Physiological Evidence for the Three Components- Theory of Color Vision

Abstract

The electrical excitability of the human eye was measured at varying intervals after the end of an illumination two seconds in duration by means of a rheobasic constant current, and the differences between the excitabilities with and without the preceding illumination were plotted as ordinates against time intervals between the end of illumination and electrical stimula-tion as abscissas. The illumination was restricted to the fovea centralis.
1. The curve so obtained has a single maximum in normal trichromats, but three maxima in deuteranomalous subjects when white light is used for illumination. The height of each maximum depends greatly upon intensities of illumination, but the crest time is entirely independent of intensities. The appearance of the three maxima is so interpreted that one of the three component-processes is too weak for such complete fusion as is found at normal subjects.
2. In some normal trichromats the three maxima appear in the excitability curve for a monochromatic light of some adequate wave-length. It was found that bluish green light is adequate for this purpose. Red light gives rise to a excitability curve with a single maximum, the crest time of which is about 1 second. The curve for blue light is also mono-phasic, the crest time being about 3 seconds. Violet light causes two maxima, one of which has the same crest time as the curve for red light, and the other of which corresponds to the maximum for blue light.
3. When electrical threshold is determined in the presence of a weak green light after an illumination with white light, the three maxima appear in normal subjects like in deuteranomalous persons. This is due to an in-hibitory effect of the green light upon one of the three component-processes.
All above findings provide physiological evidence of the three com-ponents-theory of Young-Helmholtz.