Dichromacy in humans is a moderately severe color vision defect in which one of the three basic color mechanisms is absent or not functioning. It is hereditary and sex-linked, predominantly affecting males.^[1] Dichromacy occurs when one of the cone pigments is missing and color is reduced to two dimensions.^[2]

Organisms with dichromacy are called dichromats. Dichromats can match any color they see with a mixture of no more than two pure spectral lights. By comparison, a trichromat requires three pure spectral lights to match all colors in their visual spectrum. In most modern usages of the word spectrum, there is a unifying theme of between extremes at either end. ... A trichromat is an organism for which the perceptual effect of any arbitrarily chosen light from its visible spectrum can be matched by a mixture of no more than three different pure spectral lights. ... The optical spectrum (light or visible spectrum) is the portion of the electromagnetic spectrum that is visible to the human eye. ...

There are various kinds of colour blindness. Protanopia is a severe form of red-green colour-blindness, where there is impairment in perception of very long wavelengths, such as reds. To these sufferers, reds are perceived as beige and greens tend to look like reds. Protanomaly is a less severe version. Deuteranopia consists of an impairment in perceiving medium wavelengths, such as greens. Deuteranomaly is a less severe form of deuteranopia. Those living with deuteranomaly cannot see reds and greens like normal people, however they can still distinguish them in most cases. A more rare form of colour blindness is tritanopia, where there exists an inability to perceive short wavelengths, such as blues. Sufferers have trouble distinguishing between yellow and blue and tend to mistake greens for blues and yellows for reds. Color blindness in humans is the inability to perceive differences between some or all colors that other people can distinguish. ... Please wikify (format) this article or section as suggested in the Guide to layout and the Manual of Style. ... Color blindness in humans is the inability to perceive differences between some or all colors that other people can distinguish. ... Please wikify (format) this article or section as suggested in the Guide to layout and the Manual of Style. ... Color blindness, or color vision deficiency, in humans is the inability to perceive differences between some or all colors that other people can distinguish. ...

Dichromacy in mammals

It is currently believed that most mammals are dichromats. The straightforward exceptions are primates closely related to humans, which are usually trichromats, and sea mammals (both pinnipeds and cetaceans) which are monochromats. New World monkeys are a partial exception: in most species, males are dichromats, and about 60% of females are trichromats, but the owl monkeys are monochromats, and both sexes of howler monkeys are trichromats. Recent research (e.g. Arrese et al, 2005) suggests that trichromacy may be widespread among marsupials. Subclasses & Infraclasses Subclass †Allotheria* Subclass Prototheria Subclass Theria Infraclass †Trituberculata Infraclass Metatheria Infraclass Eutheria Mammals (class Mammalia) are warm-blooded, vertebrate animals characterized by the presence of sweat glands, including milk producing sweat glands, and by the presence of: hair, three middle ear bones used in hearing, and a neocortex... Families Cercopithecidae Hylobatidae Hominidae Catarrhini is the unranked group of the Primates, one of the three major divisions of the suborder Haplorrhini. ... Families Odobenidae Otariidae Phocidae Pinnipeds (fin-feet, lit. ... Suborders Mysticeti Odontoceti (see text) The order Cetacea includes whales, dolphins and porpoises. ... A monochromat is an organism that is truly color blind. ... Families Cebidae Aotidae Pitheciidae Atelidae The New World monkeys are the four families of primates that are found in Central and South America: the Cebidae, Aotidae, Pitheciidae and Atelidae. ... Type species Simia belzebul Linnaeus, 1766 Species Alouatta coibensis Alouatta palliata Alouatta pigra Alouatta belzebul Alouatta guariba Alouatta macconnelli Alouatta nigerrima Alouatta sara Alouatta seniculus Alouatta caraya The howler monkeys (genus Alouatta monotypic in subfamily Alouattinae) are among the largest of the New World monkeys. ... This article is about mammals. ...

Notes

References

• Arrese, C. A., Oddy, A. Y., Runham, P. B., Hart, N. S., Shand, J., Hunt, D. M., * Beazley, L. D. (2005). Cone topography and spectral sensitivity in two potentially trichromatic marsupials, the quokka (Setonix brachyurus) and quenda (Isoodon obesulus). Proceedings of the Royal Society of London Series B, 272, 791-796.
• Jacobs, G. H., & Deegan, J. F. (2001). Photopigments and colour vision in New World monkeys from the family Atelidae. Proceedings of the Royal Society of London, Series B, 268, 695-702.
• Jacobs, G. H., Deegan, J. F., Neitz, J., Crognale, M. A., & Neitz, (1993). Photopigments and colour vision in the nocturnal monkey, Aotus. Vision Research, 33, 1773-1783.
• Mollon, J. D., Bowmaker, J. K., & Jacobs, G. H. (1984). Variations of colour vision in a New World primate can be explained by polymorphism of retinal photopigments. Proceedings of the Royal Society of London, Series B, 222, 373-399.
• Sternberg, Robert J. (2006): Cognitive Psychology. 4th Ed. Thomson Wadsworth.

External links

• Visual comparisons of various types of color vision impairments by Cal Henderson
• Color Vision, Color Deficiency at Firelily Designs