
A tiny group of people can see ‘invisible’ colours that no-one else can perceive - austinz
http://www.bbc.com/future/story/20140905-the-women-with-super-human-vision
======
Schiphol
Antico's painting of an eucalyptus doesn't "give us a hint of the extra shades
she is seeing". It's just another instance of the [El Greco
fallacy]([http://www.huffingtonpost.com/wray-herbert/a-new-look-at-
per...](http://www.huffingtonpost.com/wray-herbert/a-new-look-at-
perception_b_2867621.html)): art historians used to think that El Greco's
elongated figures were a result of his having a severe form of astigmatism.
But, of course, if that had been the reason, he would have also seen an
elongated canvass when painting, with the net result of figures painted in
standard proportions.

Here as well, if the tree painting was somewhow a reflection of Antico's
tetrachromatism, she would have chosen colors that matched those that she sees
on the eucalyptus. Such colors would be indistinguishable to us trichromats
from the colors the tree does have, with the net result of a normally colored
tree painting.

At best, Antico is using something of a metaphor to convey her
tetrachromatism. But no real insight on her vision.

~~~
jrs99
what about the "night vision" painting. if it's pitch black and someone has
the ability to see a vase, and then remembers the vase and paints the vase
green in another room brightly lit...

well, they wouldn't paint a pitch black canvas and claim they can see a vase
in that painting.

if el greco had some kind of condition that made him see elongated figures at
thirty feet away, would a small normally proportioned figure drawing two feet
away really look elongated also?

~~~
Schiphol
The night vision painting recovers quite a bit of the visual experiences: how
shapes are arranged in space, for example. What is recovered in the multicolor
eucalyptus from the tetrachromat's visual experience?

El Greco usually paints figures close by. Portraits, mostly. Your question
does not apply to his most famous paintings, I don't think.

------
jrapdx3
It's hard to compress what's known about the subject of color perception
differences among people with nominally normal color vision.

Hypothetical tetrachromacy has been demonstrated, that is, M and L cones with
minor differences in peak spectral response existing in a retinal mosaic. The
question arises whether this difference is capable of being propagated through
the bipolar connecting neuronal paths (which form the "blue-yellow" and "red-
green" channel paths conveying color info to the brain visual cortex).

Several studies found no evidence for a "fourth channel", and some perceptual
studies did not show confirmation of tetrachromacy. However a couple of
studies do hint at rare female subjects who do seem to have good evidence for
this trait.

It is postulated that because of the differences in the exact genetic
encodings on the 2 X chromosomes in females, that up to 50% of women have a
retinal mosaic of 4 populations of cones, S M M' L, S M L L', and so on. The
theory is that this allowed greater distinction of yellow to red color
distinction which may have helped survival by avoiding toxic plants based on
subtle color distinctions.

In art, there are great colorists and those who are virtually incapable of
subtle use of color. If anyone interested in finding out about their own
abilities, check out: [http://www.xrite.com/online-color-test-
challenge](http://www.xrite.com/online-color-test-challenge)

The on-line test is only a rough estimate, but it's fun and challenging. I
suspect there's a spectrum, aka normal distribution of color discrimination
ability. I should't say how well I did, though the results of trying it
several times were remarkably consistent despite different computer systems
that I used.

BTW I encountered one very intriguing article reporting on a large sample of
retinas obtained post-mortem. As expected, ~50% of females showed retinal
mosaic of 2 M or L cones where only one each was expected. Most fascinating
was the fact that of male retinas 8% showed a similar tetrachromat pattern.
How that could arise is a mystery considering males have only one X
chromosome. (There are pigment gene variations with greater number of CNV and
TR which could be activated? But it's still a mystery.)

~~~
jacobolus
> _Hypothetical tetrachromacy has been demonstrated, that is, M and L cones
> with minor differences in peak spectral response existing in a retinal
> mosaic. The question arises whether this difference is capable of being
> propagated through the bipolar connecting neuronal paths (which form the
> "blue-yellow" and "red-green" channel paths conveying color info to the
> brain visual cortex)._

Adding genes for extra cone types into normally dichromatic mammals (mice or
something? I don’t remember off hand and I don’t have the citation at my
fingertips) has seemed in studies to result in trichromatic vision, so it’s
not _too_ big a leap to suspect that tetrachromacy of the type described in
the article might happen for some humans.

As you say there hasn’t been any study which showed this conclusively (that
I’ve seen anyhow). I’d love to see more thorough research on these subjects
who supposedly possess such vision.

> _In art, there are great colorists and those who are virtually incapable of
> subtle use of color. If anyone interested in finding out about their own
> abilities, check out:_ [http://www.xrite.com/online-color-test-
> challenge](http://www.xrite.com/online-color-test-challenge)

Note, this online test is a bit easier than the paper version of the
Farnsworth–Munsell hue test, since the colors in the screen version end up
with some lightness differences that make it a bit easier to keep some
sections of the chart in order. Either way, the test IMO mostly measures (a)
whether someone has “normal” trichromatic vision, and (b) how patient and
willing to fiddle with fine details they are. I don’t personally think
Farnsworth–Munsell test scores are super meaningful, though a very poor score
does indicate some color vision deficiency. [FWIW, if I take the time to do
the test slowly, either on screen or on paper, I consistently score ~0,
occasionally mixing up one pair or another.]

But anyway, I think the ability to be a good colorist in art has a whole lot
to do with practice. Spending a lot of time mixing paint or color correcting
photographs is likely to heighten awareness of tiny distinctions. For
instance, I know that after a couple years of photography courses, several of
my friends got much better at noticing color casts in photographs. Not that
they couldn’t physically see them before, but after experience they more often
spontaneously noticed the casts and started to have a feel for just how much
adjustment in which direction would be necessary to counteract them.

~~~
sparkie
I scored 0 on the test first time (perfect color vision), no practice, and I
have pretty much no experience with any kind of art. (27 male for ref)

EDIT: Had another 2 tries, got 4 and 12. Turns out practice does more harm
than good - after 3 tries it's a bit disorienting trying to read off the
screen. Gonna have to take a break from machine.

~~~
theoutlander
A test like this needs to isolate the subject to only one spectrum at a time.
I gave up after the first two because of too much noise.

------
oska
I'm from Australia but hadn't heard of the Rainbow Eucalypt before (the tree
that the featured tetrachromat painted). That's not so unlikely as there are a
lot of Eucalyptus species.

Still, I was curious and so looked it up and was very interested to find that
it is a Eucalypt from outside Australia and, more than that, the only one
whose native region partly lies within the northern hemisphere. Another name
for it is the Mindanao gum, as it is native to the tropical rainforests of
Mindanao in the Philippines (north of the equator).

[http://en.wikipedia.org/wiki/Eucalyptus_deglupta](http://en.wikipedia.org/wiki/Eucalyptus_deglupta)

------
bitL
From my photography experience I noticed a lot more abnormalities than just
tetrachromacy, which is not uncommon amongst artists. I had a model that was
"seeing" colors in the sounds (synaesthesia) - she was often saying you talk
to me in blue or that person has such a nice white voice.

I've been tested for color vision and I am 100% accurate meaning I can discern
subtle shades from each other precisely with no effort. I also have a very
light form of synaesthesia manifesting itself by seeing a flash of light in
the night right before an unexpected sudden loud noise (yet with observable
latency) - like seeing a lightning just before hearing a thunder, even if the
noise is not accompanied by any light.

I was also always wondering if what I perceive as "blue" is the same as other
people perceive as "blue"? What if the neural response in my brain wires the
color sensation in the same way as other people perceive "green"? That would
help to understand individual preferences for colors. Also, we know there are
special cells in retina doing direction detection, edge detection etc. - what
if this had a profound impact on how we individually perceive world around us?
Somebody can have a strong edge or directional detection present in their view
all the time, logically assuming it's normal for the others as well that are
lacking that ability. We are just too diverse, and people are rather quiet in
order not to risk being considered abnormal and marginalized, a common problem
for artists in general.

~~~
weesals
Do you also see a pattern in the white flash (zebra stripes, lines, checkers)?
I always assumed that was a normal side-effect of being startled while
resting; changing from your brain-vision to eye-vision, though I'm not sure of
the patterns significance.

~~~
bitL
I can't recall any pattern - all I remember is a dynamic amorphous shape with
different light intensities in different parts, and this just quickly flashes
in front of my "eyes", right before loud sound hits.

------
jimmytidey
Mantis Shrimps have 12 photoreceptors, they can also see in all polarisations.
They don't do paintings so it's hard to know how they experience this.
[http://en.wikipedia.org/wiki/Mantis_shrimp#Eyes](http://en.wikipedia.org/wiki/Mantis_shrimp#Eyes)

------
joelthelion
It's not that they see a few colors that no one perceives, it's that for them
color is a 4 dimensional space instead of a 3 dimensional one. So it's a whole
new world of different colors.

~~~
Houshalter
Even though our eyes detect color in 3 dimensional space, that doesn't seem to
be how we perceive it. E.g. I can't tell you how much red, green, or blue is
in a color, just that it's close to the cluster of colors I recognize as
"purple" or "blue" or "orange" or whatever.

See this chart for example:
[http://imgs.xkcd.com/blag/satfaces_map_1024.png](http://imgs.xkcd.com/blag/satfaces_map_1024.png)

Interestingly there is some evidence that culture and language might affect
our perception of color.

~~~
jacobolus
You are incorrect about that, and Randall’s drawing is misleading you (it
shows the gamut boundary of an RGB cube, rather than the full three-
dimensional color space he asked about in his survey).

For people with “normal” trichromatic color vision, the color we perceive when
looking at a particular spot does indeed fall into a three dimensional “color
space”. You’re right that without careful attention/training it’s hard to
state colors in terms of coordinates in terms of cone cell responses directly
or color opponent signals (blue–yellow, red–green, white–black). It’s easy to
train someone to give reasonably accurate color coordinates in terms of
lightness, hue, and chroma, however.

If you want to understand human color vision in detail, I recommend this
online resource:
[http://www.handprint.com/LS/CVS/color.html](http://www.handprint.com/LS/CVS/color.html)

------
burtonator
There was a good study published recently documenting the ability for patients
with eye surgery who could see into the UV spectrum.

The cornea blocks some UV light so if you have eye correction surgery your
cornea is now modified/thinner and you can see slightly into the UV spectrum.

Probably has some downsides too.. Cataracts are probably more probable seeing
as people tend to get them more frequently at higher altitude.

The Tibetan people apparently have a high rate of cataracts since there is
higher UV light at the higher altitude.

~~~
glabifrons
It wasn't the cornea, but an artificial lens that was responsible. [0] UV
passed through the artificial lens, but not through our natural one. It was
replaced because of cataracts.

[0]
[http://science.slashdot.org/story/12/02/14/165202/followup-u...](http://science.slashdot.org/story/12/02/14/165202/followup-
ultraviolet-vision-after-cataract-surgery)

------
kazinator
The thing is, the woman doesn't seem to perceive new colors that other people
do not; the colors others don't see are being aliased to familiar colors like
"pink", and "red". (When she says "do you see that pink", is it a pink that we
could see elsewhere? Or some color that we have no concept of, but which she
relates to pinkness.)

I'd be curious if she still sees the same thing in a digital image of the
scene, or does the RGB system destroy it.

------
cjo
Also of interest is that birds have little oil droplets, often colored, as
part of their visual set up. There are five different known types of color-
filtering oil droplets (a sixth that is transparent) but it doesn't appear
every bird has all of them.

I'm no bird sight expert but it's suggested here [0] that a particular bird
may have 8 effective color receptors (5 cones, 3 cone-droplet pairs) for a
huge number of colors humans can't see. Diagrams of the receptors themselves
can be found at the wiki [1].

[0] -
[http://watchingtheworldwakeup.blogspot.com/2008/11/mountain-...](http://watchingtheworldwakeup.blogspot.com/2008/11/mountain-
biking-moonlight-color-vision.html) [1] -
[http://en.wikipedia.org/wiki/Bird_vision#Light_perception](http://en.wikipedia.org/wiki/Bird_vision#Light_perception)

------
pjbrunet
It's learnable and takes a lot of practice mixing colors and you need the
right teacher. I picked up this ability in art school and it absolutely makes
a sunset more beautiful. But to keep seeing this way you have to practice
regularly. Use it or lose it. If I'm not painting regularly, it's gone.

Like if you play chess for hours and hours every day, eventually you start to
experience everything in terms of chess moves. It's the same with color. Look
at just about any flat surface long enough and you'll notice it has a hue,
saturation and value. Just go into Photoshop and you'll see that boring white
wall has variations in hue, saturation and value, it's no medical mystery in
my opinion.

This part is a tiny more green, that part is a tiny more blue. I'm not giving
you an art lesson here but you get the idea. Artists know they can make things
look farther away by painting them blue/gray, decrease saturation with
distance, etc. The painter learns to exaggerate because she just has a 2D
surface to work with. Anyway, through the process of painting our perception
of color improves, even when we're not painting.

K-12 the goal is just paint the sky blue and the grass green, color inside the
lines and get your grade. But if you want to be a serious painter at some
point, you may want to look at things fresh, more intently. When people see
your paintings, don't expect them to care how long it took to mix the color.
Only a few artists will notice and they're not the ones buying your work.

So even for artists, seeing color is not terribly useful, because mixing color
is very time-consuming. It's more a hindrance than anything because I can
finish an ink wash in 1/100th the time and sell that for the same price as an
oil painting of the same subject.

If you have all the time in the world and don't need money, I say go for it,
buy some expensive oil paint and send me an email, I'll tell you what to buy.
Stretch the canvas yourself and go all out.

------
shutupalready
> _Jordan’s “acid test” involved coloured discs showing different mixtures of
> pigment, such as a green made of yellow and blue. The mixtures were too
> subtle for most people to notice: almost all people would see the same shade
> of olive green, but each combination should give out a subtly different
> spectrum of light that would be perceptible to someone with a fourth cone._

From what I understand, a modern monitor is capable of displaying the entire
range of colors perceptible to the human eye. Am I mistaken about that?

So would it not be possible to create a web-based version of these "coloured
discs", and then we can test ourselves.

~~~
TheSpiceIsLife
Google 'tetrachromacy test', first hit
[http://www.blogadilla.com/2008/06/08/are-you-a-
tetrachromat/](http://www.blogadilla.com/2008/06/08/are-you-a-tetrachromat/)

~~~
sigterm
that claim is quite dubious. I don't think it's possible to create metamers
for people with normal 3-color vision on an RGB monitor. To do that you need
an extra degree of freedom.

[https://en.wikipedia.org/wiki/Metamerism_(color)](https://en.wikipedia.org/wiki/Metamerism_\(color\))

~~~
Xcelerate
Hmm... I'm not sure about that. It's an interesting question. It's equivalent
to the question: can we create two images on a computer monitor that appear
the same to a person with normal color vision yet appear different to a
colorblind person?

I think it would depend on the particular mapping from 3 to 2 dimensions... it
might be possible.

~~~
bnegreve
> _can we create two images on a computer monitor that appear the same to a
> person with normal color vision yet appear different to a colorblind
> person?_

It surely depends on the type of colorblindness, there are many [1].

[1]
[http://en.wikipedia.org/wiki/Color_blindness](http://en.wikipedia.org/wiki/Color_blindness)

If you're monochromate or dichromate, I doubt that this is possible.
Monochromates or dichromates are simply missing one or two color components
out of three.

If you have anomalous trichromacy, you can by creating a monitor with pixels
of different colors.

In any case, I don't see how it is possible to identify a tetrachromate with a
trichromate (RGB) monitor. I tried to increase the contrast and change the hue
of the color test to understand what was different between the apparently
similar colors but I wasn't able to find any difference.

------
philh
> The crux of Jordan’s argument lay in the fact that the gene for our red and
> green cone types lies on the X chromosome. Since women have two X
> chromosomes, they could potentially carry two different versions of the
> gene, each encoding for a cone that is sensitive to slightly different parts
> of the spectrum. In addition to the other two, unaffected cones, they would
> therefore have four in total – making them a “tetrachromat”.

Why couln't this happen for either of the other cones?

~~~
gus_massa
The male equivalent is "Anomalous trichromacy"
[http://en.wikipedia.org/wiki/Color_blindness#Anomalous_trich...](http://en.wikipedia.org/wiki/Color_blindness#Anomalous_trichromacy).
You have one of the color receptors tuned to a slightly different frequency,
so you see the word in a different way. (Which way is the correct way?) This
condition is easy to spot with the standard Ishihara color test, so it's easy
to measure the % of the population in these cases.

\--- Green

The most common case of male anomalous trichromacy is the "wrong/unusual"
green receptor case, so the most common case of woman tetracromat is one that
has 2 copies of the usual blue receptor, 2 copies of the usual red receptor
and 1 copy of the usual green receptor 1 copy of the unusual green receptor.
This is the case discussed in the article.

To reduce the text size I'll denote this kind of tetracromat with BBGgRR,
where the capital letter denote the usual color receptor and the noncapital
letter denote the unusual color receptor. (This is unrelated to recessive and
dominant genes that are usually denoted by capital and noncapital letters.)

\--- Red

The second most common case of male anomalous trichromacy is the
"wrong/unusual" red receptor case, so the seccond most common case of woman
tetracromat is BBGGRr (1 copy of the usual red receptor an 1 copy of the
unusual red receptor).

Obviously, you can have both mixed copies, so a woman can have BBGgRr and be a
pentacromat. At least have the genes to "see" in a 5-dimensional color space.
If she can use this ability is less clear.

\--- Blue

The least common case of male anomalous trichromacy is the "wrong/unusual"
blue receptor case, so the least common case of woman tetracromat is BbGGRR.

It can be mixed with the other cases, so a woman can be pentacromat or
hexacromat.

The interesting part is that the blue gene is not in the X chromosome, so both
male and females have two copies. So a male can be tetracromat BbG_R_ . But
this chromosome is not inactivated as the 50% of the X chromosomes in females.
So I'm not sure if it's possible to have a different kind of vision in this
case.

\--- It's more complicated

Actually you can have more than 1 copy of the color genes in each chromosome,
and there are more than two variations of each gene, so it's more complicated.

------
tuzakey
The radiolab episode about colors talks about tetrachromats and some other
very interesting stuff, worth a listen:
[http://www.radiolab.org/story/211119-colors/](http://www.radiolab.org/story/211119-colors/)

------
gaius
For an excellent fantasy take on this, see Brent Weeks Lightbringer books.

------
jwatte
The frequency sensitivity curve of rods is different from reach of the cone
types, too. If some rods contribute to daylight vision, then everyone is
tetrachromatic to some extent.

------
tgb
Invisible colors? Boring. How about imaginary colors?

[http://en.wikipedia.org/wiki/Imaginary_color](http://en.wikipedia.org/wiki/Imaginary_color)

~~~
vixin
How about David Lindsay's Arcturians (Voyage to Arcturus) who were able to see
two extra colors namely jale and ulfire.
[https://en.wikipedia.org/wiki/A_Voyage_to_Arcturus](https://en.wikipedia.org/wiki/A_Voyage_to_Arcturus)

~~~
andrey-p
... and a lot more fun to be had over here:
[http://en.wikipedia.org/wiki/List_of_fictional_colors](http://en.wikipedia.org/wiki/List_of_fictional_colors)

------
edcastro
I can actually see infrared on the dark quite easily. But I think it should be
due to some falloff of the light spectrum emitted by the LED.

------
Kiro
Am I the only one who thinks her painting of the tree looks the same as the
photo color wise?

