Trichromic vision and anomalous trichromatism

Abstract

The trichromie in my classification of degrees of colour-perception are those who have only three colour sensations—red, green, and violet. They see only three colours in the bright spectrum and describe it as consisting of red, red-green, green, green-violet and violet. They apply the designation red-green to the orange and yellow regions of the spectrum and green-violet to the blue region. There are many degrees and varieties of trichromic vision (1, 2, 3, 4, 5). I have classified the colour-perception of individuals as dichromic, trichromic, tetrachromie, pentachromic, hexachromic, and heptachromic. This classifica­tion is made by estimating the number of definite colours seen in a bright spectrum, and the persons belonging to each class behave in every way as if they possessed the number of colour sensations indicated. On my theory of colour-vision each colour sensation is separate and distinct and not compounded of two or more fundamental colour sensations. For instance, there is the strongest evidence that yellow is a simple sensation (18, 24, 25, 26) and that spectral yellow light does not excite the red and green sensations.