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Brennen Jul9-04 10:52 AM

Perception of Colour
 
is it possible that everybody sees different colours but we don't realise because people are taught what colour is what according to things in the world?

example, everyone is taught the sky is blue, but what if everybody sees the sky as a different colour, no matter what they see they would know that as blue, and weneva they saw that again they would recognize it as blue.

is this possible?

Monique Jul9-04 11:36 AM

Sure, this becomes especially evident in people who are colorblind for certain colors (mostly red), more men are colorblind than woman because the gene is on the X chromosome.

You can test yourself whether you can see all colors 'properly' here:
http://www.toledo-bend.com/colorblind/Ishihara.html

Jamez Jul10-04 03:19 AM

I know i'm colour blind, i took that test just then and as usual, alot just looked like half finished numbers or just a load of dots... but i still think i can tell the difference between most red and green things. Is it just the shades of the colour green or red which make me able to disifer what is red and what is green or is it that a CAN tell the difference between red and green just not very well? By the way... traffic lights don't cause me the slightest problem, "red" is at the top and "green" is at the bottom. But the green they use is alot lighter than the red so it's easy to tell.

phreak Jul10-04 03:26 AM

Quote:

Quote by Brennen
is this possible?

I've actually thought about this quite a lot recently.

I was thinking, could someone mistake black for white and white for black if they were taught the same as everyone, but they actually WEREN'T taught the same as everyone because they couldn't see the same as everyone?

The answer is yes. It's possible and probably would happen if someone saw black where white is and white where black is. They'd just need to be taught the same as everyone else, even though they'd be taught differently because they couldn't see the same as everyone else.

The whole topic is quite confusing :confused: .

Brennen Jul10-04 03:36 AM

that was what i thought, how would we know? children are taught what colour is what, and whenever they see it, they have a name assigned to it.

regardless of whether its the same colour as every1 else sees, we'd all know it by the same name. grass is green, the sky is blue.

im tempted to rip somebody else's eyes out and pop them in my sockets (somehow attaching them to my own optic nerve as well) to see if the sky is what i know as orange, and grass is actually pink. psychadelic world.

any volunteers?

iansmith Jul10-04 06:47 AM

Quote:

Quote by Jamez
I know i'm colour blind, i took that test just then and as usual, alot just looked like half finished numbers or just a load of dots... but i still think i can tell the difference between most red and green things. Is it just the shades of the colour green or red which make me able to disifer what is red and what is green or is it that a CAN tell the difference between red and green just not very well?

You migth be a anomalous trichromate.

Quote:

Protanomaly (one out of 100 males):
Protanomaly is referred to as "red-weakness", an apt description of this form of color deficiency. Any redness seen in a color by a normal observer is seen more weakly by the protanomalous viewer, both in terms of its "coloring power" (saturation, or depth of color) and its brightness. Red, orange, yellow, yellow-green, and green, appear somewhat shifted in hue ("hue" is just another word for "color") towards green, and all appear paler than they do to the normal observer. The redness component that a normal observer sees in a violet or lavender color is so weakened for the protanomalous observer that he may fail to detect it, and therefore sees only the blue component. Hence, to him the color that normals call "violet" may look only like another shade of blue.


Under poor viewing conditions, such as when driving in dazzling sunlight or in rainy or foggy weather, it is easily possible for protanomalous individuals to mistake a blinking red traffic light from a blinking yellow or amber one, or to fail to distinguish a green traffic light from the various "white" lights in store fronts, signs, and street lights that line our streets.


Deuteranomaly (five out of 100 males):
The deuteranomalous person is considered "green weak". Similar to the protanomalous person, he is poor at discriminating small differences in hues in the red, orange, yellow, green region of the spectrum. He makes errors in the naming of hues in this region because they appear somewhat shifted towards red for him. One very important difference between deuteranomalous individuals and protanomalous individuals is deuteranomalous individuals do "not" have the loss of "brightness" problem.


From a practical stand point though, many protanomalous and deuteranomalous people breeze through life with very little difficulty doing tasks that require normal color vision. Some may not even be aware that their color perception is in any way different from normal. The only problem they have is passing that "Blank Blank" color vision test.
http://colorvisiontesting.com/color2.htm


Quote:

Anomalous Trichromacy

Like normal trichromats, anomalous trichromats need three wavelengths to match any other wavelength. But because their spectral sensitivities are somewhat different, they mix the primaries in different proportions. As for dichromats, the three types of anomalous trichromacies are named for the wavelengths to which their spectral sensitivity is shifted.

1. Protanomaly

Protanomaly is associated with a defective L photopigment, causing the sensitivity spectrum to be shifted toward medium wavelengths. Protanomalous trichromats are more likely to confuse red and green than are normal trichromats. For these individuals, the least saturated point occurs at 492 nm.

2. Deuteranomaly

Deuteranomaly is thought to be caused by an abnormal M photopigment. The absorption spectrum is shifted toward L wavelengths which also results in a confusion between red and green. The least saturated point on the absorption spectrum is at 498 nm. Deuteranomaly is the most common of the anomalous trichromacies.

3. Tritanomaly

Tritanomaly is very rare and its basis is unclear. What is known about protanomaly and deuteranomaly suggests that tritanomaly is caused by defective S photopigment. It is known that persons affected by this condition have difficulty distinguishing between yellow and blue.
http://www.psych.ucalgary.ca/pace/va...congenital.htm

And the reason why you don't you are color blind is

Quote:

2. Pseudoisochromatic Plate Tests

Pseudoisochromatic plate tests are the most commonly used tests of colour vision because they are inexpensive, simple and quick to administer. The test plates consist of a coloured number or a visual path embedded in a background that is the same brightness but different in overall colour. The colours of the figure and background fall along a dichromatic confusion line. A person with normal colour vision can correctly identify the figure based on colour differences whereas an individual with dichromatic vision cannot. The most extensively used pseudoisochromatic test is the Ishihara test (see sample plate on the right). For young children and others who cannot read, tracing paths are used instead of numbers. A limitation of pseudoisochromatic plates is that they cannot adequately differentiate dichromatic from anomalous trichromatic vision.
I probably have the same problem. When I was younger a nurse at school had the whole class pass a pseudoisochromatic plate tests. My results were unusual and she could not figure out if I was color blind or not. I could see number were normal or color blind people would see them. Sometimes I would not see any number when I should of been seeing some. I differentiate between all color but some shade don't look that different.

Phobos Jul12-04 11:58 AM

Quote:

Quote by Brennen
is it possible that everybody sees different colours but we don't realise because people are taught what colour is what according to things in the world?

example, everyone is taught the sky is blue, but what if everybody sees the sky as a different colour, no matter what they see they would know that as blue, and weneva they saw that again they would recognize it as blue.

is this possible?

Fortunately, we have a way to quantify/standardize it.

Color is based on the wavelength of the light. So, send "blue" light (440 to 500 nm) to several subjects and ask them what color they see.

I suspect you'll find that we perceive colors the same way (barring problems like color blindness of course).

Moonbear Jul12-04 06:28 PM

Actually, phobos, I think the question isn't so much do we all call a certain range of wavelengths the same color, but when those wavelengths are conducted from the eye to the brain, is the mental image we form the same as everyone else? There's really no way to know. The same could be said for information processed from any of our senses. Along related lines, let's say you applied an electric shock to someone's fingertip. An electric shock with the exact same parameters is applied to a second person's fingertip in the exact same spot. Both perceive this as an electric shock, and pull their hand back and say, "ouch" as soon as they feel it, but then you ask them to rate the pain felt on a scale of 1 (mild discomfort) to 10 (extremely painful). Person A scores it as a 3, Person B scores it as a 7. Why? Have they just experienced different pains in their lives, so rank it according to past experiences, or did they actually feel it differently? Don't know if that helped, or muddled up the question more, but I suppose it's entirely possible people see colors differently. Afterall, witness what happens when you introduce something like a brick...some will call it red, others orange, and others brown. Also, I can sit and ponder paint swatches all day, 20 different shades of beige, and not be able to make a decision because they are all slightly different...this one is warmer, that one a little cooler, that's got a hint of yellow, the other a tinge of peach, another just slightly pink, none of them quite exactly what I want...then one of my friends will walk up and just say, "they're all beige, just pick one." Clearly we see them differently! I have a friend who insists paints never look the same on the walls as they do on the swatches...he thinks it's all a big gamble...I haven't had that experience, and if I hold up the swatch to the painted wall, it looks spot on. Again, it seems we even see the same color differently in different contexts...the texture, the size of the painted area, whatever, it's still supposed to be the same color. So, hmm, maybe it's possible we do see colors differently from one another.

0TheSwerve0 Jul12-04 09:53 PM

I don't think that large proportions of the population perceive what they call "blue" as what I would call "red." That would require a huge evolutionary anomaly with no explanation. Perception may differ in small degrees, but I don't see any way in which there could possibly exist such perceptual chaos amongst members of the same species. I'm pretty certain that a cat probably doesn't see "blue" the same way I do, but why would that possibly be the case with humans, outside of the occasional exception?

Brennen Jul14-04 05:20 AM

huge evolutionary anomaly? everybody is different. everybody has different eye colour, everybody has different skin colour, hair colour etc etc. why couldn't there be a gene or something to that effect, which affects what colour the eye converts light of different wavelengths into? just like all other biological differences are determined. i know it's not likely, but perception is a difficult thing to understand. society teachers everybody what is what from the moment they are born, and even if we don't all see it the same, we'll all recognize it by the same name.

mechie Jul14-04 06:51 AM

I have a computer here that uses an RGB monitor, seperate leads for each primary colour (red,green, blue) as the old BBC computers did/do.
Sometimes I swap the leads around, I won't say which way, you don't need to know.
Now when the computer tries to show a blue screen it could be blue but it could be red or green. The computer knows this as 'blue' and can repeat the colour whenever it wants; this colour is obviously different from its idea of 'red' and 'green'.

As all humans are different isn't it possible for the optic nerve 'wiring' to vary in a similar way? I realise there are a few assumptions here about primary colours and how our eyes work but think it through! If you wear coloured sunglasses for long enough you get used to the colour cast and everything looks strange when the glasses are removed!

loseyourname Jul14-04 02:13 PM

Quote:

Quote by Brennen
huge evolutionary anomaly? everybody is different. everybody has different eye colour, everybody has different skin colour, hair colour etc etc. why couldn't there be a gene or something to that effect, which affects what colour the eye converts light of different wavelengths into?

Skin color and hair color are determined by only a couple of genes. All indications show that visual perception is determined by quite a few more. I certainly have no proof of this, but the main indication I know of is that visual perception is dependent upon so many individual neuronal processes. Read this:

Kreiman, G., Fried, I. and Koch, C. Single neuron correlates of subjective vision in the human medial temporal lobe. Proc. Natl. Acad. Sci. USA (2002) 99, 8378-8383

Quote:

Abstract

Visual information from the environment is transformed into perceptual sensations through several stages of neuronal processing. Flash suppression constitutes a striking example where the same retinal input can give rise to two different conscious visual percepts. We directly recorded the responses of individual neurons during flash suppression in the human amygdala, entorhinal cortex, hippocampus and parahippocampal gyrus, allowing us to explore for the first time the neuronal responses in untrained subjects at a high spatial and temporal resolution in the medial temporal lobe. Subjects were patients with pharmacologically intractable epilepsy implanted with depth electrodes to localize the seizure onset focus. We observed that the activity of two-thirds of all visually selective neurons followed the perceptual alternations rather than the retinal input. None of the selective neurons responded to a perceptually suppressed stimulus. Therefore, the activity of most individual neurons in the medial temporal lobe of na´ve human subjects directly correlates with the phenomenal visual experience.
This is a link to the download for the entire paper (it is too large for me to attach): http://www.klab.caltech.edu/cgi-bin/...r&paper_id=412

JohnDubYa Jul14-04 03:30 PM

Quote:

Color is based on the wavelength of the light. So, send "blue" light (440 to 500 nm) to several subjects and ask them what color they see.
Color is not based on wavelength. Rather, we have noticed that certain wavelengths induce the sensation of "blue". There are other ways of producing the same sensation that have nothing to do with the wavelength associated with blue.

Quote:

im tempted to rip somebody else's eyes out and pop them in my sockets (somehow attaching them to my own optic nerve as well) to see if the sky is what i know as orange, and grass is actually pink. psychadelic world.
Actually, the brain maps the colors to sensations, not the eye.

I have an alternative suggestion: When someone else eats mayonnaise, they go "yum." When I am forced at gunpoint to eat mayonnaise, I puke.

How is this possible, if I am of the same species as the next guy? Do we actually sense the same taste? If so, why would our reactions vary so considerably?

loseyourname Jul14-04 05:42 PM

I think that's just a matter of preference. For instance, a good deal of people look at Jennifer Lopez and think "wow, she's hot." I'm pretty sure she was once selected as the sexiest woman alive by a major magazine. When I look at her, I want to puke. Presumably we see the same person.

JohnDubYa Jul15-04 09:25 PM

But the preference is based on the SENSE of taste. So do we have the same senses?

Evo Jul16-04 01:16 AM

Perhaps a bit off topic, but along the lines of seeing color. My older daughter has synesthesia. She sees numbers and letters as colors.

She is an extremely gifted artist, one of the traits of a synesthete.

http://ucsdnews.ucsd.edu/newsrel/soc...thesiaconf.htm

chronon Jul16-04 01:44 AM

Quote:

Quote by mechie
I have a computer here that uses an RGB monitor, seperate leads for each primary colour (red,green, blue) as the old BBC computers did/do.
Sometimes I swap the leads around, I won't say which way, you don't need to know.

People have done an experiment where they wear glasses which turn their vision upside down. After a couple of weeks they get used to it and see things the right way up again, and then have difficulties when they take the glasses off. It would be interesting to do the experiment with glasses which swapped round the RGB components of vision. Would people get used to it? If so would they begin to see grass as the colour they think of as green?


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