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 Eagleman. 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 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 laiden with encouragement
Speaker 1: or criticism 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 summarize as the default
Speaker 1: mode network. And this is a network that becomes active
Speaker 1: when you're not focused on monitoring the outside world, but
Speaker 1: instead when you think about yourself, where you daydream or
Speaker 1: you reflect on your past, or you imagine your future.
Speaker 1: So all these networks are cranked up when you're talking
Speaker 1: to yourself. And one really important point, when you're generating
Speaker 1: your own speech is that you have something called corollary discharge,
Speaker 1: which just means that when your brain generates internal speech,
Speaker 1: it sends a copy of what it's doing to other
Speaker 1: parts 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 there's something wrong
Speaker 1: with the timing of the corollary discharge. Then it doesn't
Speaker 1: seem like you're the one who generated the voice, and
Speaker 1: you have to attribute the voice to someone else. The
Speaker 1: internal voice feels like it must be external. If you're
Speaker 1: interested in more on this hypothesis about schizophrenia, check out
Speaker 1: episodes thirty three and forty four. Okay, so back to
Speaker 1: the internal voice, which in normal circumstances we understand as
Speaker 1: our voice in our heads. Here's my question, is this
Speaker 1: inner monologue really the main way that we think? What
Speaker 1: if some of our thoughts don't come with words at all?
Speaker 1: So that's the question that psychologist Russell Hurlbert set out
Speaker 1: to answer with a set of experiments in the nineteen nineties.
Speaker 1: And here's how it works. Imagine that you are given
Speaker 1: a beeper that beeps off at random times during your day,
Speaker 1: and the instant a beeps, your job is to write
Speaker 1: down whatever was just in your mind. Beep, what are
Speaker 1: you thinking about right now? So when Hurlbert analyzed the data,
Speaker 1: he found that only about twenty six percent of people's
Speaker 1: thoughts were verbal, meaning that they involved actual words or
Speaker 1: inner speech. The other seventy four percent completely nonverbal. So
Speaker 1: what does nonverbal thought mean? Well, when your thoughts are
Speaker 1: suddenly probe, lots of people find that they were just
Speaker 1: thinking about, for example, vivid mental images like picturing a
Speaker 1: beach or remembering somebody's face, or thinking about some moment
Speaker 1: they just saw at the restaurant, and that's all their
Speaker 1: thought was at that moment. It was visual. There were
Speaker 1: no words involved, just pictures. So what's going on in
Speaker 1: the brain when you have these kind of vivid mental images. Well,
Speaker 1: if I were to ask you to think about a
Speaker 1: Siberian tiger, your prefrontal cortex right behind the forehead takes
Speaker 1: on the task and starts broadcasting to see who can
Speaker 1: fulfill the request. So your memory systems chug into place
Speaker 1: to determine what a Siberian tiger is, combining all the
Speaker 1: different examples of Siberian tigers that you've seen before, and
Speaker 1: your visual cortex is recruited to generate a picture. Your
Speaker 1: emotion centers might even contribute, shading this thought with feelings
Speaker 1: of alertness or awe or fear. So when you think
Speaker 1: about that Siberian tiger, hundreds of millions of neurons across
Speaker 1: different areas of your brain are lighting up, working together
Speaker 1: to create something that feels whole and immediate. And of course,
Speaker 1: if you're a musician and the pager beeps, you might
Speaker 1: find that you're thinking about something auditory. You're thinking about
Speaker 1: which notes would sound great. Right after this transition from
Speaker 1: this chord to this court. But there's no words involved
Speaker 1: in that, and in the brain we can measure activity
Speaker 1: in your auditory cortex while you're doing that, And if
Speaker 1: you're a perfumer, you might be doing smell imagery. You're
Speaker 1: thinking about the way that this other perfume smell than
Speaker 1: how you're trying to get a little closer to that.
Speaker 1: But as you are internally smelling, there are no words
Speaker 1: associated with that. It's just olfactory imagery. And this sort
Speaker 1: of sensory thinking can come in all kinds of flavors,
Speaker 1: like feeling the warmth from the sun on your face
Speaker 1: or the tightness of your chest during stress. So that's
Speaker 1: what Hurlbert found people were thinking about quite often when
Speaker 1: you probe them at random, sensory imagery without language. But
Speaker 1: that was just the beginning. The kind of thoughts that
Speaker 1: people were went beyond just sensory imagery. Lots of other
Speaker 1: times people described they were thinking about how to do
Speaker 1: something physical, like how to position their hands for reaching
Speaker 1: into the oven, or how to remove the cover off
Speaker 1: the printer, or how far to turn the steering wheel
Speaker 1: to get their car into the parking spot. But they
Speaker 1: were thinking about how to do these moves, and there
Speaker 1: were no words involved. It was a physical activity they
Speaker 1: were simulating. This is called motoric imagery. Their brains were
Speaker 1: thinking their way through something. And other thoughts are even
Speaker 1: more difficult to pin down than imagining senses or imagining
Speaker 1: movement because they're more abstract, like a vague sense of
Speaker 1: unease with no clear words or pictures attached. So thoughts
Speaker 1: come in many flavors, and I'll just make a thirty
Speaker 1: second side note here about whether it makes sense to
Speaker 1: call the activity in the unconscious brain think. For example,
Speaker 1: you're trying to remember the name of that song and
Speaker 1: it's on the tip of your tongue, but you just
Speaker 1: can't remember it. And then hours later, when you're not
Speaker 1: even thinking about it, the answer suddenly pops into your mind.
Speaker 1: Your unconscious mind has been working on it in the background,
Speaker 1: even though you had no awareness of it. So should
Speaker 1: we call that thinking even when it happens unconsciously. Just
Speaker 1: for the purposes of having a clear definition, it's probably
Speaker 1: going to make the most sense to call that something
Speaker 1: like processing, and will reserve the word thought for the
Speaker 1: conscious conclusion of that behind the scenes activity, So at
Speaker 1: least for the moment, I'm not going to call the
Speaker 1: unconscious activity thought. So this simple experiment of pinging people
Speaker 1: at random to ask them what they're thinking, what's in
Speaker 1: their minds at this exact moment, This experiment tells us
Speaker 1: something important, which is that thinking is not just talking
Speaker 1: to ourselves. It's broader than that. We have different kinds
Speaker 1: of thoughts in different formats. We have inner speech, but
Speaker 1: we also have mental imagery, like when you're visualizing what
Speaker 1: your kitchen red design could look like, and you have
Speaker 1: abstract thinking like when you're contemplating infinity or justice or love.
Speaker 1: And possibly there are still other things which could fall
Speaker 1: under the umbrella of thought. So thinking is a rich,
Speaker 1: multi dimensional experience. Okay, so here's where we are so far.
Speaker 1: We talked about the internal voice and visualization and imagining
Speaker 1: sound or smell or bodily feelings, and imagining motor movement,
Speaker 1: and even abstract sorts of thoughts. But if you've been
Speaker 1: listening to these episodes for a while, you know that
Speaker 1: I'm obsessed with the difference between people's internal experiences and
Speaker 1: thinking is no exception. When we look at the diversity
Speaker 1: of thought, some people seem to lean more towards verbal thinking.
Speaker 1: They talk things out in their heads. Others are visual things,
Speaker 1: seeing vivid mental images as their primary mode of thinking.
Speaker 1: And some people experience thoughts more like abstract concepts without
Speaker 1: the voice or the images. And this goes hand in
Speaker 1: hand with something I've talked about in many episodes, which
Speaker 1: is that, as far as we can tell, subjective experiences
Speaker 1: exist on a spectrum. So let's zoom in on the
Speaker 1: inner voice. Some people report having constant chatter in their heads,
Speaker 1: while other people have little or no inner verbalization. That's
Speaker 1: called an endophasia no internal voice. As an example, when
Speaker 1: it comes to the inner monologue, my wife's internal radio
Speaker 1: is very loud, she says, she's always hearing it at
Speaker 1: full volume. For me, it happens to be pretty quiet
Speaker 1: most of the time. I'm going to link some papers
Speaker 1: in the show notes about studies on the variation of
Speaker 1: the internal voice. And when it comes to visualization, I've
Speaker 1: talked in other episodes about this from a fantasia to hyperfantasia.
Speaker 1: In other words, the spread from not really picturing anything
Speaker 1: visually in your mind to having very rich, colorful, movie
Speaker 1: like visualizations. And everyone is somewhere along that spectrum. Now,
Speaker 1: we haven't really measured this yet, but when it comes
Speaker 1: to more subtle issues of abstract thinking, like contemplating infinity
Speaker 1: or justice or love, it may be that people are
Speaker 1: having very different experiences of how strongly or intensely they're
Speaker 1: feeling that. Now, it's a little difficult to design an
Speaker 1: experiment to probe this, because it's purely an issue of
Speaker 1: somebody's subjective report, and it's not always easy to know
Speaker 1: if people are reporting accurately. But if this subjective experience
Speaker 1: of abstract thought is like everything else we've measured so far,
Speaker 1: it is surely going to differ from person to person.
Speaker 1: So it seems to me there's probably massive of divergence
Speaker 1: in what we mean from person to person when we
Speaker 1: talk about the experience of thought. If we can only
Speaker 1: know what the experience is inside another head, we might
Speaker 1: suddenly understand why Susan immediately sees the solution to the
Speaker 1: math problem, and why Amy keeps in mind so well
Speaker 1: what everyone else's emotion is, and why Steve is so
Speaker 1: interested in fixing broken radios, and why Tim spends all
Speaker 1: his intellectual efforts figuring out how to get other people
Speaker 1: to do work for him. And so on with the
Speaker 1: differences between every person you know. And by the way,
Speaker 1: this diversity in the inner experience this has real world implications.
Speaker 1: So just think about how people learn or solve problems.
Speaker 1: Schools and workplaces often prioritize verbal reasoning. But what if
Speaker 1: somebody's thoughts arrive more like pictures or more like physical sensations.
Speaker 1: What if their best ideas can't be put in words immediately?
Speaker 1: I think as we bring the individual differences in thinking
Speaker 1: into focus, we'll be able to increasingly build education to
Speaker 1: take advantage of the full spectrum of human cognition and
Speaker 1: understanding this diversity of thought. This also has implications for
Speaker 1: mental health. Verbal thoughts, for example, are strongly linked to rumination,
Speaker 1: which is the endless loops of self talk that fuel
Speaker 1: anxiety or depression. And meanwhile, nonverbal sensations like a tight
Speaker 1: chest or a racing heart, these are the things that
Speaker 1: dominate panic attacks. So really, understanding how differently people think
Speaker 1: and how to measure that could help us to manage
Speaker 1: these mental states more effectively. Okay, so we've been talking
Speaker 1: about our private internal experience of thoughts, but we still
Speaker 1: haven't nailed down with a thought is exactly and what
Speaker 1: could this possibly have to do with a c squirt
Speaker 1: finding its home? So let's start there. The sea squirt
Speaker 1: is a small marine creature that begins life as a
Speaker 1: free swimming larva. It has a little brain and a
Speaker 1: nervous system that helps it navigate and search for a
Speaker 1: suitable place to settle. Now, once it finds its permanent spot,
Speaker 1: it attaches itself to a surface like a barnacle, and
Speaker 1: then it undergoes a dramatic transformation because in this phase,
Speaker 1: once it's docked, it no longer needs its brain for
Speaker 1: movement or navigation, so it eats its brain for nutrition.
Speaker 1: It digests its own brain, and it uses that as
Speaker 1: nutrients for other bodily functions. So this illustrates two things. First,
Speaker 1: how incredible it is that some organisms can radically adapt
Speaker 1: their anatomy to fit their new role. But more importantly,
Speaker 1: for today's purpose, the main lesson from the sea squirt
Speaker 1: is that you only we need a brain for one purpose,
Speaker 1: and that is to move. If you've stopped moving, a
Speaker 1: brain serves only as a little snack for nutrition. And
Speaker 1: that's an idea that's been floating around in neuroscience for
Speaker 1: well over a century. The reason for the brain's evolution
Speaker 1: is movement control. The need to move and interact with
Speaker 1: the environment is the driving force behind the development of
Speaker 1: the nervous system. In other words, brains exist for one purpose,
Speaker 1: and that is to get around. So now let's return
Speaker 1: to thinking. The big idea for today is that thinking
Speaker 1: is like a physical movement. You're moving stuff around on
Speaker 1: the inside, but nothing on the outside. You are moving
Speaker 1: concepts instead of limbs. In other words, thinking is simply
Speaker 1: an outgrowth of the same brain mechanisms that govern moving.
Speaker 1: This idea reached way back into the scientific literature, but
Speaker 1: the most complete version of the argument that I know
Speaker 1: comes from the neuroscientist Rudolfo Ginas in his book called
Speaker 1: Eye of the Vortex. The key is that to get
Speaker 1: good at movements, your brain works to predict the outcome
Speaker 1: of possible actions. So as brains grew more sophisticated, they
Speaker 1: could run simulations that didn't necessarily result in overt behavior.
Speaker 1: So the brain generates predictions about the environment, and then
Speaker 1: it tries things out and it adjusts things based on
Speaker 1: the feedback, and that's how it refines future predictions. The
Speaker 1: key idea is that this predictive function of the brain
Speaker 1: eventually extended into the realm of cognition. So a thought
Speaker 1: is like an internalized movement simulations of possible actions or
Speaker 1: scenarios that don't necessarily result in overt behavior. When we think,
Speaker 1: the brain is doing a kind of mental rehearsal, like
Speaker 1: motor planning. It generates and navigates through thoughts by simulating
Speaker 1: potential outcomes, but all without the body physically moving, just
Speaker 1: 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 the world, and
Speaker 1: together they communicate and collaborate to build a larger internal
Speaker 1: model of the world. So here's a clip from that
Speaker 1: interview which I didn't include in the original cut, on
Speaker 1: the topic of what the columns are coding for. And
Speaker 1: Jeff points out that the cells that you find in
Speaker 1: mammals called grid cells, seem to be coding for two
Speaker 1: dimensional space, but they can also code for three dimensional space.
Speaker 1: And once you have these mechanisms for coding for movement
Speaker 1: in space, maybe those cells can do something more. 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 cups,
Speaker 2: and it could be n dimensional. It's a little hard
Speaker 2: to think about.
Speaker 1: This, but here's the way that we maybe can think
Speaker 1: about this is people have done this in VR, where
Speaker 1: they put people in let's say a four dimensional world,
Speaker 1: so it doesn't follow the normal three You know, if
Speaker 1: I go to the right and the right and the
Speaker 1: writing again, I'm not gonna end up in the same space.
Speaker 1: I end up in a different space. And people are
Speaker 1: are quite good at learning exactly this is not that
Speaker 1: hard for them.
Speaker 3: Initially it's very disoriented exactly right exactly, but they are
Speaker 3: able to learn it, which is consistent with your idea.
Speaker 3: If I understanding that 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 can 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 gobbledygook to me,
Speaker 2: I can't and a mathematicians look at all 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 what action I have to take to get this
Speaker 2: equation to look like that equation. And so they've developed
Speaker 2: this sort of movement centro motor space for mathematics that
Speaker 2: if you haven't spent years doing it, it's like mystery,
Speaker 2: just gobblbook, right, So it takes time, and I certainly
Speaker 2: think we would be we would be really in trouble
Speaker 2: if all of our dimensional reference names and their brain
Speaker 2: changed over night, because nothing would make any sense. So
Speaker 2: but you could take some and movement of certain different directions.
Speaker 2: So a lot of practice you could become a mathematician potentially,
Speaker 2: or another lot of practice you might be good at
Speaker 2: whatever it is you know, understanding computer code, which is
Speaker 2: 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 frame,
Speaker 1: because that's the physical world we live in. But your
Speaker 1: point is these norms are actually flexible enough that you
Speaker 1: could get higher dimensionality when useful.
Speaker 2: Right, Well, it looks like you look at evolutionary point
Speaker 2: of view, the first references 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 to
Speaker 2: the floor, right. And so these early reference systems, the
Speaker 2: grid cells and the play cells, and the antirhinal cortex
Speaker 2: and the hippocampus, they seem to be predominantly two dimensional.
Speaker 2: And one could argue back a little bit, argue that
Speaker 2: that makes sense because that's the older system, that's what
Speaker 2: animals had to start with. And maybe what happened was
Speaker 2: in the neocortex they generalized the system right, Right, So
Speaker 2: it's so that it looks like the grid cells and
Speaker 2: the ant hinod projects can represent three D structure because
Speaker 2: bats can do it. But they're truly wonky. There's all
Speaker 2: this research trying to figure out what's going on. They
Speaker 2: don't really inderstand it. But it's clearly two dimensional. But
Speaker 2: it's possible that in the cortext it says, okay, we
Speaker 2: can represent any dimensional. We've generalized this thing now beyond
Speaker 2: just navigating on the ocean floor on the Earth. And
Speaker 2: maybe first I had to do it for flying or
Speaker 2: climbing in trees, but now humans could do it for
Speaker 2: math and and history, and you know, we can build
Speaker 2: 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.