If you are suffering from red-green color blindness, what are the chances that your neighbour or one of your classmates also suffers from it? What we like are numbers and one of the most often asked and searched for questions about color vision deficiencies is: How many people are affected by color blindness?

Before we digg right into some interesting numbers about red-green color blindness you should be aware of the following facts:

• Tritanopia (blue-yellow color blindness) is rare. Some sources estimate that 0.008% are affected by this type of color vision deficiency.
• Monochromacy (complete color blindness) is very rare. Different sources vary between 1 in 33’000 to 100’000 (0.001%).
• Families are not a good source of numbers concerning color blindness, because vision deficiencies are inherited and therefore some families are affected much more than others.

Red-green color blindness is the most common color vision deficiency; therefore most of the researches found regard this type of colorblind population. The following figures are listed in the book Color Vision: From genes to perception and combine many different surveys spread over the last century.

Four different deficiencies make up the common wording red-green color blindness. People suffering from an anomaly are trichromats but do report problems in color perception in the green-yellow-red sector of the spectrum. The two different types show a less sensitiveness either to red light (Protan) or green light (Deutan). In opposite people suffering from an anopia are dichromats, completely lacking one type of retinal cones.

The figures above basically show the following important facts about red-green color blindness:

• Roughly 8% of men and 0.5% of women are affected. Therefore chances that your neighbour or one of your classmates is colorblind are very high.
• Deutanomaly is by far the most common color vision deficiency regarding red-green color blindness. The other three types are occurring at nearly the same ratio and do affect about one out of 100 persons each.
• Men are approximately 100 times more often affected than women. This shows very nicely that red-green color blindness is a sex-linked trait as described in more detail at The Biology behind Red-Green Color Blindness.

A last note about the figures: If you always thought that you are someone special because of your color blindness, you might be wrong. Especially if you are male and suffering from Deuteranonmaly one could say you are one under many and you can meet fellow sufferers out on the street every day.

Further readings:
Opsin Genes, Cone Photopigments, Color Vision, and Color Blindness
The Perception of Color

Related articles:
The Biology behind Red-Green Color Blindness
Color Blindness Test by Dr Shinobu Ishihara
5 Misbeliefs about Color Blindness

According to recent studies at the Universities of California and Chicago, language affects half of what we see. The researches base on the well known Sapir-Whorf hypothesis which states, that there is a relationship between our language and our experiences and thoughts.

The Sapir-Whorf hypothesis can be tracked back to the late 19th century and started a long and lasting debate about language-and-thought. This new results provide an unexpected resolution to the debate.

The studies are primaraly based on the following experiment: A circle of 12 squares is shown to the participants. All but one square have the same color, some shade of green. The odd square was either painted in another shade of green or in some shade of blue.

Before we have a look at the results let me point out two important things: First of all language function is processed predominantly in the left hemisphere of the brain. And secondly visual impressions from the right side are mostly handled on the lefthand side of the brain and vice versa.

The results of the experiment were as follows: If the odd square was on the right half of the visual field the participants reacted faster if the color had a different name (blue) than if it had the same color name (green). But notice this happened only on the right part of the visual field. The scientists say the reason to this is because language is also processed on the left side. Whenever the odd square was on the left half of the visual field no such factor could be measured.

Due to those experiment they concluded, that language affects vision, but only if it is processed on the same side as language function. Vision is therefore at the same time filtered and not filtered through language.

And what happens if we get on top of that color blindness into the game? People suffering from color blindness share the same language but have a different visual impression. Would they perform worse, better or just the same as people with no color vision deficiency?

Of course, if you can’t see the different shades it is not worth making the test. But if you can view them but can’t exactly tell, which is a shade of blue and which a shade of green. It would be very interesting to now the answer. Unfortunately they don’t make any statements about color blindness.

What do you think? Does language affect color vision when suffering from color blindness in the same way?

Original proceeding by Aubrey L. Gilbert, Terry Regier, Paul Kay, and Richard B. Ivry at Whorf hypothesis is supported in the right visual field but not the left (subscription required).

Further readings:
Language affects half of what we see
How we see half the world through the prism of language
Sapir-Whorf hypothesis