Lack Of Self Knowledge Theory See Platos Theory Of Humor

LADD-FRANKLIN/FRANKLIN COLOR VISION THEORY. The American-German psychologist Christine Ladd-Franklin (née Christine Franklin) (1847-1930) proposed a color vision theory in 1892 that is a compromise between the Young-Helmholtz and the Hering (later, the Hering-Hurvich-Jameson) theories, and that has been called both a genetic theory and an evolutionary theory of color vision. The Ladd-Franklin theory assumes that light energy liberates respective red-, green-, and blue-stimulating substances from a complex photosensitive molecule in the retinal nerve endings. When the red- and green-stimulating substances are present, they combine to form a yellow-stimulating substance that, in turn, may combine with blue to form a white-stimulating substance. According to this theory, blue and red (or blue and green) cannot combine and, thereby, do not individually disappear in the mixtures of blue-red (or blue-green). Thus, the Ladd-Franklin theory postulates four primary colors (red, green, yellow, and blue) where separate cone mechanisms for each primary are assumed. This four-receptor theory is linked to various evolutionary facts (such as the evolutionary development of achromatic rod vision into chromatic cone vision and the relatively rapid evolution of the foveal area of the eye as compared to the periphery) and is able to give a convincing account of both color blindness and perimetry (stimulation of retinal perimeter areas) data. The genetic and evolutionary aspects of the Ladd-Franklin genetic theory may be stated in terms wherein various portions of the retina "recapitulate" the course of evolution and where all four types of color receptors are present near the fovea, but not at the periphery of the retina. The Ladd-Franklin evolutionary theory of color vision had much to recommend it, but it was never as popular as the Young-Helmholtz theory. See also COLOR VISION, THEORIES/LAWS OF; HERING-HURVICH-JAMESON COLOR VISION THEORY; RECAPITULATION, THEORY OF; YOUNG-HELMHOLTZ COLOR VISION THEORY. REFERENCES

Ladd-Franklin, C. (1892). Eine neue theorie der lichtempfindungen. Zeitschrift fur Psychologie und Physiologie Sinnesorgange, 4, 211. Ladd-Franklin, C. (1929). Colour and colour theories. New York: Harcourt, Brace.

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