Effects on employment of defects in colour vision.

The more information which can be fed into a computer the greater its power; similarly we are more efficient as individuals the finer our sense of touch, the greater the range of sounds we can hear, or the closer that two points can be detected separately by the eyes. The finer the discrimination the wider is the information available for action by the intellect. This then is the measure of the value of a fully developed colour sense. So far as colour is concerned, a majority of people (the trichromats) are able to judge its hue by reference to a three-point standard which allows accurate discrimination of a large variety of hues. A small number*, however, just over 2 per cent. of boys and about oI per cent. of girls (the dichromats) have only a two-point standard, and as a result the number of hues that can be discriminated is greatly reduced. There is also another group, perhaps 4-5 per cent. of boys and o03 per cent of girls (simple anomalous trichromats) who, although possessing three-point standards, have these in unusuLal combination; so that, while perceiving a wide range of hues, they see them differently from the generality. Figs I, 2, and 3 (after Farnsworth, I947) express these differences diagrammatically. Such persons also find themselves unable to agree with colour matches accepted by most people, and in their turn make matches inacceptable to thze majority.