker 1: specific problems lead to the loss or impairment of dreaming. 781 00:49:55,560 --> 00:50:00,239 Speaker 1: People can lose dreaming with injuries to the inferior paride 782 00:50:00,320 --> 00:50:04,080 Speaker 1: lobe on either side. Patients with certain forms of dementia 783 00:50:04,560 --> 00:50:10,200 Speaker 1: report bland dreams, involving less aggression and less narrative complexity 784 00:50:10,239 --> 00:50:14,719 Speaker 1: and less emotional content. So by looking at changes to 785 00:50:14,760 --> 00:50:19,120 Speaker 1: the brain and corresponding changes in dreaming, we can better 786 00:50:19,280 --> 00:50:23,560 Speaker 1: map out the landscape of what is involved. And fundamentally, 787 00:50:23,800 --> 00:50:28,800 Speaker 1: studying dreaming may help us to comprehend consciousness. Why because 788 00:50:28,840 --> 00:50:32,719 Speaker 1: there are so many similarities between rem sleep and the 789 00:50:33,040 --> 00:50:36,640 Speaker 1: awake conscious state. Now there are major differences as well, 790 00:50:37,080 --> 00:50:39,800 Speaker 1: but it's important to note that we find both waking 791 00:50:39,840 --> 00:50:44,080 Speaker 1: life and dreaming equally compelling and believable, which tells us 792 00:50:44,080 --> 00:50:46,319 Speaker 1: that all you need to do is strike the right 793 00:50:46,480 --> 00:50:50,280 Speaker 1: notes on the neural piano and you have your totally 794 00:50:50,400 --> 00:50:54,719 Speaker 1: believable experience. But what would be cool is if there 795 00:50:54,719 --> 00:50:58,799 Speaker 1: were something like consciousness during a dream state that was 796 00:50:58,840 --> 00:51:04,760 Speaker 1: even close to our daily, normal conscious experience. And that's 797 00:51:05,040 --> 00:51:07,239 Speaker 1: what we're going to talk about next week. We're going 798 00:51:07,320 --> 00:51:11,719 Speaker 1: to talk about the very rare circumstance when you are 799 00:51:11,880 --> 00:51:15,600 Speaker 1: dreaming and you realize that you are dreaming, and you 800 00:51:15,719 --> 00:51:20,840 Speaker 1: take control of your dream and become an active director 801 00:51:21,000 --> 00:51:25,879 Speaker 1: of the plot. You are essentially conscious but living inside 802 00:51:25,960 --> 00:51:29,360 Speaker 1: the walls of your skull. So join me next week 803 00:51:29,560 --> 00:51:33,360 Speaker 1: as we sail into the very strange and amazing territory 804 00:51:33,840 --> 00:51:41,000 Speaker 1: of lucid dreaming. Go to eagleman dot com slash podcast 805 00:51:41,040 --> 00:51:44,879 Speaker 1: for more information and find further reading. Send me an 806 00:51:44,960 --> 00:51:48,920 Speaker 1: email at podcast at eagleman dot com with questions or discussion, 807 00:51:49,400 --> 00:51:52,560 Speaker 1: and check out and subscribe to Inner Cosmos on YouTube 808 00:51:52,880 --> 00:51:56,400 Speaker 1: for videos of each episode and to leave comments. Until 809 00:51:56,440 --> 00:51:59,680 Speaker 1: next time, I'm David Eagleman, and this is in our 810 00:51:59,800 --> 00:52:00,479 Speaker 1: car is miss