Cone Photoreceptor Sensitivities and Unique Hue Chromatic Responses: Correlation and Causation Imply the Physiological Basis of Unique Hues

Abstract

This paper relates major functions at the start and end of the color vision process. The process starts with three cone photoreceptors transducing light into electrical responses. Cone sensitivities were once expected to be Red Green Blue color matching functions (to mix colors) but microspectrometry proved otherwise: they instead peak in yellowish, greenish, and blueish hues. These physiological functions are an enigma, unmatched with any set of psychophysical (behavioral) functions. The end-result of the visual process is color sensation, whose essential percepts are unique (or pure) hues red, yellow, green, blue. Unique hues cannot be described by other hues, but can describe all other hues, e.g., that hue is reddish-blue. They are carried by four opponent chromatic response curves but the literature does not specify whether each curve represents a range of hues or only one hue (a unique) over its wavelength range. Here the latter is demonstrated, confirming that opponent chromatic responses define, and may be termed, unique hue chromatic responses. These psychophysical functions also are an enigma, unmatched with any physiological functions or basis. Here both enigmas are solved by demonstrating the three cone sensitivity curves and the three spectral chromatic response curves are almost identical sets (Pearson correlation coefficients r from 0.95–1.0) in peak wavelengths, curve shapes, math functions, and curve crossover wavelengths, though previously unrecognized due to presentation of curves in different formats, e.g., log, linear. (Red chromatic response curve is largely nonspectral and thus derives from two cones.) Close correlation combined with deterministic causation implies cones are the physiological basis of unique hues. This match of three physiological and three psychophysical functions is unique in color vision.

Orthogonal Relations and Color Constancy in Dichromatic Colorblindness

“…Consider protanopia, with only two cones S and M, which directly produce the two unique hue chromatic responses blue and green as recently demonstrated [36]. The L cone is inoperative, as is its product, the unique hue chromatic response yellow [36] which normally opposes chromatic response blue .…”

“…The L cone is inoperative, as is its product, the unique hue chromatic response yellow [36] which normally opposes chromatic response blue . How will the visual system handle its need for complementarity, and the fact that S and M (and their resultant chromatic responses b and g ) are not complementary?…”

“…The relative amplitudes of these curves at a given wavelength represented hue mixtures, say of blue-green from the b and g curves. The b, y, g, and r chromatic response curves were usually assumed (without it ever being specifically stated or demonstrated) to each represent a unique hue over all its wavelength range, as was recently confirmed in [36]. Hence these curves are also termed unique hue chromatic response curves.…”

Fish are Sensitive to Expansion-Contraction Color Effects

“…The small difference in wavelength is successively amplified by the nervous system. In this regard, it is worth noting that the diction "R-G" (Red-Green) is often considered equivalent to "M-L" (Medium-Long) wavelength, which are radiation, and therefore are not colored, although yellow, and not red, is perceived by humans when the eye is stimulated by wavelengths around 572 nm, which is the peak of sensitivity of the L cone (Pridmore, 2013). However, it should be noted that color vision's appearance in mammals could be quite peculiar.…”

Wirkung der Farbtemperatur des Lichts auf Konzentration und Kreativität

“…Dass subjektiv bei unterschiedlicher Farbtemperatur und physikalisch gleicher Beleuchtungsstärke Licht mit höherem Blauanteil als heller eingeschätzt wird, wurde auch von anderen Autoren beobachtet und ist Folge der höheren Grün-Blau-Empfindlichkeit der Zapfen in der Retina des Auges [22,47,48]. In einer Untersuchung zu der Frage, für welches Licht sich ältere (n = 42 älter als 65 J.)…”