Speaker 1: What is a thought? Is it something physical? How can
Speaker 1: you hear a voice in your head? And whose voice
Speaker 1: is it anyway? And what does this have to do
Speaker 1: with a small marine animal who eats its own brain.
Speaker 1: Welcome to Intercosmos with me, David Eagelman. I'm a neuroscientist
Speaker 1: and an author at Stanford and in these episodes we
Speaker 1: sail deeply into our three pound universe to understand some
Speaker 1: of the most surprising aspects of our lives. Today's episode
Speaker 1: is about thoughts. We have them constantly, even for the
Speaker 1: best meditators. It's difficult or impossible to stop the fire
Speaker 1: hose of words and images and ideas. We all talk
Speaker 1: about our thoughts. We sometimes act on our thoughts, we
Speaker 1: draw them with little thought bubbles and cartoons. But what
Speaker 1: in the world is a thought physically? So many years ago,
Speaker 1: a person at a party begged me to watch the
Speaker 1: movie called The Secret. So I watched it for fifteen minutes,
Speaker 1: and I regret to say that I will never get
Speaker 1: those fifteen minutes back. And I knew that this was
Speaker 1: the pinnacle of moronic when the first guy states quote,
Speaker 1: what most people don't understand is a thought has a frequency.
Speaker 1: Every thought has a frequency we can measure a thought,
Speaker 1: and so if you're thinking that thought over and over again,
Speaker 1: you're emitting that frequency on a consistent basis. And then
Speaker 1: the next Schremndrick says, thoughts are sending out that magnetic
Speaker 1: signal that is drawing the parallel back to you. That's
Speaker 1: the signal you're putting out into the universe. And then
Speaker 1: a third genius says, it has now been proven scientifically
Speaker 1: that an affirmative thought is hundreds of times more powerful
Speaker 1: than a negative thought. And every time someone thinks a
Speaker 1: thought in this movie, the graphics show the person having
Speaker 1: a thinking expression on their face, and then an energy
Speaker 1: wave bursts from their head, and then it cuts to
Speaker 1: a wide shot of the planet and you see this
Speaker 1: energy wave transmit across the universe. Now, the most striking
Speaker 1: thing about these statements in the movie is not simply
Speaker 1: that they are incorrect. To me, the shocking thing was
Speaker 1: how these guys looked right at the camera and asserted
Speaker 1: them as though these were not just completely made up,
Speaker 1: and then they used phrases like it has been scientifically proven.
Speaker 1: So in a few weeks, I'm going to do an
Speaker 1: episode about how we judge the value of any scientific
Speaker 1: idea and what it would mean to even say that
Speaker 1: something is scientifically proven. But I'm going to bite my
Speaker 1: tongue for now and put that aside, because for today's episode,
Speaker 1: what I really care about is what really is a thought.
Speaker 1: So to set the table for this, I'm going to
Speaker 1: put thoughts aside for a second and tell a story
Speaker 1: that I originally wrote in my book Incognito, And this
Speaker 1: took place in nineteen forty nine. A guy named Arthur
Speaker 1: Alberts traveled from his home in New York to villages
Speaker 1: between the Gold Coast and Timbuktoo in West Africa. And
Speaker 1: he brought his wife, and he brought a camera and
Speaker 1: a jeep, and because of his love for music, he
Speaker 1: brought a tape recorder. Now he wanted to open the
Speaker 1: ears of the Western world. So what he did was
Speaker 1: record some of the most important music to ever come
Speaker 1: out of Africa. But Alberts ran into social troubles while
Speaker 1: he was using this tape recorder because none of the
Speaker 1: natives had ever seen anything even vaguely like this before.
Speaker 1: So one native heard his voice played back to him
Speaker 1: and he accused Alberts of quote stealing his tongue. And
Speaker 1: according to the biography, Albert's only narrowly averted being pummeled
Speaker 1: by taking out a mirror and convincing the man that
Speaker 1: his tongue was still intact. So it's not difficult to
Speaker 1: see why the natives found the tape recorder so strange
Speaker 1: and counterintuitive. Just imagine that you had never ever seen
Speaker 1: this technology before. The thing is that a voice seems
Speaker 1: ephemeral and ineffable, right. A voice has no weight. You
Speaker 1: can't hold voice in your hand. A voice just exists
Speaker 1: for a moment. It's totally untouchable, and then it's gone.
Speaker 1: There doesn't seem to be any physical trace. So it
Speaker 1: comes as a surprise that a voice is physical. If
Speaker 1: you build a little machine that's sensitive enough to detect
Speaker 1: tiny compressions of the molecule in the air, you can
Speaker 1: then capture those density changes and reproduce them later. We
Speaker 1: call these little machines microphones, and we reproduce the density
Speaker 1: changes on tape or with zeros and ones, And every
Speaker 1: one of the billions of podcasts and playlists on the
Speaker 1: planet is proudly serving up bags of feathers once thought irretrievable.
Speaker 1: When Alberts played the music, back from the tape recorder.
Speaker 1: One tribesman described the feat as tremendous magic. And so
Speaker 1: it goes with thoughts. What exactly is a thought? It
Speaker 1: doesn't seem to weigh anything. It feels ephemeral and ineffable.
Speaker 1: You wouldn't think that a thought has any shape or
Speaker 1: smell or any sort of physical instantiation. Thoughts seem to
Speaker 1: be a kind of tremendous magic. So it comes as
Speaker 1: a surprise that a thought is physical, just like voice is.
Speaker 1: Thoughts are underpinned by biological stuff. We know this because
Speaker 1: alterations to the brain change the kinds of thoughts we
Speaker 1: can think. In a state of deep sleep, there are
Speaker 1: no thoughts. When the brain transitions into dream sleep, there
Speaker 1: are unbidden, bizarre thoughts. During the day, we enjoy our normal,
Speaker 1: well accepted thoughts, which people enthusiastically modulate by spiking the
Speaker 1: chemical cocktails of the brain with alcohol or narcotics, or
Speaker 1: exercise or coffee. So the state of the physical material
Speaker 1: determines the state of the thoughts, and issues like obsessive
Speaker 1: compulsive disorder or schizophrenia tell us that when certain networks
Speaker 1: in the brain become overactive or miscalibrated, the character of
Speaker 1: thinking changes. It's this kind of thing that tells us
Speaker 1: that the physical stuff is irreversible, tied to the thinking.
Speaker 1: And we know this also because when people get even
Speaker 1: small bits of brain damage, let's say, because of a
Speaker 1: stroke or a tumor, that can change their capacity to
Speaker 1: understand music, or name animals or see colors, or judge risk,
Speaker 1: or make decisions, or read signals from their bodies, or
Speaker 1: understand the concept of a mirror, or hundreds of other
Speaker 1: changes in thinking that we can witness in the clinics
Speaker 1: every day, and the consequences of injury is a big
Speaker 1: part of how brain science has mapped out the general
Speaker 1: blueprints of the brain. So the bottom line lesson which
Speaker 1: has emerged over centuries is that our internal thoughts about
Speaker 1: hopes or fears or desires, they all emerge from this
Speaker 1: strange three pound organ and when the brain changes, so
Speaker 1: do our thoughts. So although it's easy to intuit that
Speaker 1: thoughts don't have a physical basis, that there are something
Speaker 1: like feathers on the wind, they in fact depend directly
Speaker 1: on what's happening in this small, enigmatic mission control center
Speaker 1: locked in the silent vault of the skull. So what
Speaker 1: is a thought. It's the result of billions of neurons
Speaker 1: firing and coordinated patterns. As we've talked about in other episodes,
Speaker 1: the neurons communicate using electrical impulses and chemical signals, and
Speaker 1: they form vast networks that operate together, such that at
Speaker 1: any moment you have some millions of neurons doing something coordinated,
Speaker 1: and in the next moment it's a different collection of
Speaker 1: neurons that are working together. Now, it may not surprise
Speaker 1: you to know that a thought is not located in
Speaker 1: one place in the brain. It's an emergent property. It's
Speaker 1: a collaboration between these millions or billions of neurons. When
Speaker 1: you have a thought, it's like a symphony playing inside
Speaker 1: your head. Every neuron involved is an instrument in the orchestra,
Speaker 1: and no single part can create the music by itself.
Speaker 1: So we're gonna come back to the brain in a moment,
Speaker 1: but before we do, I want us to really zoom
Speaker 1: in on the subjective experience. How would you describe the
Speaker 1: experience of a thought. When you try to capture what
Speaker 1: a thought is, the most commonplace to go is your
Speaker 1: inner monologue. This is the voice in your head that
Speaker 1: you use to problem solve, or criticize, or plan or reflect.
Speaker 1: So take just a second to pay attention to the
Speaker 1: voice inside your head, that constant stream of chatter. Now
Speaker 1: you might think, what voice inside my head? That's the voice? Now.
Speaker 1: Your internal voice can involve deliberate problem solving, like what
Speaker 1: should I do next here? Or it can involve involuntary
Speaker 1: commentary like oh so stupid to me, why did I
Speaker 1: do that? Or it can be whole imagined conversations like Okay,
Speaker 1: I say this, and then she says that, and then
Speaker 1: I respond like this. It can be helpful for things
Speaker 1: like working memory. So for example, you're trying to log
Speaker 1: into a website and you get texted some six digit
Speaker 1: pass code, and you need to remember that code while
Speaker 1: you switch windows, So you internally say the numbers over
Speaker 1: and over. So you're using the internal voice to keep
Speaker 1: the information in mind as part of your working memory.
Speaker 1: There's so many places where the internal voice comes in.
Speaker 1: We tend to talk to ourselves when we're planning something,
Speaker 1: when we're weighing options. The internal dialogue seems to be
Speaker 1: really helpful in simulating different scenarios. So you're running your
Speaker 1: internal voice all the time and subjectively, it seems to
Speaker 1: be a mental space that can seem almost as vivid
Speaker 1: as external speech. It follows all the rules of grammar
Speaker 1: and syntax, and it can be emotionally laden with encouragement
Speaker 1: or or anywhere in between. Now, how does this happen?
Speaker 1: How can you generate a voice internally and hear it well?
Speaker 1: When we eavesdrop on the brain, let's say, using brain
Speaker 1: imaging like fMRI, what we find is a network of
Speaker 1: areas involved in speech production, like Broca's area, which is
Speaker 1: a key region involved in talking out loud. And we
Speaker 1: find areas involved in language comprehension like Wernicke's area and
Speaker 1: the auditory cortex more generally, as though you're listening to
Speaker 1: spoken language from somebody else talking. And also what we
Speaker 1: see is a network that we summarizes the default mode network,
Speaker 1: and this is a network that becomes active when you're
Speaker 1: not focused on monitoring the outside world, but instead when
Speaker 1: you think about yourself, where you daydream, or you reflect
Speaker 1: on your past, or you imagine your future. So all
Speaker 1: these networks are cranked up when you're talking to yourself.
Speaker 1: And one really important point when you're generating your own
Speaker 1: speech is that you have something called corollary discharge, which
Speaker 1: just means that when your brain generates internal speech, it
Speaker 1: sends a copy of what it's doing to other parts
Speaker 1: of the brain to let them know this is coming.
Speaker 1: I'm the one who did this. That's how the rest
Speaker 1: of the brain knows that the inner voice is self
Speaker 1: generated instead of confusing it with external speech. As a
Speaker 1: side note, if you're a regular listener to this podcast,
Speaker 1: you know that I've been publishing on the topic of
Speaker 1: schizophrenia for many years, and my hypothesis is that auditory
Speaker 1: hallucinations in schizophrenia might have to do with a miscalibration
Speaker 1: of the timing of signals, such that the internal voice
Speaker 1: gets misinterpreted as someone else's voice. In other words, when
Speaker 1: you're talking to yourself under normal conditions, you generate the voice,
Speaker 1: then you hear the voice, and the corollary discharge tells
Speaker 1: you that it was your own. But if there's something
Speaker 1: wrong with the timing of the corollary discharge, then it
Speaker 1: doesn't seem like you're the one who generated the voice,
Speaker 1: and you have to attribute the voice to someone else.
Speaker 1: The internal voice feels like it must be external. If
Speaker 1: you're interested in more on this, hypothesis about schizophrenia. Check
Speaker 1: out episodes thirty three and forty four. Okay, so back
Speaker 1: to the internal voice, which in normal circumstances we understand
Speaker 1: as our voice in our heads. Here's my question, is
Speaker 1: this inner monologue really the main way that we think?
Speaker 1: What if some of our thoughts don't come with words
Speaker 1: at all? So that's the question that psychologist Russell Hurlbert
Speaker 1: set out to answer with a set of experiments in
Speaker 1: the nineteen nineties. And here's how it works. Imagine that
Speaker 1: you are given a beeper that beeps off at random
Speaker 1: times during your day, and the instant it beeps, your
Speaker 1: job is to write down whatever was just in your mind. Beep,
Speaker 1: what are you thinking about right now? So when Hurlbert
Speaker 1: analyzed the data, he found that only about twenty six
Speaker 1: percent of people's thoughts were verbal, meaning that they involved
Speaker 1: actual words or inner speech. The other seventy four percent
Speaker 1: completely nonverbal. So what does nonverbal thought mean? Well, when
Speaker 1: your thoughts are suddenly probed, lots of people find that
Speaker 1: they were just thinking about, for example, vivid mental images
Speaker 1: like picturing a beach or remembering somebody's face, or thinking
Speaker 1: about some moment they just saw at the restaurant, and
Speaker 1: that's all their thought was at that moment. It was visual.
Speaker 1: There were no words involved, just pictures. So what's go
Speaker 1: going on in the brain when you have these kind
Speaker 1: of vivid mental images. Well, if I were to ask
Speaker 1: you to think about a Siberian tiger, your prefrontal cortex
Speaker 1: right behind the forehead takes on the task and starts
Speaker 1: broadcasting to see who can fulfill the request. So your
Speaker 1: memory systems chug into place to determine what a Siberian
Speaker 1: tiger is, combining all the different examples of Siberian tigers
Speaker 1: that you've seen before, and your visual cortex is recruited
Speaker 1: to generate a picture. Your emotion centers might even contribute,
Speaker 1: shading this thought with feelings of alertness or awe or fear.
Speaker 1: So when you think about that Siberian tiger, hundreds of
Speaker 1: millions of neurons across different areas of your brain are
Speaker 1: lighting up, working together to create something that feels whole
Speaker 1: and immediate. And of course, if you're a musician and
Speaker 1: the pager beeps, you might find that you're thinking about
Speaker 1: something auditory. You're thinking about which notes would sound great.
Speaker 1: Right after this transition from this cord to this court.
Speaker 1: But there's no words involved in that. And in the
Speaker 1: brain we can measure activity in your auditory cortex while
Speaker 1: you're doing that, And if you're a perfumer, you might
Speaker 1: be doing smell imagery. You're thinking about the way that
Speaker 1: this other perfume smell than how you're trying to get
Speaker 1: a little closer to that. But as you are internally smelling,
Speaker 1: there are no words associated with that. It's just olfactory imagery.
Speaker 1: And this sort of sensory thinking can come in all
Speaker 1: kinds of flavors, like feeling the warmth from the sun
Speaker 1: on your face or the tightness of your chest during stress.
Speaker 1: So that's what Hurlbert found people were thinking about quite
Speaker 1: often when you probe them at random, sensory imagery without language.
Speaker 1: But that was just the beginning. The kind of thoughts
Speaker 1: that people were thing went beyond just sensory imagery. Lots
Speaker 1: of other times people described they were thinking about how
Speaker 1: to do something physical, like how to position their hands
Speaker 1: for reaching into the oven, or how to remove the
Speaker 1: cover off the printer, or how far to turn the
Speaker 1: steering wheel to get their car into the parking spot.
Speaker 1: But they were thinking about how to do these moves,
Speaker 1: and there were no words involved. It was a physical
Speaker 1: activity they were simulating. This is called motoric imagery. Their
Speaker 1: brains were thinking their way through something. And other thoughts
Speaker 1: are even more difficult to pin down than imagining senses
Speaker 1: or imagining movement because they're more abstract, like a vague
Speaker 1: sense of unease with no clear words or pictures attached.
Speaker 1: So thoughts come in many flavors, and I'll just make
Speaker 1: a thirty second side note here about whether it makes
Speaker 1: sense to call the activity in the unconscious brain think.
Speaker 1: For example, you're trying to remember the name of that
Speaker 1: song and it's on the tip of your tongue, but
Speaker 1: you just can't remember it. And then hours later, when
Speaker 1: you're not even thinking about it, the answer suddenly pops
Speaker 1: into your mind. Your unconscious mind has been working on
Speaker 1: it in the background, even though you had no awareness
Speaker 1: of it. So should we call that thinking even when
Speaker 1: it happens unconsciously. Just for the purposes of having a
Speaker 1: clear definition, it's probably going to make the most sense
Speaker 1: to call that something like processing, and will reserve the
Speaker 1: word thought for the conscious conclusion of that behind the
Speaker 1: scenes activity, so at least for the moment I'm not
Speaker 1: going to call the unconscious activity thought. So this simple
Speaker 1: experiment of pinging people at random to ask them what
Speaker 1: they're thinking, what's in their minds at this exact moment,
Speaker 1: This experiment tells us something important, which is that thinking
Speaker 1: is not just talking to ourselves. It's broader than that.
Speaker 1: We have different kinds of thoughts in different formats. We
Speaker 1: have inner speech, but we also have mental imagery, like
Speaker 1: when you're visualizing what your kitchen reed design could look like,
Speaker 1: and you have abstract thinking like when you're contemplating infinity
Speaker 1: or justice or love. And possibly there are still other
Speaker 1: things which could fall under the umbrella of thought. So
Speaker 1: thinking is a rich, multi dimensional experience. Okay, so here's
Speaker 1: where we are. So far. We talked about the internal
Speaker 1: voice and visualization and imagining sound or smell or bodily feelings,
Speaker 1: and imagining motor movement, and even abstract sorts of thoughts.
Speaker 1: But if you've been listening to these episodes for a while,
Speaker 1: you know that I'm obsessed with the difference between people's
Speaker 1: internal experiences and thinking is no exception. When we look
Speaker 1: at the diversity of thought, some people seem to lean
Speaker 1: more towards verbal thinking, they talk things out in their heads.
Speaker 1: Others are visual things, seeing vivid mental images as their
Speaker 1: primary mode of thinking. And some people experience thoughts more
Speaker 1: like abstract concepts without the voice or the images. And
Speaker 1: this goes hand in hand with something I've talked about
Speaker 1: in many episodes, which is that, as far as we
Speaker 1: can tell, subjective experiences exist on a spectrum. So let's
Speaker 1: zoom in on the inner voice. Some people report having
Speaker 1: constant chatter in their heads, while other people have little
Speaker 1: or no inner verbalization. That's called an endophasia no internal voice.
Speaker 1: As an example, when it comes to the inner monologue,
Speaker 1: my wife's internal radio is very loud, she says, she's
Speaker 1: always hearing it at full volume. For me, it happens
Speaker 1: to be pretty quiet most of the time. I'm going
Speaker 1: to link some papers in the show notes about studies
Speaker 1: on the variation of the internal voice. And when it
Speaker 1: comes to visualization, I've talked in other episodes about this,
Speaker 1: from a fantasia to hyperfantasia. In other words, the spread
Speaker 1: from not really picturing anything visually in your mind to
Speaker 1: having very rich, colorful, movie like visualizations, and everyone is
Speaker 1: somewhere along that spectrum. Now we haven't really measured this yet,
Speaker 1: But when it comes to more subtle issues of abstract thinking,
Speaker 1: like contemplating infinity or justice or love, it may be
Speaker 1: that people are having very different experiences of how strongly
Speaker 1: or intensely they're feeling that. Now, it's a little difficult
Speaker 1: to design an experiment to probe this, because it's purely
Speaker 1: an issue of somebody's subjective report, and it's not always
Speaker 1: easy to know if people are reporting accurately. But if
Speaker 1: this subjective experience of abstract thought is like everything else
Speaker 1: we've measured so far, it is surely going to differ
Speaker 1: from person to person. So it seems to me there's
Speaker 1: probably massive of divergence in what we mean from person
Speaker 1: to person when we talk about the experience of thought.
Speaker 1: If we can only know what the experience is inside
Speaker 1: another head, we might suddenly understand why Susan immediately sees
Speaker 1: the solution to the math problem, and why Amy keeps
Speaker 1: in mind so well what everyone else's emotion is, and
Speaker 1: why Steve is so interested in fixing broken radios, and
Speaker 1: why Tim spends all his intellectual efforts figuring out how
Speaker 1: to get other people to do work for him, and
Speaker 1: so on with the differences between every person you know,
Speaker 1: and by the way this diversity in the inner experience,
Speaker 1: this has real world implications. So just think about how
Speaker 1: people learn or solve problems. Schools and workplaces often prioritize
Speaker 1: verbal reasoning. But what if somebody's thoughts arrive more like
Speaker 1: pictures or more like physical sensations. What if their best
Speaker 1: ideas can't be put into words immediately? I think as
Speaker 1: we bring the individual differences in thinking into focus, we'll
Speaker 1: be able to increasingly build education to take advantage of
Speaker 1: the full spectrum of human cognition and understanding this diversity
Speaker 1: of thought. This also has implications for mental health. Verbal thoughts,
Speaker 1: for example, are strongly linked to rumination, which is the
Speaker 1: endless loops of self talk that fuel anxiety or depression.
Speaker 1: And meanwhile, nonverbal sensations like a tight chest or a
Speaker 1: racing heart, these are the things that dominate panic attacks.
Speaker 1: So really understanding how differently people think and how to
Speaker 1: measure that could help us to manage these mental states
Speaker 1: more effectively. Okay, so we've been talking about our private
Speaker 1: internal experience of thoughts, but we still have a nailed
Speaker 1: down what a thought is exactly and what could this
Speaker 1: possibly have to do with a c squirt finding its home,
Speaker 1: So let's start there. The sea squirt is a small
Speaker 1: marine creature that begins life as a free swimming larva.
Speaker 1: It has a little brain and a nervous system that
Speaker 1: helps it navigate and search for a suitable place to settle. Now,
Speaker 1: once it finds its permanent spot, it attaches itself to
Speaker 1: a surface like a barnacle, and then it undergoes a
Speaker 1: dramatic transformation because in this phase, once it's docked, it
Speaker 1: no longer needs its brain for movement or navigation, so
Speaker 1: it eats its brain for nutrition. It digests its own brain,
Speaker 1: and it uses that as nutrients for other bodily functions.
Speaker 1: So this illustrates two things. First, how incredible it is
Speaker 1: that some organisms can radically adapt their anatomy to fit
Speaker 1: their new role. But more importantly, for today's purpose, the
Speaker 1: main lesson from the sea squirt is that you only
Speaker 1: need a brain for one purpose, and that is to move.
Speaker 1: If you've stopped moving, a brain serves only as a
Speaker 1: little snack for nutrition, and that's an idea that's been
Speaker 1: floating around in neuroscience for well over a century. The
Speaker 1: reason for the brain's evolution is movement control. The need
Speaker 1: to move and interact with the environment is the driving
Speaker 1: force behind the development of the nervous system. In other words,
Speaker 1: brains exist for one purpose, and that is to get around.
Speaker 1: So now let's return to thinking. The big idea for
Speaker 1: today is that thinking is like a physical movement. You're
Speaker 1: moving stuff around on the inside, but nothing on the outside.
Speaker 1: You are moving concepts instead of limbs. In other words,
Speaker 1: thinking is simply an outgrowth of the same brain mechanisms
Speaker 1: that govern moving. This idea reach way back into the
Speaker 1: scientific literature, but the most complete version of the argument
Speaker 1: that I know comes from the neuroscientist Rudolfo Ginas in
Speaker 1: his book called Eye of the Vortex. The key is
Speaker 1: that to get good at movements, your brain works to
Speaker 1: predict the outcome of possible actions. So as brains grew
Speaker 1: more sophisticated, they could run simulations that didn't necessarily result
Speaker 1: in overt behavior. So the brain generates predictions about the environment,
Speaker 1: and then it tries things out and it adjusts things
Speaker 1: based on the feedback, and that's how it refines future predictions.
Speaker 1: The key idea is that this predictive function of the
Speaker 1: brain eventually extended into the realm of cognition. So a
Speaker 1: thought is like an internalized movement simulations of possible actions
Speaker 1: or scenarios that don't necessarily result in overt behavior. When
Speaker 1: we think, the brain is doing a kind of mental rehearsal,
Speaker 1: like motor planning. It generates and navigates through thoughts by
Speaker 1: simulating potential outcomes, but all without the body physically moving,
Speaker 1: just the way that athletes mentally practice movements before performing them.
Speaker 1: In other words, thought can be viewed as the brain's
Speaker 1: way of moving through abstract mental landscapes, just as it
Speaker 1: would move through physical space. And what this means is
Speaker 1: that the mind is inseparable from the body's motor control systems.
Speaker 1: And I just want to note that this framework has
Speaker 1: far reaching implications for how we understand brains and brain disorders,
Speaker 1: because conditions that affect movement, like Parkinson's disease or motor
Speaker 1: neuron disease, might also give us insights into disorders of
Speaker 1: thought and consciousness and things that we lump into cognitive
Speaker 1: disorders like schizophrenia or obsessive compulsive disorder. These could perhaps
Speaker 1: be viewed through the lens of disrupted internal movements, the
Speaker 1: way to understand all of this is that the brain
Speaker 1: is loopy. Very primitive brains have inputs that lead to outputs,
Speaker 1: but our brains became more sophisticated such that you find
Speaker 1: all kinds of internal loops. One piece of brain anatomy
Speaker 1: worth mentioning here is a structure deep inside the brain
Speaker 1: called the thalamus. All the inputs and outputs of the
Speaker 1: brain stop in the thalamus like a trainway station, and
Speaker 1: what you get are these very sophisticated loops called the
Speaker 1: lamo cortical loops, which allows information to move around internally
Speaker 1: as though things are moving in the world, but without
Speaker 1: actually moving them. In this way, instead of the brain
Speaker 1: generating a movement and it happens right away, instead the
Speaker 1: brain can run a simulation internally to see what would
Speaker 1: be predicted to happen if the movement were to be made,
Speaker 1: and then eventually the simulations can be not just about
Speaker 1: pushing this button or lifting this coffee cup, but more abstract,
Speaker 1: like what would it be like if I got that
Speaker 1: job promotion, or how should I break this news to
Speaker 1: my friend? Or what is the optimal path to build
Speaker 1: a society for peace and justice? Now, with new data
Speaker 1: about the brain. We can go even deeper to see
Speaker 1: how this would work. For example, in a recent episode,
Speaker 1: I talked with neuroscientist Jeff Hawkins on his theory about
Speaker 1: cortical columns. Think of cortical columns like little rice grain
Speaker 1: sized units that are all packed together in the cortex,
Speaker 1: and you have hundreds of thousands of them, and each
Speaker 1: one takes care of little overlapping aspects of the world,
Speaker 1: and together they communicate and collaborate to build a larger
Speaker 1: internal model of the world. So here's a clip from
Speaker 1: that interview which I didn't include in the original cut,
Speaker 1: on the topic of what the columns are coding for.
Speaker 1: And Jeff points out that the cells that you find
Speaker 1: in mammals called grid cells, seem to be coding for
Speaker 1: two dimensional space, but they can also code for three
Speaker 1: dimensional space. And once you have these mechanisms for coding
Speaker 1: for movement in space, maybe those cells can do something more.
Speaker 1: Here's Jeff.
Speaker 2: It looks like the neurons. It's a speculative, but it
Speaker 2: looks like the neurons can learn whatever is the proper
Speaker 2: space for a particular problem. Yeah, so math may have
Speaker 2: a different sort of space than what you learn for
Speaker 2: cups and it could be n dimensional. It's a little
Speaker 2: hard to think about this.
Speaker 1: But here's the way that we maybe can think about
Speaker 1: this is people have done this in VR, where they
Speaker 1: put people in let's say a four dimensional world, so
Speaker 1: it doesn't follow the normal three You know, if I
Speaker 1: go to the right and the right and the right again,
Speaker 1: I'm not gonna end up in the same space. I
Speaker 1: end up in a different space. And people are quite
Speaker 1: good at learning know exactly this is not that hard
Speaker 1: for them.
Speaker 2: Initially it's very disoriented.
Speaker 1: Exactly right exactly, but they are able to learn it,
Speaker 1: which is consistent with your idea. If I understanding that
Speaker 1: the neurons are flexible about which dimension.
Speaker 2: The neurals don't know what they're representing. They don't know
Speaker 2: what where they're getting input from. They don't know what
Speaker 2: the input represents. It's just some pattern that's coming in
Speaker 2: from something that's moving, and in the movement could be
Speaker 2: can be expressed as a set of one dimensional vectors,
Speaker 2: and you're some intersection of those. So we could learn anything.
Speaker 2: It could learn fourth dimensional space. Now I would think
Speaker 2: it would be hard to learn these things because you
Speaker 2: have to practice a lot, but this is why a
Speaker 2: mathematician might be really good and a non mathematician look
Speaker 2: at some math and say this is all gobbledgook to me.
Speaker 2: I can't And a mathematicians look at ah, these are
Speaker 2: like friends. These numbers are friends, these equations are friends.
Speaker 2: I know where they are, I know the relationship. I
Speaker 2: know how to move from here to here. I know
Speaker 2: what action I have to take to get this equation
Speaker 2: to look like that equation. And so they've developed this
Speaker 2: sort of movement centro motor space for mathematics that if
Speaker 2: you haven't spent years doing it, it's like mystery, just goblbook, right.
Speaker 1: So it takes.
Speaker 2: Time, and I certainly think we would be we would
Speaker 2: be really in trouble if all of our dimensional reference
Speaker 2: names and their brain changed over night, because nothing would
Speaker 2: make any sense. So but you could take some and
Speaker 2: movement of certain different directions. So a lot of practice
Speaker 2: you could become a mathematician potentially, or another lot of
Speaker 2: practice you might be good at whatever it is, you know,
Speaker 2: understanding computer code, which is a totally different set of problems.
Speaker 1: That's a really it's a really cool answer to that,
Speaker 1: because one would think we have a three dimensional reference
Speaker 1: frame because that's the physical world we live in. But
Speaker 1: your point is these norms are actually flexible enough that
Speaker 1: you could get higher dimensionality when useful.
Speaker 2: Right, it looks like we look at evolutionary point of view,
Speaker 2: The first reference ang you needed were two dimensional, right,
Speaker 2: if you're moving on the surface of the of the
Speaker 2: of the ground, or you're moving along the floor the floor, right.
Speaker 2: And so these early reference systems, the grid cells and
Speaker 2: the play cells, and the ant Ronald cortex and the hippocampus,
Speaker 2: they seem to be predominantly two dimensional. And one could
Speaker 2: argue back a little bit, argue that that makes sense
Speaker 2: because that's the older system, that's what animals had to
Speaker 2: start with. And maybe what happened was in the neocortex
Speaker 2: they generalized the system right. Right, So it's so that
Speaker 2: it looks like the grid cells and the ant hinod
Speaker 2: projects can represent three D structure because bats can do it.
Speaker 2: But there's really wonky, there's all this research trying to
Speaker 2: figure out what's going on. They don't really inderstand it.
Speaker 2: But it's clearly two dimensional. But it's possible that in
Speaker 2: the cortext it says, okay, we can rempresent any dimensionality
Speaker 2: we've generalized this thing now beyond just navigating on the
Speaker 2: ocean floor on the Earth, And maybe first I had
Speaker 2: to do for flying or climbing in trees, but now
Speaker 2: humans could do it for math and that history, and
Speaker 2: you know, we can build reference frames for everything.
Speaker 1: So that was my interview with Jeff Hawkins from a
Speaker 1: couple of months ago, and I include that to illustrate
Speaker 1: the degree to which different scientists are scratching at different
Speaker 1: versions of this idea that brains evolve to move through space.
Speaker 1: But once you've got that solved, the mechanisms can generalize
Speaker 1: to represent higher order concepts. So let's wrap today's episode.
Speaker 1: We saw two main lessons. The first is that thoughts
Speaker 1: are much more than words. Thinking comes in many formats,
Speaker 1: and the second is that to the brain, thinking may
Speaker 1: be just like moving, but it's internal moving through a
Speaker 1: cognitive landscape. In other words, the brain's capacity to control
Speaker 1: the body extends to its ability to simulate and navigate
Speaker 1: mental spaces. Through this lens, thinking is mental motion, and
Speaker 1: consciousness arises as the brain's continuous orchestration of movements both
Speaker 1: real and imagined. Understanding how we think can enrich how
Speaker 1: we see ourselves. So here's a challenge. Spend today paying
Speaker 1: attention to your thoughts. Notice how often they're verbal, or visual,
Speaker 1: or emotional or something else entirely. If you get a chance,
Speaker 1: download an app that randomly beeps your phone throughout the
Speaker 1: day and jot down exactly what you were thinking. What
Speaker 1: were you thinking about right then? Was it words? Was
Speaker 1: it a feeling, a picture, something else. Our thoughts aren't
Speaker 1: always what we naively expect, and if most of our
Speaker 1: thoughts don't come in words, what does that say about
Speaker 1: who we are? How much of your identity is tied
Speaker 1: to the words in your head, and how much of
Speaker 1: it lies in the massive nonverbal undercurrents of your mind.
Speaker 1: Go to Eagleman dot com slash podcast for more information
Speaker 1: and to find further reading. Send me an email at
Speaker 1: podcasts at eagleman dot com with questions or discussion, and
Speaker 1: check out and subscribe to Inner Cosmos on YouTube for
Speaker 1: videos of each episode and to leave comments until next time.
Speaker 1: I'm David Eagleman, and this is Inner Cosmos.