[tlhIngan Hol] On Klingon colours: Is the Klingon vision bichromatic?

[Rhona Fenwick]

The Land theory you describe is an interesting sidebar in the history of our understanding of colour vision, but it simply doesn't match with what we've subsequently discovered using methods of genetics, embryology, histology, and anatomy that are available now but weren't when Land was doing his research.

jatlhpu' charghwI':
> He then experimented and discovered that if any one of
> the three filters was removed, so that that projector showed
> the black and white picture without its filter... then the full
> spectrum of color still showed in the projected image."

Of course it does. That's because white light is fundamentally emitting at a wide range of wavelengths, which has been well-known ever since Newton and his prisms. Land's finding makes perfect sense: the filtered light from the other two projectors supplies all the necessary light of those colours, whereas the white light, which is multi-frequency (provable with a prism) and therefore providing light at "all three" colours of the filters, will always supply whichever of the three colours is missing. Taking the red filter off a white light doesn't "take away" the red light, it only masks it by adding the other two colours back into the mix.

taH:
> But if you instead simply break up our retina sensors into the
> two types we actually find there, rods and cones, then have
> one create a low frequency image while the other creates a
> high frequency image and compare and contrast the two
> images to mentally invent the colors that we see..."

The problem there is that we know from anatomy and histology of the retina that the rods and the cones are not equally spread across the whole area, which means that under Land's theory we should see better in (say) the red wavelengths in the centre of vision, and the blue wavelengths in the peripheral vision. But that isn't at all what happens. The cones are concentrated in the macula of the retina, which is where our central vision is focused, giving us excellent colour vision (of all colours) in the centre of vision. The rods, though, are spread out at the periphery, giving poor colour vision (which has been demonstrated by numerous experiments with colour perception in peripheral vision) but excellent perception in less intense light (which is also why the most distant stars are often only visible if you don't look directly at them).

taH:
> But, dominant theories don’t die easily, even when they have
> no basis in reality, so we still teach that there are three kinds
> of color cones in the eye, despite the lack of any physical
> evidence to that effect"

But we have extensive physical evidence. We've sequenced the genes that code for the opsins, the photosensitive proteins, that are expressed in the three different cone types (humans have nine opsin genes altogether, of which three are expressed in cone cells), and we have embryogenic evidence showing that cones never express all three opsins at the same time.

Link to a study of macaque retinae showing this: https://bit.ly/2lWfQ3z

taH:
> nor any explanation why three types of cones would become
> confused between red and green more often than between
> blue and green or red and blue

The explanation of that one is very simple indeed: the gene for the opsin with peak sensitivity to green light (i.e. the medium-wavelength opsin) isn't autosomal, but is located on the X chromosome. As such, it requires only a single-gene knockout for men to be affected (though the more usual double knockout for women to be affected). And this is what's seen in population studies: about 8% of men of European ancestry are red/green colour-blind, whereas only about 0.4% of women of the same ancestry are, which matches quite nicely with an X-linked recessive genetic phenomenon.

And we've drifted a long way from Klingon here, so I'll cut my response there. Suffice it to say that human vision is far better understood than you give it credit for, and we know just about as certainly as it's possible to know that a three-peak receptive system is necessary to explain the facts of human vision. Klingon anatomy and histology, on the other hand, we just don't know much about, but a simpler two-peak receptive system could also explain the colour terminology attested in canon.

QeS 'utlh

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