1 00:00:05,240 --> 00:00:10,040 Speaker 1: What is a thought? Is it something physical? How can 2 00:00:10,080 --> 00:00:13,240 Speaker 1: you hear a voice in your head? And whose voice 3 00:00:13,280 --> 00:00:15,440 Speaker 1: is it anyway? And what does this have to do 4 00:00:15,560 --> 00:00:19,760 Speaker 1: with a small marine animal who eats its own brain. 5 00:00:23,160 --> 00:00:27,200 Speaker 1: Welcome to Intercosmos with me, David Eagleman. I'm a neuroscientist 6 00:00:27,280 --> 00:00:30,200 Speaker 1: and an author at Stanford and in these episodes we 7 00:00:30,280 --> 00:00:34,199 Speaker 1: sail deeply into our three pound universe to understand some 8 00:00:34,240 --> 00:00:47,559 Speaker 1: of the most surprising aspects of our lives. Today's episode 9 00:00:47,600 --> 00:00:52,320 Speaker 1: is about thoughts. We have them constantly, even for the 10 00:00:52,360 --> 00:00:57,200 Speaker 1: best meditators. It's difficult or impossible to stop the fire 11 00:00:57,240 --> 00:01:01,400 Speaker 1: hose of words and images and ideas. We all talk 12 00:01:01,400 --> 00:01:04,280 Speaker 1: about our thoughts. We sometimes act on our thoughts, we 13 00:01:04,400 --> 00:01:08,000 Speaker 1: draw them with little thought bubbles and cartoons. But what 14 00:01:08,160 --> 00:01:12,679 Speaker 1: in the world is a thought physically? So many years ago, 15 00:01:12,840 --> 00:01:16,120 Speaker 1: a person at a party begged me to watch the 16 00:01:16,160 --> 00:01:20,080 Speaker 1: movie called The Secret. So I watched it for fifteen minutes, 17 00:01:20,080 --> 00:01:22,760 Speaker 1: and I regret to say that I will never get 18 00:01:22,800 --> 00:01:25,679 Speaker 1: those fifteen minutes back. And I knew that this was 19 00:01:25,720 --> 00:01:29,760 Speaker 1: the pinnacle of moronic when the first guy states quote, 20 00:01:30,600 --> 00:01:34,680 Speaker 1: what most people don't understand is a thought has a frequency. 21 00:01:34,800 --> 00:01:38,399 Speaker 1: Every thought has a frequency we can measure a thought, 22 00:01:38,600 --> 00:01:41,920 Speaker 1: and so if you're thinking that thought over and over again, 23 00:01:42,319 --> 00:01:46,880 Speaker 1: you're emitting that frequency on a consistent basis. And then 24 00:01:46,920 --> 00:01:51,560 Speaker 1: the next Schremndrick says, thoughts are sending out that magnetic 25 00:01:51,760 --> 00:01:54,840 Speaker 1: signal that is drawing the parallel back to you. That's 26 00:01:54,920 --> 00:01:58,840 Speaker 1: the signal you're putting out into the universe. And then 27 00:01:58,880 --> 00:02:02,960 Speaker 1: a third genius says, it has now been proven scientifically 28 00:02:03,600 --> 00:02:07,680 Speaker 1: that an affirmative thought is hundreds of times more powerful 29 00:02:07,760 --> 00:02:10,720 Speaker 1: than a negative thought. And every time someone thinks a 30 00:02:10,880 --> 00:02:14,760 Speaker 1: thought in this movie, the graphics show the person having 31 00:02:14,800 --> 00:02:18,160 Speaker 1: a thinking expression on their face, and then an energy 32 00:02:18,200 --> 00:02:20,560 Speaker 1: wave bursts from their head, and then it cuts to 33 00:02:20,639 --> 00:02:23,120 Speaker 1: a wide shot of the planet and you see this 34 00:02:23,360 --> 00:02:29,040 Speaker 1: energy wave transmit across the universe. Now, the most striking 35 00:02:29,080 --> 00:02:32,840 Speaker 1: thing about these statements in the movie is not simply 36 00:02:32,919 --> 00:02:35,520 Speaker 1: that they are incorrect. To me, the shocking thing was 37 00:02:35,960 --> 00:02:39,000 Speaker 1: how these guys looked right at the camera and asserted 38 00:02:39,040 --> 00:02:43,240 Speaker 1: them as though these were not just completely made up, 39 00:02:43,280 --> 00:02:46,840 Speaker 1: and then they used phrases like it has been scientifically proven. 40 00:02:47,160 --> 00:02:49,160 Speaker 1: So in a few weeks, I'm going to do an 41 00:02:49,160 --> 00:02:52,960 Speaker 1: episode about how we judge the value of any scientific 42 00:02:53,040 --> 00:02:55,959 Speaker 1: idea and what it would mean to even say that 43 00:02:56,040 --> 00:02:58,800 Speaker 1: something is scientifically proven. But I'm going to bite my 44 00:02:58,880 --> 00:03:02,320 Speaker 1: tongue for now put that aside, because for today's episode, 45 00:03:02,400 --> 00:03:08,200 Speaker 1: what I really care about is what really is a thought. 46 00:03:08,840 --> 00:03:12,200 Speaker 1: So to set the table for this, I'm going to 47 00:03:12,200 --> 00:03:15,520 Speaker 1: put thoughts aside for a second and tell a story 48 00:03:15,800 --> 00:03:18,919 Speaker 1: that I originally wrote in my book Incognito, And this 49 00:03:19,200 --> 00:03:23,480 Speaker 1: took place in nineteen forty nine. A guy named Arthur 50 00:03:23,560 --> 00:03:27,519 Speaker 1: Alberts traveled from his home in New York to villages 51 00:03:27,680 --> 00:03:31,200 Speaker 1: between the Gold Coast and Timbuktoo in West Africa. And 52 00:03:31,240 --> 00:03:32,960 Speaker 1: he brought his wife, and he brought a camera and 53 00:03:33,000 --> 00:03:36,520 Speaker 1: a jeep, and because of his love for music, he 54 00:03:36,680 --> 00:03:40,560 Speaker 1: brought a tape recorder. Now he wanted to open the 55 00:03:40,600 --> 00:03:43,960 Speaker 1: ears of the Western world. So what he did was 56 00:03:44,040 --> 00:03:47,200 Speaker 1: record some of the most important music to ever come 57 00:03:47,240 --> 00:03:52,480 Speaker 1: out of Africa. But Alberts ran into social troubles while 58 00:03:52,520 --> 00:03:55,120 Speaker 1: he was using this tape recorder because none of the 59 00:03:55,240 --> 00:03:59,360 Speaker 1: natives had ever seen anything even vaguely like this before. 60 00:04:00,080 --> 00:04:04,040 Speaker 1: So one native heard his voice played back to him, 61 00:04:04,640 --> 00:04:09,320 Speaker 1: and he accused Alberts of quote stealing his tongue and 62 00:04:09,360 --> 00:04:13,880 Speaker 1: According to the biography, Albert's only narrowly averted being pummeled 63 00:04:13,880 --> 00:04:17,240 Speaker 1: by taking out a mirror and convincing the man that 64 00:04:17,320 --> 00:04:21,240 Speaker 1: his tongue was still intact. So it's not difficult to 65 00:04:21,279 --> 00:04:25,800 Speaker 1: see why the natives found the tape recorder so strange 66 00:04:25,839 --> 00:04:30,239 Speaker 1: and counterintuitive. Just imagine that you had never ever seen 67 00:04:30,279 --> 00:04:34,760 Speaker 1: this technology before. The thing is that a voice seems 68 00:04:35,200 --> 00:04:39,400 Speaker 1: ephemeral and ineffable, right. A voice has no weight. You 69 00:04:39,440 --> 00:04:43,080 Speaker 1: can't hold voice in your hand. A voice just exists 70 00:04:43,120 --> 00:04:46,320 Speaker 1: for a moment. It's totally untouchable, and then it's gone. 71 00:04:46,760 --> 00:04:49,800 Speaker 1: There doesn't seem to be any physical trace. So it 72 00:04:49,880 --> 00:04:54,520 Speaker 1: comes as a surprise that a voice is physical. If 73 00:04:54,560 --> 00:04:57,960 Speaker 1: you build a little machine that's sensitive enough to detect 74 00:04:58,200 --> 00:05:01,640 Speaker 1: tiny compressions of the molecule in the air, you can 75 00:05:01,680 --> 00:05:06,240 Speaker 1: then capture those density changes and reproduce them later. We 76 00:05:06,320 --> 00:05:10,440 Speaker 1: call these little machines microphones, and we reproduce the density 77 00:05:10,520 --> 00:05:15,559 Speaker 1: changes on tape or with zeros and ones, And every 78 00:05:15,600 --> 00:05:19,080 Speaker 1: one of the billions of podcasts and playlists on the 79 00:05:19,120 --> 00:05:24,920 Speaker 1: planet is proudly serving up bags of feathers once thought irretrievable. 80 00:05:25,640 --> 00:05:28,600 Speaker 1: When Alberts played the music back from the tape recorder. 81 00:05:28,640 --> 00:05:35,320 Speaker 1: One tribesman described the feat as tremendous magic. And so 82 00:05:35,440 --> 00:05:39,120 Speaker 1: it goes with thoughts. What exactly is a thought? It 83 00:05:39,160 --> 00:05:44,159 Speaker 1: doesn't seem to weigh anything. It feels ephemeral and ineffable. 84 00:05:44,640 --> 00:05:47,320 Speaker 1: You wouldn't think that a thought has any shape or 85 00:05:47,360 --> 00:05:51,919 Speaker 1: smell or any sort of physical instantiation. Thoughts seem to 86 00:05:51,960 --> 00:05:56,120 Speaker 1: be a kind of tremendous magic. So it comes as 87 00:05:56,160 --> 00:06:00,320 Speaker 1: a surprise that a thought is physical, just like voice is. 88 00:06:00,920 --> 00:06:06,599 Speaker 1: Thoughts are underpinned by biological stuff. We know this because 89 00:06:06,680 --> 00:06:10,400 Speaker 1: alterations to the brain change the kinds of thoughts we 90 00:06:10,440 --> 00:06:14,240 Speaker 1: can think. In a state of deep sleep, there are 91 00:06:14,279 --> 00:06:19,240 Speaker 1: no thoughts. When the brain transitions into dream sleep, there 92 00:06:19,279 --> 00:06:23,720 Speaker 1: are unbidden, bizarre thoughts. During the day, we enjoy our normal, 93 00:06:23,839 --> 00:06:29,560 Speaker 1: well accepted thoughts, which people enthusiastically modulate by spiking the 94 00:06:29,640 --> 00:06:33,760 Speaker 1: chemical cocktails of the brain with alcohol or narcotics, or 95 00:06:34,160 --> 00:06:38,799 Speaker 1: exercise or coffee. So the state of the physical material 96 00:06:39,279 --> 00:06:43,799 Speaker 1: determines the state of the thoughts, and issues like obsessive 97 00:06:43,880 --> 00:06:48,760 Speaker 1: compulsive disorder or schizophrenia tell us that when certain networks 98 00:06:48,760 --> 00:06:53,279 Speaker 1: in the brain become overactive or miscalibrated, the character of 99 00:06:53,400 --> 00:06:57,400 Speaker 1: thinking changes. It's this kind of thing that tells us 100 00:06:57,440 --> 00:07:01,960 Speaker 1: that the physical stuff is irreversible, tied to the thinking. 101 00:07:02,000 --> 00:07:04,520 Speaker 1: And we know this also because when people get even 102 00:07:04,640 --> 00:07:08,159 Speaker 1: small bits of brain damage, let's say, because of a 103 00:07:08,200 --> 00:07:11,880 Speaker 1: stroke or a tumor, that can change their capacity to 104 00:07:12,600 --> 00:07:16,960 Speaker 1: understand music, or name animals or see colors, or judge risk, 105 00:07:17,080 --> 00:07:20,960 Speaker 1: or make decisions, or read signals from their bodies, or 106 00:07:21,080 --> 00:07:24,600 Speaker 1: understand the concept of a mirror, or hundreds of other 107 00:07:24,800 --> 00:07:28,400 Speaker 1: changes in thinking that we can witness in the clinics 108 00:07:28,480 --> 00:07:32,360 Speaker 1: every day, and the consequences of injury is a big 109 00:07:32,440 --> 00:07:36,200 Speaker 1: part of how brain science has mapped out the general 110 00:07:36,320 --> 00:07:39,880 Speaker 1: blueprints of the brain. So the bottom line lesson which 111 00:07:39,880 --> 00:07:45,000 Speaker 1: has emerged over centuries is that our internal thoughts about 112 00:07:45,080 --> 00:07:49,000 Speaker 1: hopes or fears or desires, they all emerge from this 113 00:07:49,600 --> 00:07:53,720 Speaker 1: strange three pound organ and when the brain changes, so 114 00:07:53,920 --> 00:07:57,480 Speaker 1: do our thoughts. So although it's easy to intuit that 115 00:07:57,680 --> 00:08:01,360 Speaker 1: thoughts don't have a physical basis, that there are something 116 00:08:01,440 --> 00:08:04,800 Speaker 1: like feathers on the wind, they in fact depend directly 117 00:08:04,880 --> 00:08:09,920 Speaker 1: on what's happening in this small, enigmatic mission control center 118 00:08:10,400 --> 00:08:15,120 Speaker 1: locked in the silent vault of the skull. So what 119 00:08:15,440 --> 00:08:19,160 Speaker 1: is a thought. It's the result of billions of neurons 120 00:08:19,240 --> 00:08:23,760 Speaker 1: firing and coordinated patterns. As we've talked about in other episodes, 121 00:08:23,840 --> 00:08:28,200 Speaker 1: the neurons communicate using electrical impulses and chemical signals, and 122 00:08:28,280 --> 00:08:32,640 Speaker 1: they form vast networks that operate together, such that at 123 00:08:32,640 --> 00:08:37,679 Speaker 1: any moment you have some millions of neurons doing something coordinated, 124 00:08:37,720 --> 00:08:40,120 Speaker 1: and in the next moment it's a different collection of 125 00:08:40,160 --> 00:08:43,840 Speaker 1: neurons that are working together. Now, it may not surprise 126 00:08:43,880 --> 00:08:46,200 Speaker 1: you to know that a thought is not located in 127 00:08:46,240 --> 00:08:49,880 Speaker 1: one place in the brain. It's an emergent property. It's 128 00:08:49,880 --> 00:08:54,880 Speaker 1: a collaboration between these millions or billions of neurons. When 129 00:08:54,960 --> 00:08:58,880 Speaker 1: you have a thought, it's like a symphony playing inside 130 00:08:58,880 --> 00:09:02,920 Speaker 1: your head. Every neuron involved is an instrument in the orchestra, 131 00:09:03,400 --> 00:09:06,840 Speaker 1: and no single part can create the music by itself. 132 00:09:07,360 --> 00:09:09,319 Speaker 1: So we're gonna come back to the brain in a moment, 133 00:09:09,400 --> 00:09:11,920 Speaker 1: but before we do, I want us to really zoom 134 00:09:11,920 --> 00:09:16,640 Speaker 1: in on the subjective experience. How would you describe the 135 00:09:16,880 --> 00:09:21,040 Speaker 1: experience of a thought. When you try to capture what 136 00:09:21,160 --> 00:09:25,400 Speaker 1: a thought is, the most commonplace to go is your 137 00:09:25,880 --> 00:09:29,520 Speaker 1: inner monologue. This is the voice in your head that 138 00:09:29,600 --> 00:09:33,800 Speaker 1: you use to problem solve or criticize, or plan or reflect. 139 00:09:34,320 --> 00:09:37,200 Speaker 1: So take just a second to pay attention to the 140 00:09:37,360 --> 00:09:42,439 Speaker 1: voice inside your head, that constant stream of chatter. Now 141 00:09:42,559 --> 00:09:46,840 Speaker 1: you might think, what voice inside my head? That's the voice? Now. 142 00:09:47,000 --> 00:09:51,320 Speaker 1: Your internal voice can involve deliberate problem solving, like what 143 00:09:51,360 --> 00:09:55,199 Speaker 1: should I do next here? Or it can involve involuntary 144 00:09:55,360 --> 00:09:58,040 Speaker 1: commentary like oh so stupid to me, why did I 145 00:09:58,080 --> 00:10:03,199 Speaker 1: do that? Or it can be whole imagined conversations like Okay, 146 00:10:03,200 --> 00:10:04,920 Speaker 1: I say this, and then she says that, and then 147 00:10:04,960 --> 00:10:07,360 Speaker 1: I respond like this. It can be helpful for things 148 00:10:07,440 --> 00:10:11,440 Speaker 1: like working memory. So for example, you're trying to log 149 00:10:11,480 --> 00:10:14,680 Speaker 1: into a website and you get texted some six digit 150 00:10:14,800 --> 00:10:17,600 Speaker 1: pass code, and you need to remember that code while 151 00:10:17,640 --> 00:10:21,720 Speaker 1: you switch windows, So you internally say the numbers over 152 00:10:21,760 --> 00:10:24,920 Speaker 1: and over. So you're using the internal voice to keep 153 00:10:24,960 --> 00:10:27,600 Speaker 1: the information in mind as part of your working memory. 154 00:10:27,920 --> 00:10:30,480 Speaker 1: There's so many places where the internal voice comes in. 155 00:10:30,559 --> 00:10:34,199 Speaker 1: We tend to talk to ourselves when we're planning something, 156 00:10:34,240 --> 00:10:38,400 Speaker 1: when we're weighing options. The internal dialogue seems to be 157 00:10:38,679 --> 00:10:43,240 Speaker 1: really helpful in simulating different scenarios. So you're running your 158 00:10:43,280 --> 00:10:47,000 Speaker 1: internal voice all the time and subjectively, it seems to 159 00:10:47,040 --> 00:10:51,360 Speaker 1: be a mental space that can seem almost as vivid 160 00:10:51,440 --> 00:10:55,200 Speaker 1: as external speech. It follows all the rules of grammar 161 00:10:55,240 --> 00:10:59,520 Speaker 1: and syntax, and it can be emotionally laiden with encouragement 162 00:10:59,640 --> 00:11:05,080 Speaker 1: or criticism or anywhere in between. Now, how does this happen? 163 00:11:05,160 --> 00:11:09,240 Speaker 1: How can you generate a voice internally and hear it well? 164 00:11:09,320 --> 00:11:12,680 Speaker 1: When we eavesdrop on the brain, let's say, using brain 165 00:11:12,760 --> 00:11:16,360 Speaker 1: imaging like fMRI, what we find is a network of 166 00:11:16,520 --> 00:11:22,040 Speaker 1: areas involved in speech production, like Broca's area, which is 167 00:11:22,080 --> 00:11:25,200 Speaker 1: a key region involved in talking out loud. And we 168 00:11:25,280 --> 00:11:30,560 Speaker 1: find areas involved in language comprehension like Wernicke's area and 169 00:11:30,600 --> 00:11:34,040 Speaker 1: the auditory cortex more generally, as though you're listening to 170 00:11:34,160 --> 00:11:38,080 Speaker 1: spoken language from somebody else talking. And also what we 171 00:11:38,200 --> 00:11:42,439 Speaker 1: see is a network that we summarize as the default 172 00:11:42,559 --> 00:11:45,880 Speaker 1: mode network. And this is a network that becomes active 173 00:11:45,960 --> 00:11:49,600 Speaker 1: when you're not focused on monitoring the outside world, but 174 00:11:49,720 --> 00:11:53,000 Speaker 1: instead when you think about yourself, where you daydream or 175 00:11:53,080 --> 00:11:55,800 Speaker 1: you reflect on your past, or you imagine your future. 176 00:11:56,520 --> 00:11:59,360 Speaker 1: So all these networks are cranked up when you're talking 177 00:11:59,360 --> 00:12:02,440 Speaker 1: to yourself. And one really important point, when you're generating 178 00:12:02,480 --> 00:12:06,800 Speaker 1: your own speech is that you have something called corollary discharge, 179 00:12:06,920 --> 00:12:10,080 Speaker 1: which just means that when your brain generates internal speech, 180 00:12:10,160 --> 00:12:13,000 Speaker 1: it sends a copy of what it's doing to other 181 00:12:13,080 --> 00:12:16,000 Speaker 1: parts of the brain to let them know this is coming. 182 00:12:16,080 --> 00:12:18,320 Speaker 1: I'm the one who did this. That's how the rest 183 00:12:18,360 --> 00:12:21,360 Speaker 1: of the brain knows that the inner voice is self 184 00:12:21,480 --> 00:12:26,520 Speaker 1: generated instead of confusing it with external speech. As a 185 00:12:26,559 --> 00:12:29,559 Speaker 1: side note, if you're a regular listener to this podcast, 186 00:12:29,640 --> 00:12:31,840 Speaker 1: you know that I've been publishing on the topic of 187 00:12:31,880 --> 00:12:36,760 Speaker 1: schizophrenia for many years, and my hypothesis is that auditory 188 00:12:36,800 --> 00:12:41,880 Speaker 1: hallucinations in schizophrenia might have to do with a miscalibration 189 00:12:42,080 --> 00:12:46,040 Speaker 1: of the timing of signals such that the internal voice 190 00:12:46,559 --> 00:12:51,160 Speaker 1: gets misinterpreted as someone else's voice. In other words, when 191 00:12:51,160 --> 00:12:54,880 Speaker 1: you're talking to yourself under normal conditions, you generate the voice, 192 00:12:55,080 --> 00:12:58,280 Speaker 1: then you hear the voice, and the corollary discharge tells 193 00:12:58,320 --> 00:13:00,880 Speaker 1: you that it was your own. But there's something wrong 194 00:13:00,920 --> 00:13:04,199 Speaker 1: with the timing of the corollary discharge. Then it doesn't 195 00:13:04,200 --> 00:13:06,480 Speaker 1: seem like you're the one who generated the voice, and 196 00:13:06,559 --> 00:13:09,719 Speaker 1: you have to attribute the voice to someone else. The 197 00:13:09,760 --> 00:13:13,920 Speaker 1: internal voice feels like it must be external. If you're 198 00:13:13,960 --> 00:13:17,960 Speaker 1: interested in more on this hypothesis about schizophrenia, check out 199 00:13:18,000 --> 00:13:21,880 Speaker 1: episodes thirty three and forty four. Okay, so back to 200 00:13:21,920 --> 00:13:25,680 Speaker 1: the internal voice, which in normal circumstances we understand as 201 00:13:25,880 --> 00:13:29,520 Speaker 1: our voice in our heads. Here's my question, is this 202 00:13:29,679 --> 00:13:33,880 Speaker 1: inner monologue really the main way that we think? What 203 00:13:34,000 --> 00:13:38,160 Speaker 1: if some of our thoughts don't come with words at all? 204 00:13:38,240 --> 00:13:41,520 Speaker 1: So that's the question that psychologist Russell Hurlbert set out 205 00:13:41,559 --> 00:13:44,640 Speaker 1: to answer with a set of experiments in the nineteen nineties. 206 00:13:44,640 --> 00:13:48,440 Speaker 1: And here's how it works. Imagine that you are given 207 00:13:48,480 --> 00:13:54,559 Speaker 1: a beeper that beeps off at random times during your day, 208 00:13:54,600 --> 00:13:57,280 Speaker 1: and the instant a beeps, your job is to write 209 00:13:57,360 --> 00:14:01,240 Speaker 1: down whatever was just in your mind. Beep, what are 210 00:14:01,240 --> 00:14:05,960 Speaker 1: you thinking about right now? So when Hurlbert analyzed the data, 211 00:14:06,000 --> 00:14:09,360 Speaker 1: he found that only about twenty six percent of people's 212 00:14:09,400 --> 00:14:13,199 Speaker 1: thoughts were verbal, meaning that they involved actual words or 213 00:14:13,240 --> 00:14:19,360 Speaker 1: inner speech. The other seventy four percent completely nonverbal. So 214 00:14:19,440 --> 00:14:23,840 Speaker 1: what does nonverbal thought mean? Well, when your thoughts are 215 00:14:24,040 --> 00:14:27,120 Speaker 1: suddenly probe, lots of people find that they were just 216 00:14:27,200 --> 00:14:32,000 Speaker 1: thinking about, for example, vivid mental images like picturing a 217 00:14:32,040 --> 00:14:36,680 Speaker 1: beach or remembering somebody's face, or thinking about some moment 218 00:14:36,760 --> 00:14:38,920 Speaker 1: they just saw at the restaurant, and that's all their 219 00:14:38,960 --> 00:14:41,320 Speaker 1: thought was at that moment. It was visual. There were 220 00:14:41,360 --> 00:15:00,600 Speaker 1: no words involved, just pictures. So what's going on in 221 00:15:00,640 --> 00:15:05,000 Speaker 1: the brain when you have these kind of vivid mental images. Well, 222 00:15:05,200 --> 00:15:07,560 Speaker 1: if I were to ask you to think about a 223 00:15:07,840 --> 00:15:12,760 Speaker 1: Siberian tiger, your prefrontal cortex right behind the forehead takes 224 00:15:12,800 --> 00:15:16,280 Speaker 1: on the task and starts broadcasting to see who can 225 00:15:16,560 --> 00:15:20,600 Speaker 1: fulfill the request. So your memory systems chug into place 226 00:15:20,680 --> 00:15:24,600 Speaker 1: to determine what a Siberian tiger is, combining all the 227 00:15:24,720 --> 00:15:29,040 Speaker 1: different examples of Siberian tigers that you've seen before, and 228 00:15:29,080 --> 00:15:34,480 Speaker 1: your visual cortex is recruited to generate a picture. Your 229 00:15:34,480 --> 00:15:38,880 Speaker 1: emotion centers might even contribute, shading this thought with feelings 230 00:15:38,880 --> 00:15:42,560 Speaker 1: of alertness or awe or fear. So when you think 231 00:15:42,600 --> 00:15:47,560 Speaker 1: about that Siberian tiger, hundreds of millions of neurons across 232 00:15:47,720 --> 00:15:51,440 Speaker 1: different areas of your brain are lighting up, working together 233 00:15:51,560 --> 00:15:56,560 Speaker 1: to create something that feels whole and immediate. And of course, 234 00:15:56,600 --> 00:16:00,000 Speaker 1: if you're a musician and the pager beeps, you might 235 00:16:00,080 --> 00:16:03,400 Speaker 1: find that you're thinking about something auditory. You're thinking about 236 00:16:03,840 --> 00:16:07,000 Speaker 1: which notes would sound great. Right after this transition from 237 00:16:07,000 --> 00:16:10,000 Speaker 1: this chord to this court. But there's no words involved 238 00:16:10,040 --> 00:16:13,000 Speaker 1: in that, and in the brain we can measure activity 239 00:16:13,040 --> 00:16:16,480 Speaker 1: in your auditory cortex while you're doing that, And if 240 00:16:16,520 --> 00:16:21,080 Speaker 1: you're a perfumer, you might be doing smell imagery. You're 241 00:16:21,120 --> 00:16:24,440 Speaker 1: thinking about the way that this other perfume smell than 242 00:16:24,480 --> 00:16:26,280 Speaker 1: how you're trying to get a little closer to that. 243 00:16:26,880 --> 00:16:31,360 Speaker 1: But as you are internally smelling, there are no words 244 00:16:31,400 --> 00:16:36,040 Speaker 1: associated with that. It's just olfactory imagery. And this sort 245 00:16:36,080 --> 00:16:39,800 Speaker 1: of sensory thinking can come in all kinds of flavors, 246 00:16:39,880 --> 00:16:43,360 Speaker 1: like feeling the warmth from the sun on your face 247 00:16:43,920 --> 00:16:47,800 Speaker 1: or the tightness of your chest during stress. So that's 248 00:16:47,800 --> 00:16:51,840 Speaker 1: what Hurlbert found people were thinking about quite often when 249 00:16:51,880 --> 00:16:56,960 Speaker 1: you probe them at random, sensory imagery without language. But 250 00:16:57,040 --> 00:16:58,880 Speaker 1: that was just the beginning. The kind of thoughts that 251 00:16:59,000 --> 00:17:03,840 Speaker 1: people were went beyond just sensory imagery. Lots of other 252 00:17:03,880 --> 00:17:07,840 Speaker 1: times people described they were thinking about how to do 253 00:17:07,920 --> 00:17:11,480 Speaker 1: something physical, like how to position their hands for reaching 254 00:17:11,520 --> 00:17:14,520 Speaker 1: into the oven, or how to remove the cover off 255 00:17:14,560 --> 00:17:17,240 Speaker 1: the printer, or how far to turn the steering wheel 256 00:17:17,240 --> 00:17:20,040 Speaker 1: to get their car into the parking spot. But they 257 00:17:20,080 --> 00:17:23,399 Speaker 1: were thinking about how to do these moves, and there 258 00:17:23,440 --> 00:17:27,080 Speaker 1: were no words involved. It was a physical activity they 259 00:17:27,080 --> 00:17:31,640 Speaker 1: were simulating. This is called motoric imagery. Their brains were 260 00:17:32,040 --> 00:17:35,680 Speaker 1: thinking their way through something. And other thoughts are even 261 00:17:35,720 --> 00:17:39,879 Speaker 1: more difficult to pin down than imagining senses or imagining 262 00:17:39,960 --> 00:17:45,040 Speaker 1: movement because they're more abstract, like a vague sense of 263 00:17:45,280 --> 00:17:50,719 Speaker 1: unease with no clear words or pictures attached. So thoughts 264 00:17:50,800 --> 00:17:53,520 Speaker 1: come in many flavors, and I'll just make a thirty 265 00:17:53,560 --> 00:17:56,439 Speaker 1: second side note here about whether it makes sense to 266 00:17:56,600 --> 00:18:01,120 Speaker 1: call the activity in the unconscious brain think. For example, 267 00:18:01,400 --> 00:18:04,040 Speaker 1: you're trying to remember the name of that song and 268 00:18:04,080 --> 00:18:05,919 Speaker 1: it's on the tip of your tongue, but you just 269 00:18:06,000 --> 00:18:09,639 Speaker 1: can't remember it. And then hours later, when you're not 270 00:18:09,680 --> 00:18:13,800 Speaker 1: even thinking about it, the answer suddenly pops into your mind. 271 00:18:14,240 --> 00:18:17,800 Speaker 1: Your unconscious mind has been working on it in the background, 272 00:18:17,880 --> 00:18:20,600 Speaker 1: even though you had no awareness of it. So should 273 00:18:20,600 --> 00:18:25,320 Speaker 1: we call that thinking even when it happens unconsciously. Just 274 00:18:25,359 --> 00:18:28,320 Speaker 1: for the purposes of having a clear definition, it's probably 275 00:18:28,359 --> 00:18:30,320 Speaker 1: going to make the most sense to call that something 276 00:18:30,440 --> 00:18:34,760 Speaker 1: like processing, and will reserve the word thought for the 277 00:18:35,040 --> 00:18:38,919 Speaker 1: conscious conclusion of that behind the scenes activity, So at 278 00:18:39,000 --> 00:18:41,159 Speaker 1: least for the moment, I'm not going to call the 279 00:18:41,320 --> 00:18:47,760 Speaker 1: unconscious activity thought. So this simple experiment of pinging people 280 00:18:47,760 --> 00:18:50,439 Speaker 1: at random to ask them what they're thinking, what's in 281 00:18:50,480 --> 00:18:54,119 Speaker 1: their minds at this exact moment, This experiment tells us 282 00:18:54,160 --> 00:18:58,359 Speaker 1: something important, which is that thinking is not just talking 283 00:18:58,359 --> 00:19:01,679 Speaker 1: to ourselves. It's broader than that. We have different kinds 284 00:19:01,680 --> 00:19:04,679 Speaker 1: of thoughts in different formats. We have inner speech, but 285 00:19:04,720 --> 00:19:08,919 Speaker 1: we also have mental imagery, like when you're visualizing what 286 00:19:09,000 --> 00:19:11,439 Speaker 1: your kitchen red design could look like, and you have 287 00:19:11,840 --> 00:19:17,879 Speaker 1: abstract thinking like when you're contemplating infinity or justice or love. 288 00:19:18,240 --> 00:19:20,840 Speaker 1: And possibly there are still other things which could fall 289 00:19:20,920 --> 00:19:24,560 Speaker 1: under the umbrella of thought. So thinking is a rich, 290 00:19:25,040 --> 00:19:28,600 Speaker 1: multi dimensional experience. Okay, so here's where we are so far. 291 00:19:28,680 --> 00:19:32,440 Speaker 1: We talked about the internal voice and visualization and imagining 292 00:19:32,480 --> 00:19:35,879 Speaker 1: sound or smell or bodily feelings, and imagining motor movement, 293 00:19:36,200 --> 00:19:39,040 Speaker 1: and even abstract sorts of thoughts. But if you've been 294 00:19:39,040 --> 00:19:41,040 Speaker 1: listening to these episodes for a while, you know that 295 00:19:41,119 --> 00:19:47,320 Speaker 1: I'm obsessed with the difference between people's internal experiences and 296 00:19:47,440 --> 00:19:50,800 Speaker 1: thinking is no exception. When we look at the diversity 297 00:19:50,880 --> 00:19:55,800 Speaker 1: of thought, some people seem to lean more towards verbal thinking. 298 00:19:55,840 --> 00:20:00,439 Speaker 1: They talk things out in their heads. Others are visual things, 299 00:20:00,480 --> 00:20:05,120 Speaker 1: seeing vivid mental images as their primary mode of thinking. 300 00:20:05,600 --> 00:20:09,919 Speaker 1: And some people experience thoughts more like abstract concepts without 301 00:20:09,960 --> 00:20:12,399 Speaker 1: the voice or the images. And this goes hand in 302 00:20:12,480 --> 00:20:15,440 Speaker 1: hand with something I've talked about in many episodes, which 303 00:20:15,480 --> 00:20:19,280 Speaker 1: is that, as far as we can tell, subjective experiences 304 00:20:19,440 --> 00:20:23,080 Speaker 1: exist on a spectrum. So let's zoom in on the 305 00:20:23,160 --> 00:20:27,000 Speaker 1: inner voice. Some people report having constant chatter in their heads, 306 00:20:27,280 --> 00:20:32,680 Speaker 1: while other people have little or no inner verbalization. That's 307 00:20:32,680 --> 00:20:37,280 Speaker 1: called an endophasia no internal voice. As an example, when 308 00:20:37,280 --> 00:20:41,200 Speaker 1: it comes to the inner monologue, my wife's internal radio 309 00:20:41,359 --> 00:20:43,879 Speaker 1: is very loud, she says, she's always hearing it at 310 00:20:43,920 --> 00:20:47,360 Speaker 1: full volume. For me, it happens to be pretty quiet 311 00:20:47,400 --> 00:20:49,880 Speaker 1: most of the time. I'm going to link some papers 312 00:20:49,920 --> 00:20:53,720 Speaker 1: in the show notes about studies on the variation of 313 00:20:53,800 --> 00:20:58,080 Speaker 1: the internal voice. And when it comes to visualization, I've 314 00:20:58,119 --> 00:21:03,720 Speaker 1: talked in other episodes about this from a fantasia to hyperfantasia. 315 00:21:03,760 --> 00:21:06,960 Speaker 1: In other words, the spread from not really picturing anything 316 00:21:07,040 --> 00:21:12,119 Speaker 1: visually in your mind to having very rich, colorful, movie 317 00:21:12,359 --> 00:21:17,320 Speaker 1: like visualizations. And everyone is somewhere along that spectrum. Now, 318 00:21:17,320 --> 00:21:19,720 Speaker 1: we haven't really measured this yet, but when it comes 319 00:21:19,720 --> 00:21:24,880 Speaker 1: to more subtle issues of abstract thinking, like contemplating infinity 320 00:21:24,960 --> 00:21:27,760 Speaker 1: or justice or love, it may be that people are 321 00:21:27,800 --> 00:21:33,080 Speaker 1: having very different experiences of how strongly or intensely they're 322 00:21:33,200 --> 00:21:36,680 Speaker 1: feeling that. Now, it's a little difficult to design an 323 00:21:36,720 --> 00:21:39,960 Speaker 1: experiment to probe this, because it's purely an issue of 324 00:21:40,000 --> 00:21:43,879 Speaker 1: somebody's subjective report, and it's not always easy to know 325 00:21:43,920 --> 00:21:49,560 Speaker 1: if people are reporting accurately. But if this subjective experience 326 00:21:49,560 --> 00:21:52,800 Speaker 1: of abstract thought is like everything else we've measured so far, 327 00:21:53,200 --> 00:21:57,119 Speaker 1: it is surely going to differ from person to person. 328 00:21:57,640 --> 00:22:01,159 Speaker 1: So it seems to me there's probably massive of divergence 329 00:22:01,280 --> 00:22:04,240 Speaker 1: in what we mean from person to person when we 330 00:22:04,320 --> 00:22:09,280 Speaker 1: talk about the experience of thought. If we can only 331 00:22:09,400 --> 00:22:13,520 Speaker 1: know what the experience is inside another head, we might 332 00:22:13,760 --> 00:22:18,040 Speaker 1: suddenly understand why Susan immediately sees the solution to the 333 00:22:18,080 --> 00:22:22,159 Speaker 1: math problem, and why Amy keeps in mind so well 334 00:22:22,400 --> 00:22:25,520 Speaker 1: what everyone else's emotion is, and why Steve is so 335 00:22:25,680 --> 00:22:29,800 Speaker 1: interested in fixing broken radios, and why Tim spends all 336 00:22:29,840 --> 00:22:32,840 Speaker 1: his intellectual efforts figuring out how to get other people 337 00:22:32,880 --> 00:22:35,000 Speaker 1: to do work for him. And so on with the 338 00:22:35,080 --> 00:22:38,400 Speaker 1: differences between every person you know. And by the way, 339 00:22:38,440 --> 00:22:42,280 Speaker 1: this diversity in the inner experience this has real world implications. 340 00:22:42,640 --> 00:22:46,439 Speaker 1: So just think about how people learn or solve problems. 341 00:22:47,000 --> 00:22:52,280 Speaker 1: Schools and workplaces often prioritize verbal reasoning. But what if 342 00:22:52,280 --> 00:22:57,119 Speaker 1: somebody's thoughts arrive more like pictures or more like physical sensations. 343 00:22:57,200 --> 00:23:01,080 Speaker 1: What if their best ideas can't be put in words immediately? 344 00:23:01,640 --> 00:23:04,880 Speaker 1: I think as we bring the individual differences in thinking 345 00:23:05,320 --> 00:23:09,879 Speaker 1: into focus, we'll be able to increasingly build education to 346 00:23:10,000 --> 00:23:14,800 Speaker 1: take advantage of the full spectrum of human cognition and 347 00:23:14,960 --> 00:23:18,439 Speaker 1: understanding this diversity of thought. This also has implications for 348 00:23:18,640 --> 00:23:24,240 Speaker 1: mental health. Verbal thoughts, for example, are strongly linked to rumination, 349 00:23:24,440 --> 00:23:27,959 Speaker 1: which is the endless loops of self talk that fuel 350 00:23:28,080 --> 00:23:33,200 Speaker 1: anxiety or depression. And meanwhile, nonverbal sensations like a tight 351 00:23:33,320 --> 00:23:36,359 Speaker 1: chest or a racing heart, these are the things that 352 00:23:36,440 --> 00:23:40,679 Speaker 1: dominate panic attacks. So really, understanding how differently people think 353 00:23:40,960 --> 00:23:43,879 Speaker 1: and how to measure that could help us to manage 354 00:23:43,920 --> 00:23:48,320 Speaker 1: these mental states more effectively. Okay, so we've been talking 355 00:23:48,359 --> 00:23:52,160 Speaker 1: about our private internal experience of thoughts, but we still 356 00:23:52,200 --> 00:23:55,399 Speaker 1: haven't nailed down with a thought is exactly and what 357 00:23:55,560 --> 00:23:59,080 Speaker 1: could this possibly have to do with a c squirt 358 00:23:59,520 --> 00:24:03,520 Speaker 1: finding its home? So let's start there. The sea squirt 359 00:24:04,200 --> 00:24:07,679 Speaker 1: is a small marine creature that begins life as a 360 00:24:08,200 --> 00:24:11,639 Speaker 1: free swimming larva. It has a little brain and a 361 00:24:11,680 --> 00:24:15,240 Speaker 1: nervous system that helps it navigate and search for a 362 00:24:15,320 --> 00:24:20,600 Speaker 1: suitable place to settle. Now, once it finds its permanent spot, 363 00:24:20,800 --> 00:24:24,399 Speaker 1: it attaches itself to a surface like a barnacle, and 364 00:24:24,480 --> 00:24:29,800 Speaker 1: then it undergoes a dramatic transformation because in this phase, 365 00:24:29,920 --> 00:24:34,119 Speaker 1: once it's docked, it no longer needs its brain for 366 00:24:34,400 --> 00:24:39,040 Speaker 1: movement or navigation, so it eats its brain for nutrition. 367 00:24:39,200 --> 00:24:42,959 Speaker 1: It digests its own brain, and it uses that as 368 00:24:43,080 --> 00:24:47,720 Speaker 1: nutrients for other bodily functions. So this illustrates two things. First, 369 00:24:48,040 --> 00:24:52,600 Speaker 1: how incredible it is that some organisms can radically adapt 370 00:24:52,720 --> 00:24:55,960 Speaker 1: their anatomy to fit their new role. But more importantly, 371 00:24:55,960 --> 00:24:59,000 Speaker 1: for today's purpose, the main lesson from the sea squirt 372 00:24:59,080 --> 00:25:02,560 Speaker 1: is that you only we need a brain for one purpose, 373 00:25:02,920 --> 00:25:07,919 Speaker 1: and that is to move. If you've stopped moving, a 374 00:25:08,000 --> 00:25:12,520 Speaker 1: brain serves only as a little snack for nutrition. And 375 00:25:12,560 --> 00:25:15,320 Speaker 1: that's an idea that's been floating around in neuroscience for 376 00:25:15,400 --> 00:25:19,000 Speaker 1: well over a century. The reason for the brain's evolution 377 00:25:19,720 --> 00:25:22,720 Speaker 1: is movement control. The need to move and interact with 378 00:25:22,760 --> 00:25:27,399 Speaker 1: the environment is the driving force behind the development of 379 00:25:27,560 --> 00:25:30,879 Speaker 1: the nervous system. In other words, brains exist for one purpose, 380 00:25:30,920 --> 00:25:34,280 Speaker 1: and that is to get around. So now let's return 381 00:25:34,320 --> 00:25:38,920 Speaker 1: to thinking. The big idea for today is that thinking 382 00:25:39,600 --> 00:25:44,720 Speaker 1: is like a physical movement. You're moving stuff around on 383 00:25:44,760 --> 00:25:48,560 Speaker 1: the inside, but nothing on the outside. You are moving 384 00:25:49,040 --> 00:25:53,280 Speaker 1: concepts instead of limbs. In other words, thinking is simply 385 00:25:53,320 --> 00:25:58,520 Speaker 1: an outgrowth of the same brain mechanisms that govern moving. 386 00:26:00,000 --> 00:26:02,879 Speaker 1: This idea reached way back into the scientific literature, but 387 00:26:02,920 --> 00:26:05,119 Speaker 1: the most complete version of the argument that I know 388 00:26:05,240 --> 00:26:08,920 Speaker 1: comes from the neuroscientist Rudolfo Ginas in his book called 389 00:26:09,280 --> 00:26:12,000 Speaker 1: Eye of the Vortex. The key is that to get 390 00:26:12,119 --> 00:26:16,600 Speaker 1: good at movements, your brain works to predict the outcome 391 00:26:16,680 --> 00:26:20,760 Speaker 1: of possible actions. So as brains grew more sophisticated, they 392 00:26:20,760 --> 00:26:25,879 Speaker 1: could run simulations that didn't necessarily result in overt behavior. 393 00:26:26,160 --> 00:26:29,920 Speaker 1: So the brain generates predictions about the environment, and then 394 00:26:30,000 --> 00:26:32,679 Speaker 1: it tries things out and it adjusts things based on 395 00:26:32,760 --> 00:26:36,879 Speaker 1: the feedback, and that's how it refines future predictions. The 396 00:26:37,000 --> 00:26:40,560 Speaker 1: key idea is that this predictive function of the brain 397 00:26:41,080 --> 00:26:45,480 Speaker 1: eventually extended into the realm of cognition. So a thought 398 00:26:45,560 --> 00:26:51,119 Speaker 1: is like an internalized movement simulations of possible actions or 399 00:26:51,119 --> 00:27:12,960 Speaker 1: scenarios that don't necessarily result in overt behavior. When we think, 400 00:27:13,080 --> 00:27:16,760 Speaker 1: the brain is doing a kind of mental rehearsal, like 401 00:27:17,040 --> 00:27:23,280 Speaker 1: motor planning. It generates and navigates through thoughts by simulating 402 00:27:23,280 --> 00:27:27,560 Speaker 1: potential outcomes, but all without the body physically moving, just 403 00:27:27,600 --> 00:27:32,520 Speaker 1: the way that athletes mentally practice movements before performing them. 404 00:27:32,840 --> 00:27:36,119 Speaker 1: In other words, thought can be viewed as the brain's 405 00:27:36,200 --> 00:27:41,040 Speaker 1: way of moving through abstract mental landscapes, just as it 406 00:27:41,040 --> 00:27:44,040 Speaker 1: would move through physical space. And what this means is 407 00:27:44,080 --> 00:27:49,359 Speaker 1: that the mind is inseparable from the body's motor control systems. 408 00:27:49,560 --> 00:27:51,400 Speaker 1: And I just want to note that this framework has 409 00:27:51,840 --> 00:27:56,760 Speaker 1: far reaching implications for how we understand brains and brain disorders, 410 00:27:57,040 --> 00:28:02,480 Speaker 1: because conditions that affect movement, like Parkinson's disease or motor 411 00:28:02,560 --> 00:28:06,679 Speaker 1: neuron disease, might also give us insights into disorders of 412 00:28:07,119 --> 00:28:11,280 Speaker 1: thought and consciousness and things that we lump into cognitive 413 00:28:11,280 --> 00:28:16,680 Speaker 1: disorders like schizophrenia or obsessive compulsive disorder. These could perhaps 414 00:28:16,720 --> 00:28:22,359 Speaker 1: be viewed through the lens of disrupted internal movements. The 415 00:28:22,400 --> 00:28:24,639 Speaker 1: way to understand all of this is that the brain 416 00:28:25,240 --> 00:28:29,400 Speaker 1: is loopy. Very primitive brains have inputs that lead to outputs, 417 00:28:29,840 --> 00:28:34,200 Speaker 1: but our brains became more sophisticated such that you find 418 00:28:34,280 --> 00:28:38,600 Speaker 1: all kinds of internal loops. One piece of brain anatomy 419 00:28:38,640 --> 00:28:41,560 Speaker 1: worth mentioning here is a structure deep inside the brain 420 00:28:41,600 --> 00:28:44,760 Speaker 1: called the thalamus. All the inputs and outputs of the 421 00:28:44,800 --> 00:28:49,200 Speaker 1: brain stop in the thalamus like a trainway station, and 422 00:28:49,200 --> 00:28:51,560 Speaker 1: what you get are these very sophisticated loops called the 423 00:28:51,600 --> 00:28:56,120 Speaker 1: lamo cortical loops, which allows information to move around internally 424 00:28:56,280 --> 00:28:59,600 Speaker 1: as though things are moving in the world, but without 425 00:28:59,640 --> 00:29:02,760 Speaker 1: actually moving them. In this way, instead of the brain 426 00:29:03,240 --> 00:29:07,280 Speaker 1: generating a movement and it happens right away, instead the 427 00:29:07,320 --> 00:29:12,080 Speaker 1: brain can run a simulation internally to see what would 428 00:29:12,120 --> 00:29:15,240 Speaker 1: be predicted to happen if the movement were to be made, 429 00:29:15,480 --> 00:29:18,320 Speaker 1: and then eventually the simulations can be not just about 430 00:29:18,600 --> 00:29:21,840 Speaker 1: pushing this button or lifting this coffee cup, but more abstract, 431 00:29:22,040 --> 00:29:24,520 Speaker 1: like what would it be like if I got that 432 00:29:24,640 --> 00:29:27,719 Speaker 1: job promotion, or how should I break this news to 433 00:29:27,760 --> 00:29:31,880 Speaker 1: my friend? Or what is the optimal path to build 434 00:29:31,920 --> 00:29:36,320 Speaker 1: a society for peace and justice. Now with new data 435 00:29:36,320 --> 00:29:38,800 Speaker 1: about the brain, we can go even deeper to see 436 00:29:38,800 --> 00:29:41,720 Speaker 1: how this would work. For example, in a recent episode, 437 00:29:41,800 --> 00:29:46,080 Speaker 1: I talked with neuroscientist Jeff Hawkins on his theory about 438 00:29:46,120 --> 00:29:50,640 Speaker 1: cortical columns. Think of cortical columns like little rice grain 439 00:29:50,800 --> 00:29:53,760 Speaker 1: sized units that are all packed together in the cortex, 440 00:29:54,000 --> 00:29:56,680 Speaker 1: and you have hundreds of thousands of them, and each 441 00:29:56,720 --> 00:30:00,680 Speaker 1: one takes care of little overlapping aspects the world, and 442 00:30:00,760 --> 00:30:06,320 Speaker 1: together they communicate and collaborate to build a larger internal 443 00:30:06,400 --> 00:30:09,320 Speaker 1: model of the world. So here's a clip from that 444 00:30:09,440 --> 00:30:12,560 Speaker 1: interview which I didn't include in the original cut, on 445 00:30:12,680 --> 00:30:16,960 Speaker 1: the topic of what the columns are coding for. And 446 00:30:17,040 --> 00:30:19,840 Speaker 1: Jeff points out that the cells that you find in 447 00:30:19,880 --> 00:30:23,000 Speaker 1: mammals called grid cells, seem to be coding for two 448 00:30:23,040 --> 00:30:26,600 Speaker 1: dimensional space, but they can also code for three dimensional space. 449 00:30:26,920 --> 00:30:31,479 Speaker 1: And once you have these mechanisms for coding for movement 450 00:30:31,480 --> 00:30:36,560 Speaker 1: in space, maybe those cells can do something more. Here's Jeff. 451 00:30:41,280 --> 00:30:43,280 Speaker 2: It looks like the neurons. It's a speculative, but it 452 00:30:43,320 --> 00:30:46,160 Speaker 2: looks like the neurons can learn whatever is the proper 453 00:30:47,040 --> 00:30:51,719 Speaker 2: space for a particular problem. Yeah, so math may have 454 00:30:51,760 --> 00:30:56,480 Speaker 2: a different sort of space than what you learn for cups, 455 00:30:57,800 --> 00:31:00,840 Speaker 2: and it could be n dimensional. It's a little hard 456 00:31:00,880 --> 00:31:01,840 Speaker 2: to think about. 457 00:31:01,520 --> 00:31:03,760 Speaker 1: This, but here's the way that we maybe can think 458 00:31:03,760 --> 00:31:06,880 Speaker 1: about this is people have done this in VR, where 459 00:31:06,920 --> 00:31:09,840 Speaker 1: they put people in let's say a four dimensional world, 460 00:31:10,400 --> 00:31:12,440 Speaker 1: so it doesn't follow the normal three You know, if 461 00:31:12,480 --> 00:31:14,280 Speaker 1: I go to the right and the right and the 462 00:31:14,280 --> 00:31:16,000 Speaker 1: writing again, I'm not gonna end up in the same space. 463 00:31:16,080 --> 00:31:17,640 Speaker 1: I end up in a different space. And people are 464 00:31:17,760 --> 00:31:22,280 Speaker 1: are quite good at learning exactly this is not that 465 00:31:22,320 --> 00:31:22,880 Speaker 1: hard for them. 466 00:31:23,360 --> 00:31:26,360 Speaker 3: Initially it's very disoriented exactly right exactly, but they are 467 00:31:26,440 --> 00:31:28,880 Speaker 3: able to learn it, which is consistent with your idea. 468 00:31:28,880 --> 00:31:33,400 Speaker 3: If I understanding that the neurons are flexible about which dimension. 469 00:31:33,360 --> 00:31:36,400 Speaker 2: The neurals don't know what they're representing. They don't know 470 00:31:36,800 --> 00:31:38,840 Speaker 2: what where they're getting input from. They don't know what 471 00:31:38,840 --> 00:31:41,400 Speaker 2: the input represents. It's just some pattern that's coming in 472 00:31:41,480 --> 00:31:44,440 Speaker 2: from something that's moving, and in the movement could be 473 00:31:44,640 --> 00:31:47,840 Speaker 2: can be expressed as a set of one dimensional vectors, 474 00:31:47,880 --> 00:31:50,600 Speaker 2: and you're some intersection of those. So we could learn anything. 475 00:31:51,120 --> 00:31:53,160 Speaker 2: It can learn fourth dimensional space. Now, I would think 476 00:31:53,160 --> 00:31:54,920 Speaker 2: it would be hard to learn these things because you 477 00:31:55,000 --> 00:31:57,160 Speaker 2: have to practice a lot. But this is why a 478 00:31:57,160 --> 00:32:00,320 Speaker 2: mathematician might be really good and a non mathematician look 479 00:32:00,320 --> 00:32:02,280 Speaker 2: at some math and say this is all gobbledygook to me, 480 00:32:02,360 --> 00:32:04,560 Speaker 2: I can't and a mathematicians look at all these are 481 00:32:04,560 --> 00:32:06,720 Speaker 2: like friends. These numbers are friends, these equations are friends. 482 00:32:06,760 --> 00:32:08,240 Speaker 2: I know where they are, I know the relationship. I 483 00:32:08,240 --> 00:32:09,560 Speaker 2: know how to move from here to here. I know 484 00:32:09,600 --> 00:32:11,560 Speaker 2: what what action I have to take to get this 485 00:32:11,640 --> 00:32:14,560 Speaker 2: equation to look like that equation. And so they've developed 486 00:32:14,560 --> 00:32:18,760 Speaker 2: this sort of movement centro motor space for mathematics that 487 00:32:19,080 --> 00:32:21,719 Speaker 2: if you haven't spent years doing it, it's like mystery, 488 00:32:22,360 --> 00:32:27,440 Speaker 2: just gobblbook, right, So it takes time, and I certainly 489 00:32:27,440 --> 00:32:29,840 Speaker 2: think we would be we would be really in trouble 490 00:32:29,880 --> 00:32:32,880 Speaker 2: if all of our dimensional reference names and their brain 491 00:32:32,960 --> 00:32:35,080 Speaker 2: changed over night, because nothing would make any sense. So 492 00:32:35,400 --> 00:32:37,800 Speaker 2: but you could take some and movement of certain different directions. 493 00:32:37,800 --> 00:32:40,760 Speaker 2: So a lot of practice you could become a mathematician potentially, 494 00:32:40,880 --> 00:32:43,720 Speaker 2: or another lot of practice you might be good at 495 00:32:43,720 --> 00:32:46,200 Speaker 2: whatever it is you know, understanding computer code, which is 496 00:32:46,240 --> 00:32:48,560 Speaker 2: a totally different set of problems. 497 00:32:47,920 --> 00:32:50,520 Speaker 1: That's a really it's a really cool answer to that, 498 00:32:50,640 --> 00:32:55,360 Speaker 1: because one would think we have a three dimensional reference frame, 499 00:32:55,400 --> 00:32:57,640 Speaker 1: because that's the physical world we live in. But your 500 00:32:57,680 --> 00:33:00,400 Speaker 1: point is these norms are actually flexible enough that you 501 00:33:00,440 --> 00:33:02,880 Speaker 1: could get higher dimensionality when useful. 502 00:33:02,960 --> 00:33:05,040 Speaker 2: Right, Well, it looks like you look at evolutionary point 503 00:33:05,040 --> 00:33:09,280 Speaker 2: of view, the first references you needed were two dimensional, right, 504 00:33:09,280 --> 00:33:12,040 Speaker 2: if you're moving on the surface of the of the 505 00:33:12,080 --> 00:33:14,760 Speaker 2: of the ground, or you're moving along the floor to 506 00:33:14,880 --> 00:33:18,600 Speaker 2: the floor, right. And so these early reference systems, the 507 00:33:18,640 --> 00:33:21,120 Speaker 2: grid cells and the play cells, and the antirhinal cortex 508 00:33:21,120 --> 00:33:24,480 Speaker 2: and the hippocampus, they seem to be predominantly two dimensional. 509 00:33:25,640 --> 00:33:28,200 Speaker 2: And one could argue back a little bit, argue that 510 00:33:28,200 --> 00:33:30,080 Speaker 2: that makes sense because that's the older system, that's what 511 00:33:30,200 --> 00:33:32,560 Speaker 2: animals had to start with. And maybe what happened was 512 00:33:32,880 --> 00:33:39,600 Speaker 2: in the neocortex they generalized the system right, Right, So 513 00:33:39,000 --> 00:33:41,200 Speaker 2: it's so that it looks like the grid cells and 514 00:33:41,200 --> 00:33:43,840 Speaker 2: the ant hinod projects can represent three D structure because 515 00:33:44,040 --> 00:33:46,719 Speaker 2: bats can do it. But they're truly wonky. There's all 516 00:33:46,760 --> 00:33:48,200 Speaker 2: this research trying to figure out what's going on. They 517 00:33:48,200 --> 00:33:51,040 Speaker 2: don't really inderstand it. But it's clearly two dimensional. But 518 00:33:51,720 --> 00:33:53,920 Speaker 2: it's possible that in the cortext it says, okay, we 519 00:33:53,960 --> 00:33:57,880 Speaker 2: can represent any dimensional. We've generalized this thing now beyond 520 00:33:58,000 --> 00:34:00,959 Speaker 2: just navigating on the ocean floor on the Earth. And 521 00:34:01,080 --> 00:34:02,600 Speaker 2: maybe first I had to do it for flying or 522 00:34:02,680 --> 00:34:05,640 Speaker 2: climbing in trees, but now humans could do it for 523 00:34:05,800 --> 00:34:09,200 Speaker 2: math and and history, and you know, we can build 524 00:34:09,239 --> 00:34:10,400 Speaker 2: reference frames for everything. 525 00:34:15,200 --> 00:34:17,319 Speaker 1: So that was my interview with Jeff Hawkins from a 526 00:34:17,320 --> 00:34:20,320 Speaker 1: couple of months ago, and I include that to illustrate 527 00:34:20,360 --> 00:34:23,800 Speaker 1: the degree to which different scientists are scratching at different 528 00:34:23,880 --> 00:34:28,320 Speaker 1: versions of this idea that brains evolve to move through space. 529 00:34:28,360 --> 00:34:32,960 Speaker 1: But once you've got that solved, the mechanisms can generalize 530 00:34:33,239 --> 00:34:38,160 Speaker 1: to represent higher order concepts. So let's wrap today's episode. 531 00:34:38,280 --> 00:34:42,000 Speaker 1: We saw two main lessons. The first is that thoughts 532 00:34:42,040 --> 00:34:46,000 Speaker 1: are much more than words. Thinking comes in many formats, 533 00:34:46,520 --> 00:34:49,879 Speaker 1: and the second is that to the brain, thinking may 534 00:34:49,880 --> 00:34:55,000 Speaker 1: be just like moving, but it's internal moving through a 535 00:34:55,400 --> 00:34:59,320 Speaker 1: cognitive landscape. In other words, the brain's capacity to control 536 00:34:59,400 --> 00:35:03,960 Speaker 1: the body extends to its ability to simulate and navigate 537 00:35:04,360 --> 00:35:09,000 Speaker 1: mental spaces. Through this lens, thinking is mental motion, and 538 00:35:09,120 --> 00:35:15,000 Speaker 1: consciousness arises as the brain's continuous orchestration of movements, both 539 00:35:15,040 --> 00:35:20,359 Speaker 1: real and imagined. Understanding how we think can enrich how 540 00:35:20,360 --> 00:35:25,160 Speaker 1: we see ourselves. So here's a challenge. Spend today paying 541 00:35:25,200 --> 00:35:30,160 Speaker 1: attention to your thoughts. Notice how often they're verbal, or visual, 542 00:35:30,480 --> 00:35:34,040 Speaker 1: or emotional or something else entirely. If you get a chance, 543 00:35:34,280 --> 00:35:38,239 Speaker 1: download an app that randomly beeps your phone throughout the 544 00:35:38,320 --> 00:35:43,640 Speaker 1: day and jot down exactly what you were thinking. What 545 00:35:43,640 --> 00:35:46,239 Speaker 1: were you thinking about right then? Was it words? Was 546 00:35:46,239 --> 00:35:50,440 Speaker 1: it a feeling, a picture, something else. Our thoughts aren't 547 00:35:50,480 --> 00:35:54,399 Speaker 1: always what we naively expect, and if most of our 548 00:35:54,440 --> 00:35:57,440 Speaker 1: thoughts don't come in words, what does that say about 549 00:35:57,680 --> 00:36:00,880 Speaker 1: who we are? How much of your identity is tied 550 00:36:00,920 --> 00:36:03,360 Speaker 1: to the words in your head, and how much of 551 00:36:03,400 --> 00:36:09,240 Speaker 1: it lies in the massive nonverbal undercurrents of your mind. 552 00:36:15,000 --> 00:36:18,040 Speaker 1: Go to Eagleman dot com slash podcast for more information 553 00:36:18,200 --> 00:36:21,200 Speaker 1: and to find further reading. Send me an email at 554 00:36:21,239 --> 00:36:24,680 Speaker 1: podcasts at eagleman dot com with questions or discussion, and 555 00:36:24,800 --> 00:36:27,920 Speaker 1: check out and subscribe to Inner Cosmos on YouTube for 556 00:36:28,080 --> 00:36:33,480 Speaker 1: videos of each episode and to leave comments Until next time. 557 00:36:33,640 --> 00:36:36,839 Speaker 1: I'm David Eagleman, and this is inner Cosmos.