填空题 An average human, utterly unremarkable in every way, can perceive a million different colors. Vermilion, puce, cerulean, periwinkle, chartreuse—we have thousands of words for them, but mere language can never 1 our extraordinary range of hues. Our powers of color vision 2 cells in our eyes called cones (视锥), three types in all, each 3 different wavelengths of light. Every moment our eyes are open, those three flavors of cone fire off messages to the brain. The brain then combines the signals to produce the 4 we call color.
Vision is complex, but the calculus of color is strangely simple: Each cone confers the ability to 5 around a hundred shades, so the total number of 6 is at least 1003, or a million. The richness of the world we see is 7 only by that of birds and some insects, which also perceive the ultraviolet part of the spectrum.
Researchers 8 , though, that some people see even more. Living among us are people with four cones, who might experience 9 colors invisible to the rest. It"s possible these so-called tetrachromats see a hundred million colors, with each familiar hue fracturing into a hundred more 10 shades for which there are no names, no paint swatches (样品). And because perceiving color is a personal experience, they would have no way of knowing they see far beyond what we consider the limits of human vision.