Color blindness and the Ishihara test (thing)
Some people have impaired color perception, called color-blindness. Studies show women are rarely affected, and around 15% of men have some color-blindness. That difference is related to the X chromosome. Women have two X's, men have one. If a man's one (recessive) X chromosome is a little different, vision can be a different picture.
A few cases of color blindness are related to medical conditions, but the common cause is genetic. The result can be various types of color blindness. Red/green color blindness is most common.
I think the term "color blind" is a misnomer, because most color blind people do see various colors, but their total color perception is different. It's extremely unusual for sighted people to see no colors at all, although there are very rare reports of people who can see, but see little or no color. I think that is total color blindness.
So, what's going on here?
The non-color light sensors in the eye are called rods. The rods detect shades of gray, and are more important for night vision.
Color is seen by parts of the eye, called cones, detecting different frequencies of light. Studies confirm that different cones have peak light detection at 3 different wavelengths. A blend of signals from the cones, detecting different frequencies and intensities of light, produces color vision.
I know my color perception is decidedly not normal. I can describe what's it like for me.
Good news, I think someone can be "color-blind" and rarely notice it!
Really, it only seems to bother other people when they notice I don't see things quite the same way. Well, it's better than being totally blind (unless you're Stevie Wonder, maybe?). I guess most people don't need to worry much about it, if it's not a bother to them or other people.
There are some web sites that have the Ishihara test plates.
So, see for yourself. (Don't worry about the French, scroll to the bottom, it's all numbers.)
There are many other websites that have color tests, it's not hard to find the Ishihara test.
If you see numbers in all those dots, which is likely, then good for you, because to me almost all of them are just a bunch of dots. What one person sees is not always the same as what others see, and some cannot see that-- What can't be seen, well, you can't see it!
I have difficulty differentiating reds and greens. This does not mean I can't see reds and greens. Put me in front of a red brick wall, or a green field. I think I see red and green. They definitely look different to me, when I can see them! Sometimes I need a broader expanse of color or else I may not see it. In order to see little red berries on a big green holly bush, I may need to get closer. That must be because I have a different distribution of those cones, compared to most people.
I discovered my color blindness when I was six. My grandfather
brought home a book with the Ishihara color plates and showed them to me.
I never thought much more about it until a couple years ago,
when I found some Ishihara color test plates on a website
and reviewed them. Again, confirmation I do not see colors the way most people see them. I printed some of those on glossy photo paper, and showed them to about twenty friends, a mix of men and women. None of my friends had as many problems as I did seeing things "normally", although a few of the men noticed they didn't see some things.
For me, the most interesting Ishihara plates are the ones that have two different numbers represented in the colored dots. You might see either 29 or 70, or maybe you don't see any numbers at all!
I'm OK with that, a bunch of dots where different people say they see different numbers, and I don't see any numbers. Where's the problem? Heh.
It's nice when people notice I am color coordinated when it comes to dress, fashion and design. Maybe that is compensation. I try harder, I have to think about color. You will never catch me wearing a white T-shirt! I guess there is a point there, color blindness has never really bothered me, and that's what I hear from others who have it.
I am used to not always seeing some of the things that other people see, tulips out in a field, raspberries on bushes, or berries on holly. They might mention them, and I squint a little and say "They are pretty for you to mention them", or I might have said, "I can't see that", but I've learned not to do that, it sometimes makes others uncomfortable.
When I showed the Ishihara color plates to my friends a couple years ago, and told them that I did not see the numbers in them, some of them said they felt sorry for me, and I was quite surprised. It was touching. I told them not to worry, it's never bothered me.
Update:
Regarding the genetics, there are a couple other ideas that seem to make sense. Women are less affected, so think about a hunter-gatherer society and imagine who's doing what: women gather fruits, berries and, nuts, while the men chase down the game? There are also references somewhere about modern military research indicating color-blind men are better at distinguishing camouflaged targets.
Update:
Color perception is unique to every individual, because every eye has a different mixture and distribution of varying cones and rods.
Update:
It finally dawned on me computer users with color blindness can tweak RGB in the display monitor screen, to see "more normal" images. So, I bumped up the red a good bit, lowered the blue a bit, and see more on the screen. I will continue to tweak this. Perhaps one day I will be able to see all the Ishihara numbers, on my computer screen.