Free Republic
Browse · Search
General/Chat
Topics · Post Article

Skip to comments.

Purple exists only in our brains...The color is our brain’s solution to a puzzling problem
Science News Explores ^ | January 28, 2025 | Tammy Awtry

Posted on 02/03/2025 6:36:50 PM PST by Red Badger

There is something unique about the color purple: Our brain makes it up. So you might just call purple a pigment of our imagination.

It’s also a fascinating example of how the brain creates something beautiful when faced with a systems error.

To understand where purple comes from, we need to know how our eyes and brain work together to perceive color. And that all begins with light.

Light is another term for electromagnetic radiation. Most comes from the sun and travels to Earth in waves. There are many different types of light, which scientists group based on the lengths of those waves. (The wavelength is the distance between one wave peak and the next.) Together, all of those wavelengths make up the electromagnetic spectrum.

Our eyes can’t see most wavelengths, such as the microwaves used to cook food or the ultraviolet light that can burn our skin when we don’t wear sunscreen. We can directly see only a teeny, tiny sliver of the spectrum — just 0.0035 percent! This slice is known as the visible-light spectrum. It spans wavelengths between roughly 350 and 700 nanometers.

The acronym ROYGBIV (pronounced Roy-gee-biv) can be used to remember the order of colors in that visible spectrum: red, orange, yellow, green, blue, indigo and violet. You can see these colors in a rainbow stretching across the sky after a rainstorm or when light shines through a prism. In the visible spectrum, red light has the longest wavelength. Blue and violet are the shortest. Green and yellow sit toward the middle.

Although violet is in the visible spectrum, purple is not. Indeed, violet and purple are not the same color. They look similar, but the way our brain perceives them is very different.

How we see color

Color perception starts in our eyes. The backs of our eyes contain light-sensitive cells called cones. Most people have three types. They’re sometimes called red, green and blue cones because each is most sensitive to one of those colors.

But cones don’t “see” color, notes Zab Johnson. Instead, they detect certain wavelengths of light.

Johnson works at the University of Pennsylvania in Philadelphia. She and other scientists who study how we perceive color prefer to classify cones based on the range of wavelengths they detect: long, mid or short.

So-called red cones detect long wavelengths of light. Green cones respond most strongly to light in the middle of the visible spectrum. Blue cones best detect wavelengths toward the shorter end of the visible spectrum.

When light enters our eyes, the specific combination of cones it activates is like a code. Our brain deciphers that code and then translates it into a color.

Consider light that stimulates long- and mid-wavelength cones but few, if any, short-wavelength cones. Our brain interprets this as orange. When light triggers mostly short-wavelength cones, we see blue or violet. A combination of mid- and short-wavelength cones looks green. Any color within the visible rainbow can be created by a single wavelength of light stimulating a specific combination of cones.

Notice that the visible spectrum is a gradient. One color gradually shifts into the next. The activity of cones activated by the light also gradually shifts from one type to the next. At the red end of the spectrum, for instance, long-wavelength cones do most of the work. As you move from red to orange, the mid-wavelength cones help more and the long-wavelength cones do less.

In the middle of the rainbow — colors like green and yellow — the mid-wavelength cones are busiest, with help from both long- and short-wavelength cones. At the blue end of the spectrum, short-wavelength cones do most of the work.

But there is no color on the spectrum that’s created by combining long- and short-wavelength cones.

This makes purple a puzzle.

Purple is a mix of red (long) and blue (short) wavelengths. Seeing something that’s purple, such as eggplants or lilacs, stimulates both short- and long-wavelength cones. This confuses the brain. If long-wavelength cones are excited, the color should be red or near to that. If short-wavelength cones are excited, the color should be near to blue.

The problem: Those colors are on opposite ends of the spectrum. How can a color be close to both ends at once?

To cope, the brain improvises. It takes the visible spectrum — usually a straight line — and bends it into a circle. This puts blue and red next to each other.

“Blue and red should be on opposite ends of that linear scale,” Johnson explains. “Yet at some point, blue and red start to come together. And that coming-together point is called purple.”

Our brain now remodels the visible spectrum into a color wheel and pops in a palette of purples — which don’t exist — as a solution to why it’s receiving information from opposite ends of the visible spectrum.

Colors that are part of the visible spectrum are known as spectral colors. It only takes one wavelength of light for our brain to perceive shades of each color. Purple, however, is a nonspectral color. That means it’s made of two wavelengths of light (one long and one short).

This is the difference between violet and purple. Violet is a spectral color — part of the visible spectrum. Purple is a nonspectral color that the brain creates to make sense of confusing information.

Purple thus arises from a unique quirk of how we process light. And it’s a beautiful example of how our brains respond when faced with something out of the norm. But it’s not the only color that deserves our admiration, says Anya Hurlbert.

“All colors are made up by the brain. Full stop,” says this visual scientist at Newcastle University in England. They’re our brain’s way of interpreting signals from our eyes. And they add so much meaning to things we perceive, she says.

“The color of a bruise tells me how old it is. The color of a fruit tells me how ripe it is. The color of a piece of fabric tells me whether it’s been washed many times or it’s fresh off the factory line,” she says. “There’s almost nothing else that starts with something so simple [like a wavelength of light] and ends with something so deep and rich.”


TOPICS: Health/Medicine; Science; Society; Weird Stuff
KEYWORDS: 0000iqkeywordtroll; 0001totalbs; 0001totalpottymouth; angrykeywordtroll; applesandoranges; baloney; color; cones; eyes; fakescience; godsgravesglyphs; ifhfakescience; imadeitup; physicsnotpsychology; purple; rods; roygbiv; sciencehatingtrolls; sciencenewsexplores; sloppyphilosophy; tammyawtry; tldr; vision
Navigation: use the links below to view more comments.
first previous 1-2021-4041-6061-80 ... 201-211 next last
To: Red Badger

Now explain Homer’s ‘wine dark sea’.


21 posted on 02/03/2025 6:58:52 PM PST by Jamestown1630 ("A Republic, if you can keep it.")
[ Post Reply | Private Reply | To 1 | View Replies]

To: TexasGator
Why do science articles here always draw stupid comments?

Because you show up.

22 posted on 02/03/2025 7:00:12 PM PST by Harmless Teddy Bear ( Not my circus. Not my monkeys. But I can pick out the clowns at 100 yards.)
[ Post Reply | Private Reply | To 20 | View Replies]

To: Red Badger

I had to read almost to the end to see that they’re saying violet isn’t purple.


23 posted on 02/03/2025 7:00:24 PM PST by ifinnegan (Democrats kill babies and harvest their organs to sell)
[ Post Reply | Private Reply | To 1 | View Replies]

To: nopardons

“This is ridiculous and worse, is the claim that NO LONG and SHORT WAVE LENGTH MAKES A COLOR!”

That was not stated in the article. You get an F in reading comprehension.


24 posted on 02/03/2025 7:00:31 PM PST by TexasGator (11'r/11111.111''!11)
[ Post Reply | Private Reply | To 13 | View Replies]

To: Red Badger

And this is why just three wavelengths in video displays and photos can appear realistic to us. It’s a gift from God for our enjoyment.


25 posted on 02/03/2025 7:02:39 PM PST by old-ager
[ Post Reply | Private Reply | To 1 | View Replies]

To: BipolarBob

And blue jays aren’t ‘blue’. They just look that way due to how their feathers are constructed.

(What difference does any of it make?)


26 posted on 02/03/2025 7:02:40 PM PST by Jamestown1630 ("A Republic, if you can keep it.")
[ Post Reply | Private Reply | To 3 | View Replies]

To: nopardons

You may know colors but you know nothing about how we process colors.

Read the article and learn.


27 posted on 02/03/2025 7:02:51 PM PST by TexasGator (11'r/11111.111''!11)
[ Post Reply | Private Reply | To 13 | View Replies]

To: Drew68
Inside a color band are many different shades and violet IS a shade of PURPLE!

Every color has shades within its colorway. < p> Even a single pigment color DOES have different qualities/shades within in it. Re watercolor...the shade depends on how much or how little water is added to the color, as well as if you use a dry ( none wet paper) or wet ( a dampened paper ) on which to paint.

By adding more water and/or painting "wet", you are able to paint a violet hue, by using a purple ( and there are many different shades, as well as mixes in the purple range ) color and a LOT of water.

28 posted on 02/03/2025 7:03:04 PM PST by nopardons
[ Post Reply | Private Reply | To 15 | View Replies]

To: nopardons

> Red and blue make PURPLE

You’re wrong, like almost every painter.

Red + Blue = Magenta.


29 posted on 02/03/2025 7:04:05 PM PST by old-ager
[ Post Reply | Private Reply | To 13 | View Replies]

To: TexasGator

Proof by assertion.


30 posted on 02/03/2025 7:04:33 PM PST by Olog-hai ("No Republican, no matter how liberal, is going to woo a Democratic vote." -- Ronald Reagan, 1960)
[ Post Reply | Private Reply | To 12 | View Replies]

To: nopardons

“The article is hogwash and even cointradicts itself.”

Very good article. You should learn from it.


31 posted on 02/03/2025 7:04:45 PM PST by TexasGator (11'r/11111.111''!11)
[ Post Reply | Private Reply | To 17 | View Replies]

To: Red Badger

If purple exists only in my brain, what’s it doing on my mattress?


32 posted on 02/03/2025 7:04:49 PM PST by Migraine
[ Post Reply | Private Reply | To 1 | View Replies]

To: Harmless Teddy Bear

Your stupid comments came before I showed up.


33 posted on 02/03/2025 7:05:53 PM PST by TexasGator (11'r/11111.111''!11)
[ Post Reply | Private Reply | To 22 | View Replies]

To: LastDayz
LOL...I haven't counted, but I don't think that there are 50 different shades of purple. :-)

OTOH....there ARE different shades of VIOLET and PURPLE, that one can buy, instead of doing the mixes yourself.

34 posted on 02/03/2025 7:06:02 PM PST by nopardons
[ Post Reply | Private Reply | To 19 | View Replies]

To: Migraine

You were drinking some weird wine?


35 posted on 02/03/2025 7:06:24 PM PST by Jamestown1630 ("A Republic, if you can keep it.")
[ Post Reply | Private Reply | To 32 | View Replies]

To: Red Badger
Rods, cones, high school flashbacks...

36 posted on 02/03/2025 7:06:43 PM PST by SunkenCiv (The Demagogic Party is a collection of violent, rival street gangs.)
[ Post Reply | Private Reply | View Replies]

To: Jamestown1630
It means something. It must mean something. Once we get the TOE, then we'll know.

TOE = Theory of Everything

37 posted on 02/03/2025 7:06:44 PM PST by BipolarBob (FBI Agent "I spied, lied and stole for the Bureau but by gawd I never lost my integrity".)
[ Post Reply | Private Reply | To 26 | View Replies]

To: Red Badger

38 posted on 02/03/2025 7:09:46 PM PST by Alas Babylon! (Repeal the Patriot Act; Abolish the DHS; reform FBI top to bottom!)
[ Post Reply | Private Reply | To 1 | View Replies]

To: Red Badger

I only wanted to see you
Laughing in the purple rain


39 posted on 02/03/2025 7:10:21 PM PST by packagingguy
[ Post Reply | Private Reply | To 1 | View Replies]

To: BipolarBob

I like the idea that our minds aren’t in our brains - mind is ‘Out There’ somewhere; and the brain is just a ‘receiver’...


40 posted on 02/03/2025 7:14:12 PM PST by Jamestown1630 ("A Republic, if you can keep it.")
[ Post Reply | Private Reply | To 37 | View Replies]


Navigation: use the links below to view more comments.
first previous 1-2021-4041-6061-80 ... 201-211 next last

Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.

Free Republic
Browse · Search
General/Chat
Topics · Post Article

FreeRepublic, LLC, PO BOX 9771, FRESNO, CA 93794
FreeRepublic.com is powered by software copyright 2000-2008 John Robinson