Vision

(Name (Professor (Subject

xx February 2007

Vision

In psychology , two theories of vision are well recognized . These are the Trichromatic Theory and Opponent - Process Theory ( Theories of Colour Vision ' Trichromatic Theory of Color Vision . These two theories are not opposing rather , they complement each other by respectively explaining processes involved in various levels of the visual system ( Theories of Colour Vision

The Trichromatic Theory

The Trichromatic theory is also known as the Young-Helmholtz theory Young and Helmholtz developed it after conducting studies on color matching and color mixing

( Theories of Colour Vision . Their studies show that individuals with normal color vision needed three light sources of different wavelengths . These wavelengths shall match other wavelength in the visible spectrum ( Theories of Colour Vision Proceeding from this premise , Young and Helmholtz hypothesized that the activity of three different types of receptors influences normal color vision . These receptors have different peak sensitivities . Later , it was discovered that these three wavelengths consist of the short , medium and long wavelengths , which activities determine color perception

The Opponent - Process Theory

On the other hand , Ewald Hering developed the Opponent-Process Theory ( Theories of Colour Vision ' Van Wagner . Hering observed that people never see some color combinations , such as blue and yellow (Van Wagner Hering thus hypothesized that there are opponent systems that that control color perception (Van Wagner

Under the Opponent-Process Theory , there are three opposing color pairs , namely , the blue /yellow , red /green , and black /white pairs . These color pairs , called the primaries , are formed when cone photoreceptors are connected to each other . This theory holds that [A]ctivation of one member of the pair inhibits activity in the other ( Theories of Colour Vision . This means that the two colors that form a primary pair cannot be seen simultaneously at the same location ( Theories of Colour Vision

Analysis

Both theories are relevant to the study of color perception . There is no need to choose which is the better theory , because these theories are not in conflict with each other . On the contrary , these theories go together because they address different stages in the color vision system ( Trichromatic Theory of Color Vision

On the one hand , the trichromatic theory looks at the color vision phenomena from the viewpoint of photoreceptors ( Theories of Colour Vision . On the other hand , the opponent-process theory explains color vision phenomena at the point when photoreceptors are interconnected neurally ( Theories of Colour Vision

In understanding the color vision system , it is important to consider both theories because one theory is not sufficient to fully explain various aspects of the system . For example , the Trichromatic theory could not elucidate the phenomenon of complementary afterimages that results after one color is inspected for a long period . This phenomenon is better explained by the Opponent-Process theory ( Theories of Colour Vision

Works Cited

Theories of Colour Vision ' 20 Feb . 2007

Trichromatic Theory of Color Vision ' 20 Feb . 2007

Van Wagner , Kendra . What is the Opponent-Process Theory of Color Vision ' About Psychology . 20 Feb . 2007

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