May 5, 2025 • 39 mins
What would it take to get inside someone else's head, and could new brain technologies ever help us get there? Will there be dream celebrities, in which uploads go viral? What does consciousness feel like from the inside, and why do movies always get this wrong? Why don't you see your own blinks? What would it be like if exactly 1/2 of your brain was numbed to sleep? And what would it be like to become a horse?
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Episode Transcript
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Speaker 1 (00:05):
In the last episode, I tackled the question of whether
we could really know what it's like to be someone else,
as in empathize with them so completely that we actually
really understand what it is to be in their shoes. Today,
we're going to ask could technology help us to get there?
Could we have dreams celebrities in which some people upload
(00:29):
their dreams and other people watch them and a dream
can go viral? How am I going to explain what
consciousness actually feels like through four movies that got it wrong?
Speaker 2 (00:41):
Why don't you see your own blinks?
Speaker 1 (00:44):
What would it be like to numb exactly one half
of your brain with barbituates? And what would it be
like to become a horse? Welcome to Intercosmos with me
David Eagelman. I'm a neuroscientist and author at Stanford and
in these episodes we sail deeply into our three pound
universe to understand why and how our lives look the
(01:07):
way they do. Today's episode is about the question of
whether we can ever really know what it is like
(01:29):
to be someone else. In the last episode, we discussed
why we humans are all so different on the inside
and whether it's possible that the gaps are unbridgable, and
we examine this from the point of view of neuroscience
and philosophy and literature. But today we're going to turn
to the angle of technology. Could new technology ever allow
(01:51):
us to better understand other people? So let's start with
an old movie that I saw back in nineteen ninety five.
The movie is called Strange Days, and it explores the
idea of wearing this special helmet, and the helmet records
the activity in your brain, all of your memories, your feelings,
(02:13):
your thoughts. It records that, and the recorded event is
frozen in time on a data disk. It's like an
MP four file, but one that captures not just audio
and video but everything. And then another person can put
on the helmet and they can experience it all. They
remember your memories, they feel your feelings, they think your
(02:38):
thoughts in that moment. In other words, you can live
a moment in the life of another person, and you
can also live the same moment of your life more
than once. So in the movie, a guy named Lenny
Nero is a former police officer who now works as
a playback artist in Los Angeles and ends up finding
(03:00):
a recording of a woman's last moments alive, and he
becomes involved in a murder investigation, and this leads him
to a group of people who are planning a terrorist attack,
and so he has to use his skills as a
playback artist to stop the attack and save the city. Okay,
but here's the part I want to concentrate on. Could
a helmet like this be possible? Could we get our
(03:24):
neurotechnology to a point where you could record one person's
experience and have a second person live it. And while
we're holding that question, I want to give a related example.
Some years ago, a futurist named Michael Andisimov proposed the
idea of dream celebrities. The idea here was that someday
(03:44):
in the future, presumably using nano robotics, people would be
able to record and upload their dreams and then other
people could watch them. So, could these versions of the
future be possible even though people are so different on
the inside, Could we leverage this imaginary futuristic tech in
(04:05):
this way to know what it is like to be
someone else? Now, I'm not speaking of this just in
terms of empathy, which I talked about in the last episode,
but in terms of uploading the experience of one person
and then downloading it into the head of another. So
let's start today's journey with an idea that I started
chewing on a very long time ago when I was
(04:27):
in graduate school and learned about a medical procedure called
the Wata test WADA. Now, this is something that was
commonly used before brain surgery when the neurosurgeon is trying
to determine which side of the brain, which hemisphere is
responsible for language, because you want to make sure, as
(04:49):
the surgeon, not to damage critical areas involved in speech.
So what you do is inject a sedative, usually sodium
amma barbitol, into one hemisphere of the brain and that
hemisphere essentially goes to sleep for about five or ten minutes,
while the other hemisphere, the other half of your brain,
(05:11):
remains active. And this is what allows the neurosurgeon to
test which side of the brain is dominant for language.
While one half of the brain is anesthetized, the patient
is asked to speak, to count, to name objects, to
follow commands, to recognize pictures, and you see if language
(05:32):
is impaired, and if so, then whichever hemisphere is anesthetized
is the one dominant for speech. Now, after the barbiturate
wears off, wham, then you do it on the other side,
putting the other half of the brain to sleep and
testing everything again. Now you might say, isn't language always
in the left hemisphere. No, it's about fifty to fifty
(05:53):
for left handed people. But also some people have a
typical brain organization, for example, if they've had early brain injuries,
so their language areas might end up in the right
hemisphere instead of the left. So this is why you
really want to make sure you know where language is
before you go cutting around in the brain, because obviously
one of the worst things you can do to somebody
(06:15):
is damage their ability to communicate with the outside world. Okay,
so what I told you is that this water test
temporarily shuts down one hemisphere at a time so that
you can assess things. Now, the first time I heard
about this as a student, I wondered if it would
be possible to repurpose and expand this technique. For example,
(06:39):
a cat's brain is a lot like ours, except that
we have an enormous cerebrum while they have a larger cerebellum.
So could you put a very specific pattern of sedatives
into the brain in just the right regions to mold
your brain to be like a cat's. Now, this is
(07:02):
just fantasy, of course, no one's ever done this, and
it's hard to know.
Speaker 2 (07:05):
How you would even know if you're doing it right.
Speaker 1 (07:08):
If I do something and I get a very strange feeling,
how can I ever know that that's exactly what a
cat feels, as opposed to just some other interesting, weird feeling. Nonetheless,
you could get closer in theory than you might otherwise.
But there's a fundamental problem with this idea. And I
was chewing on this many years ago, and this became
(07:30):
the intellectual seed for one of my short stories in
my book some called Descent of Species. Now, I read
this story on the podcast about a year and a
half ago, but I'm going to read it again now
for a different purpose. And I'd like you to keep
your ears out for what the problem is about turning
your brain into someone else's. So here's the story descentive
(07:54):
Species from some in the afterlife, you are treated to
a generous opportunity. You can choose whatever you would like
to be in the next life. Would you like to
be a member of the opposite sex, born into royalty
a philosopher with bottomless profundity, a soldier facing triumphant battles.
(08:15):
But perhaps you've just returned here from a hard life.
Perhaps you were tortured by the enormity of the decisions
and responsibilities that surrounded you. And now there's only one
thing you yearn for, simplicity that's permissible. So for the
next round, you choose to be a horse. You covet
(08:38):
the bliss of that simple life afternoons of grazing in
grassy fields, the handsome angles of your skeleton and the
prominence of your muscles, the piece of the slow flicking tail,
or the steam rifling through your nostrils. As you lope
across snow blanketed planes. You announce your decision. Incantations are muttered,
(09:02):
a wand is waved, and your body begins to metamorphose
into a horse. Your muscles start to bulge, A mat
of strong hair erupts to cover you like a comfortable
blanket in winter. The thickening and lengthening of your neck
immediately feels normal as it comes about. Your carotid arteries
(09:24):
grow in diameter, your fingers blend hoofward, your knees stiffen,
your hips strengthen, and meanwhile, as your skull lengthens into
its new shape, your brain races in its changes. Your
cortex retreats as your cerebellum grows, the homunculus melts man
(09:44):
to horse. Neurons redirect, synapses, unplug and replug on their
way to equestrian patterns, and your dream of understanding what
it is like to be a horse gallops towards you
from the distance. Your concern about human affairs begins to
slip away, your cynicism about human behavior melts, and even
(10:08):
your human way of thinking begins to drift away from you. Suddenly,
for just a moment, you are aware of the problem
you overlooked. The more you become a horse, the more
you forget the original wish. You forget what it was
like to be a human wondering what it was like
(10:29):
to be a horse. This moment of lucidity does not
last long, but it serves as the punishment for your sins.
A Promethean entrails pecking moment, crouching half horse, half man,
with the knowledge that you cannot appreciate the destination without
knowing the starting point. You cannot revel in the simplicity
(10:52):
unless you remember the alternatives. And that's not the worst
of your revelation. You realize that the next time you
reach here with your thick horse brain, you won't have
the capacity to ask to become a human again.
Speaker 2 (11:07):
You won't understand what a human is.
Speaker 1 (11:11):
Your choice to slide down the intelligent ladder is irreversible,
and just before you lose your final human faculties, you
painfully ponder what magnificent extraterrestrial creature, enthralled with the idea
of finding a simpler life chose in the last round
(11:33):
to become a human that was dessentive species from my
book sum and the punchline of the story tells you
everything you need to know for the context of today's question,
Can you really know what it's like to be something
else or someone else? The problem is, the more your
(11:54):
brain becomes something else, then the less you would be
able to keep track of the original you who was
asking the question. So could you modify your brain to
make it like a cat's brain? When you got there,
you wouldn't be able to remember what the original question was.
So let's think about this and extend this. This is
(12:14):
the same as saying I want to be the actor
John Malkovich. If you were actually being John Malkovich, you
wouldn't remember what it was like to be you, wondering
what it was like to be he. And this is
the same problem with the movie Strange Days. During playback
with this helmet, the conceit is that the observer temporarily
(12:37):
quits his own memories in state of consciousness and takes
on that of someone else. Okay, so you can't change
(13:03):
your brain to be exactly someone else's and still retain
any notion of you.
Speaker 2 (13:08):
But could you have an experience.
Speaker 1 (13:10):
More like VR where you're still you, but you are
experiencing someone else's senses, like you're.
Speaker 2 (13:17):
Seeing through their eyes. Well sort of.
Speaker 1 (13:21):
But there's a very interesting thing that happens here which
exposes something very deep about perception. So to understand this,
we're gonna dive into four movies that try to do this, because,
as we'll see, this is actually a tougher challenge than
you might imagine. Okay, so, there was in fact a
movie called Being John Malkovich. You may have seen it.
(13:42):
In that movie, there's a struggling puppeteer who discovers a
hidden door that leads directly into the mind of the
actor John Malkovich. So for fifteen minutes at a time,
people can experience the world through Malkovich's eyes until they're
ejected onto the side of the New Jersey Turnpike.
Speaker 2 (14:03):
Now, how did the.
Speaker 1 (14:04):
Director Spike Jones actually implement this on camera? Well, when
a character enters the portal, the film switches to a
first person perspective, literally showing what John Malkovich sees through
his eyes. Now, to simulate the feeling of inhabiting another
person's body, what the camera does is mimic the movement
(14:25):
of the head and it shows us when Malkovich is blinking.
Essentially the curtain drops because we're on the inside of
his head and we're seeing those eyelids. And there's also
a confined feeling of a tunnel. In these shots. The
edges of the frame are darker, giving the sense that
you're looking through a peopole or wearing blinkers. Now, this
(14:47):
is very interesting, right, because that's not actually your experience
of the world when you're inside your own head. So first,
what is the reason that you don't see your own blinks?
Is it because a blink is too fast to notice?
After all, it only takes eighty milliseconds. Well, no, that's
(15:09):
not it, because if you are looking out in a
well lit room and I flick the lights on it
off for just eighty milliseconds, you have no problem at
all detecting that. In fact, you can detect something much
shorter than that. So what's going on why don't you
see your own blinks? Well, the answer is that you
have circuitry in your midbrain that sends the motor command
(15:29):
to blink your eyelids, and it also sends a copy
of this command to your visual system so that it
knows a blink is coming. But there's even a deeper
answer here. The general story, as you have heard me
talk about in many other episodes, is that you're not
seeing the world out there. Exactly what you're seeing is
your internal model of what you believe is out there.
(15:52):
It's a construction of your brain. Only five percent of
the input to your visual cortex is coming from the eye.
All the rest is feedback. It's internally generated activity telling
you what you expect to see given your entire history
with the world. And it turns out you don't need
(16:13):
your eyes at all for vision. You can have full,
rich visual experience even with your eyes closed. This is
the experience you have every night when you're dreaming, So
you only see your internal model of the world. And
this is why a blink does not disrupt your vision
because your brain knows it's coming, and so your model
(16:35):
that I am in this room or I'm walking along
the sidewalk, that show continues on even though the data
is interrupted every few seconds. So all this is to
say that if you were inside someone else's sensory experience,
you wouldn't see blinks, and also you wouldn't have tunnel vision.
Speaker 2 (16:52):
Why not? After all, your visual field is only.
Speaker 1 (16:56):
About one hundred and twenty degrees across out of the
three hundred and six degree world. You're only seeing a
slice of about a third of the vision that's available
around you. So why do we feel like the world
doesn't have edges. It's because what you experience is your
internal model of a full three hundred and sixty degree world.
(17:16):
And that's because you've looked around and you've filled in
the picture, sometimes with very low resolution and sometimes just
with assumption. But in any case, you have a sense
of a full world around you. So again, if you
were actually experiencing someone else's vision, it wouldn't look like
a tunnel. So this is a very difficult problem to
(17:38):
solve if you are Spike Jones or any movie director
and you're given this challenge of presenting what it would
be like to be inside someone else's head experiencing their vision.
And in fact, something that struck me is that Jones
put in the blinks and the tunnel vision, but he
didn't display, for example, the fact that your eyes are
(17:58):
making large jump three times a second. These are called
the CODs. Even when you feel like you're just calmly
observing the world in front of you, your eyes are
constantly dashing around to find new information. Again, we're not
aware of this because all we experience is our internal model,
and our eyes are just seeking new data to put
(18:20):
into that. By the way, if it doesn't feel like
your eyes are always dashing around, just get in the
habit of watching other people's eyes and you'll see that
they're making large jumps every third of a second.
Speaker 2 (18:30):
So look, I want you to try this.
Speaker 1 (18:32):
Take the video camera on your phone and record the
scene around you, but jerk the camera around three times
a second, just like your eyes are doing. Now play
the video back, and you're gonna see that. It looks terrible.
It's nauseating to try to watch this. Why because you're
not experiencing those movements. You're just experiencing your internal model.
(18:56):
And if your spike Jones and you really really wanted
to capture the information directly from somebody's eyeballs, you'd have
to take into account that you only have color vision
right at the very center of your visual field, because
that's where you have cones, the color photoreceptors, and your
retina and everything in your periphery is taken care of
(19:18):
by rods.
Speaker 2 (19:19):
So that's black and white vision. Most of your.
Speaker 1 (19:23):
Vision is black and white. But you never noticed this.
You think the whole world is in color simply because
you are moving your eyes around and your internal model
is keeping track of everything in color. Again, if you
don't believe me on this, ask your friend to take
some colored dry erase markers and hold them in his
hand and whatever order he wants to put them in. Now,
(19:45):
stand just a few feet away from him and look
straight at his nose, and have him hold the markers
out at his arm's length, but don't look at the markers.
Stay fixed right on his nose and try to name
the order of the colors of the markers, and what
you'll see is that you can't even see the colors.
If you're actually trying to do a task that involves
(20:08):
color out in your periphery, you just can't do it
because there is no color out there. You have to
move your eyes there to see any color. Okay, So
let's get back to being John Malkovich. So Spike Jones
didn't include all these other flourishes about ciccads and black
(20:28):
and white vision in the periphery, but obviously it wouldn't
have helped if he did, it would have just made
it worse, because real vision is nothing like seeing blinks
and looking down a tunnel and seeing siccads and seeing
most of the world in black and white. Instead, the
experience of vision is like being embedded directly in a full, rich,
(20:51):
colorful world. So this is a tough challenge for a
movie director to make an attempt to step into someone
else's head. And it's not just being John Malkovich, but
lots of movies try this sort of thing, trying to
show what it's like for you to be inside someone
else experiencing what it's like to be them. So let's
(21:14):
return to the movie Strange Days. As I mentioned earlier,
in that movie, you can record an experience from someone,
let's say, while they're committing a robbery, and so we'll
put aside the problem that you can't experience the whole thing,
the emotions, the thoughts, the feelings. But again, we're just
going to ask what the movie director did to make
us feel like we were inside the visual system of another.
(21:36):
So when the director needed to show us this, he
showed us from a first person point of view, because
after all, that's what was being sold in the helmet.
And what we saw was the camera bouncing up and down,
indicating that the first person point of view we were
in was running on foot from the cops. Now, that
cracked me up because it represents a basic error of
(21:59):
what it's really like to be running. When you are running,
your visible world does not bounce up and down. Your
visual system takes account of the movement of your muscles
and it compensates for that. As a result, your view
of the outside world is steady. And this is because
(22:19):
your conscious view is a notion of the world outside
of you. Your visual system isn't simply there to register
the data coming in. Whatever hits your eyes is simply
contributing to the model of a stable outside world. And
as I said, a lot of this has to do
with your body making predictions about how the world will
(22:41):
change when it moves. Just as one quick example of this,
do you think it would have helped if the director
in Strange Days had the protagonist's hands reaching in in
front of the camera. Would this look more realistic as
though your own hands were coming into your field of view.
That would have made things even worse, even less convincing,
(23:03):
because although we do see our own hands reaching from
below our visual fields, we are the ones controlling them,
and that makes all the difference. We can predict exactly
where they are and when they'll appear, because the regions
of your brain that sends commands out to your body
also sends copies of those commands all around to the
(23:25):
rest of your brain, so that your visual system, for example,
knows what's coming. If you want to read more about this,
this is what's known as the motor efherence copy. Let
me give you a good example of this point. So
let's look at the movie Hatchi. This movie is about
a college professor Richard Gere, who finds an abandoned puppy
(23:45):
at a train station and takes them home, and they
form a very close bond. And every day Hotchi waits
at the train station for the Professor to return from work.
But then the Professor dies unexpectedly, but Hotchie continues to
return to the train station every day, waiting faithfully for
(24:07):
nearly a decade, unaware that his owner is gone. It's
a total tear jerker. Now here's the thing. The director
wanted to show some of the shots from the dog's
point of view, so here's how he went about this.
Speaker 2 (24:21):
First, he films the dog lying on.
Speaker 1 (24:24):
The grass with legs stretched in front and chin on
the ground, watching the professor clipping the rose bushes, and
suddenly we cut to the dog's point of view. We
see the professor from a very low angle and in
black and white. Okay, fine, but to drive this point home,
we are then back outside the dog and we see
(24:45):
the dog roll over sideways onto the grass, and then
the director cuts to the internal dog camera and we
see the horizon rotate to vertical, and then we're back
outside the dog and we see the dog roll over
until his paws are sticking up in the air and
his head is upside down. And now the camera jumps
(25:05):
back into the dog and shows us the world of
the garden flipped.
Speaker 2 (25:09):
One hundred and eighty degrees.
Speaker 1 (25:12):
Now, this seems like a clever way to use the
camera to personalize the dog's experience.
Speaker 2 (25:17):
Right wrong.
Speaker 1 (25:18):
There's an interesting rookie error of perception here. When your
head turns sideways, the world doesn't turn sideways. Try it.
Try it turning your head the world remains stable, and
your internal model remains stable because you have a sense
of where gravity is. So seeing the world through someone's eyes,
(25:38):
whether John Malkovich or with the Strange Day's Helmet or
with Hatchie the Dog, it's not so straightforward to show.
And sometimes the difficulty is even more subtle than that.
For our fourth movie, take The Terminator played by Arnold Schwarzenegger,
where he's this killing machine from the future. So how
(26:00):
does the director try to show us the experience of
the robot. Well, occasionally the camera switches to the robots
first person point of view, and what does that look like? Well,
the shot shows the familiar cinematic landscape, whether he's in
a hallway or a city street or whatever. But it's
overlaid now with flickering data. You've got these red gridlines
(26:25):
and numbers scrolling past, and words pop up and flickers
of infrared and occasional diagnostic information. So this is meant
to communicate to us. Now you're seeing what the terminator sees.
But there's a funny paradox here because what we're really
being shown isn't a first person experience at all. It's
(26:46):
like the robot has a little film crew living inside
his head, filming the world through his eyes and then
adding the heads up display. But that's not how brains
or machines work. As we've been talking about, well, to
be inside of you is not the same as peering
out of your eyes like a camera. Consciousness is our
(27:07):
experience of being in the world. So in this case,
if your consciousness showed numbers, who's watching those numbers? What
this actually suggests is that there's a little Schwarzenegger sitting
at the back of his head watching and reading these numbers.
In other words, you don't have a screen inside your mind,
even for a robot, even if it were conscious, you
(27:30):
wouldn't experience an image with data superimposed. Information is encoded
and interpreted in processed, but there's no need to visually
represent numbers for itself to read.
Speaker 2 (27:42):
Think about it this way. Your brain doesn't.
Speaker 1 (27:44):
Need to overlay subtitles when you recognize somebody's face. Imagine
there were words that read you are now looking at
the face of Susiq, and then you had to read
those words and then you understand that you're looking at
her face. That's not how it works.
Speaker 2 (28:01):
You just have a direct experience.
Speaker 1 (28:03):
There's nobody else for whom you would need to display
the words. So when filmmakers try to show us what
it is like to be someone or something else, what
they're really doing is showing us what they think it
might be to look out from behind someone's eyes. But
consciousness is not like that. You don't see blinks, you
(28:24):
don't see a tunnel, you don't see the world bouncing
when you run, you don't see the world turn sideways
when you turn sideways, and you don't see words displayed
in your mind just for you to read and then
understand them. So what does this tell us? It reminds
us that conscious experience isn't about what your eyeballs are doing,
but instead what you're experiencing as your internal model. And
(28:49):
that's why, as clever as these movies are, they can
never really show us what it's like to be someone
else from the inside. At best, they give us a
visual metaphor, but that kind of metaphor is not even
close to actual experience. So what we're seeing is that
the plot of Strange Days, where you live someone else's
(29:09):
experience and the way that they experienced it, is presumably impossible.
So to pull this all together, let's return to the
idea of dream celebrities, this idea of recording your dreams
and playing them to someone else and becoming a social
media star of the nocturnal world. So let's make sure
(29:45):
this is clear. You could imagine just getting the visuals
of what someone else saw, but there are a couple
of things to note here. If I just measured the
activity in your visual cortex while you dreamed, and then
I fed that same data into stimulation of my visual cortex,
it wouldn't be exactly the same because even in the
primary visual cortex there are individual differences, So what I
(30:07):
saw would be a warped version of what you saw. Okay,
no problem. Some day in the future we could morph
from your visual cortex to my visual cortex and warp
the show appropriately. But the deeper problem is your experience
would just be like a VR visual experience, which is
different than you sharing your thoughts and emotions. For example,
(30:32):
let's say a particular face comes into your dream. I'd
see that face, but I wouldn't have any idea that
to you, to face strikes terror, or maybe the face
is someone you have a deep crush on, whereas I
don't know who it is. To me, it's just the
visual of two eyes and a nose and a mouth.
That's the difference between a purely visual facsimile on my
(30:56):
visual cortex and my brain becoming your brain and.
Speaker 2 (31:00):
Experiencing what you experience.
Speaker 1 (31:07):
So let's even imagine that you said, fine, let's figure
out all the rest of the circuitry and we warp
it so that you can have exactly what I have.
But this is just a bigger issue of what I
mentioned about the visual cortex. The detailed, three dimensional microstructure
of your brain is unique to you. That's why you
have your own thoughts and see the world your own way.
(31:28):
This is the major challenge of transferring thoughts from one
mind to another. I mentioned in an episode a while
ago this scene from the Matrix where Trinity says, tank,
I need a program for a B two twelve helicopter
and he the operator, finds one and loads one, and
the knowledge is immediately present in her head. But the
(31:50):
problem is that Trinity's new knowledge rests in a network
of her old experiences. For example, pulling on the helicopter
stick is similar or to pulling on horses reins. And
the only way to get at this and put that
new knowledge in is if you knew every detail of
Trinity's brain. But again, that's not even the deepest problem.
(32:12):
The deepest problem is whether you could ever be two
people at once. If you were able to figure out
the mapping from your brain to someone else's brain so
that you could somehow download his dream state into your head,
you wouldn't be you anymore experiencing his dream You would
be someone else with no knowledge of you. And what's
(32:34):
the point of that? Okay, so what we talked about
so far is the possibility that becoming someone else is
going to be impossible.
Speaker 2 (32:45):
But could you nonetheless get.
Speaker 1 (32:47):
Closer by adding new inputs to the brain. Way back
in episode twelve, I talked about the technology that we
built in my lab, for example, a vest covered and
vibratory motors that can put specific patterns onto your torso
and you can feed in new data streams to the
brain that way. Could this give you some little window
(33:10):
into someone else's experience. So as one example, we shrunk
this vest down to a wristband, and then we had
people wear the wristband on one hand and a smart
watch on the other, and the smart watch tracks all
kinds of things about their physiology, like their heart rate
and heart rate variability and galvanic skin response. And we
(33:31):
had that data stream from the watch over the Internet
and into the wristband. So you are feeling a summarized
version of your physiological signals that are normally invisible. But
that's not the really interesting part. The really interesting part
was that we now put the wristband on someone else.
(33:52):
Say you're a romantic partner, and now he or she
can be across the country, but can be constantly feeling
your physiology and know when you're stressed and when your
heart rate is going up and your galvanic skin response
is rising. Now, I'm not totally clear whether this would
be good or bad for couples. But it is a
way of opening up a small channel into the experience
(34:16):
of someone else. And I think there are many ways
that adding new senses could bring you closer to someone
else's experience. For example, someone who is born blind is
not able to understand what vision is. If you have
a friend who's born blind and you say, yeah, I'm
capturing photons from half a mile away, and I can
(34:36):
perceive what's out there, and the person walking towards me
from a distance, your friend.
Speaker 2 (34:41):
Has no way of understanding that. Because they're your friend.
Speaker 1 (34:44):
They might pretend that they sort of get it, but
they can't because they've never had the experience of this
super spy technology of capturing distant photons. So if you
took someone like Helen Keller who was born deaf and blind,
and you fed in the auditory and visual data, let's
(35:05):
say through a vest or wristband, so she could tap
into those experiences, I do think that would get her
slightly closer to understanding what it is like to be
a hearing and cited person. So I think as we
get better at figuring out how to add senses directly
to the brain, we can at least get closer to
(35:27):
understanding the sensory experiences that other people may have. And
I'll just mention that in an earlier episode, I've also
talked about how flexible the brain is in terms of
adding new interfaces for moving, like robotic arms that you
could control with your brain. The only point I want
to make today is that by coming to have a
(35:48):
different body, like let's say you're able to control a
robotic trunk, you might be able to get closer to
understanding what it is like to be another creature, like
an elephant. Okay, so let's wrap up. We set out
today chasing a timeless question. Can we ever truly know
what it is like to be someone else? Not just
(36:10):
to guess or to empathize or imagine, but to be
in their skin, to see through their eyes, to feel
with their nervous system. Technology peases us with this dream,
from the mind recording helmets of strange days to the
dream sharing fantasies of tomorrow's celebrity subconscious. But the closer
(36:35):
we approach the boundaries of another mind, the more we
find the self slipping through our fingers. To become someone
else is to lose the very self who wants to
know that, and we saw that consciousness is not a
camera looking out, but a story being told from the inside,
(36:55):
a model stitched together from prediction and memory and bodily anchoring.
And that story can't be exported wholesale. It's inseparable from
the teller. Now, movies try to do this. Directors try
to jump into other heads with first person shots and
(37:15):
tilted frames and blinking eyelids and bouncing camera rigs. But
even the cleverest cinematography can't breach the firewall of subjectivity.
You can mimic a viewpoint, but not the viewing. You
can borrow the eyes, but not the mind behind them.
(37:38):
And so every attempt to simulate another's experience is like
trying to paint a dream with a camera. The image
may flicker with familiarity, but the feeling remains out of reach. Okay,
but still, when we're trying to understand someone else, we
can build bridges. Maybe they're not full crossings, but they're footpaths.
(38:02):
With wearable technology or shared biofeedback or sensory augmentation, we
can inch closer, not to being one another, but to
understanding one another a little more richly, And.
Speaker 2 (38:15):
Perhaps that's enough.
Speaker 1 (38:16):
Perhaps the future is not about dissolving the boundaries between selves,
but about illuminating those boundaries, tracing their contours with data
and compassion and curiosity.
Speaker 2 (38:31):
We may never fully be each other, but we.
Speaker 1 (38:35):
Might, with the right tools and intentions, meet more meaningfully
at the borders. Go to eagleman dot com slash podcast
more information and to find further reading. Find me on
substack or send me an email at podcasts at eagleman
(38:55):
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.
In the last episode, I tackled the question of whether
we could really know what it's like to be someone else,
as in empathize with them so completely that we actually
really understand what it is to be in their shoes. Today,
we're going to ask could technology help us to get there?
Could we have dreams celebrities in which some people upload
(00:29):
their dreams and other people watch them and a dream
can go viral? How am I going to explain what
consciousness actually feels like through four movies that got it wrong?
Speaker 2 (00:41):
Why don't you see your own blinks?
Speaker 1 (00:44):
What would it be like to numb exactly one half
of your brain with barbituates? And what would it be
like to become a horse? Welcome to Intercosmos with me
David Eagelman. I'm a neuroscientist and author at Stanford and
in these episodes we sail deeply into our three pound
universe to understand why and how our lives look the
(01:07):
way they do. Today's episode is about the question of
whether we can ever really know what it is like
(01:29):
to be someone else. In the last episode, we discussed
why we humans are all so different on the inside
and whether it's possible that the gaps are unbridgable, and
we examine this from the point of view of neuroscience
and philosophy and literature. But today we're going to turn
to the angle of technology. Could new technology ever allow
(01:51):
us to better understand other people? So let's start with
an old movie that I saw back in nineteen ninety five.
The movie is called Strange Days, and it explores the
idea of wearing this special helmet, and the helmet records
the activity in your brain, all of your memories, your feelings,
(02:13):
your thoughts. It records that, and the recorded event is
frozen in time on a data disk. It's like an
MP four file, but one that captures not just audio
and video but everything. And then another person can put
on the helmet and they can experience it all. They
remember your memories, they feel your feelings, they think your
(02:38):
thoughts in that moment. In other words, you can live
a moment in the life of another person, and you
can also live the same moment of your life more
than once. So in the movie, a guy named Lenny
Nero is a former police officer who now works as
a playback artist in Los Angeles and ends up finding
(03:00):
a recording of a woman's last moments alive, and he
becomes involved in a murder investigation, and this leads him
to a group of people who are planning a terrorist attack,
and so he has to use his skills as a
playback artist to stop the attack and save the city. Okay,
but here's the part I want to concentrate on. Could
a helmet like this be possible? Could we get our
(03:24):
neurotechnology to a point where you could record one person's
experience and have a second person live it. And while
we're holding that question, I want to give a related example.
Some years ago, a futurist named Michael Andisimov proposed the
idea of dream celebrities. The idea here was that someday
(03:44):
in the future, presumably using nano robotics, people would be
able to record and upload their dreams and then other
people could watch them. So, could these versions of the
future be possible even though people are so different on
the inside, Could we leverage this imaginary futuristic tech in
(04:05):
this way to know what it is like to be
someone else? Now, I'm not speaking of this just in
terms of empathy, which I talked about in the last episode,
but in terms of uploading the experience of one person
and then downloading it into the head of another. So
let's start today's journey with an idea that I started
chewing on a very long time ago when I was
(04:27):
in graduate school and learned about a medical procedure called
the Wata test WADA. Now, this is something that was
commonly used before brain surgery when the neurosurgeon is trying
to determine which side of the brain, which hemisphere is
responsible for language, because you want to make sure, as
(04:49):
the surgeon, not to damage critical areas involved in speech.
So what you do is inject a sedative, usually sodium
amma barbitol, into one hemisphere of the brain and that
hemisphere essentially goes to sleep for about five or ten minutes,
while the other hemisphere, the other half of your brain,
(05:11):
remains active. And this is what allows the neurosurgeon to
test which side of the brain is dominant for language.
While one half of the brain is anesthetized, the patient
is asked to speak, to count, to name objects, to
follow commands, to recognize pictures, and you see if language
(05:32):
is impaired, and if so, then whichever hemisphere is anesthetized
is the one dominant for speech. Now, after the barbiturate
wears off, wham, then you do it on the other side,
putting the other half of the brain to sleep and
testing everything again. Now you might say, isn't language always
in the left hemisphere. No, it's about fifty to fifty
(05:53):
for left handed people. But also some people have a
typical brain organization, for example, if they've had early brain injuries,
so their language areas might end up in the right
hemisphere instead of the left. So this is why you
really want to make sure you know where language is
before you go cutting around in the brain, because obviously
one of the worst things you can do to somebody
(06:15):
is damage their ability to communicate with the outside world. Okay,
so what I told you is that this water test
temporarily shuts down one hemisphere at a time so that
you can assess things. Now, the first time I heard
about this as a student, I wondered if it would
be possible to repurpose and expand this technique. For example,
(06:39):
a cat's brain is a lot like ours, except that
we have an enormous cerebrum while they have a larger cerebellum.
So could you put a very specific pattern of sedatives
into the brain in just the right regions to mold
your brain to be like a cat's. Now, this is
(07:02):
just fantasy, of course, no one's ever done this, and
it's hard to know.
Speaker 2 (07:05):
How you would even know if you're doing it right.
Speaker 1 (07:08):
If I do something and I get a very strange feeling,
how can I ever know that that's exactly what a
cat feels, as opposed to just some other interesting, weird feeling. Nonetheless,
you could get closer in theory than you might otherwise.
But there's a fundamental problem with this idea. And I
was chewing on this many years ago, and this became
(07:30):
the intellectual seed for one of my short stories in
my book some called Descent of Species. Now, I read
this story on the podcast about a year and a
half ago, but I'm going to read it again now
for a different purpose. And I'd like you to keep
your ears out for what the problem is about turning
your brain into someone else's. So here's the story descentive
(07:54):
Species from some in the afterlife, you are treated to
a generous opportunity. You can choose whatever you would like
to be in the next life. Would you like to
be a member of the opposite sex, born into royalty
a philosopher with bottomless profundity, a soldier facing triumphant battles.
(08:15):
But perhaps you've just returned here from a hard life.
Perhaps you were tortured by the enormity of the decisions
and responsibilities that surrounded you. And now there's only one
thing you yearn for, simplicity that's permissible. So for the
next round, you choose to be a horse. You covet
(08:38):
the bliss of that simple life afternoons of grazing in
grassy fields, the handsome angles of your skeleton and the
prominence of your muscles, the piece of the slow flicking tail,
or the steam rifling through your nostrils. As you lope
across snow blanketed planes. You announce your decision. Incantations are muttered,
(09:02):
a wand is waved, and your body begins to metamorphose
into a horse. Your muscles start to bulge, A mat
of strong hair erupts to cover you like a comfortable
blanket in winter. The thickening and lengthening of your neck
immediately feels normal as it comes about. Your carotid arteries
(09:24):
grow in diameter, your fingers blend hoofward, your knees stiffen,
your hips strengthen, and meanwhile, as your skull lengthens into
its new shape, your brain races in its changes. Your
cortex retreats as your cerebellum grows, the homunculus melts man
(09:44):
to horse. Neurons redirect, synapses, unplug and replug on their
way to equestrian patterns, and your dream of understanding what
it is like to be a horse gallops towards you
from the distance. Your concern about human affairs begins to
slip away, your cynicism about human behavior melts, and even
(10:08):
your human way of thinking begins to drift away from you. Suddenly,
for just a moment, you are aware of the problem
you overlooked. The more you become a horse, the more
you forget the original wish. You forget what it was
like to be a human wondering what it was like
(10:29):
to be a horse. This moment of lucidity does not
last long, but it serves as the punishment for your sins.
A Promethean entrails pecking moment, crouching half horse, half man,
with the knowledge that you cannot appreciate the destination without
knowing the starting point. You cannot revel in the simplicity
(10:52):
unless you remember the alternatives. And that's not the worst
of your revelation. You realize that the next time you
reach here with your thick horse brain, you won't have
the capacity to ask to become a human again.
Speaker 2 (11:07):
You won't understand what a human is.
Speaker 1 (11:11):
Your choice to slide down the intelligent ladder is irreversible,
and just before you lose your final human faculties, you
painfully ponder what magnificent extraterrestrial creature, enthralled with the idea
of finding a simpler life chose in the last round
(11:33):
to become a human that was dessentive species from my
book sum and the punchline of the story tells you
everything you need to know for the context of today's question,
Can you really know what it's like to be something
else or someone else? The problem is, the more your
(11:54):
brain becomes something else, then the less you would be
able to keep track of the original you who was
asking the question. So could you modify your brain to
make it like a cat's brain? When you got there,
you wouldn't be able to remember what the original question was.
So let's think about this and extend this. This is
(12:14):
the same as saying I want to be the actor
John Malkovich. If you were actually being John Malkovich, you
wouldn't remember what it was like to be you, wondering
what it was like to be he. And this is
the same problem with the movie Strange Days. During playback
with this helmet, the conceit is that the observer temporarily
(12:37):
quits his own memories in state of consciousness and takes
on that of someone else. Okay, so you can't change
(13:03):
your brain to be exactly someone else's and still retain
any notion of you.
Speaker 2 (13:08):
But could you have an experience.
Speaker 1 (13:10):
More like VR where you're still you, but you are
experiencing someone else's senses, like you're.
Speaker 2 (13:17):
Seeing through their eyes. Well sort of.
Speaker 1 (13:21):
But there's a very interesting thing that happens here which
exposes something very deep about perception. So to understand this,
we're gonna dive into four movies that try to do this, because,
as we'll see, this is actually a tougher challenge than
you might imagine. Okay, so, there was in fact a
movie called Being John Malkovich. You may have seen it.
(13:42):
In that movie, there's a struggling puppeteer who discovers a
hidden door that leads directly into the mind of the
actor John Malkovich. So for fifteen minutes at a time,
people can experience the world through Malkovich's eyes until they're
ejected onto the side of the New Jersey Turnpike.
Speaker 2 (14:03):
Now, how did the.
Speaker 1 (14:04):
Director Spike Jones actually implement this on camera? Well, when
a character enters the portal, the film switches to a
first person perspective, literally showing what John Malkovich sees through
his eyes. Now, to simulate the feeling of inhabiting another
person's body, what the camera does is mimic the movement
(14:25):
of the head and it shows us when Malkovich is blinking.
Essentially the curtain drops because we're on the inside of
his head and we're seeing those eyelids. And there's also
a confined feeling of a tunnel. In these shots. The
edges of the frame are darker, giving the sense that
you're looking through a peopole or wearing blinkers. Now, this
(14:47):
is very interesting, right, because that's not actually your experience
of the world when you're inside your own head. So first,
what is the reason that you don't see your own blinks?
Is it because a blink is too fast to notice?
After all, it only takes eighty milliseconds. Well, no, that's
(15:09):
not it, because if you are looking out in a
well lit room and I flick the lights on it
off for just eighty milliseconds, you have no problem at
all detecting that. In fact, you can detect something much
shorter than that. So what's going on why don't you
see your own blinks? Well, the answer is that you
have circuitry in your midbrain that sends the motor command
(15:29):
to blink your eyelids, and it also sends a copy
of this command to your visual system so that it
knows a blink is coming. But there's even a deeper
answer here. The general story, as you have heard me
talk about in many other episodes, is that you're not
seeing the world out there. Exactly what you're seeing is
your internal model of what you believe is out there.
(15:52):
It's a construction of your brain. Only five percent of
the input to your visual cortex is coming from the eye.
All the rest is feedback. It's internally generated activity telling
you what you expect to see given your entire history
with the world. And it turns out you don't need
(16:13):
your eyes at all for vision. You can have full,
rich visual experience even with your eyes closed. This is
the experience you have every night when you're dreaming, So
you only see your internal model of the world. And
this is why a blink does not disrupt your vision
because your brain knows it's coming, and so your model
(16:35):
that I am in this room or I'm walking along
the sidewalk, that show continues on even though the data
is interrupted every few seconds. So all this is to
say that if you were inside someone else's sensory experience,
you wouldn't see blinks, and also you wouldn't have tunnel vision.
Speaker 2 (16:52):
Why not? After all, your visual field is only.
Speaker 1 (16:56):
About one hundred and twenty degrees across out of the
three hundred and six degree world. You're only seeing a
slice of about a third of the vision that's available
around you. So why do we feel like the world
doesn't have edges. It's because what you experience is your
internal model of a full three hundred and sixty degree world.
(17:16):
And that's because you've looked around and you've filled in
the picture, sometimes with very low resolution and sometimes just
with assumption. But in any case, you have a sense
of a full world around you. So again, if you
were actually experiencing someone else's vision, it wouldn't look like
a tunnel. So this is a very difficult problem to
(17:38):
solve if you are Spike Jones or any movie director
and you're given this challenge of presenting what it would
be like to be inside someone else's head experiencing their vision.
And in fact, something that struck me is that Jones
put in the blinks and the tunnel vision, but he
didn't display, for example, the fact that your eyes are
(17:58):
making large jump three times a second. These are called
the CODs. Even when you feel like you're just calmly
observing the world in front of you, your eyes are
constantly dashing around to find new information. Again, we're not
aware of this because all we experience is our internal model,
and our eyes are just seeking new data to put
(18:20):
into that. By the way, if it doesn't feel like
your eyes are always dashing around, just get in the
habit of watching other people's eyes and you'll see that
they're making large jumps every third of a second.
Speaker 2 (18:30):
So look, I want you to try this.
Speaker 1 (18:32):
Take the video camera on your phone and record the
scene around you, but jerk the camera around three times
a second, just like your eyes are doing. Now play
the video back, and you're gonna see that. It looks terrible.
It's nauseating to try to watch this. Why because you're
not experiencing those movements. You're just experiencing your internal model.
(18:56):
And if your spike Jones and you really really wanted
to capture the information directly from somebody's eyeballs, you'd have
to take into account that you only have color vision
right at the very center of your visual field, because
that's where you have cones, the color photoreceptors, and your
retina and everything in your periphery is taken care of
(19:18):
by rods.
Speaker 2 (19:19):
So that's black and white vision. Most of your.
Speaker 1 (19:23):
Vision is black and white. But you never noticed this.
You think the whole world is in color simply because
you are moving your eyes around and your internal model
is keeping track of everything in color. Again, if you
don't believe me on this, ask your friend to take
some colored dry erase markers and hold them in his
hand and whatever order he wants to put them in. Now,
(19:45):
stand just a few feet away from him and look
straight at his nose, and have him hold the markers
out at his arm's length, but don't look at the markers.
Stay fixed right on his nose and try to name
the order of the colors of the markers, and what
you'll see is that you can't even see the colors.
If you're actually trying to do a task that involves
(20:08):
color out in your periphery, you just can't do it
because there is no color out there. You have to
move your eyes there to see any color. Okay, So
let's get back to being John Malkovich. So Spike Jones
didn't include all these other flourishes about ciccads and black
(20:28):
and white vision in the periphery, but obviously it wouldn't
have helped if he did, it would have just made
it worse, because real vision is nothing like seeing blinks
and looking down a tunnel and seeing siccads and seeing
most of the world in black and white. Instead, the
experience of vision is like being embedded directly in a full, rich,
(20:51):
colorful world. So this is a tough challenge for a
movie director to make an attempt to step into someone
else's head. And it's not just being John Malkovich, but
lots of movies try this sort of thing, trying to
show what it's like for you to be inside someone
else experiencing what it's like to be them. So let's
(21:14):
return to the movie Strange Days. As I mentioned earlier,
in that movie, you can record an experience from someone,
let's say, while they're committing a robbery, and so we'll
put aside the problem that you can't experience the whole thing,
the emotions, the thoughts, the feelings. But again, we're just
going to ask what the movie director did to make
us feel like we were inside the visual system of another.
(21:36):
So when the director needed to show us this, he
showed us from a first person point of view, because
after all, that's what was being sold in the helmet.
And what we saw was the camera bouncing up and down,
indicating that the first person point of view we were
in was running on foot from the cops. Now, that
cracked me up because it represents a basic error of
(21:59):
what it's really like to be running. When you are running,
your visible world does not bounce up and down. Your
visual system takes account of the movement of your muscles
and it compensates for that. As a result, your view
of the outside world is steady. And this is because
(22:19):
your conscious view is a notion of the world outside
of you. Your visual system isn't simply there to register
the data coming in. Whatever hits your eyes is simply
contributing to the model of a stable outside world. And
as I said, a lot of this has to do
with your body making predictions about how the world will
(22:41):
change when it moves. Just as one quick example of this,
do you think it would have helped if the director
in Strange Days had the protagonist's hands reaching in in
front of the camera. Would this look more realistic as
though your own hands were coming into your field of view.
That would have made things even worse, even less convincing,
(23:03):
because although we do see our own hands reaching from
below our visual fields, we are the ones controlling them,
and that makes all the difference. We can predict exactly
where they are and when they'll appear, because the regions
of your brain that sends commands out to your body
also sends copies of those commands all around to the
(23:25):
rest of your brain, so that your visual system, for example,
knows what's coming. If you want to read more about this,
this is what's known as the motor efherence copy. Let
me give you a good example of this point. So
let's look at the movie Hatchi. This movie is about
a college professor Richard Gere, who finds an abandoned puppy
(23:45):
at a train station and takes them home, and they
form a very close bond. And every day Hotchi waits
at the train station for the Professor to return from work.
But then the Professor dies unexpectedly, but Hotchie continues to
return to the train station every day, waiting faithfully for
(24:07):
nearly a decade, unaware that his owner is gone. It's
a total tear jerker. Now here's the thing. The director
wanted to show some of the shots from the dog's
point of view, so here's how he went about this.
Speaker 2 (24:21):
First, he films the dog lying on.
Speaker 1 (24:24):
The grass with legs stretched in front and chin on
the ground, watching the professor clipping the rose bushes, and
suddenly we cut to the dog's point of view. We
see the professor from a very low angle and in
black and white. Okay, fine, but to drive this point home,
we are then back outside the dog and we see
(24:45):
the dog roll over sideways onto the grass, and then
the director cuts to the internal dog camera and we
see the horizon rotate to vertical, and then we're back
outside the dog and we see the dog roll over
until his paws are sticking up in the air and
his head is upside down. And now the camera jumps
(25:05):
back into the dog and shows us the world of
the garden flipped.
Speaker 2 (25:09):
One hundred and eighty degrees.
Speaker 1 (25:12):
Now, this seems like a clever way to use the
camera to personalize the dog's experience.
Speaker 2 (25:17):
Right wrong.
Speaker 1 (25:18):
There's an interesting rookie error of perception here. When your
head turns sideways, the world doesn't turn sideways. Try it.
Try it turning your head the world remains stable, and
your internal model remains stable because you have a sense
of where gravity is. So seeing the world through someone's eyes,
(25:38):
whether John Malkovich or with the Strange Day's Helmet or
with Hatchie the Dog, it's not so straightforward to show.
And sometimes the difficulty is even more subtle than that.
For our fourth movie, take The Terminator played by Arnold Schwarzenegger,
where he's this killing machine from the future. So how
(26:00):
does the director try to show us the experience of
the robot. Well, occasionally the camera switches to the robots
first person point of view, and what does that look like? Well,
the shot shows the familiar cinematic landscape, whether he's in
a hallway or a city street or whatever. But it's
overlaid now with flickering data. You've got these red gridlines
(26:25):
and numbers scrolling past, and words pop up and flickers
of infrared and occasional diagnostic information. So this is meant
to communicate to us. Now you're seeing what the terminator sees.
But there's a funny paradox here because what we're really
being shown isn't a first person experience at all. It's
(26:46):
like the robot has a little film crew living inside
his head, filming the world through his eyes and then
adding the heads up display. But that's not how brains
or machines work. As we've been talking about, well, to
be inside of you is not the same as peering
out of your eyes like a camera. Consciousness is our
(27:07):
experience of being in the world. So in this case,
if your consciousness showed numbers, who's watching those numbers? What
this actually suggests is that there's a little Schwarzenegger sitting
at the back of his head watching and reading these numbers.
In other words, you don't have a screen inside your mind,
even for a robot, even if it were conscious, you
(27:30):
wouldn't experience an image with data superimposed. Information is encoded
and interpreted in processed, but there's no need to visually
represent numbers for itself to read.
Speaker 2 (27:42):
Think about it this way. Your brain doesn't.
Speaker 1 (27:44):
Need to overlay subtitles when you recognize somebody's face. Imagine
there were words that read you are now looking at
the face of Susiq, and then you had to read
those words and then you understand that you're looking at
her face. That's not how it works.
Speaker 2 (28:01):
You just have a direct experience.
Speaker 1 (28:03):
There's nobody else for whom you would need to display
the words. So when filmmakers try to show us what
it is like to be someone or something else, what
they're really doing is showing us what they think it
might be to look out from behind someone's eyes. But
consciousness is not like that. You don't see blinks, you
(28:24):
don't see a tunnel, you don't see the world bouncing
when you run, you don't see the world turn sideways
when you turn sideways, and you don't see words displayed
in your mind just for you to read and then
understand them. So what does this tell us? It reminds
us that conscious experience isn't about what your eyeballs are doing,
but instead what you're experiencing as your internal model. And
(28:49):
that's why, as clever as these movies are, they can
never really show us what it's like to be someone
else from the inside. At best, they give us a
visual metaphor, but that kind of metaphor is not even
close to actual experience. So what we're seeing is that
the plot of Strange Days, where you live someone else's
(29:09):
experience and the way that they experienced it, is presumably impossible.
So to pull this all together, let's return to the
idea of dream celebrities, this idea of recording your dreams
and playing them to someone else and becoming a social
media star of the nocturnal world. So let's make sure
(29:45):
this is clear. You could imagine just getting the visuals
of what someone else saw, but there are a couple
of things to note here. If I just measured the
activity in your visual cortex while you dreamed, and then
I fed that same data into stimulation of my visual cortex,
it wouldn't be exactly the same because even in the
primary visual cortex there are individual differences, So what I
(30:07):
saw would be a warped version of what you saw. Okay,
no problem. Some day in the future we could morph
from your visual cortex to my visual cortex and warp
the show appropriately. But the deeper problem is your experience
would just be like a VR visual experience, which is
different than you sharing your thoughts and emotions. For example,
(30:32):
let's say a particular face comes into your dream. I'd
see that face, but I wouldn't have any idea that
to you, to face strikes terror, or maybe the face
is someone you have a deep crush on, whereas I
don't know who it is. To me, it's just the
visual of two eyes and a nose and a mouth.
That's the difference between a purely visual facsimile on my
(30:56):
visual cortex and my brain becoming your brain and.
Speaker 2 (31:00):
Experiencing what you experience.
Speaker 1 (31:07):
So let's even imagine that you said, fine, let's figure
out all the rest of the circuitry and we warp
it so that you can have exactly what I have.
But this is just a bigger issue of what I
mentioned about the visual cortex. The detailed, three dimensional microstructure
of your brain is unique to you. That's why you
have your own thoughts and see the world your own way.
(31:28):
This is the major challenge of transferring thoughts from one
mind to another. I mentioned in an episode a while
ago this scene from the Matrix where Trinity says, tank,
I need a program for a B two twelve helicopter
and he the operator, finds one and loads one, and
the knowledge is immediately present in her head. But the
(31:50):
problem is that Trinity's new knowledge rests in a network
of her old experiences. For example, pulling on the helicopter
stick is similar or to pulling on horses reins. And
the only way to get at this and put that
new knowledge in is if you knew every detail of
Trinity's brain. But again, that's not even the deepest problem.
(32:12):
The deepest problem is whether you could ever be two
people at once. If you were able to figure out
the mapping from your brain to someone else's brain so
that you could somehow download his dream state into your head,
you wouldn't be you anymore experiencing his dream You would
be someone else with no knowledge of you. And what's
(32:34):
the point of that? Okay, so what we talked about
so far is the possibility that becoming someone else is
going to be impossible.
Speaker 2 (32:45):
But could you nonetheless get.
Speaker 1 (32:47):
Closer by adding new inputs to the brain. Way back
in episode twelve, I talked about the technology that we
built in my lab, for example, a vest covered and
vibratory motors that can put specific patterns onto your torso
and you can feed in new data streams to the
brain that way. Could this give you some little window
(33:10):
into someone else's experience. So as one example, we shrunk
this vest down to a wristband, and then we had
people wear the wristband on one hand and a smart
watch on the other, and the smart watch tracks all
kinds of things about their physiology, like their heart rate
and heart rate variability and galvanic skin response. And we
(33:31):
had that data stream from the watch over the Internet
and into the wristband. So you are feeling a summarized
version of your physiological signals that are normally invisible. But
that's not the really interesting part. The really interesting part
was that we now put the wristband on someone else.
(33:52):
Say you're a romantic partner, and now he or she
can be across the country, but can be constantly feeling
your physiology and know when you're stressed and when your
heart rate is going up and your galvanic skin response
is rising. Now, I'm not totally clear whether this would
be good or bad for couples. But it is a
way of opening up a small channel into the experience
(34:16):
of someone else. And I think there are many ways
that adding new senses could bring you closer to someone
else's experience. For example, someone who is born blind is
not able to understand what vision is. If you have
a friend who's born blind and you say, yeah, I'm
capturing photons from half a mile away, and I can
(34:36):
perceive what's out there, and the person walking towards me
from a distance, your friend.
Speaker 2 (34:41):
Has no way of understanding that. Because they're your friend.
Speaker 1 (34:44):
They might pretend that they sort of get it, but
they can't because they've never had the experience of this
super spy technology of capturing distant photons. So if you
took someone like Helen Keller who was born deaf and blind,
and you fed in the auditory and visual data, let's
(35:05):
say through a vest or wristband, so she could tap
into those experiences, I do think that would get her
slightly closer to understanding what it is like to be
a hearing and cited person. So I think as we
get better at figuring out how to add senses directly
to the brain, we can at least get closer to
(35:27):
understanding the sensory experiences that other people may have. And
I'll just mention that in an earlier episode, I've also
talked about how flexible the brain is in terms of
adding new interfaces for moving, like robotic arms that you
could control with your brain. The only point I want
to make today is that by coming to have a
(35:48):
different body, like let's say you're able to control a
robotic trunk, you might be able to get closer to
understanding what it is like to be another creature, like
an elephant. Okay, so let's wrap up. We set out
today chasing a timeless question. Can we ever truly know
what it is like to be someone else? Not just
(36:10):
to guess or to empathize or imagine, but to be
in their skin, to see through their eyes, to feel
with their nervous system. Technology peases us with this dream,
from the mind recording helmets of strange days to the
dream sharing fantasies of tomorrow's celebrity subconscious. But the closer
(36:35):
we approach the boundaries of another mind, the more we
find the self slipping through our fingers. To become someone
else is to lose the very self who wants to
know that, and we saw that consciousness is not a
camera looking out, but a story being told from the inside,
(36:55):
a model stitched together from prediction and memory and bodily anchoring.
And that story can't be exported wholesale. It's inseparable from
the teller. Now, movies try to do this. Directors try
to jump into other heads with first person shots and
(37:15):
tilted frames and blinking eyelids and bouncing camera rigs. But
even the cleverest cinematography can't breach the firewall of subjectivity.
You can mimic a viewpoint, but not the viewing. You
can borrow the eyes, but not the mind behind them.
(37:38):
And so every attempt to simulate another's experience is like
trying to paint a dream with a camera. The image
may flicker with familiarity, but the feeling remains out of reach. Okay,
but still, when we're trying to understand someone else, we
can build bridges. Maybe they're not full crossings, but they're footpaths.
(38:02):
With wearable technology or shared biofeedback or sensory augmentation, we
can inch closer, not to being one another, but to
understanding one another a little more richly, And.
Speaker 2 (38:15):
Perhaps that's enough.
Speaker 1 (38:16):
Perhaps the future is not about dissolving the boundaries between selves,
but about illuminating those boundaries, tracing their contours with data
and compassion and curiosity.
Speaker 2 (38:31):
We may never fully be each other, but we.
Speaker 1 (38:35):
Might, with the right tools and intentions, meet more meaningfully
at the borders. Go to eagleman dot com slash podcast
more information and to find further reading. Find me on
substack or send me an email at podcasts at eagleman
(38:55):
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.
Host
David Eagleman
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