Dr. Adele Fielde, of Swatow, China, among 1,200 Chinese of both sexes examined by Thomson's wool test, found that more than half mixed up green and blue, and many even seemed to be quite blind to violet. Ernest Krause also has argued that primitive man was most sensitive to the red end of the spectrum, hence setting about to obtain red pigments and acquiring definite names for them, an explanation which is accepted by Karl von den Steinen to account for the phenomena among the Central Brazilians. The recent investigations of Rivers at Torres Straits have confirmed the conclusions of Magnus. He found that, corresponding to the defect of color terminology, though to a much less degree, there appeared to be an actual defect of vision for colors of short wave-length; in testing with colored wools no mistake was ever made with reds, but blues and greens were constantly confused, as were blue and violet.
It may even be argued that the same defect exists to a minor degree not only among the peoples of Eastern Asia whose æsthetic sense is highly developed, but among civilized Europeans when any kind of color blindness is altogether excluded. This was noted long since by Holmgren, who remarked that some persons, though able to distinguish between blue and green wools when placed together, were liable to call the blue wool green, and the green blue, when they saw them separately. Magnus also showed that such an inability is apt to appear at a very early stage in some persons when the illumination is diminished, although the perception of red and yellow remains perfectly distinct. He further showed that blue and green at certain distances are often much more difficult to recognize than red. Most people probably are conscious of difficulty in distinguishing blue and green pigments with diminished light and find that blue easily passes into black. Violet also appears for many people to be merely a variety of blue; the word itself, we may note, is recent in our language, and plays a very small part in our poetic literature, and in fact the color itself, if we rigidly exclude purple, is extremely rare in nature. It is a noteworthy fact in this connection that in normal persons the color sense may be easily educated; this is not merely a fact of daily observation, but has been exactly demonstrated by Féré, who by means of his chromoptoscopic boxes, containing very dilute colored solutions, found that with practice it was possible to recognize solutions which had previously seemed uncolored. It is also noteworthy that in the achromatopsia of the hysterical, as Charcot showed and as Parimand has since confirmed, the order in which the colors usually disappear is violet, green, blue, red; sometimes the paradoxical fact is found that red will give a luminous sensation in a contracted visual field when even white gives no luminous sensation. This persistence of red vision in the hysterical is only one instance of a predilection for red which has often been