Section I of this communication contains a very brief summary of previous work of the author on the application of the method of the critical frequency of flicker to the determination of the primary color sensations. Attention is specially directed to the fact that former investigations were conducted in a dark room, so that while the right eye was stimulated by light from the spectrum, the left eye was in darkness adaptation. It was generally believed that darkness adaptation of one eye had no influence upon the other.
Section II contains descriptions of experiments made in a room illuminated by ordinary daylight. The right eye was in daylight adaptation while the left eye was fatigued with spectral lights. All measurements of the critical frequency of flicker were made with the right eye. It was found that the stimulus applied to the left eye was transferred to the right eye by some reflex process resulting in an enhancement of the brightness of three colors, which were always red, green, and violet. Six colors were found, viz., .660μ, .570μ, .520μ, .505μ, .480μ. and .425μ, which produced no effect. The reflex and normal curves always coincided in two places which averaged about .653μ and .50μ. The magnitude of the reflex effect is greatest for the violet color, and seems to vary as some inverse function of the wave length.
Section III contains the description of experiments performed when the right eye was fatigued and the left was always in daylight adaptation.
It was found that fatigue produced both a direct and a reflex effect. The red, green, and violet colors showed one elevation of the fatigue curve above the normal in the part corresponding to the color used, and two reflex depressions in parts corresponding to the remaining primary colors. The compound colors, yellow and blue, produced two elevations in the parts of the curves corresponding to the color sensations of which they are compounded, and one reflex depression in the part corresponding to the remaining color. The number of elevations or depressions in each curve was always three, corresponding to red, green, and violet.
The six colors mentioned above produced no effect, and are termed equilibrium colors.
The effect of darkness adaptation of one eye upon the other is shown to cause a diminution of brightness of the whole spectrum. This is applied to explain Fechner’s paradox.
Section IV contains theoretical applications to explain the cause of the whiteness underlying all color sensations, successive contrast, binocular contrast, non-saturation of colors, saturation of colors in after images, the duplicity theory of von Kries, complementary colors and to theories of color vision.
Section V contains anatomical and physiological considerations which render it probable that the effects discovered are due to a new kind of physiological reflex which is termed a sensory reflex.
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