August 11, 2025 • 37 mins
Are there new colors you could see? And why are they impossible to imagine before you've seen them? Can you lose your color vision? And what does any of this have to do with linguistic color terms, why the military likes colorblind people for a particular task, and why Eagleman suggests that the cultural history of Thailand was influenced by one single, unknown neurodivergent?
Mark as Played
Transcript
Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
Speaker 1 (00:05):
Today's episode is part two about color and the brain.
Why did royals wear purple? It's not accidental And if
you rewound history ten thousand years and ran it again,
you'd find exactly the same outcome. So what's going on?
And how do we see colors that our recent ancestors
(00:26):
never saw in their lives? Why can't you imagine a
new color? Are there, in fact new colors that you
could see? Yes, and I'm going to show you how
to do that. Can you lose your color vision? And
what does any of this have to do with language
or culture? Or why the military likes color blind people
(00:46):
for a particular task, and why I suggest that the
cultural history of Thailand was influenced by one single, unknown neurodivergent.
Welcome to Dinner Cosmos with me David Eagleman. I'm a
neuroscientist and author at Stanford and in these episodes we
(01:07):
look at the world inside us and around us to
understand why and how our lives look the way they do.
(01:30):
Today's episode is part two about the absolutely amazing and
often underappreciated topic of color. And if I do my
job right, this is going to allow you to see
the world with totally fresh eyes. So we're going to
start with a quick catch up from last week so
we can continue this incredible story about color and the brain.
(01:50):
Last week, we talked about the fact that color is
not a property of the physical world, but it's a
creation of the brain. Color doesn't exist in light itself.
Light is just electromagnetic radiation of various wavelengths, and our
brains interpret those wavelengths by constructing the experience of color.
(02:15):
This private interpretation of color begins in the retina with
a special type of photoreceptor cones, which detect wavelengths and
come in three flavors sensitive to short, medium, and long wavelengths,
which corresponds approximately to red, green, and blue. The brain
then processes patterns of activation across these cells to produce
(02:38):
the experience of color, and last week we talked about
color constancy, which allows us to perceive colors as stable
despite the changing lighting conditions, something that we see all
the time in visual illusions. We also talked about evolution.
For example, we humans have three types of giving us
(03:01):
trichromatic vision, but this is a rare trait among mammals,
most of whom are dichromatic, meaning they have two types
of cones, and this is likely because of a nocturnal
bottleneck where during the age of dinosaurs, the ancestors of
mammals how to avoid getting stomped on and eaten, and
(03:22):
so they scampered around at night and got better night vision,
but lost some of their color vision. Now humans and
some other primates reevolved trichromatic vision, possibly not just for
spotting ripe fruit, but for social reasons, detecting subtle changes
(03:43):
in skin coloration due to emotions. But in any case,
lots of our neighbors in the mammalian kingdom can't see
red and orange, which is why deer hunters wear orange vests,
because that allows the hunters to see each other clearly,
but the deer just can't see them. And finally we
(04:03):
saw how other species like bees and snakes and manta
shrimp they presumably perceive the world very differently because their
eyes pick up on ultraviolet light or infrared light or
polarized light. And if you tune into last week's episode,
you'll hear lots of other stories about how color serves
many functions like camouflage or warning or mating signals or
(04:26):
deception or emotional communication. Now we're ready to continue our
story this week. So let's start with something that I
think is amazing, which is that we see so many
more colors than even our recent ancestors did. This is
not because of a change in our biology. It's because
(04:46):
our current collection of technologies can generate so much more.
For example, your great great grandparents never saw a lot
of neon, or the bright ultra red of attack esla,
or the blaze orange of a caution sign on the road.
But we see these colors all the time. Now I
(05:07):
want you to try this. Imagine a new color. Go ahead, Okay,
you can't do it. The fact that you can't do
it is very revealing, and it's very important because it
illustrates for us the fence lines of our perceptions, beyond
which we just can't walk. And by the way, if
you could envision a new color, you wouldn't be able
(05:29):
to explain the sensation of it to another person. For example,
you have to experience purple to know what purple is.
There's no amount of description on a podcast or in
a textbook that's ever going to allow a totally color
blind person to understand purpleness. Here's an analogy, just to
(05:49):
make this clear, try explaining vision to a friend of
yours who is born blind. You can try all you want,
and your blind friend might even pretend to understan what
you're talking about, but it is a fruitless attempt because
to understand vision requires experiencing vision. And that's the same
with experiencing purple or canary yellow or cobalt blue. You
(06:16):
have to experience it to know it. There's no way
to describe it. Language is just a way of tagging
shared experiences, and if it's not shared in some way,
no amount of language will do the trick. Okay, so
let's come back to the idea of whether you will
ever have the chance to see a new color. Well,
(06:38):
it seems pretty clear that the answer is no, because
the space of possible colors that humans can see are
pretty well represented in our world, but under special circumstances
you can see new ones. So first, let's start with
what are known as impossible colors. These are colors that
are outside what our cones can put together. For example,
(07:01):
you can't have a reddish green or a yellowish blue.
These are combinations that the visual system just isn't wired
to perceive simultaneously. But under certain conditions. Using tricks in
the laboratory, some people do report glimpsing these colors. These
perceptions are fleeting, but they hint at the boundaries and
(07:23):
the flexibility of color perception. So here's something that you
can try easily. Let's say that you stare at a
square that is cyan in color, and you just stare
at that for twenty or thirty seconds. Then if you
look over to a white piece of paper, you'll see
an orange after image. Okay, fine, but now after staring
(07:44):
at the cyan, try looking over at an orange piece
of paper, and you will see what we call hyperbolic orange,
which is an orange so orange that you never can
normally see that. Now, there are a bunch of ways
to see impossible colors. Here's one. Stare at a yellow
square for a while, and then look at a piece
(08:06):
of paper that's black. You'll see what is called stygian blue,
which is a blue that is darker than black. Or
stare at a green square for a while and then
look at a white background and you'll see what's called
self luminous red, a red that is brighter than white.
(08:28):
These are some ways to see outside the normal fence
lines of color, and I'll put demos of these on
the show notes at Eagleman dot com. Now, there are
other ways to see new colors that require doing so
in the laboratory, and I'm going to come back to
that near the end of the episode when I'm going
to talk about the future of seeing color. But for now,
I want to mention something else, which is the issue
(08:50):
of seeing data outside the normal visual spectrum that we
can see. For example, it might sound impossible to see
in the altar for violet range, but it turns out
your photoreceptors can do that. It's just that the lens
of your eye blocks out UV light. But then something
was accidentally discovered in the last couple of decades. A
(09:13):
lot of people go in for cataract surgery and they
get their lens exchanged for a synthetic replacement. Your natural
lens blocks UV, but the replacement lens does not, So
patients found themselves tapping into ranges of the electromagnetic spectrum
that they couldn't see before. I wrote about one guy
(09:34):
in my book Live Wire. His name is Alec, and
he got a lens replacement for his cataracts, and he
now describes a lot of things that he looks at
as having a blue violet glow that other people just
don't see. He noticed this the day after his cataract
surgery when he was looking at his son's Colorado Rockies shorts.
Everyone else saw the shorts as black, but he saw
(09:56):
them with a blue violet sheen. When he put a
UV filter over his eye to block out the UV,
he saw them like everyone else. Here's another example. When
you look at what's called a black light that's turned on,
you don't see anything, but Alec sees a bright purple glow.
So this gives him a new superpower, seeing past the
(10:17):
normal spectrum of colors. Alec has different kinds of experiences
than we do when he looks at sunsets, or gas
stoves or flowers. Now I want to flip the question
to examine the other side. Could you lose your color vision. Yes,
it's rare, but it happens, and it's called a chromatopsia.
(10:38):
People with this condition see the world entirely in shades
of gray, as if life were filmed through the lens
of an old black and white movie. It's not just
muted color or red green confusion. It's the complete absence
of color perception. Just imagine this, The vibrant world that
we all take for granted gets rendered by your brain
(10:59):
in a perpetual gray scale, where even a rainbow is
just a smooth gradient of light and dark. Now, the
thing I want to note is that achromatopsia results from
brain damage, specifically to a region called area V four
in the visual cortex. Because color vision doesn't happen in
your eyes alone. While the cone cells in your retina
(11:21):
detects different wavelengths of light, the experience of color is
assembled in the brain, and one of the key regions
responsible for putting those wavelengths together into color perception is
this area of V four, located in what's known as
the ventral visual pathway in the brain. The point is,
if this area is damaged from a stroke, from head trauma,
(11:44):
from a brain tumor, the person gets this cortical color blindness.
The eyes are perfectly healthy, but the brain can't interpret
color signals anymore, so the person experiences the world in grayscale.
So this once again illustrates the simple but critical point
that color is a construction of the brain, and you
(12:05):
have to have all the right pieces and parts running
or else. You can see just fine, but you can't
see color. Now. Some people, of course, are born color blind,
(12:32):
but not because of brain damage, but instead because they
don't have some of the types of cones in their eye.
As a reminder, most people are born with three different
types of cones color photo receptors, but some people are
born with only two types, or one type or none,
giving them a diminished or no ability to distinguish between colors. Now,
(12:54):
the military excludes colorblind soldiers from certain jobs, but they
have come to realize that colorblind people do have a
secret superpower. They can spot enemy camouflage better than people
with normal color vision. Why because they're better at distinguishing
between shades of gray. This is because they have the
(13:17):
same amount of visual cortex at the back of their brain,
but fewer color dimensions to worry about. So they're using
the same cortical territory, but for a simpler task, just
gray scale instead of color, and this gives them improved
performance in distinguishing very subtle differences in brightness. So although
it would be a real bummer to be colorblind, there
(13:39):
are some advantages as well. So now let's return to color.
Everything we've talked about so far as a reminder that
color is not just about the electromagnetic radiation hitting the eye,
but about what happens in the brain. And one very
good example of that is something I've talked about before, synesthesia.
This is a brain phenomenon in which color blurs with
(14:03):
different concept a typical citisteit will perceive letters or numbers
as having fixed colors, like a is always red, or
the number seven is ce foam green, and it can
commonly be with weekdays or months like Wednesday is indigo
blue or August is yellow. Now it's not a hallucination,
(14:25):
but to the person, it's just self evidently true that
that's what that letter or number or weekday or month is.
Of course it's purple or yellow or green. So I've
studied synesthesia in my lab for many years because it's
such a good inroad into conscious experience and also the
differences between one person's experience and another's, and the difference
(14:46):
is between people's experiences on the inside when they're perceiving
the world. If you're interested in synesthesia, please listen to
episode four. But for now, I want to zoom in
on the issue of colored weekdays, which is a common form.
The thing I want to emphasize is that the color
palette ends up being different for each cynisthees. So one
(15:08):
person might say, oh, Monday is clearly green and Tuesday
is purple, and Wednesday is yellow, and a different cinisthee
has a different color palette. Now, I've studied literally thousands
of such cynthtes, but here's something I just learned that
really surprised me. I learned that in Thailand there's an
(15:29):
ancient tradition in which each day of the week has
a corresponding color, rooted in Hindu based astrology. So Monday
is yellow, Tuesday is pink, Wednesday is green, and so on.
Apparently these colors are tied to planetary deities like Mars,
for Tuesday is associated with pink, Mercury, for Wednesday is green,
(15:53):
and so on, and traditionally it was believed to bring
luck if you wore that color or use color on
the corresponding day. This apparently used to be very common
in Thailand to wear the right color every single day.
Today it's a little less common. Now. You can probably
guess what I'm wondering about, which is where did this
colored weekday idea come from Well, if you consult any
(16:15):
Taie book on this, they'll say it comes from the
colors of their deities. But of course gods don't really exist,
and if they did, it's not obvious they would have colors,
or that anyone would have seen those colors. So my
suspicion is that if we really did get to the
bottom of this very ancient history, we'd find a very
(16:36):
influential Cinistheite at bottom, someone who said, well, of course
Tuesday is pink and Wednesday is green and so on,
and because of some cult of personality, it stuck, and
millennia later, kids are still told that this deity is
this color, so that day is the color and you
should wear that shirt. And so, like all stories with
(16:58):
cultural momentum, people accept it. Why because everyone else accepts
it and for thousands of years, So there must be
something to it. But that's something I suggest is a
single influential Cynistheide whose quirky neural network determined what everyone
wore for hundreds of generations. So if you ever think
(17:20):
neuroscience doesn't affect culture, take that. And on that topic
of the intersection between neuroscience and culture, I want to
zoom the camera out to see what happens when lots
of humans start talking together about color. So we're going
to turn now to language. For most listeners of this podcast,
we look at a rainbow and divide it into red, orange, yellow, green, blue, indigo, violet.
(17:44):
But not every culture divides the spectrum the same way
or sees the same number of colors. In some languages,
there is no distinct word for blue. In other languages,
green and blue are considered shades of the same color.
As an example of the kinds of differences here, the
Himba people of Namibia group colors differently from English speakers.
(18:07):
They have multiple words for what we call green and
none for what we call blue. Even ancient texts reveal
this difference in color vocabularies, So in Homer's Odyssey, the
sea is never described as blue, but it's described as
wine dark. Scholars have long puzzled over this poetic phrase.
(18:28):
Was it a metaphor or was it that the ancient
Greeks didn't categorize blue the way that we do. Blue
appears almost nowhere in ancient Greek language, and where it
does is often ambiguous. Why while in ancient Greece there
were few blue dyes or paints, and by the way,
blue animals are extraordinarily rare in nature. So while the
(18:50):
Egyptians used a synthetic pigment, which we call Egyptian blue,
the Greeks didn't use or produce blue. So it meant
that blue was less present in their daily life, or
in their clothing or in their art, and the thought
goes that it was therefore less common in the language,
in the same way that cultures on the equator have
(19:11):
fewer words for distinguishing types of snow than do northern cultures.
Now zooming out a moment, there were two researchers, Berlin
and k who proposed that even though language might have
different color terms, they all follow a predictable order in
the development of these terms. In other words, the first
two terms to appear historically in any language are always
(19:34):
black and white or dark and light. Then comes red.
Then when cultures get more culture as they introduce green
or yellow. Only later do you get things like blue
and brown and more nuanced shades like pink or orange.
The hypothesis is that this progression matches the salience of
(19:55):
colors in the environment. The contrast of light and dark
is really important, the presence of blood, the ripeness of fruit,
the necessity of distinguishing between plants. So it's only when
society has become more complex and encounter more dyes and
materials and artistic traditions then you get new color terms emerging.
(20:16):
So different languages have different color terms, and one idea
that has emerged is called linguistic relativity, which is this
notion that the language that you speak shapes how you
perceive the world. The idea is that although all people
can see blue, if your language doesn't label it distinctly,
you might not really pay attention to it as a
(20:38):
separate category. And this is indeed what a lot of
cognitive science studies have found. Your language shapes at least
a little bit your color distinctions. For example, the Russian
language has distinct words for light blue and dark blue,
and when Russians are tested on their ability to distinguish
(20:59):
shades of blue, they're faster at spotting the difference between
light and dark blues than English speakers, who use one
word for both blue. In other words, Russian speaking brains
process the difference more quickly, suggesting that having a word
for something helps you see it. If your language has
(21:19):
more precise blue terms, like Russian, you can distinguish shades
faster than languages that don't, like English, and you can
see the same story in babies. Infants can see color
long before they learn to speak, but once they acquire
the words for specific colors, their ability to distinguish them improves.
(21:40):
Language tunes the brain to attend to specific aspects of
the scene. So if the Greeks didn't have a strong
word for blue, they might have grouped it with other
colors like green or gray and not really noticed it
as blue. The Greeks didn't lack the ability to see blue,
(22:00):
but in their culture they didn't isolate it with language,
likely because blue was rare in their environment and their
language hadn't evolved to distinguish it clearly. So when Homer
describes the sea as wine dark, it's not because he
was colorblind. It's because the way his culture saw and
named colors was a little different from ours. And by
(22:22):
the way this issue about the Greeks and blue, the
same is true of many ancient languages, including Hebrew and
Chinese and Japanese, and in modern studies we can look
at the Himba people who as I mentioned have multiple
words for green and none for blue. In experiments, they
can easily distinguish green shades that we Westerners struggle to
(22:43):
tell apart, but they find it difficult to pick out
a blue square from a field of green. Now we've
been talking about biology and language, but what's fascinating is
how this private phenomenon of color takes on cultural meaning.
A million examples of this. I'll just do a quick whistlestop, TORP.
So just look at the way we organize our world
(23:06):
through color. We have red states and blue states. We
have green energy, we have black markets, we have white lies.
Color becomes shorthand for complex social and political ideas. Even
our moral frameworks become color coded. You've got the white
hat and the black hat, and the old Westerns. You've
got the white dove of peace, you have the red
(23:27):
devil of temptation. And colors very commonly come to signal
identity and allegiance. You have teams and uniforms that define
us versus them by color. Movements adopt symbolic palettes. So
the Suffragettes wore white and green and violet. AIDS awareness
uses red, environmental causes green. You see rainbow flags and
(23:49):
pride parades. You see orange worn by anti gun violence advocates.
So in this way, when we look around, we see
that color comes to serve as a quick symbol flag. Now,
not surprisingly, there's nothing fundamental about these associations and therefore
they aren't static. So in the eighteen hundreds, pink was
(24:11):
considered a strong masculine color related to red. Blue was
seen as delicate and feminine. These meanings flipped in the
twentieth century, and it had to do with shifts in
fashion and marketing and cultural signaling. Color, like language, evolves
and political colors vary. So you've got red for the
(24:32):
left in Europe, blue for conservatives in the UK, and
it's reversed in the United States. What I recently read
is that the colors in the United States blue for
liberals and red for conservatives. This got nailed down just
around the year two thousand, when the major television networks
started using this as a visual shorthand for liberal and conservative,
(24:52):
and that's how it got crystallized into public consciousness. I
don't really know the history of this, but I suspect
then in the day decades of black and white newspapers,
it was easier to use a donkey and an elephant
to distinguish the parties. And only when color television became
ubiquitous did it make sense to introduce a quick color flag. Okay, So,
(25:14):
now coming back to cultural messages, what is conveyed by
a color depends on your local context. In Western traditions,
white is associated with purity and innocence and weddings, but
in many Eastern cultures, white symbolizes death and is worn
by mourners. In South Africa, red can be a color
(25:36):
of mourning. In Brazil, purple is reserved for funerals. I'll
give you another example. Red, which in the West can
symbolize danger or passion, is associated in China with celebration
and joy and luck. A bride in India might wear
a bright red sorry, while a Western bride walks down
the aisle in white. So the point here is that
(25:58):
cultural colors symbols are learned. They're not innate. They are
built from shared stories and traditions and rituals. Now, despite
(26:24):
this variation, as far as what color means what sometimes,
there is a logic to it. Now, one thing I've
always found fascinating is that purple is always associated with royalty.
Why purple, why not orange or yellow or something else. Well,
it turns out that started in ancient Rome with a
die called Tyrian purple. This was a deep hue and
(26:47):
it was unlike any other dye that was available at
the time, and the color became irreversibly associated in their
society with nobility and wealth and the divine aura of emperors.
But what was so special about it? While Tyrian purple
was made from the mucus of a specific sea snail,
(27:07):
so producing just one gram of dye required thousands of
snails and days of labor. In other words, the die
was extremely labor intensive and therefore very expensive. Only the
wealthiest could afford it, and so that's how a particular
color came to represent something. What's interesting is that it
(27:30):
started off as an economic issue, but by the Roman
imperial era, the association between purple and power was codified
in the law. So you weren't allowed to wear garments
dyed in Tyrian purple unless you were an emperor or
a high ranking official. Apparently you could be sighted with
treason if you did this. So purple started out as expensive,
(27:54):
but it eventually became politically exclusive and By the way,
this wasn't just Rome. In various societies you find these
laws called sumptuary laws, which are like dress codes backed
by law, and these are there to restrict which people
can wear which colors. For example, you find the same
kind of sumptuary law in Elizabethan, England, where only royalty
(28:18):
and nobility were allowed to wear certain dies. The idea
with these laws is that they're designed to visibly maintain
the social order. So again, colors become a shorthand label
for larger concepts. Okay, so we've talked about this terrific
history of colors where certain colors came to have particular meaning.
(28:39):
But then what happened was the invention of synthetic dyes
in the nineteenth century, and suddenly you had this explosion
of vibrant hues that became accessible to the masses. The
first synthetic dye was mauve, and that was discovered accidentally
in eighteen fifty six, and that sparked a fashion because
(29:00):
what followed was an explosion of new hues, artificial magentas
and bright greens and vivid blues and optimistic yellow and
eventually drunk tank pink and ultramarine and atomic tangerine and
Nato green and millennial pink and safety orange and on
and on. So the world in a very short period
(29:23):
of time became much more colorful. So that's the recent
history of color. But I'm also interested in the flip
side question, which is what is the future of color,
because we're beginning to enter an era where color doesn't
have to be limited to what the ie evolved to
see or the dyes that we're able to make. First
(29:43):
of all, we're well beyond dies now because our modern
technology has changed how we see color. We have digital
screens that use RGB red, green, blue, and they mix
light instead of pigment, and any typical screen now displays
over sixteen million different colors. But the future of color
(30:04):
is going to go way further than that. As a
simple example, we've talked about how color can be used
to label information, so we can use augmented reality glasses
to map colors on the fly. Imagine that you are
in a factory where some machines are hot and some
are cold, and you just map the temperature data onto
red or blue so that you can see the temperature
(30:26):
at a distance. And of course it doesn't have to
be temperature. It could be anything like how full the
tanks are, or how many cycles per second are running
on the chips, or whatever information you need to carry.
You can encode that in color. But it gets better
than that, because new technologies are actually expanding the colors
(30:46):
that you can see. You can zap particular photoreceptors and
not others to see more saturated colors than you've ever
seen before. So at Berkeley, my colleagues have pulled off
a new project where a bypass your eyes normal machinery
and paint directly on your retina with light. And what
(31:07):
they can create is a brand new color, a literally
never before seen Hugh, a supersaturated blue green that the
research team calls ololo. What does olo look like? So
picture the most saturated peel that you can imagine, then
crank it up past anything nature offers. The green of
(31:29):
a laser pointer feels dull in comparison. Here's how it works.
Using very tiny doses of laser light, they individually target
photoreceptors in your eye. They don't just hit one photoreceptor,
but an entire constellation of about one thousand cones. It's
like they're painting on a tiny movie screen the size
of your fingernail. They're painting with light directly on your retina.
(31:52):
The key is that normally, each one of your cone
cells responds to different wavelengths short, medium, or long. But
there's so much overlap in the green and the red
cones that has been impossible to isolate just the green
cones the medium wavelength cones. But using this technique, that's
what they can do. So when only the medium cones
(32:13):
are stimulated, the result is Olo, a color that doesn't
exist anywhere in the natural world. Now, if the laser
jitters accidentally so that it activates nearby cones, the illusion
collapses in your back to just plain green, and that
shows how fragile this new color really is. So this
is how we can unlock entirely new sensory experiences. Your
(32:37):
brain is seeing something it never evolved to see, and
that brings us back to a deep question in neuroscience.
What happens when you feed the brain new information it's
never had before, And we see that the brain just
makes up a new color Olo, which is not born
of the saun or of nature, but of precise cellular
targeting in the lab. And so the possibility is there
(33:00):
that maybe we're just at the beginning of what human
perception is capable of. What amazes me is that we
can't imagine new colors, but once we've seen them, then
it's part of what we can imagine. And this tells
us that there's always more beyond the fence lines of
our internal models, which is what my next book is on,
(33:22):
which will hopefully come out next year. Okay, now I
want to get back to how science is going to
expand our perception. I think it's inevitable that genetic tools
are going to make it possible someday to modify our
eyes to detect new parts of the spectrum. So, for example,
will someday genetically give humans new flavors of photoreceptor cells?
(33:46):
Could you add a fourth type of cone to the retina?
I told you last week about tetrachromacy, in which a
tiny fraction of women see hundreds of millions of colors
rather than let's say a million, which is what most
of us can see. And this is because they have
a genetic mutation that gives them a fourth cone type.
So you could genetically engineer tetrachromacy like this. But you
(34:10):
could also engineer a fourth cone type to see beyond
the current limits of visible light. Imagine your great grandkids
being able to see magnetic fields like soft glows of color,
or to see other things that are totally invisible to you,
like infrared or ultraviolet, like snakes or bees do This
(34:31):
would just be an extension of the way that our
brains use colors as a way of tagging information in
the world. But now we'll be extending our perception beyond
its biological history. So let's wrap up. Color feels like
one of the most real and immediate and obvious aspects
(34:53):
of our experience. We fall in love with somebody's eyes,
we remember the yellow walls of a child bedroom. We
mourn in black, we celebrate in white or red or gold.
But what we've seen in this episode, in the last
is that color isn't fundamentally a property of the outside world.
It's a creation of the brain. There's no color in
(35:16):
a photon, there's just energy, just wavelength, and your retina
receives that input, and your brain compares and contrasts it
with other inputs, and out of this massive internal computation,
you experience something radiant and vivid, and by the way.
It's quite personal, which is why a blue and black
(35:36):
dress can divide the Internet. So the next time you
admire a sunset, or choose a shirt, or linger over
a painting, remember that you're translating physics into a subjective interpretation.
Color is a collaboration between the external world and your
(35:57):
internal model of it. It's where physics color lies with perception. Finally,
I just want to revisit how crazy I think it
is that we see colors every day that Julius Caesar
never did, and not just Caesar, but Shakespeare and Pocahontas
and Abraham Lincoln everyone. Until the proliferation of synthetic dies
(36:19):
and eventually digital screens, the world before us just didn't
see that many colors, colors that we get to see
every day, and typically don't even consider the size of
the palette that we get to appreciate. So spend a
few minutes today just looking around and thinking about the
millions of hues that you're looking at. Look at the
(36:41):
fashion around you, the clothing, the car colors, the paints,
even the annoying stuff like the advertising posters and the
road signs, even these are quite extraordinary when you look
at them. Through a new lens of appreciation, and I'm
really fascinated in thinking about how iotech will reach into
(37:01):
new color territories that we can't currently imagine. I told
you about the new color olo made by zapping specific
photoreceptors and not others in the lab. Just imagine what
things are going to look like in a century. Our
descendants might feel as sorry for us and our pitiful
little spectrum as we feel for our distant ancestors. Go
(37:30):
to eagleman dot com slash podcast for more information and
to find further reading. Join the weekly discussions on my substack,
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.
Today's episode is part two about color and the brain.
Why did royals wear purple? It's not accidental And if
you rewound history ten thousand years and ran it again,
you'd find exactly the same outcome. So what's going on?
And how do we see colors that our recent ancestors
(00:26):
never saw in their lives? Why can't you imagine a
new color? Are there, in fact new colors that you
could see? Yes, and I'm going to show you how
to do that. Can you lose your color vision? And
what does any of this have to do with language
or culture? Or why the military likes color blind people
(00:46):
for a particular task, and why I suggest that the
cultural history of Thailand was influenced by one single, unknown neurodivergent.
Welcome to Dinner Cosmos with me David Eagleman. I'm a
neuroscientist and author at Stanford and in these episodes we
(01:07):
look at the world inside us and around us to
understand why and how our lives look the way they do.
(01:30):
Today's episode is part two about the absolutely amazing and
often underappreciated topic of color. And if I do my
job right, this is going to allow you to see
the world with totally fresh eyes. So we're going to
start with a quick catch up from last week so
we can continue this incredible story about color and the brain.
(01:50):
Last week, we talked about the fact that color is
not a property of the physical world, but it's a
creation of the brain. Color doesn't exist in light itself.
Light is just electromagnetic radiation of various wavelengths, and our
brains interpret those wavelengths by constructing the experience of color.
(02:15):
This private interpretation of color begins in the retina with
a special type of photoreceptor cones, which detect wavelengths and
come in three flavors sensitive to short, medium, and long wavelengths,
which corresponds approximately to red, green, and blue. The brain
then processes patterns of activation across these cells to produce
(02:38):
the experience of color, and last week we talked about
color constancy, which allows us to perceive colors as stable
despite the changing lighting conditions, something that we see all
the time in visual illusions. We also talked about evolution.
For example, we humans have three types of giving us
(03:01):
trichromatic vision, but this is a rare trait among mammals,
most of whom are dichromatic, meaning they have two types
of cones, and this is likely because of a nocturnal
bottleneck where during the age of dinosaurs, the ancestors of
mammals how to avoid getting stomped on and eaten, and
(03:22):
so they scampered around at night and got better night vision,
but lost some of their color vision. Now humans and
some other primates reevolved trichromatic vision, possibly not just for
spotting ripe fruit, but for social reasons, detecting subtle changes
(03:43):
in skin coloration due to emotions. But in any case,
lots of our neighbors in the mammalian kingdom can't see
red and orange, which is why deer hunters wear orange vests,
because that allows the hunters to see each other clearly,
but the deer just can't see them. And finally we
(04:03):
saw how other species like bees and snakes and manta
shrimp they presumably perceive the world very differently because their
eyes pick up on ultraviolet light or infrared light or
polarized light. And if you tune into last week's episode,
you'll hear lots of other stories about how color serves
many functions like camouflage or warning or mating signals or
(04:26):
deception or emotional communication. Now we're ready to continue our
story this week. So let's start with something that I
think is amazing, which is that we see so many
more colors than even our recent ancestors did. This is
not because of a change in our biology. It's because
(04:46):
our current collection of technologies can generate so much more.
For example, your great great grandparents never saw a lot
of neon, or the bright ultra red of attack esla,
or the blaze orange of a caution sign on the road.
But we see these colors all the time. Now I
(05:07):
want you to try this. Imagine a new color. Go ahead, Okay,
you can't do it. The fact that you can't do
it is very revealing, and it's very important because it
illustrates for us the fence lines of our perceptions, beyond
which we just can't walk. And by the way, if
you could envision a new color, you wouldn't be able
(05:29):
to explain the sensation of it to another person. For example,
you have to experience purple to know what purple is.
There's no amount of description on a podcast or in
a textbook that's ever going to allow a totally color
blind person to understand purpleness. Here's an analogy, just to
(05:49):
make this clear, try explaining vision to a friend of
yours who is born blind. You can try all you want,
and your blind friend might even pretend to understan what
you're talking about, but it is a fruitless attempt because
to understand vision requires experiencing vision. And that's the same
with experiencing purple or canary yellow or cobalt blue. You
(06:16):
have to experience it to know it. There's no way
to describe it. Language is just a way of tagging
shared experiences, and if it's not shared in some way,
no amount of language will do the trick. Okay, so
let's come back to the idea of whether you will
ever have the chance to see a new color. Well,
(06:38):
it seems pretty clear that the answer is no, because
the space of possible colors that humans can see are
pretty well represented in our world, but under special circumstances
you can see new ones. So first, let's start with
what are known as impossible colors. These are colors that
are outside what our cones can put together. For example,
(07:01):
you can't have a reddish green or a yellowish blue.
These are combinations that the visual system just isn't wired
to perceive simultaneously. But under certain conditions. Using tricks in
the laboratory, some people do report glimpsing these colors. These
perceptions are fleeting, but they hint at the boundaries and
(07:23):
the flexibility of color perception. So here's something that you
can try easily. Let's say that you stare at a
square that is cyan in color, and you just stare
at that for twenty or thirty seconds. Then if you
look over to a white piece of paper, you'll see
an orange after image. Okay, fine, but now after staring
(07:44):
at the cyan, try looking over at an orange piece
of paper, and you will see what we call hyperbolic orange,
which is an orange so orange that you never can
normally see that. Now, there are a bunch of ways
to see impossible colors. Here's one. Stare at a yellow
square for a while, and then look at a piece
(08:06):
of paper that's black. You'll see what is called stygian blue,
which is a blue that is darker than black. Or
stare at a green square for a while and then
look at a white background and you'll see what's called
self luminous red, a red that is brighter than white.
(08:28):
These are some ways to see outside the normal fence
lines of color, and I'll put demos of these on
the show notes at Eagleman dot com. Now, there are
other ways to see new colors that require doing so
in the laboratory, and I'm going to come back to
that near the end of the episode when I'm going
to talk about the future of seeing color. But for now,
I want to mention something else, which is the issue
(08:50):
of seeing data outside the normal visual spectrum that we
can see. For example, it might sound impossible to see
in the altar for violet range, but it turns out
your photoreceptors can do that. It's just that the lens
of your eye blocks out UV light. But then something
was accidentally discovered in the last couple of decades. A
(09:13):
lot of people go in for cataract surgery and they
get their lens exchanged for a synthetic replacement. Your natural
lens blocks UV, but the replacement lens does not, So
patients found themselves tapping into ranges of the electromagnetic spectrum
that they couldn't see before. I wrote about one guy
(09:34):
in my book Live Wire. His name is Alec, and
he got a lens replacement for his cataracts, and he
now describes a lot of things that he looks at
as having a blue violet glow that other people just
don't see. He noticed this the day after his cataract
surgery when he was looking at his son's Colorado Rockies shorts.
Everyone else saw the shorts as black, but he saw
(09:56):
them with a blue violet sheen. When he put a
UV filter over his eye to block out the UV,
he saw them like everyone else. Here's another example. When
you look at what's called a black light that's turned on,
you don't see anything, but Alec sees a bright purple glow.
So this gives him a new superpower, seeing past the
(10:17):
normal spectrum of colors. Alec has different kinds of experiences
than we do when he looks at sunsets, or gas
stoves or flowers. Now I want to flip the question
to examine the other side. Could you lose your color vision. Yes,
it's rare, but it happens, and it's called a chromatopsia.
(10:38):
People with this condition see the world entirely in shades
of gray, as if life were filmed through the lens
of an old black and white movie. It's not just
muted color or red green confusion. It's the complete absence
of color perception. Just imagine this, The vibrant world that
we all take for granted gets rendered by your brain
(10:59):
in a perpetual gray scale, where even a rainbow is
just a smooth gradient of light and dark. Now, the
thing I want to note is that achromatopsia results from
brain damage, specifically to a region called area V four
in the visual cortex. Because color vision doesn't happen in
your eyes alone. While the cone cells in your retina
(11:21):
detects different wavelengths of light, the experience of color is
assembled in the brain, and one of the key regions
responsible for putting those wavelengths together into color perception is
this area of V four, located in what's known as
the ventral visual pathway in the brain. The point is,
if this area is damaged from a stroke, from head trauma,
(11:44):
from a brain tumor, the person gets this cortical color blindness.
The eyes are perfectly healthy, but the brain can't interpret
color signals anymore, so the person experiences the world in grayscale.
So this once again illustrates the simple but critical point
that color is a construction of the brain, and you
(12:05):
have to have all the right pieces and parts running
or else. You can see just fine, but you can't
see color. Now. Some people, of course, are born color blind,
(12:32):
but not because of brain damage, but instead because they
don't have some of the types of cones in their eye.
As a reminder, most people are born with three different
types of cones color photo receptors, but some people are
born with only two types, or one type or none,
giving them a diminished or no ability to distinguish between colors. Now,
(12:54):
the military excludes colorblind soldiers from certain jobs, but they
have come to realize that colorblind people do have a
secret superpower. They can spot enemy camouflage better than people
with normal color vision. Why because they're better at distinguishing
between shades of gray. This is because they have the
(13:17):
same amount of visual cortex at the back of their brain,
but fewer color dimensions to worry about. So they're using
the same cortical territory, but for a simpler task, just
gray scale instead of color, and this gives them improved
performance in distinguishing very subtle differences in brightness. So although
it would be a real bummer to be colorblind, there
(13:39):
are some advantages as well. So now let's return to color.
Everything we've talked about so far as a reminder that
color is not just about the electromagnetic radiation hitting the eye,
but about what happens in the brain. And one very
good example of that is something I've talked about before, synesthesia.
This is a brain phenomenon in which color blurs with
(14:03):
different concept a typical citisteit will perceive letters or numbers
as having fixed colors, like a is always red, or
the number seven is ce foam green, and it can
commonly be with weekdays or months like Wednesday is indigo
blue or August is yellow. Now it's not a hallucination,
(14:25):
but to the person, it's just self evidently true that
that's what that letter or number or weekday or month is.
Of course it's purple or yellow or green. So I've
studied synesthesia in my lab for many years because it's
such a good inroad into conscious experience and also the
differences between one person's experience and another's, and the difference
(14:46):
is between people's experiences on the inside when they're perceiving
the world. If you're interested in synesthesia, please listen to
episode four. But for now, I want to zoom in
on the issue of colored weekdays, which is a common form.
The thing I want to emphasize is that the color
palette ends up being different for each cynisthees. So one
(15:08):
person might say, oh, Monday is clearly green and Tuesday
is purple, and Wednesday is yellow, and a different cinisthee
has a different color palette. Now, I've studied literally thousands
of such cynthtes, but here's something I just learned that
really surprised me. I learned that in Thailand there's an
(15:29):
ancient tradition in which each day of the week has
a corresponding color, rooted in Hindu based astrology. So Monday
is yellow, Tuesday is pink, Wednesday is green, and so on.
Apparently these colors are tied to planetary deities like Mars,
for Tuesday is associated with pink, Mercury, for Wednesday is green,
(15:53):
and so on, and traditionally it was believed to bring
luck if you wore that color or use color on
the corresponding day. This apparently used to be very common
in Thailand to wear the right color every single day.
Today it's a little less common. Now. You can probably
guess what I'm wondering about, which is where did this
colored weekday idea come from Well, if you consult any
(16:15):
Taie book on this, they'll say it comes from the
colors of their deities. But of course gods don't really exist,
and if they did, it's not obvious they would have colors,
or that anyone would have seen those colors. So my
suspicion is that if we really did get to the
bottom of this very ancient history, we'd find a very
(16:36):
influential Cinistheite at bottom, someone who said, well, of course
Tuesday is pink and Wednesday is green and so on,
and because of some cult of personality, it stuck, and
millennia later, kids are still told that this deity is
this color, so that day is the color and you
should wear that shirt. And so, like all stories with
(16:58):
cultural momentum, people accept it. Why because everyone else accepts
it and for thousands of years, So there must be
something to it. But that's something I suggest is a
single influential Cynistheide whose quirky neural network determined what everyone
wore for hundreds of generations. So if you ever think
(17:20):
neuroscience doesn't affect culture, take that. And on that topic
of the intersection between neuroscience and culture, I want to
zoom the camera out to see what happens when lots
of humans start talking together about color. So we're going
to turn now to language. For most listeners of this podcast,
we look at a rainbow and divide it into red, orange, yellow, green, blue, indigo, violet.
(17:44):
But not every culture divides the spectrum the same way
or sees the same number of colors. In some languages,
there is no distinct word for blue. In other languages,
green and blue are considered shades of the same color.
As an example of the kinds of differences here, the
Himba people of Namibia group colors differently from English speakers.
(18:07):
They have multiple words for what we call green and
none for what we call blue. Even ancient texts reveal
this difference in color vocabularies, So in Homer's Odyssey, the
sea is never described as blue, but it's described as
wine dark. Scholars have long puzzled over this poetic phrase.
(18:28):
Was it a metaphor or was it that the ancient
Greeks didn't categorize blue the way that we do. Blue
appears almost nowhere in ancient Greek language, and where it
does is often ambiguous. Why while in ancient Greece there
were few blue dyes or paints, and by the way,
blue animals are extraordinarily rare in nature. So while the
(18:50):
Egyptians used a synthetic pigment, which we call Egyptian blue,
the Greeks didn't use or produce blue. So it meant
that blue was less present in their daily life, or
in their clothing or in their art, and the thought
goes that it was therefore less common in the language,
in the same way that cultures on the equator have
(19:11):
fewer words for distinguishing types of snow than do northern cultures.
Now zooming out a moment, there were two researchers, Berlin
and k who proposed that even though language might have
different color terms, they all follow a predictable order in
the development of these terms. In other words, the first
two terms to appear historically in any language are always
(19:34):
black and white or dark and light. Then comes red.
Then when cultures get more culture as they introduce green
or yellow. Only later do you get things like blue
and brown and more nuanced shades like pink or orange.
The hypothesis is that this progression matches the salience of
(19:55):
colors in the environment. The contrast of light and dark
is really important, the presence of blood, the ripeness of fruit,
the necessity of distinguishing between plants. So it's only when
society has become more complex and encounter more dyes and
materials and artistic traditions then you get new color terms emerging.
(20:16):
So different languages have different color terms, and one idea
that has emerged is called linguistic relativity, which is this
notion that the language that you speak shapes how you
perceive the world. The idea is that although all people
can see blue, if your language doesn't label it distinctly,
you might not really pay attention to it as a
(20:38):
separate category. And this is indeed what a lot of
cognitive science studies have found. Your language shapes at least
a little bit your color distinctions. For example, the Russian
language has distinct words for light blue and dark blue,
and when Russians are tested on their ability to distinguish
(20:59):
shades of blue, they're faster at spotting the difference between
light and dark blues than English speakers, who use one
word for both blue. In other words, Russian speaking brains
process the difference more quickly, suggesting that having a word
for something helps you see it. If your language has
(21:19):
more precise blue terms, like Russian, you can distinguish shades
faster than languages that don't, like English, and you can
see the same story in babies. Infants can see color
long before they learn to speak, but once they acquire
the words for specific colors, their ability to distinguish them improves.
(21:40):
Language tunes the brain to attend to specific aspects of
the scene. So if the Greeks didn't have a strong
word for blue, they might have grouped it with other
colors like green or gray and not really noticed it
as blue. The Greeks didn't lack the ability to see blue,
(22:00):
but in their culture they didn't isolate it with language,
likely because blue was rare in their environment and their
language hadn't evolved to distinguish it clearly. So when Homer
describes the sea as wine dark, it's not because he
was colorblind. It's because the way his culture saw and
named colors was a little different from ours. And by
(22:22):
the way this issue about the Greeks and blue, the
same is true of many ancient languages, including Hebrew and
Chinese and Japanese, and in modern studies we can look
at the Himba people who as I mentioned have multiple
words for green and none for blue. In experiments, they
can easily distinguish green shades that we Westerners struggle to
(22:43):
tell apart, but they find it difficult to pick out
a blue square from a field of green. Now we've
been talking about biology and language, but what's fascinating is
how this private phenomenon of color takes on cultural meaning.
A million examples of this. I'll just do a quick whistlestop, TORP.
So just look at the way we organize our world
(23:06):
through color. We have red states and blue states. We
have green energy, we have black markets, we have white lies.
Color becomes shorthand for complex social and political ideas. Even
our moral frameworks become color coded. You've got the white
hat and the black hat, and the old Westerns. You've
got the white dove of peace, you have the red
(23:27):
devil of temptation. And colors very commonly come to signal
identity and allegiance. You have teams and uniforms that define
us versus them by color. Movements adopt symbolic palettes. So
the Suffragettes wore white and green and violet. AIDS awareness
uses red, environmental causes green. You see rainbow flags and
(23:49):
pride parades. You see orange worn by anti gun violence advocates.
So in this way, when we look around, we see
that color comes to serve as a quick symbol flag. Now,
not surprisingly, there's nothing fundamental about these associations and therefore
they aren't static. So in the eighteen hundreds, pink was
(24:11):
considered a strong masculine color related to red. Blue was
seen as delicate and feminine. These meanings flipped in the
twentieth century, and it had to do with shifts in
fashion and marketing and cultural signaling. Color, like language, evolves
and political colors vary. So you've got red for the
(24:32):
left in Europe, blue for conservatives in the UK, and
it's reversed in the United States. What I recently read
is that the colors in the United States blue for
liberals and red for conservatives. This got nailed down just
around the year two thousand, when the major television networks
started using this as a visual shorthand for liberal and conservative,
(24:52):
and that's how it got crystallized into public consciousness. I
don't really know the history of this, but I suspect
then in the day decades of black and white newspapers,
it was easier to use a donkey and an elephant
to distinguish the parties. And only when color television became
ubiquitous did it make sense to introduce a quick color flag. Okay, So,
(25:14):
now coming back to cultural messages, what is conveyed by
a color depends on your local context. In Western traditions,
white is associated with purity and innocence and weddings, but
in many Eastern cultures, white symbolizes death and is worn
by mourners. In South Africa, red can be a color
(25:36):
of mourning. In Brazil, purple is reserved for funerals. I'll
give you another example. Red, which in the West can
symbolize danger or passion, is associated in China with celebration
and joy and luck. A bride in India might wear
a bright red sorry, while a Western bride walks down
the aisle in white. So the point here is that
(25:58):
cultural colors symbols are learned. They're not innate. They are
built from shared stories and traditions and rituals. Now, despite
(26:24):
this variation, as far as what color means what sometimes,
there is a logic to it. Now, one thing I've
always found fascinating is that purple is always associated with royalty.
Why purple, why not orange or yellow or something else. Well,
it turns out that started in ancient Rome with a
die called Tyrian purple. This was a deep hue and
(26:47):
it was unlike any other dye that was available at
the time, and the color became irreversibly associated in their
society with nobility and wealth and the divine aura of emperors.
But what was so special about it? While Tyrian purple
was made from the mucus of a specific sea snail,
(27:07):
so producing just one gram of dye required thousands of
snails and days of labor. In other words, the die
was extremely labor intensive and therefore very expensive. Only the
wealthiest could afford it, and so that's how a particular
color came to represent something. What's interesting is that it
(27:30):
started off as an economic issue, but by the Roman
imperial era, the association between purple and power was codified
in the law. So you weren't allowed to wear garments
dyed in Tyrian purple unless you were an emperor or
a high ranking official. Apparently you could be sighted with
treason if you did this. So purple started out as expensive,
(27:54):
but it eventually became politically exclusive and By the way,
this wasn't just Rome. In various societies you find these
laws called sumptuary laws, which are like dress codes backed
by law, and these are there to restrict which people
can wear which colors. For example, you find the same
kind of sumptuary law in Elizabethan, England, where only royalty
(28:18):
and nobility were allowed to wear certain dies. The idea
with these laws is that they're designed to visibly maintain
the social order. So again, colors become a shorthand label
for larger concepts. Okay, so we've talked about this terrific
history of colors where certain colors came to have particular meaning.
(28:39):
But then what happened was the invention of synthetic dyes
in the nineteenth century, and suddenly you had this explosion
of vibrant hues that became accessible to the masses. The
first synthetic dye was mauve, and that was discovered accidentally
in eighteen fifty six, and that sparked a fashion because
(29:00):
what followed was an explosion of new hues, artificial magentas
and bright greens and vivid blues and optimistic yellow and
eventually drunk tank pink and ultramarine and atomic tangerine and
Nato green and millennial pink and safety orange and on
and on. So the world in a very short period
(29:23):
of time became much more colorful. So that's the recent
history of color. But I'm also interested in the flip
side question, which is what is the future of color,
because we're beginning to enter an era where color doesn't
have to be limited to what the ie evolved to
see or the dyes that we're able to make. First
(29:43):
of all, we're well beyond dies now because our modern
technology has changed how we see color. We have digital
screens that use RGB red, green, blue, and they mix
light instead of pigment, and any typical screen now displays
over sixteen million different colors. But the future of color
(30:04):
is going to go way further than that. As a
simple example, we've talked about how color can be used
to label information, so we can use augmented reality glasses
to map colors on the fly. Imagine that you are
in a factory where some machines are hot and some
are cold, and you just map the temperature data onto
red or blue so that you can see the temperature
(30:26):
at a distance. And of course it doesn't have to
be temperature. It could be anything like how full the
tanks are, or how many cycles per second are running
on the chips, or whatever information you need to carry.
You can encode that in color. But it gets better
than that, because new technologies are actually expanding the colors
(30:46):
that you can see. You can zap particular photoreceptors and
not others to see more saturated colors than you've ever
seen before. So at Berkeley, my colleagues have pulled off
a new project where a bypass your eyes normal machinery
and paint directly on your retina with light. And what
(31:07):
they can create is a brand new color, a literally
never before seen Hugh, a supersaturated blue green that the
research team calls ololo. What does olo look like? So
picture the most saturated peel that you can imagine, then
crank it up past anything nature offers. The green of
(31:29):
a laser pointer feels dull in comparison. Here's how it works.
Using very tiny doses of laser light, they individually target
photoreceptors in your eye. They don't just hit one photoreceptor,
but an entire constellation of about one thousand cones. It's
like they're painting on a tiny movie screen the size
of your fingernail. They're painting with light directly on your retina.
(31:52):
The key is that normally, each one of your cone
cells responds to different wavelengths short, medium, or long. But
there's so much overlap in the green and the red
cones that has been impossible to isolate just the green
cones the medium wavelength cones. But using this technique, that's
what they can do. So when only the medium cones
(32:13):
are stimulated, the result is Olo, a color that doesn't
exist anywhere in the natural world. Now, if the laser
jitters accidentally so that it activates nearby cones, the illusion
collapses in your back to just plain green, and that
shows how fragile this new color really is. So this
is how we can unlock entirely new sensory experiences. Your
(32:37):
brain is seeing something it never evolved to see, and
that brings us back to a deep question in neuroscience.
What happens when you feed the brain new information it's
never had before, And we see that the brain just
makes up a new color Olo, which is not born
of the saun or of nature, but of precise cellular
targeting in the lab. And so the possibility is there
(33:00):
that maybe we're just at the beginning of what human
perception is capable of. What amazes me is that we
can't imagine new colors, but once we've seen them, then
it's part of what we can imagine. And this tells
us that there's always more beyond the fence lines of
our internal models, which is what my next book is on,
(33:22):
which will hopefully come out next year. Okay, now I
want to get back to how science is going to
expand our perception. I think it's inevitable that genetic tools
are going to make it possible someday to modify our
eyes to detect new parts of the spectrum. So, for example,
will someday genetically give humans new flavors of photoreceptor cells?
(33:46):
Could you add a fourth type of cone to the retina?
I told you last week about tetrachromacy, in which a
tiny fraction of women see hundreds of millions of colors
rather than let's say a million, which is what most
of us can see. And this is because they have
a genetic mutation that gives them a fourth cone type.
So you could genetically engineer tetrachromacy like this. But you
(34:10):
could also engineer a fourth cone type to see beyond
the current limits of visible light. Imagine your great grandkids
being able to see magnetic fields like soft glows of color,
or to see other things that are totally invisible to you,
like infrared or ultraviolet, like snakes or bees do This
(34:31):
would just be an extension of the way that our
brains use colors as a way of tagging information in
the world. But now we'll be extending our perception beyond
its biological history. So let's wrap up. Color feels like
one of the most real and immediate and obvious aspects
(34:53):
of our experience. We fall in love with somebody's eyes,
we remember the yellow walls of a child bedroom. We
mourn in black, we celebrate in white or red or gold.
But what we've seen in this episode, in the last
is that color isn't fundamentally a property of the outside world.
It's a creation of the brain. There's no color in
(35:16):
a photon, there's just energy, just wavelength, and your retina
receives that input, and your brain compares and contrasts it
with other inputs, and out of this massive internal computation,
you experience something radiant and vivid, and by the way.
It's quite personal, which is why a blue and black
(35:36):
dress can divide the Internet. So the next time you
admire a sunset, or choose a shirt, or linger over
a painting, remember that you're translating physics into a subjective interpretation.
Color is a collaboration between the external world and your
(35:57):
internal model of it. It's where physics color lies with perception. Finally,
I just want to revisit how crazy I think it
is that we see colors every day that Julius Caesar
never did, and not just Caesar, but Shakespeare and Pocahontas
and Abraham Lincoln everyone. Until the proliferation of synthetic dies
(36:19):
and eventually digital screens, the world before us just didn't
see that many colors, colors that we get to see
every day, and typically don't even consider the size of
the palette that we get to appreciate. So spend a
few minutes today just looking around and thinking about the
millions of hues that you're looking at. Look at the
(36:41):
fashion around you, the clothing, the car colors, the paints,
even the annoying stuff like the advertising posters and the
road signs, even these are quite extraordinary when you look
at them. Through a new lens of appreciation, and I'm
really fascinated in thinking about how iotech will reach into
(37:01):
new color territories that we can't currently imagine. I told
you about the new color olo made by zapping specific
photoreceptors and not others in the lab. Just imagine what
things are going to look like in a century. Our
descendants might feel as sorry for us and our pitiful
little spectrum as we feel for our distant ancestors. Go
(37:30):
to eagleman dot com slash podcast for more information and
to find further reading. Join the weekly discussions on my substack,
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
Popular Podcasts
Stuff You Should Know
If you've ever wanted to know about champagne, satanism, the Stonewall Uprising, chaos theory, LSD, El Nino, true crime and Rosa Parks, then look no further. Josh and Chuck have you covered.
My Favorite Murder with Karen Kilgariff and Georgia Hardstark
My Favorite Murder is a true crime comedy podcast hosted by Karen Kilgariff and Georgia Hardstark. Each week, Karen and Georgia share compelling true crimes and hometown stories from friends and listeners. Since MFM launched in January of 2016, Karen and Georgia have shared their lifelong interest in true crime and have covered stories of infamous serial killers like the Night Stalker, mysterious cold cases, captivating cults, incredible survivor stories and important events from history like the Tulsa race massacre of 1921. My Favorite Murder is part of the Exactly Right podcast network that provides a platform for bold, creative voices to bring to life provocative, entertaining and relatable stories for audiences everywhere. The Exactly Right roster of podcasts covers a variety of topics including historic true crime, comedic interviews and news, science, pop culture and more. Podcasts on the network include Buried Bones with Kate Winkler Dawson and Paul Holes, That's Messed Up: An SVU Podcast, This Podcast Will Kill You, Bananas and more.
The Joe Rogan Experience
The official podcast of comedian Joe Rogan.