V. THE COLOR-BLIND
Between 3 and 5 per cent of boys, and apparently fewer girls, inherit a special defect of vision, called “color blindness.” A color-blind child may be gifted in drawing, except in color drawing, but he will be incompetent as a painter.
There are several forms of this special defect. Very rarely it may happen that no discrimination among colors is possible, the world appearing, as in a photograph, to consist only of light and shade. In the late evening, or in any sufficient dimness, color is not perceived by ordinary eyes. Those who are blind to all colors do not see color with the brightening of the light, as ordinarily happens.
The most common form of color blindness is, however, that in which only red-green sensations are absent, other colors being distinguishable. There is no disease present in such cases. The defect is hereditary, and consists in deviation from the typical in structure of the retina. The eyes of color-blind persons are as healthy and normal as those of others, in respect to functions other than acting as receptors for certain waves of light.
A few cases of blue-yellow color blindness have been reported, these resulting from pathological causes.
A color-blind child does not, of course, know from his own experience that he is so. He supposes that everyone sees what he sees, until informed by test or disaster of his deviation from the usual.
Color blindness seems to bear no relation to intelligence, so that in drawing where color is used teachers will find a certain percentage of generally very able children producing absurd results. A color-blind child with a great gift for drawing, may succeed in etching or in black and white work of various kinds, as has been shown by the actual rise to eminence of etchers who are color-blind.