Ep85 "What is a Thought?"

Brains bear thoughts like a peach tree bears peaches. Even for meditators it's almost impossible to stop the firehose of words and images and ideas. But what in the world is a thought, physically? How can you hear a voice in your head when there's no one speaking in the outside world? And what does any of this have to do with a small marine animal who eats its own brain? Join Eagleman for this week's deep dive into our inner life.

Episode Transcript

Speaker 1 (00:05):
What is a thought? Is it something physical? How can
you hear a voice in your head? And whose voice
is it anyway? And what does this have to do
with a small marine animal who eats its own brain.
Welcome to Intercosmos with me, David Eagleman. I'm a neuroscientist

(00:27):
and an author at Stanford and in these episodes we
sail deeply into our three pound universe to understand some
of the most surprising aspects of our lives. Today's episode

(00:47):
is about thoughts. We have them constantly, even for the
best meditators. It's difficult or impossible to stop the fire
hose of words and images and ideas. We all talk
about our thoughts. We sometimes act on our thoughts, we
draw them with little thought bubbles and cartoons. But what

(01:08):
in the world is a thought physically? So many years ago,
a person at a party begged me to watch the
movie called The Secret. So I watched it for fifteen minutes,
and I regret to say that I will never get
those fifteen minutes back. And I knew that this was
the pinnacle of moronic when the first guy states quote,

(01:30):
what most people don't understand is a thought has a frequency.
Every thought has a frequency we can measure a thought,
and so if you're thinking that thought over and over again,
you're emitting that frequency on a consistent basis. And then
the next Schremndrick says, thoughts are sending out that magnetic

(01:51):
signal that is drawing the parallel back to you. That's
the signal you're putting out into the universe. And then
a third genius says, it has now been proven scientifically
that an affirmative thought is hundreds of times more powerful
than a negative thought. And every time someone thinks a
thought in this movie, the graphics show the person having

(02:14):
a thinking expression on their face, and then an energy
wave bursts from their head, and then it cuts to
a wide shot of the planet and you see this
energy wave transmit across the universe. Now, the most striking
thing about these statements in the movie is not simply
that they are incorrect. To me, the shocking thing was

(02:35):
how these guys looked right at the camera and asserted
them as though these were not just completely made up,
and then they used phrases like it has been scientifically proven.
So in a few weeks, I'm going to do an
episode about how we judge the value of any scientific
idea and what it would mean to even say that

(02:56):
something is scientifically proven. But I'm going to bite my
tongue for now put that aside, because for today's episode,
what I really care about is what really is a thought.
So to set the table for this, I'm going to
put thoughts aside for a second and tell a story
that I originally wrote in my book Incognito, And this

(03:19):
took place in nineteen forty nine. A guy named Arthur
Alberts traveled from his home in New York to villages
between the Gold Coast and Timbuktoo in West Africa. And
he brought his wife, and he brought a camera and
a jeep, and because of his love for music, he
brought a tape recorder. Now he wanted to open the

(03:40):
ears of the Western world. So what he did was
record some of the most important music to ever come
out of Africa. But Alberts ran into social troubles while
he was using this tape recorder because none of the
natives had ever seen anything even vaguely like this before.
So one native heard his voice played back to him,

(04:04):
and he accused Alberts of quote stealing his tongue and
According to the biography, Albert's only narrowly averted being pummeled
by taking out a mirror and convincing the man that
his tongue was still intact. So it's not difficult to
see why the natives found the tape recorder so strange

(04:25):
and counterintuitive. Just imagine that you had never ever seen
this technology before. The thing is that a voice seems
ephemeral and ineffable, right. A voice has no weight. You
can't hold voice in your hand. A voice just exists
for a moment. It's totally untouchable, and then it's gone.

(04:46):
There doesn't seem to be any physical trace. So it
comes as a surprise that a voice is physical. If
you build a little machine that's sensitive enough to detect
tiny compressions of the molecule in the air, you can
then capture those density changes and reproduce them later. We
call these little machines microphones, and we reproduce the density

(05:10):
changes on tape or with zeros and ones, And every
one of the billions of podcasts and playlists on the
planet is proudly serving up bags of feathers once thought irretrievable.
When Alberts played the music back from the tape recorder.
One tribesman described the feat as tremendous magic. And so

(05:35):
it goes with thoughts. What exactly is a thought? It
doesn't seem to weigh anything. It feels ephemeral and ineffable.
You wouldn't think that a thought has any shape or
smell or any sort of physical instantiation. Thoughts seem to
be a kind of tremendous magic. So it comes as

(05:56):
a surprise that a thought is physical, just like voice is.
Thoughts are underpinned by biological stuff. We know this because
alterations to the brain change the kinds of thoughts we
can think. In a state of deep sleep, there are
no thoughts. When the brain transitions into dream sleep, there

(06:19):
are unbidden, bizarre thoughts. During the day, we enjoy our normal,
well accepted thoughts, which people enthusiastically modulate by spiking the
chemical cocktails of the brain with alcohol or narcotics, or
exercise or coffee. So the state of the physical material
determines the state of the thoughts, and issues like obsessive

(06:43):
compulsive disorder or schizophrenia tell us that when certain networks
in the brain become overactive or miscalibrated, the character of
thinking changes. It's this kind of thing that tells us
that the physical stuff is irreversible, tied to the thinking.
And we know this also because when people get even

(07:04):
small bits of brain damage, let's say, because of a
stroke or a tumor, that can change their capacity to
understand music, or name animals or see colors, or judge risk,
or make decisions, or read signals from their bodies, or
understand the concept of a mirror, or hundreds of other

(07:24):
changes in thinking that we can witness in the clinics
every day, and the consequences of injury is a big
part of how brain science has mapped out the general
blueprints of the brain. So the bottom line lesson which
has emerged over centuries is that our internal thoughts about

(07:45):
hopes or fears or desires, they all emerge from this
strange three pound organ and when the brain changes, so
do our thoughts. So although it's easy to intuit that
thoughts don't have a physical basis, that there are something
like feathers on the wind, they in fact depend directly
on what's happening in this small, enigmatic mission control center

(08:10):
locked in the silent vault of the skull. So what
is a thought. It's the result of billions of neurons
firing and coordinated patterns. As we've talked about in other episodes,
the neurons communicate using electrical impulses and chemical signals, and
they form vast networks that operate together, such that at

(08:32):
any moment you have some millions of neurons doing something coordinated,
and in the next moment it's a different collection of
neurons that are working together. Now, it may not surprise
you to know that a thought is not located in
one place in the brain. It's an emergent property. It's
a collaboration between these millions or billions of neurons. When

(08:54):
you have a thought, it's like a symphony playing inside
your head. Every neuron involved is an instrument in the orchestra,
and no single part can create the music by itself.
So we're gonna come back to the brain in a moment,
but before we do, I want us to really zoom
in on the subjective experience. How would you describe the

(09:16):
experience of a thought. When you try to capture what
a thought is, the most commonplace to go is your
inner monologue. This is the voice in your head that
you use to problem solve or criticize, or plan or reflect.
So take just a second to pay attention to the

(09:37):
voice inside your head, that constant stream of chatter. Now
you might think, what voice inside my head? That's the voice? Now.
Your internal voice can involve deliberate problem solving, like what
should I do next here? Or it can involve involuntary
commentary like oh so stupid to me, why did I

(09:58):
do that? Or it can be whole imagined conversations like Okay,
I say this, and then she says that, and then
I respond like this. It can be helpful for things
like working memory. So for example, you're trying to log
into a website and you get texted some six digit
pass code, and you need to remember that code while
you switch windows, So you internally say the numbers over

(10:21):
and over. So you're using the internal voice to keep
the information in mind as part of your working memory.
There's so many places where the internal voice comes in.
We tend to talk to ourselves when we're planning something,
when we're weighing options. The internal dialogue seems to be
really helpful in simulating different scenarios. So you're running your

(10:43):
internal voice all the time and subjectively, it seems to
be a mental space that can seem almost as vivid
as external speech. It follows all the rules of grammar
and syntax, and it can be emotionally laiden with encouragement
or criticism or anywhere in between. Now, how does this happen?

(11:05):
How can you generate a voice internally and hear it well?
When we eavesdrop on the brain, let's say, using brain
imaging like fMRI, what we find is a network of
areas involved in speech production, like Broca's area, which is
a key region involved in talking out loud. And we

(11:25):
find areas involved in language comprehension like Wernicke's area and
the auditory cortex more generally, as though you're listening to
spoken language from somebody else talking. And also what we
see is a network that we summarize as the default
mode network. And this is a network that becomes active

(11:45):
when you're not focused on monitoring the outside world, but
instead when you think about yourself, where you daydream or
you reflect on your past, or you imagine your future.
So all these networks are cranked up when you're talking
to yourself. And one really important point, when you're generating
your own speech is that you have something called corollary discharge,

(12:06):
which just means that when your brain generates internal speech,
it sends a copy of what it's doing to other
parts of the brain to let them know this is coming.
I'm the one who did this. That's how the rest
of the brain knows that the inner voice is self
generated instead of confusing it with external speech. As a
side note, if you're a regular listener to this podcast,

(12:29):
you know that I've been publishing on the topic of
schizophrenia for many years, and my hypothesis is that auditory
hallucinations in schizophrenia might have to do with a miscalibration
of the timing of signals such that the internal voice
gets misinterpreted as someone else's voice. In other words, when

(12:51):
you're talking to yourself under normal conditions, you generate the voice,
then you hear the voice, and the corollary discharge tells
you that it was your own. But there's something wrong
with the timing of the corollary discharge. Then it doesn't
seem like you're the one who generated the voice, and
you have to attribute the voice to someone else. The
internal voice feels like it must be external. If you're

(13:13):
interested in more on this hypothesis about schizophrenia, check out
episodes thirty three and forty four. Okay, so back to
the internal voice, which in normal circumstances we understand as
our voice in our heads. Here's my question, is this
inner monologue really the main way that we think? What

(13:34):
if some of our thoughts don't come with words at all?
So that's the question that psychologist Russell Hurlbert set out
to answer with a set of experiments in the nineteen nineties.
And here's how it works. Imagine that you are given
a beeper that beeps off at random times during your day,

(13:54):
and the instant a beeps, your job is to write
down whatever was just in your mind. Beep, what are
you thinking about right now? So when Hurlbert analyzed the data,
he found that only about twenty six percent of people's
thoughts were verbal, meaning that they involved actual words or
inner speech. The other seventy four percent completely nonverbal. So

(14:19):
what does nonverbal thought mean? Well, when your thoughts are
suddenly probe, lots of people find that they were just
thinking about, for example, vivid mental images like picturing a
beach or remembering somebody's face, or thinking about some moment
they just saw at the restaurant, and that's all their
thought was at that moment. It was visual. There were

(14:41):
no words involved, just pictures. So what's going on in
the brain when you have these kind of vivid mental images. Well,

(15:05):
if I were to ask you to think about a
Siberian tiger, your prefrontal cortex right behind the forehead takes
on the task and starts broadcasting to see who can
fulfill the request. So your memory systems chug into place
to determine what a Siberian tiger is, combining all the
different examples of Siberian tigers that you've seen before, and

(15:29):
your visual cortex is recruited to generate a picture. Your
emotion centers might even contribute, shading this thought with feelings
of alertness or awe or fear. So when you think
about that Siberian tiger, hundreds of millions of neurons across
different areas of your brain are lighting up, working together

(15:51):
to create something that feels whole and immediate. And of course,
if you're a musician and the pager beeps, you might
find that you're thinking about something auditory. You're thinking about
which notes would sound great. Right after this transition from
this chord to this court. But there's no words involved
in that, and in the brain we can measure activity

(16:13):
in your auditory cortex while you're doing that, And if
you're a perfumer, you might be doing smell imagery. You're
thinking about the way that this other perfume smell than
how you're trying to get a little closer to that.
But as you are internally smelling, there are no words
associated with that. It's just olfactory imagery. And this sort

(16:36):
of sensory thinking can come in all kinds of flavors,
like feeling the warmth from the sun on your face
or the tightness of your chest during stress. So that's
what Hurlbert found people were thinking about quite often when
you probe them at random, sensory imagery without language. But

(16:57):
that was just the beginning. The kind of thoughts that
people were went beyond just sensory imagery. Lots of other
times people described they were thinking about how to do
something physical, like how to position their hands for reaching
into the oven, or how to remove the cover off
the printer, or how far to turn the steering wheel

(17:17):
to get their car into the parking spot. But they
were thinking about how to do these moves, and there
were no words involved. It was a physical activity they
were simulating. This is called motoric imagery. Their brains were
thinking their way through something. And other thoughts are even
more difficult to pin down than imagining senses or imagining

(17:39):
movement because they're more abstract, like a vague sense of
unease with no clear words or pictures attached. So thoughts
come in many flavors, and I'll just make a thirty
second side note here about whether it makes sense to
call the activity in the unconscious brain think. For example,

(18:01):
you're trying to remember the name of that song and
it's on the tip of your tongue, but you just
can't remember it. And then hours later, when you're not
even thinking about it, the answer suddenly pops into your mind.
Your unconscious mind has been working on it in the background,
even though you had no awareness of it. So should
we call that thinking even when it happens unconsciously. Just

(18:25):
for the purposes of having a clear definition, it's probably
going to make the most sense to call that something
like processing, and will reserve the word thought for the
conscious conclusion of that behind the scenes activity, So at
least for the moment, I'm not going to call the
unconscious activity thought. So this simple experiment of pinging people

(18:47):
at random to ask them what they're thinking, what's in
their minds at this exact moment, This experiment tells us
something important, which is that thinking is not just talking
to ourselves. It's broader than that. We have different kinds
of thoughts in different formats. We have inner speech, but
we also have mental imagery, like when you're visualizing what

(19:09):
your kitchen red design could look like, and you have
abstract thinking like when you're contemplating infinity or justice or love.
And possibly there are still other things which could fall
under the umbrella of thought. So thinking is a rich,
multi dimensional experience. Okay, so here's where we are so far.
We talked about the internal voice and visualization and imagining

(19:32):
sound or smell or bodily feelings, and imagining motor movement,
and even abstract sorts of thoughts. But if you've been
listening to these episodes for a while, you know that
I'm obsessed with the difference between people's internal experiences and
thinking is no exception. When we look at the diversity
of thought, some people seem to lean more towards verbal thinking.

(19:55):
They talk things out in their heads. Others are visual things,
seeing vivid mental images as their primary mode of thinking.
And some people experience thoughts more like abstract concepts without
the voice or the images. And this goes hand in
hand with something I've talked about in many episodes, which
is that, as far as we can tell, subjective experiences

(20:19):
exist on a spectrum. So let's zoom in on the
inner voice. Some people report having constant chatter in their heads,
while other people have little or no inner verbalization. That's
called an endophasia no internal voice. As an example, when
it comes to the inner monologue, my wife's internal radio

(20:41):
is very loud, she says, she's always hearing it at
full volume. For me, it happens to be pretty quiet
most of the time. I'm going to link some papers
in the show notes about studies on the variation of
the internal voice. And when it comes to visualization, I've
talked in other episodes about this from a fantasia to hyperfantasia.

(21:03):
In other words, the spread from not really picturing anything
visually in your mind to having very rich, colorful, movie
like visualizations. And everyone is somewhere along that spectrum. Now,
we haven't really measured this yet, but when it comes
to more subtle issues of abstract thinking, like contemplating infinity

(21:24):
or justice or love, it may be that people are
having very different experiences of how strongly or intensely they're
feeling that. Now, it's a little difficult to design an
experiment to probe this, because it's purely an issue of
somebody's subjective report, and it's not always easy to know
if people are reporting accurately. But if this subjective experience

(21:49):
of abstract thought is like everything else we've measured so far,
it is surely going to differ from person to person.
So it seems to me there's probably massive of divergence
in what we mean from person to person when we
talk about the experience of thought. If we can only
know what the experience is inside another head, we might

(22:13):
suddenly understand why Susan immediately sees the solution to the
math problem, and why Amy keeps in mind so well
what everyone else's emotion is, and why Steve is so
interested in fixing broken radios, and why Tim spends all
his intellectual efforts figuring out how to get other people
to do work for him. And so on with the

(22:35):
differences between every person you know. And by the way,
this diversity in the inner experience this has real world implications.
So just think about how people learn or solve problems.
Schools and workplaces often prioritize verbal reasoning. But what if
somebody's thoughts arrive more like pictures or more like physical sensations.

(22:57):
What if their best ideas can't be put in words immediately?
I think as we bring the individual differences in thinking
into focus, we'll be able to increasingly build education to
take advantage of the full spectrum of human cognition and
understanding this diversity of thought. This also has implications for

(23:18):
mental health. Verbal thoughts, for example, are strongly linked to rumination,
which is the endless loops of self talk that fuel
anxiety or depression. And meanwhile, nonverbal sensations like a tight
chest or a racing heart, these are the things that
dominate panic attacks. So really, understanding how differently people think

(23:40):
and how to measure that could help us to manage
these mental states more effectively. Okay, so we've been talking
about our private internal experience of thoughts, but we still
haven't nailed down with a thought is exactly and what
could this possibly have to do with a c squirt
finding its home? So let's start there. The sea squirt

(24:04):
is a small marine creature that begins life as a
free swimming larva. It has a little brain and a
nervous system that helps it navigate and search for a
suitable place to settle. Now, once it finds its permanent spot,
it attaches itself to a surface like a barnacle, and

(24:24):
then it undergoes a dramatic transformation because in this phase,
once it's docked, it no longer needs its brain for
movement or navigation, so it eats its brain for nutrition.
It digests its own brain, and it uses that as
nutrients for other bodily functions. So this illustrates two things. First,

(24:48):
how incredible it is that some organisms can radically adapt
their anatomy to fit their new role. But more importantly,
for today's purpose, the main lesson from the sea squirt
is that you only we need a brain for one purpose,
and that is to move. If you've stopped moving, a
brain serves only as a little snack for nutrition. And

(25:12):
that's an idea that's been floating around in neuroscience for
well over a century. The reason for the brain's evolution
is movement control. The need to move and interact with
the environment is the driving force behind the development of
the nervous system. In other words, brains exist for one purpose,
and that is to get around. So now let's return

(25:34):
to thinking. The big idea for today is that thinking
is like a physical movement. You're moving stuff around on
the inside, but nothing on the outside. You are moving
concepts instead of limbs. In other words, thinking is simply
an outgrowth of the same brain mechanisms that govern moving.

(26:00):
This idea reached way back into the scientific literature, but
the most complete version of the argument that I know
comes from the neuroscientist Rudolfo Ginas in his book called
Eye of the Vortex. The key is that to get
good at movements, your brain works to predict the outcome
of possible actions. So as brains grew more sophisticated, they

(26:20):
could run simulations that didn't necessarily result in overt behavior.
So the brain generates predictions about the environment, and then
it tries things out and it adjusts things based on
the feedback, and that's how it refines future predictions. The
key idea is that this predictive function of the brain

(26:41):
eventually extended into the realm of cognition. So a thought
is like an internalized movement simulations of possible actions or
scenarios that don't necessarily result in overt behavior. When we think,

(27:13):
the brain is doing a kind of mental rehearsal, like
motor planning. It generates and navigates through thoughts by simulating
potential outcomes, but all without the body physically moving, just
the way that athletes mentally practice movements before performing them.
In other words, thought can be viewed as the brain's

(27:36):
way of moving through abstract mental landscapes, just as it
would move through physical space. And what this means is
that the mind is inseparable from the body's motor control systems.
And I just want to note that this framework has
far reaching implications for how we understand brains and brain disorders,

(27:57):
because conditions that affect movement, like Parkinson's disease or motor
neuron disease, might also give us insights into disorders of
thought and consciousness and things that we lump into cognitive
disorders like schizophrenia or obsessive compulsive disorder. These could perhaps
be viewed through the lens of disrupted internal movements. The

(28:22):
way to understand all of this is that the brain
is loopy. Very primitive brains have inputs that lead to outputs,
but our brains became more sophisticated such that you find
all kinds of internal loops. One piece of brain anatomy
worth mentioning here is a structure deep inside the brain
called the thalamus. All the inputs and outputs of the

(28:44):
brain stop in the thalamus like a trainway station, and
what you get are these very sophisticated loops called the
lamo cortical loops, which allows information to move around internally
as though things are moving in the world, but without
actually moving them. In this way, instead of the brain
generating a movement and it happens right away, instead the

(29:07):
brain can run a simulation internally to see what would
be predicted to happen if the movement were to be made,
and then eventually the simulations can be not just about
pushing this button or lifting this coffee cup, but more abstract,
like what would it be like if I got that
job promotion, or how should I break this news to

(29:27):
my friend? Or what is the optimal path to build
a society for peace and justice. Now with new data
about the brain, we can go even deeper to see
how this would work. For example, in a recent episode,
I talked with neuroscientist Jeff Hawkins on his theory about
cortical columns. Think of cortical columns like little rice grain

(29:50):
sized units that are all packed together in the cortex,
and you have hundreds of thousands of them, and each
one takes care of little overlapping aspects the world, and
together they communicate and collaborate to build a larger internal
model of the world. So here's a clip from that
interview which I didn't include in the original cut, on

(30:12):
the topic of what the columns are coding for. And
Jeff points out that the cells that you find in
mammals called grid cells, seem to be coding for two
dimensional space, but they can also code for three dimensional space.
And once you have these mechanisms for coding for movement
in space, maybe those cells can do something more. Here's Jeff.

Speaker 2 (30:41):
It looks like the neurons. It's a speculative, but it
looks like the neurons can learn whatever is the proper
space for a particular problem. Yeah, so math may have
a different sort of space than what you learn for cups,
and it could be n dimensional. It's a little hard
to think about.

Speaker 1 (31:01):
This, but here's the way that we maybe can think
about this is people have done this in VR, where
they put people in let's say a four dimensional world,
so it doesn't follow the normal three You know, if
I go to the right and the right and the
writing again, I'm not gonna end up in the same space.
I end up in a different space. And people are
are quite good at learning exactly this is not that

(31:22):
hard for them.

Speaker 3 (31:23):
Initially it's very disoriented exactly right exactly, but they are
able to learn it, which is consistent with your idea.
If I understanding that the neurons are flexible about which dimension.

Speaker 2 (31:33):
The neurals don't know what they're representing. They don't know
what where they're getting input from. They don't know what
the input represents. It's just some pattern that's coming in
from something that's moving, and in the movement could be
can be expressed as a set of one dimensional vectors,
and you're some intersection of those. So we could learn anything.
It can learn fourth dimensional space. Now, I would think
it would be hard to learn these things because you

(31:55):
have to practice a lot. But this is why a
mathematician might be really good and a non mathematician look
at some math and say this is all gobbledygook to me,
I can't and a mathematicians look at all these are
like friends. These numbers are friends, these equations are friends.
I know where they are, I know the relationship. I
know how to move from here to here. I know
what what action I have to take to get this
equation to look like that equation. And so they've developed
this sort of movement centro motor space for mathematics that

(32:19):
if you haven't spent years doing it, it's like mystery,
just gobblbook, right, So it takes time, and I certainly
think we would be we would be really in trouble
if all of our dimensional reference names and their brain
changed over night, because nothing would make any sense. So
but you could take some and movement of certain different directions.
So a lot of practice you could become a mathematician potentially,

(32:40):
or another lot of practice you might be good at
whatever it is you know, understanding computer code, which is
a totally different set of problems.

Speaker 1 (32:47):
That's a really it's a really cool answer to that,
because one would think we have a three dimensional reference frame,
because that's the physical world we live in. But your
point is these norms are actually flexible enough that you
could get higher dimensionality when useful.

Speaker 2 (33:02):
Right, Well, it looks like you look at evolutionary point
of view, the first references you needed were two dimensional, right,
if you're moving on the surface of the of the
of the ground, or you're moving along the floor to
the floor, right. And so these early reference systems, the
grid cells and the play cells, and the antirhinal cortex
and the hippocampus, they seem to be predominantly two dimensional.

(33:25):
And one could argue back a little bit, argue that
that makes sense because that's the older system, that's what
animals had to start with. And maybe what happened was
in the neocortex they generalized the system right, Right, So
it's so that it looks like the grid cells and
the ant hinod projects can represent three D structure because
bats can do it. But they're truly wonky. There's all

(33:46):
this research trying to figure out what's going on. They
don't really inderstand it. But it's clearly two dimensional. But
it's possible that in the cortext it says, okay, we
can represent any dimensional. We've generalized this thing now beyond
just navigating on the ocean floor on the Earth. And
maybe first I had to do it for flying or
climbing in trees, but now humans could do it for
math and and history, and you know, we can build

(34:09):
reference frames for everything.

Speaker 1 (34:15):
So that was my interview with Jeff Hawkins from a
couple of months ago, and I include that to illustrate
the degree to which different scientists are scratching at different
versions of this idea that brains evolve to move through space.
But once you've got that solved, the mechanisms can generalize
to represent higher order concepts. So let's wrap today's episode.

(34:38):
We saw two main lessons. The first is that thoughts
are much more than words. Thinking comes in many formats,
and the second is that to the brain, thinking may
be just like moving, but it's internal moving through a
cognitive landscape. In other words, the brain's capacity to control

(34:59):
the body extends to its ability to simulate and navigate
mental spaces. Through this lens, thinking is mental motion, and
consciousness arises as the brain's continuous orchestration of movements, both
real and imagined. Understanding how we think can enrich how

(35:20):
we see ourselves. So here's a challenge. Spend today paying
attention to your thoughts. Notice how often they're verbal, or visual,
or emotional or something else entirely. If you get a chance,
download an app that randomly beeps your phone throughout the
day and jot down exactly what you were thinking. What

(35:43):
were you thinking about right then? Was it words? Was
it a feeling, a picture, something else. Our thoughts aren't
always what we naively expect, and if most of our
thoughts don't come in words, what does that say about
who we are? How much of your identity is tied
to the words in your head, and how much of
it lies in the massive nonverbal undercurrents of your mind.

(36:15):
Go to Eagleman dot com slash podcast for more information
and to find further reading. Send me an email at
podcasts at eagleman dot com with questions or discussion, and
check out and subscribe to Inner Cosmos on YouTube for
videos of each episode and to leave comments Until next time.
I'm David Eagleman, and this is inner Cosmos.