Physiology
The visual system consists of two chromatic neural channels and one achromatic neural channel. The chromatic channels consist of a red-green channel and a yellow-blue channel and are responsible for color and wavelength. The achromatic channel is responsible for luminance, or white-black detection. Hue and saturation are perceived due to varying amounts of activity in these neural channels consisting of axon pathways from retinal ganglion cells. These three channels are tied closely to reaction time in response to colors. The achromatic neural channel has a faster response time than the chromatic neural channels under most conditions. The functions of these channels are task-dependent. Some activities are dependent on one channel or the other, as well as both channels. When a colored stimulus is summed with white stimulus, both the chromatic and achromatic channels are activated. The achromatic channel will have a slightly slowed response time since it must adjust to the different luminance; however, despite this delayed response, the speed of the achromatic channel response time will still be faster than the speed of response of the chromatic channel. In these conditions of summed stimuli, the magnitude of the signal emitted by the achromatic channel will be stronger than the chromatic channel. The coupling of faster response with higher amplitude signal from the achromatic channel means that reaction time will most likely depend on the luminance and saturation levels of the stimuli.
The customary explanations for color vision explain the difference in hue perception as elemental sensations that are inherent to the physiology of the observer. However, no specific physiological constraints or theories have been able to explain the response to each unique hue. To this end, both the observer’s spectral sensitivity and relative number of cone types have proven to not play any significant role in perceiving different hues. Perhaps the environment plays more of a role on the perception of unique hues than the different physiological features across individuals. This is supported by the fact that color judgments can vary depending on differences in the color environment across long periods of time, but these same chromatic and achromatic judgments are held constant if the color environment is the same, despite aging and other individual physiological factors affecting the retina.
Read more about this topic: Abney Effect
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