Tetrachromacy & Pentachromacy

[JCurwen3]

Tetrachromacy
Pentachromacy

Basically, you have one (tetrachromacy) or two (pentachromacy) more colour channels than the average human. Beings with these traits would see up to 100 million and 10 billion different colours, respectively (trichromats like the average human see up to 1 million). As many as half of human women may be tetrachromats; no human could be a pentachromat without some major mutation.

Would these just be perks in GURPS (maybe levelled, for each additional colour channel)? They might confer some relative advantage. If a human had to interact with primarily tetra- or pentachromatic aliens / entities, they'd certainly be at a disadvantage when it came to judging, producing, appreciating, and differentiating as far as the alien culture's visual arts were concerned, among other things, for instance.

What game mechanical benefits, if any, should they provide?

[Anders]

A bonus to Connoisseur (visual arts)?

[CoyoteGestalt]

Perks, surely, and probably giving an occasional conditional bonus to certain Connoisseur, Artist, or Jeweler rolls (or at least canceling a penalty in preparing works for others with more sensitive eyes), and to some analytical Chemistry and Astronomy rolls at TL 5-7.

[Anthony]

Assuming it exists and is something relevant (not just 'two slightly different versions of the same receptor'), it's basically a bonus to vision rolls in situation where color discrimination is important, probably +1 for 4-5 color receptors (ultratech sensors can have hundreds to thousands of color bands).

[Ketsuban]

Tetra- and pentachromacy are at best one-point perks (the latter possibly an Unusual Background) and I can't see it conveying any game-mechanical bonuses. If the additional opsin(s) corresponds to visual sensitivity to infrared and/or ultraviolet, then buy them as the corresponding advantage.

[Bruno]

Originally Posted by JCurwen3

As many as half of human women may be tetrachromats; no human could be a pentachromat without some major mutation.

It's actually possible without mutation, but it takes chimerization with a fraternal twin (not totally uncommon); one twin would have to have one form of non-red-green colour blindness while the other has red-green tetrachomacy.

Which further implies that one cell donor is probably male, and the other is definitely female, so the resulting child may be intersexed to some degree if chimeric tissue ends up in the reproductive glands, and immune system problems may be a recurring issue.

But it's possible without mutation :D

[JCurwen3]

Originally Posted by Bruno

It's actually possible without mutation, but it takes chimerization with a fraternal twin (not totally uncommon); one twin would have to have one form of non-red-green colour blindness while the other has red-green tetrachomacy.

HA! I always forget about chimerization. Which is odd because whenever it comes up as a topic in conversation I'm the most vocal in pointing out that it may be much more common than we know (after all, it'd only be discovered in the obvious cases, and even then only with DNA tests).

[Anders]

However, you should also remember that we need functional tetrachromacy, i.e. we need a difference between rods 3 and 4 (or is that cones? I always forget). Otherwise you get a lopsided distribution of color-sensitive bits but not really tetrachromacy.

[Bruno]

Cones IIRC. C for Colour, and I hope I'm not mis-remembering my mnemonic :)

Traditional deuteranomaly/normal or protanomoly/deuteranomaly tetrachomacy would give you even more sensitivity in the red-green spectrum than humans already have.

Not a big surprise as fruit and leaf eaters, but primates are highly interested in whether something is green, how green, subtle variations in green vs yellow vs brown or red, different reds, yadda yadda. So our "extra" cone type compared to other mammals is very close to another type, making the red-green area pretty crowded.

Your most common tetrachromat is going to be even more sensitive than we already are, by adding another peak in that area. So, amazingly good at judging if those avocados are ripe by sight alone, and pretty picky about tomatoes.

deuteranomaly/tritanomaly on the other hand would give you three cone types in the red-green region instead of two (two normal, one abnormal), and two blue-area types instead of one. Depending on how far apart the "blue" cones end up (I can't find a good number on the "average" wavelength sensitivity for tritanomolous blue cones) that can produce an improvement over tetrachromacy in overall bredth of colour discrimination.

Otherwise you just end up subdividing the same area of sensitivity even more.

I'm not sure "tetrachromatic" is worth even a quirk on its own. It would take either familiarity with your condition combined with a particularly acute awareness of colour sense (aka being able to exploit it to the fullest) or particularly well-suited tetrachromacy for it to justify a +1 in some situations to some skills. Pentachromacy is just a slightly easier justification for that perk IMO.

I'd just call it some sort of short pithy name for "unusually good colour discrimination" and allow players to justify it any number of ways.

[Anaraxes]

Originally Posted by Bruno

Cones IIRC. C for Colour, and I hope I'm not mis-remembering my mnemonic :)

Evidently it's time for a little review from the Blue Man Group.