WEBVTT - Ep85 rebroadcast - "What is a Thought?" 0:00:05.240 --> 0:00:10.039 What is a thought? Is it something physical? How can 0:00:10.080 --> 0:00:13.160 you hear a voice in your head? And whose voice 0:00:13.240 --> 0:00:15.400 is it anyway? And what does this have to do 0:00:15.520 --> 0:00:19.720 with a small marine animal who eats its own brain. 0:00:23.160 --> 0:00:27.160 Welcome to Intercosmos with me, David Eagelman. I'm a neuroscientist 0:00:27.240 --> 0:00:30.200 and an author at Stanford and in these episodes we 0:00:30.240 --> 0:00:34.159 sail deeply into our three pound universe to understand some 0:00:34.200 --> 0:00:47.519 of the most surprising aspects of our lives. Today's episode 0:00:47.600 --> 0:00:52.280 is about thoughts. We have them constantly, even for the 0:00:52.320 --> 0:00:57.160 best meditators. It's difficult or impossible to stop the fire 0:00:57.240 --> 0:01:01.360 hose of words and images and ideas. We all talk 0:01:01.400 --> 0:01:04.280 about our thoughts. We sometimes act on our thoughts, we 0:01:04.400 --> 0:01:07.959 draw them with little thought bubbles and cartoons. But what 0:01:08.120 --> 0:01:12.640 in the world is a thought physically? So many years ago, 0:01:12.800 --> 0:01:16.119 a person at a party begged me to watch the 0:01:16.160 --> 0:01:20.039 movie called The Secret. So I watched it for fifteen minutes, 0:01:20.080 --> 0:01:22.759 and I regret to say that I will never get 0:01:22.760 --> 0:01:25.640 those fifteen minutes back. And I knew that this was 0:01:25.720 --> 0:01:29.679 the pinnacle of moronic when the first guy states quote, 0:01:30.600 --> 0:01:34.679 what most people don't understand is a thought has a frequency. 0:01:34.760 --> 0:01:38.360 Every thought has a frequency we can measure a thought, 0:01:38.560 --> 0:01:41.880 and so if you're thinking that thought over and over again, 0:01:42.280 --> 0:01:46.880 you're emitting that frequency on a consistent basis. And then 0:01:46.920 --> 0:01:51.520 the next Schremndrick says, thoughts are sending out that magnetic 0:01:51.720 --> 0:01:54.840 signal that is drawing the parallel back to you. That's 0:01:54.920 --> 0:01:58.800 the signal you're putting out into the universe. And then 0:01:58.880 --> 0:02:02.960 a third genius says, it has now been proven scientifically 0:02:03.560 --> 0:02:07.680 that an affirmative thought is hundreds of times more powerful 0:02:07.720 --> 0:02:10.799 than a negative thought. And every time someone thinks a 0:02:10.840 --> 0:02:14.720 thought in this movie, the graphics show the person having 0:02:14.760 --> 0:02:18.120 a thinking expression on their face, and then an energy 0:02:18.160 --> 0:02:20.520 wave bursts from their head, and then it cuts to 0:02:20.600 --> 0:02:23.080 a wide shot of the planet and you see this 0:02:23.320 --> 0:02:29.000 energy wave transmit across the universe. Now, the most striking 0:02:29.040 --> 0:02:32.840 thing about these statements in the movie is not simply 0:02:32.880 --> 0:02:35.480 that they are incorrect. To me, the shocking thing was 0:02:35.960 --> 0:02:38.959 how these guys looked right at the camera and asserted 0:02:39.040 --> 0:02:43.240 them as though these were not just completely made up, 0:02:43.280 --> 0:02:46.800 and then they used phrases like it has been scientifically proven. 0:02:47.160 --> 0:02:49.120 So in a few weeks, I'm going to do an 0:02:49.120 --> 0:02:52.960 episode about how we judge the value of any scientific 0:02:53.000 --> 0:02:55.960 idea and what it would mean to even say that 0:02:56.040 --> 0:02:58.800 something is scientifically proven. But I'm going to bite my 0:02:58.840 --> 0:03:02.320 tongue for now and put that aside, because for today's episode, 0:03:02.360 --> 0:03:08.200 what I really care about is what really is a thought. 0:03:08.800 --> 0:03:11.680 So to set the table for this, I'm going to 0:03:12.200 --> 0:03:15.480 put thoughts aside for a second and tell a story 0:03:15.800 --> 0:03:18.880 that I originally wrote in my book Incognito, And this 0:03:19.200 --> 0:03:23.480 took place in nineteen forty nine. A guy named Arthur 0:03:23.560 --> 0:03:27.519 Alberts traveled from his home in New York to villages 0:03:27.639 --> 0:03:31.160 between the Gold Coast and Timbuktoo in West Africa. And 0:03:31.200 --> 0:03:32.920 he brought his wife, and he brought a camera and 0:03:32.960 --> 0:03:36.480 a jeep, and because of his love for music, he 0:03:36.680 --> 0:03:40.560 brought a tape recorder. Now he wanted to open the 0:03:40.600 --> 0:03:43.960 ears of the Western world. So what he did was 0:03:44.000 --> 0:03:47.200 record some of the most important music to ever come 0:03:47.200 --> 0:03:52.480 out of Africa. But Alberts ran into social troubles while 0:03:52.480 --> 0:03:55.120 he was using this tape recorder because none of the 0:03:55.200 --> 0:03:59.360 natives had ever seen anything even vaguely like this before. 0:04:00.040 --> 0:04:04.040 So one native heard his voice played back to him 0:04:04.600 --> 0:04:09.320 and he accused Alberts of quote stealing his tongue. And 0:04:09.360 --> 0:04:13.840 according to the biography, Albert's only narrowly averted being pummeled 0:04:13.880 --> 0:04:17.200 by taking out a mirror and convincing the man that 0:04:17.279 --> 0:04:21.200 his tongue was still intact. So it's not difficult to 0:04:21.240 --> 0:04:25.760 see why the natives found the tape recorder so strange 0:04:25.800 --> 0:04:30.200 and counterintuitive. Just imagine that you had never ever seen 0:04:30.279 --> 0:04:34.760 this technology before. The thing is that a voice seems 0:04:35.200 --> 0:04:39.360 ephemeral and ineffable, right. A voice has no weight. You 0:04:39.400 --> 0:04:43.080 can't hold voice in your hand. A voice just exists 0:04:43.080 --> 0:04:46.320 for a moment. It's totally untouchable, and then it's gone. 0:04:46.720 --> 0:04:49.800 There doesn't seem to be any physical trace. So it 0:04:49.880 --> 0:04:54.480 comes as a surprise that a voice is physical. If 0:04:54.520 --> 0:04:57.960 you build a little machine that's sensitive enough to detect 0:04:58.200 --> 0:05:01.600 tiny compressions of the molecule in the air, you can 0:05:01.640 --> 0:05:06.200 then capture those density changes and reproduce them later. We 0:05:06.279 --> 0:05:10.400 call these little machines microphones, and we reproduce the density 0:05:10.520 --> 0:05:15.559 changes on tape or with zeros and ones, And every 0:05:15.600 --> 0:05:19.039 one of the billions of podcasts and playlists on the 0:05:19.080 --> 0:05:24.880 planet is proudly serving up bags of feathers once thought irretrievable. 0:05:25.600 --> 0:05:28.560 When Alberts played the music, back from the tape recorder. 0:05:28.640 --> 0:05:35.320 One tribesman described the feat as tremendous magic. And so 0:05:35.440 --> 0:05:39.120 it goes with thoughts. What exactly is a thought? It 0:05:39.120 --> 0:05:44.120 doesn't seem to weigh anything. It feels ephemeral and ineffable. 0:05:44.600 --> 0:05:47.279 You wouldn't think that a thought has any shape or 0:05:47.320 --> 0:05:51.920 smell or any sort of physical instantiation. Thoughts seem to 0:05:51.920 --> 0:05:56.120 be a kind of tremendous magic. So it comes as 0:05:56.120 --> 0:06:00.320 a surprise that a thought is physical, just like voice is. 0:06:00.920 --> 0:06:06.560 Thoughts are underpinned by biological stuff. We know this because 0:06:06.640 --> 0:06:10.359 alterations to the brain change the kinds of thoughts we 0:06:10.440 --> 0:06:14.200 can think. In a state of deep sleep, there are 0:06:14.240 --> 0:06:19.200 no thoughts. When the brain transitions into dream sleep, there 0:06:19.240 --> 0:06:23.680 are unbidden, bizarre thoughts. During the day, we enjoy our normal, 0:06:23.800 --> 0:06:29.560 well accepted thoughts, which people enthusiastically modulate by spiking the 0:06:29.640 --> 0:06:33.800 chemical cocktails of the brain with alcohol or narcotics, or 0:06:34.160 --> 0:06:38.760 exercise or coffee. So the state of the physical material 0:06:39.240 --> 0:06:43.840 determines the state of the thoughts, and issues like obsessive 0:06:43.880 --> 0:06:48.719 compulsive disorder or schizophrenia tell us that when certain networks 0:06:48.720 --> 0:06:53.279 in the brain become overactive or miscalibrated, the character of 0:06:53.400 --> 0:06:57.400 thinking changes. It's this kind of thing that tells us 0:06:57.400 --> 0:07:01.920 that the physical stuff is irreversible, tied to the thinking. 0:07:01.960 --> 0:07:04.520 And we know this also because when people get even 0:07:04.640 --> 0:07:08.160 small bits of brain damage, let's say, because of a 0:07:08.200 --> 0:07:12.480 stroke or a tumor, that can change their capacity to 0:07:12.600 --> 0:07:16.960 understand music, or name animals or see colors, or judge risk, 0:07:17.080 --> 0:07:20.960 or make decisions, or read signals from their bodies, or 0:07:21.040 --> 0:07:24.560 understand the concept of a mirror, or hundreds of other 0:07:24.760 --> 0:07:28.400 changes in thinking that we can witness in the clinics 0:07:28.440 --> 0:07:32.360 every day, and the consequences of injury is a big 0:07:32.400 --> 0:07:36.160 part of how brain science has mapped out the general 0:07:36.320 --> 0:07:39.840 blueprints of the brain. So the bottom line lesson which 0:07:39.840 --> 0:07:45.040 has emerged over centuries is that our internal thoughts about 0:07:45.080 --> 0:07:48.960 hopes or fears or desires, they all emerge from this 0:07:49.600 --> 0:07:53.720 strange three pound organ and when the brain changes, so 0:07:53.880 --> 0:07:57.440 do our thoughts. So although it's easy to intuit that 0:07:57.640 --> 0:08:01.360 thoughts don't have a physical basis, that there are something 0:08:01.400 --> 0:08:04.760 like feathers on the wind, they in fact depend directly 0:08:04.880 --> 0:08:09.920 on what's happening in this small, enigmatic mission control center 0:08:10.400 --> 0:08:15.080 locked in the silent vault of the skull. So what 0:08:15.440 --> 0:08:19.120 is a thought. It's the result of billions of neurons 0:08:19.240 --> 0:08:23.720 firing and coordinated patterns. As we've talked about in other episodes, 0:08:23.800 --> 0:08:28.200 the neurons communicate using electrical impulses and chemical signals, and 0:08:28.240 --> 0:08:32.560 they form vast networks that operate together, such that at 0:08:32.640 --> 0:08:37.640 any moment you have some millions of neurons doing something coordinated, 0:08:37.679 --> 0:08:40.080 and in the next moment it's a different collection of 0:08:40.120 --> 0:08:43.800 neurons that are working together. Now, it may not surprise 0:08:43.880 --> 0:08:46.160 you to know that a thought is not located in 0:08:46.200 --> 0:08:49.839 one place in the brain. It's an emergent property. It's 0:08:49.880 --> 0:08:54.880 a collaboration between these millions or billions of neurons. When 0:08:54.920 --> 0:08:58.800 you have a thought, it's like a symphony playing inside 0:08:58.840 --> 0:09:02.920 your head. Every neuron involved is an instrument in the orchestra, 0:09:03.360 --> 0:09:06.800 and no single part can create the music by itself. 0:09:07.320 --> 0:09:09.319 So we're gonna come back to the brain in a moment, 0:09:09.360 --> 0:09:11.880 but before we do, I want us to really zoom 0:09:11.920 --> 0:09:16.640 in on the subjective experience. How would you describe the 0:09:16.880 --> 0:09:21.040 experience of a thought. When you try to capture what 0:09:21.120 --> 0:09:25.320 a thought is, the most commonplace to go is your 0:09:25.840 --> 0:09:29.520 inner monologue. This is the voice in your head that 0:09:29.559 --> 0:09:33.800 you use to problem solve, or criticize, or plan or reflect. 0:09:34.280 --> 0:09:37.200 So take just a second to pay attention to the 0:09:37.320 --> 0:09:42.400 voice inside your head, that constant stream of chatter. Now 0:09:42.559 --> 0:09:46.839 you might think, what voice inside my head? That's the voice? Now. 0:09:46.960 --> 0:09:51.320 Your internal voice can involve deliberate problem solving, like what 0:09:51.360 --> 0:09:55.160 should I do next here? Or it can involve involuntary 0:09:55.360 --> 0:09:58.040 commentary like oh so stupid to me, why did I 0:09:58.080 --> 0:10:03.120 do that? Or it can be whole imagined conversations like Okay, 0:10:03.200 --> 0:10:04.920 I say this, and then she says that, and then 0:10:04.920 --> 0:10:07.319 I respond like this. It can be helpful for things 0:10:07.400 --> 0:10:11.439 like working memory. So for example, you're trying to log 0:10:11.480 --> 0:10:14.640 into a website and you get texted some six digit 0:10:14.760 --> 0:10:17.600 pass code, and you need to remember that code while 0:10:17.600 --> 0:10:21.680 you switch windows, So you internally say the numbers over 0:10:21.720 --> 0:10:24.880 and over. So you're using the internal voice to keep 0:10:24.920 --> 0:10:27.600 the information in mind as part of your working memory. 0:10:27.920 --> 0:10:30.440 There's so many places where the internal voice comes in. 0:10:30.520 --> 0:10:34.160 We tend to talk to ourselves when we're planning something, 0:10:34.200 --> 0:10:38.560 when we're weighing options. The internal dialogue seems to be 0:10:38.640 --> 0:10:43.240 really helpful in simulating different scenarios. So you're running your 0:10:43.240 --> 0:10:46.960 internal voice all the time and subjectively, it seems to 0:10:47.000 --> 0:10:51.320 be a mental space that can seem almost as vivid 0:10:51.400 --> 0:10:55.120 as external speech. It follows all the rules of grammar 0:10:55.240 --> 0:10:59.480 and syntax, and it can be emotionally laden with encouragement 0:10:59.600 --> 0:11:05.080 or or anywhere in between. Now, how does this happen? 0:11:05.160 --> 0:11:09.240 How can you generate a voice internally and hear it well? 0:11:09.280 --> 0:11:12.640 When we eavesdrop on the brain, let's say, using brain 0:11:12.760 --> 0:11:16.320 imaging like fMRI, what we find is a network of 0:11:16.520 --> 0:11:22.040 areas involved in speech production, like Broca's area, which is 0:11:22.040 --> 0:11:25.200 a key region involved in talking out loud. And we 0:11:25.240 --> 0:11:30.520 find areas involved in language comprehension like Wernicke's area and 0:11:30.559 --> 0:11:34.000 the auditory cortex more generally, as though you're listening to 0:11:34.120 --> 0:11:38.080 spoken language from somebody else talking. And also what we 0:11:38.160 --> 0:11:43.640 see is a network that we summarizes the default mode network, 0:11:43.800 --> 0:11:46.320 and this is a network that becomes active when you're 0:11:46.360 --> 0:11:50.199 not focused on monitoring the outside world, but instead when 0:11:50.240 --> 0:11:53.680 you think about yourself, where you daydream, or you reflect 0:11:53.760 --> 0:11:57.240 on your past, or you imagine your future. So all 0:11:57.280 --> 0:11:59.840 these networks are cranked up when you're talking to yourself. 0:11:59.840 --> 0:12:02.840 And one really important point when you're generating your own 0:12:02.880 --> 0:12:07.160 speech is that you have something called corollary discharge, which 0:12:07.320 --> 0:12:10.200 just means that when your brain generates internal speech, it 0:12:10.320 --> 0:12:13.360 sends a copy of what it's doing to other parts 0:12:13.360 --> 0:12:16.000 of the brain to let them know this is coming. 0:12:16.040 --> 0:12:18.320 I'm the one who did this. That's how the rest 0:12:18.320 --> 0:12:21.360 of the brain knows that the inner voice is self 0:12:21.480 --> 0:12:26.480 generated instead of confusing it with external speech. As a 0:12:26.520 --> 0:12:29.559 side note, if you're a regular listener to this podcast, 0:12:29.600 --> 0:12:31.800 you know that I've been publishing on the topic of 0:12:31.880 --> 0:12:36.720 schizophrenia for many years, and my hypothesis is that auditory 0:12:36.760 --> 0:12:41.880 hallucinations in schizophrenia might have to do with a miscalibration 0:12:42.080 --> 0:12:46.000 of the timing of signals, such that the internal voice 0:12:46.559 --> 0:12:51.079 gets misinterpreted as someone else's voice. In other words, when 0:12:51.160 --> 0:12:54.800 you're talking to yourself under normal conditions, you generate the voice, 0:12:55.080 --> 0:12:58.240 then you hear the voice, and the corollary discharge tells 0:12:58.280 --> 0:13:00.560 you that it was your own. But if there's something 0:13:00.600 --> 0:13:03.880 wrong with the timing of the corollary discharge, then it 0:13:03.880 --> 0:13:06.240 doesn't seem like you're the one who generated the voice, 0:13:06.320 --> 0:13:09.199 and you have to attribute the voice to someone else. 0:13:09.520 --> 0:13:13.719 The internal voice feels like it must be external. If 0:13:13.720 --> 0:13:17.720 you're interested in more on this, hypothesis about schizophrenia. Check 0:13:17.760 --> 0:13:21.720 out episodes thirty three and forty four. Okay, so back 0:13:21.760 --> 0:13:25.400 to the internal voice, which in normal circumstances we understand 0:13:25.480 --> 0:13:29.280 as our voice in our heads. Here's my question, is 0:13:29.320 --> 0:13:33.560 this inner monologue really the main way that we think? 0:13:33.800 --> 0:13:36.600 What if some of our thoughts don't come with words 0:13:36.800 --> 0:13:41.119 at all? So that's the question that psychologist Russell Hurlbert 0:13:41.120 --> 0:13:43.599 set out to answer with a set of experiments in 0:13:43.640 --> 0:13:47.640 the nineteen nineties. And here's how it works. Imagine that 0:13:47.720 --> 0:13:51.400 you are given a beeper that beeps off at random 0:13:51.480 --> 0:13:56.160 times during your day, and the instant it beeps, your 0:13:56.320 --> 0:14:00.679 job is to write down whatever was just in your mind. Beep, 0:14:00.880 --> 0:14:04.720 what are you thinking about right now? So when Hurlbert 0:14:04.840 --> 0:14:08.280 analyzed the data, he found that only about twenty six 0:14:08.360 --> 0:14:12.160 percent of people's thoughts were verbal, meaning that they involved 0:14:12.240 --> 0:14:16.000 actual words or inner speech. The other seventy four percent 0:14:16.720 --> 0:14:23.080 completely nonverbal. So what does nonverbal thought mean? Well, when 0:14:23.120 --> 0:14:26.560 your thoughts are suddenly probed, lots of people find that 0:14:26.600 --> 0:14:31.160 they were just thinking about, for example, vivid mental images 0:14:31.280 --> 0:14:35.840 like picturing a beach or remembering somebody's face, or thinking 0:14:35.840 --> 0:14:38.320 about some moment they just saw at the restaurant, and 0:14:38.360 --> 0:14:40.960 that's all their thought was at that moment. It was visual. 0:14:41.000 --> 0:14:59.920 There were no words involved, just pictures. So what's go 0:15:00.000 --> 0:15:02.080 going on in the brain when you have these kind 0:15:02.120 --> 0:15:06.440 of vivid mental images. Well, if I were to ask 0:15:06.520 --> 0:15:11.000 you to think about a Siberian tiger, your prefrontal cortex 0:15:11.120 --> 0:15:14.200 right behind the forehead takes on the task and starts 0:15:14.280 --> 0:15:18.360 broadcasting to see who can fulfill the request. So your 0:15:18.440 --> 0:15:22.760 memory systems chug into place to determine what a Siberian 0:15:22.800 --> 0:15:27.360 tiger is, combining all the different examples of Siberian tigers 0:15:27.360 --> 0:15:31.119 that you've seen before, and your visual cortex is recruited 0:15:31.640 --> 0:15:36.400 to generate a picture. Your emotion centers might even contribute, 0:15:36.520 --> 0:15:41.320 shading this thought with feelings of alertness or awe or fear. 0:15:41.880 --> 0:15:45.800 So when you think about that Siberian tiger, hundreds of 0:15:45.920 --> 0:15:49.360 millions of neurons across different areas of your brain are 0:15:49.440 --> 0:15:54.480 lighting up, working together to create something that feels whole 0:15:54.720 --> 0:15:58.120 and immediate. And of course, if you're a musician and 0:15:58.320 --> 0:16:01.160 the pager beeps, you might find that you're thinking about 0:16:01.160 --> 0:16:05.360 something auditory. You're thinking about which notes would sound great. 0:16:05.480 --> 0:16:07.960 Right after this transition from this cord to this court. 0:16:08.280 --> 0:16:11.240 But there's no words involved in that. And in the 0:16:11.240 --> 0:16:14.920 brain we can measure activity in your auditory cortex while 0:16:14.960 --> 0:16:18.720 you're doing that, And if you're a perfumer, you might 0:16:18.760 --> 0:16:22.920 be doing smell imagery. You're thinking about the way that 0:16:22.960 --> 0:16:25.200 this other perfume smell than how you're trying to get 0:16:25.200 --> 0:16:29.920 a little closer to that. But as you are internally smelling, 0:16:30.440 --> 0:16:34.960 there are no words associated with that. It's just olfactory imagery. 0:16:35.480 --> 0:16:38.680 And this sort of sensory thinking can come in all 0:16:38.800 --> 0:16:42.520 kinds of flavors, like feeling the warmth from the sun 0:16:42.600 --> 0:16:46.520 on your face or the tightness of your chest during stress. 0:16:47.280 --> 0:16:51.240 So that's what Hurlbert found people were thinking about quite 0:16:51.320 --> 0:16:56.520 often when you probe them at random, sensory imagery without language. 0:16:56.840 --> 0:16:58.760 But that was just the beginning. The kind of thoughts 0:16:58.760 --> 0:17:03.520 that people were thing went beyond just sensory imagery. Lots 0:17:03.560 --> 0:17:07.280 of other times people described they were thinking about how 0:17:07.320 --> 0:17:10.960 to do something physical, like how to position their hands 0:17:11.000 --> 0:17:13.960 for reaching into the oven, or how to remove the 0:17:14.040 --> 0:17:16.520 cover off the printer, or how far to turn the 0:17:16.560 --> 0:17:19.120 steering wheel to get their car into the parking spot. 0:17:19.480 --> 0:17:22.840 But they were thinking about how to do these moves, 0:17:23.160 --> 0:17:26.159 and there were no words involved. It was a physical 0:17:26.280 --> 0:17:30.960 activity they were simulating. This is called motoric imagery. Their 0:17:31.000 --> 0:17:35.160 brains were thinking their way through something. And other thoughts 0:17:35.200 --> 0:17:39.040 are even more difficult to pin down than imagining senses 0:17:39.200 --> 0:17:44.360 or imagining movement because they're more abstract, like a vague 0:17:44.560 --> 0:17:49.359 sense of unease with no clear words or pictures attached. 0:17:50.119 --> 0:17:52.760 So thoughts come in many flavors, and I'll just make 0:17:52.760 --> 0:17:55.560 a thirty second side note here about whether it makes 0:17:55.600 --> 0:17:59.840 sense to call the activity in the unconscious brain think. 0:18:00.400 --> 0:18:03.480 For example, you're trying to remember the name of that 0:18:03.640 --> 0:18:05.439 song and it's on the tip of your tongue, but 0:18:05.480 --> 0:18:09.320 you just can't remember it. And then hours later, when 0:18:09.359 --> 0:18:13.080 you're not even thinking about it, the answer suddenly pops 0:18:13.080 --> 0:18:16.520 into your mind. Your unconscious mind has been working on 0:18:16.560 --> 0:18:19.320 it in the background, even though you had no awareness 0:18:19.320 --> 0:18:22.720 of it. So should we call that thinking even when 0:18:22.760 --> 0:18:26.600 it happens unconsciously. Just for the purposes of having a 0:18:26.640 --> 0:18:29.320 clear definition, it's probably going to make the most sense 0:18:29.359 --> 0:18:32.760 to call that something like processing, and will reserve the 0:18:32.800 --> 0:18:37.480 word thought for the conscious conclusion of that behind the 0:18:37.480 --> 0:18:40.280 scenes activity, so at least for the moment I'm not 0:18:40.400 --> 0:18:46.040 going to call the unconscious activity thought. So this simple 0:18:46.119 --> 0:18:49.159 experiment of pinging people at random to ask them what 0:18:49.200 --> 0:18:51.919 they're thinking, what's in their minds at this exact moment, 0:18:52.760 --> 0:18:55.920 This experiment tells us something important, which is that thinking 0:18:56.480 --> 0:18:59.920 is not just talking to ourselves. It's broader than that. 0:19:00.520 --> 0:19:03.720 We have different kinds of thoughts in different formats. We 0:19:03.800 --> 0:19:07.280 have inner speech, but we also have mental imagery, like 0:19:07.760 --> 0:19:10.760 when you're visualizing what your kitchen reed design could look like, 0:19:11.040 --> 0:19:16.040 and you have abstract thinking like when you're contemplating infinity 0:19:16.280 --> 0:19:19.720 or justice or love. And possibly there are still other 0:19:19.800 --> 0:19:22.840 things which could fall under the umbrella of thought. So 0:19:23.400 --> 0:19:27.760 thinking is a rich, multi dimensional experience. Okay, so here's 0:19:27.760 --> 0:19:30.280 where we are. So far. We talked about the internal 0:19:30.400 --> 0:19:34.400 voice and visualization and imagining sound or smell or bodily feelings, 0:19:34.440 --> 0:19:38.080 and imagining motor movement, and even abstract sorts of thoughts. 0:19:38.359 --> 0:19:40.520 But if you've been listening to these episodes for a while, 0:19:40.640 --> 0:19:44.959 you know that I'm obsessed with the difference between people's 0:19:45.040 --> 0:19:49.160 internal experiences and thinking is no exception. When we look 0:19:49.200 --> 0:19:53.640 at the diversity of thought, some people seem to lean 0:19:53.760 --> 0:19:57.879 more towards verbal thinking, they talk things out in their heads. 0:19:58.280 --> 0:20:02.920 Others are visual things, seeing vivid mental images as their 0:20:03.320 --> 0:20:07.600 primary mode of thinking. And some people experience thoughts more 0:20:07.680 --> 0:20:11.439 like abstract concepts without the voice or the images. And 0:20:11.480 --> 0:20:13.840 this goes hand in hand with something I've talked about 0:20:14.000 --> 0:20:16.399 in many episodes, which is that, as far as we 0:20:16.440 --> 0:20:22.480 can tell, subjective experiences exist on a spectrum. So let's 0:20:22.560 --> 0:20:25.080 zoom in on the inner voice. Some people report having 0:20:25.280 --> 0:20:29.560 constant chatter in their heads, while other people have little 0:20:29.720 --> 0:20:36.080 or no inner verbalization. That's called an endophasia no internal voice. 0:20:36.119 --> 0:20:39.160 As an example, when it comes to the inner monologue, 0:20:39.320 --> 0:20:42.640 my wife's internal radio is very loud, she says, she's 0:20:42.680 --> 0:20:46.000 always hearing it at full volume. For me, it happens 0:20:46.040 --> 0:20:48.960 to be pretty quiet most of the time. I'm going 0:20:49.000 --> 0:20:51.959 to link some papers in the show notes about studies 0:20:52.080 --> 0:20:55.840 on the variation of the internal voice. And when it 0:20:55.880 --> 0:20:59.600 comes to visualization, I've talked in other episodes about this, 0:21:00.800 --> 0:21:04.800 from a fantasia to hyperfantasia. In other words, the spread 0:21:04.840 --> 0:21:08.679 from not really picturing anything visually in your mind to 0:21:08.800 --> 0:21:14.639 having very rich, colorful, movie like visualizations, and everyone is 0:21:14.720 --> 0:21:18.920 somewhere along that spectrum. Now we haven't really measured this yet, 0:21:18.960 --> 0:21:22.640 But when it comes to more subtle issues of abstract thinking, 0:21:23.359 --> 0:21:27.040 like contemplating infinity or justice or love, it may be 0:21:27.119 --> 0:21:31.560 that people are having very different experiences of how strongly 0:21:31.720 --> 0:21:36.000 or intensely they're feeling that. Now, it's a little difficult 0:21:36.040 --> 0:21:39.359 to design an experiment to probe this, because it's purely 0:21:39.440 --> 0:21:43.320 an issue of somebody's subjective report, and it's not always 0:21:43.359 --> 0:21:47.440 easy to know if people are reporting accurately. But if 0:21:47.520 --> 0:21:51.840 this subjective experience of abstract thought is like everything else 0:21:51.840 --> 0:21:55.320 we've measured so far, it is surely going to differ 0:21:55.720 --> 0:21:58.880 from person to person. So it seems to me there's 0:21:58.920 --> 0:22:03.359 probably massive of divergence in what we mean from person 0:22:03.400 --> 0:22:08.160 to person when we talk about the experience of thought. 0:22:08.560 --> 0:22:11.840 If we can only know what the experience is inside 0:22:11.840 --> 0:22:17.199 another head, we might suddenly understand why Susan immediately sees 0:22:17.240 --> 0:22:20.960 the solution to the math problem, and why Amy keeps 0:22:20.960 --> 0:22:24.440 in mind so well what everyone else's emotion is, and 0:22:24.480 --> 0:22:28.240 why Steve is so interested in fixing broken radios, and 0:22:28.280 --> 0:22:32.040 why Tim spends all his intellectual efforts figuring out how 0:22:32.040 --> 0:22:34.200 to get other people to do work for him, and 0:22:34.240 --> 0:22:37.359 so on with the differences between every person you know, 0:22:37.760 --> 0:22:40.520 and by the way this diversity in the inner experience, 0:22:40.560 --> 0:22:44.040 this has real world implications. So just think about how 0:22:44.119 --> 0:22:50.160 people learn or solve problems. Schools and workplaces often prioritize 0:22:50.520 --> 0:22:54.399 verbal reasoning. But what if somebody's thoughts arrive more like 0:22:54.480 --> 0:22:57.960 pictures or more like physical sensations. What if their best 0:22:58.000 --> 0:23:02.040 ideas can't be put into words immediately? I think as 0:23:02.080 --> 0:23:06.720 we bring the individual differences in thinking into focus, we'll 0:23:06.760 --> 0:23:11.440 be able to increasingly build education to take advantage of 0:23:11.480 --> 0:23:16.200 the full spectrum of human cognition and understanding this diversity 0:23:16.240 --> 0:23:20.600 of thought. This also has implications for mental health. Verbal thoughts, 0:23:20.600 --> 0:23:24.840 for example, are strongly linked to rumination, which is the 0:23:24.960 --> 0:23:29.480 endless loops of self talk that fuel anxiety or depression. 0:23:30.080 --> 0:23:33.919 And meanwhile, nonverbal sensations like a tight chest or a 0:23:34.080 --> 0:23:37.840 racing heart, these are the things that dominate panic attacks. 0:23:38.040 --> 0:23:41.359 So really understanding how differently people think and how to 0:23:41.440 --> 0:23:44.960 measure that could help us to manage these mental states 0:23:45.040 --> 0:23:49.680 more effectively. Okay, so we've been talking about our private 0:23:49.840 --> 0:23:52.680 internal experience of thoughts, but we still have a nailed 0:23:52.720 --> 0:23:55.879 down what a thought is exactly and what could this 0:23:56.080 --> 0:24:00.760 possibly have to do with a c squirt finding its home, 0:24:01.200 --> 0:24:05.080 So let's start there. The sea squirt is a small 0:24:05.240 --> 0:24:09.600 marine creature that begins life as a free swimming larva. 0:24:10.119 --> 0:24:12.520 It has a little brain and a nervous system that 0:24:12.760 --> 0:24:17.960 helps it navigate and search for a suitable place to settle. Now, 0:24:18.000 --> 0:24:22.080 once it finds its permanent spot, it attaches itself to 0:24:22.160 --> 0:24:26.159 a surface like a barnacle, and then it undergoes a 0:24:26.320 --> 0:24:31.800 dramatic transformation because in this phase, once it's docked, it 0:24:32.000 --> 0:24:36.640 no longer needs its brain for movement or navigation, so 0:24:36.720 --> 0:24:41.080 it eats its brain for nutrition. It digests its own brain, 0:24:41.640 --> 0:24:45.119 and it uses that as nutrients for other bodily functions. 0:24:45.440 --> 0:24:49.119 So this illustrates two things. First, how incredible it is 0:24:49.160 --> 0:24:53.800 that some organisms can radically adapt their anatomy to fit 0:24:53.840 --> 0:24:57.320 their new role. But more importantly, for today's purpose, the 0:24:57.359 --> 0:24:59.920 main lesson from the sea squirt is that you only 0:25:00.200 --> 0:25:05.000 need a brain for one purpose, and that is to move. 0:25:05.760 --> 0:25:09.439 If you've stopped moving, a brain serves only as a 0:25:09.440 --> 0:25:13.560 little snack for nutrition, and that's an idea that's been 0:25:13.600 --> 0:25:16.720 floating around in neuroscience for well over a century. The 0:25:16.760 --> 0:25:21.439 reason for the brain's evolution is movement control. The need 0:25:21.480 --> 0:25:25.240 to move and interact with the environment is the driving 0:25:25.440 --> 0:25:29.399 force behind the development of the nervous system. In other words, 0:25:29.400 --> 0:25:32.280 brains exist for one purpose, and that is to get around. 0:25:33.280 --> 0:25:37.240 So now let's return to thinking. The big idea for 0:25:37.320 --> 0:25:43.240 today is that thinking is like a physical movement. You're 0:25:43.359 --> 0:25:47.600 moving stuff around on the inside, but nothing on the outside. 0:25:47.720 --> 0:25:51.960 You are moving concepts instead of limbs. In other words, 0:25:52.280 --> 0:25:56.680 thinking is simply an outgrowth of the same brain mechanisms 0:25:57.160 --> 0:26:01.720 that govern moving. This idea reach way back into the 0:26:01.720 --> 0:26:04.679 scientific literature, but the most complete version of the argument 0:26:04.720 --> 0:26:08.080 that I know comes from the neuroscientist Rudolfo Ginas in 0:26:08.160 --> 0:26:11.439 his book called Eye of the Vortex. The key is 0:26:11.440 --> 0:26:14.560 that to get good at movements, your brain works to 0:26:15.040 --> 0:26:19.400 predict the outcome of possible actions. So as brains grew 0:26:19.480 --> 0:26:24.400 more sophisticated, they could run simulations that didn't necessarily result 0:26:24.440 --> 0:26:29.280 in overt behavior. So the brain generates predictions about the environment, 0:26:29.600 --> 0:26:32.200 and then it tries things out and it adjusts things 0:26:32.240 --> 0:26:36.119 based on the feedback, and that's how it refines future predictions. 0:26:36.800 --> 0:26:40.199 The key idea is that this predictive function of the 0:26:40.240 --> 0:26:45.119 brain eventually extended into the realm of cognition. So a 0:26:45.200 --> 0:26:50.960 thought is like an internalized movement simulations of possible actions 0:26:51.000 --> 0:27:12.400 or scenarios that don't necessarily result in overt behavior. When 0:27:12.440 --> 0:27:16.400 we think, the brain is doing a kind of mental rehearsal, 0:27:16.640 --> 0:27:22.600