Yasser’s color-blindness is likely linked to deficiencies in one or more types of cones (the most common form in males is a deficiency in red- and green-sensitive cones. the normal functioning of these cones, as described by the young-helmholtz trichromatic theory, explains how humans are able to perceive a wide variety of colors from differential activation of red-, green-, and blue-sensitive cones.

Yasser’s color-blindness is likely linked to deficiencies in one or more types of cones (the most common form in males is a deficiency in red- and green-sensitive cones. As described by the Young-Helmholtz trichromatic theory, the differential activation the three types of cones are each receptive to one of the colors.

Explanation:

Based on the work and research of Thomas Young and Hermann von Helmholtz in the 19th century, the resulting findings is know as the Young–Helmholtz theory, or trichromatic color vision, stating the existence of three different kinds of photoreceptors system which allows the phenomenon of detectings assorted colors. These cone cells in the eye are sensitive to a particular range of visible light and, in 1850 Hermann von Helmholtz developed the theory further stating that the three types of cone photoreceptors could be classified as short-preferring (violet), middle-preferring (green), and long-preferring (red), according to their response to the wavelengths of light striking the retina. The relative strengths of the signals detected by the three types of cones are interpreted by the brain as a visible color.

as university of miami psychologists debra lieberman and adam smith pointed out in a recent article in the journal current directions in psychological science, humans have social and psychological mechanisms to deter incest. with very few exceptions, marriages between brothers and sisters and between parents and their children are verboten in every human culture. the primary psychological anti-incest mechanism is the yuck response. even the idea of sex with their mom or dad, bro or sis is upsetting to most people. the psychologist jonathan haidt has found that nearly everyone is repelled by the prospect of brother-sister sex, even in hypothetical situations in which there is no chance of pregnancy).

the biological cost of incest

this raises an interesting question: just what’s so bad about incest? sure, having sex with your dad or your sister seems gross — but why? some anthropologists have argued that incest taboos are learned social conventions. this explanation, however, doesn’t make sense to me as it does not explain the widespread existence of anti-incest mechanisms in creatures ranging from cockroaches to chimpanzees. second, the incest taboo is about as close to a universal law as human moral rules get.

why should mechanisms to avoid incest be so widespread both in nature and across human societies? the answer is simple. the problem with having sex close with relatives is that there is an astonishingly high chance that your offspring will be born with a serious birth defect.