For a world I am working on humans managed to create a race of demi-human cat people. These people where tradionality treated as slaves/property but have in recent times been gaining some degree of freedom. Slavery has not been outlawed and there still exists large numbers of slaves many of who live in very poor conditions. However many have moved to become indentured servents, bonded labourers, 2nd class citizens or even just better treated slaves. This has created a lot of low income ghetos which are primarily dominated by the demi-cats.

What I am trying to figure out is how cats having different eyesight could be used in this story. From what I've found cats are red/green colourblind, they also have trouble seeing far away objects. Mostly I see this being used in different aspects of art or in advertising/signage. For example:

  • A somewhat racist sign warning you to beware of demi-cat thiefs/gangs could be done in red/green style so only a human could read it.

  • Billboard advertisements aimed at humans on the edge of these ghetos with offensive messages (eg. selling slaves) could be done in red/green as well.

  • Some demi-cat gangs/artists could make graffiti in a way that would make it hard/impossible to read for human eyes (is this possible?)

  • Artists making art that appears slightly differently depending on if you can see full colour. Optical illusions/hidden images in the art.

The idea behind the first two is not to make it impossible for them to read the message but rather make it easier for them to ignore. Due to cross-breading there would be a small number of demi-cats with human eyes that could understand these signs. Rumours and gossip would probably spread about what these signs say but my thoughts are a lot would not want to talk about it, and children especially might just not know they say anything.

The first part of my question is it reasonable for signs to exist in this manner but for people to not know what they say? And would making signs in this manner be an effective way of reducing unrest?

The second part of my question is how hard would it be for people to simulate what the other sees?

This society is similar technologically to our own but access to computers is extremely limited (only upper class humans would have transportable computers). From what I've found lenses can simulate or give colourblind a glimpse of full colour (EnChroma lenses). But I'm not sure how hard these would be to make and if these would be widely available to a low income environment.

On the other side from what I've found it seems computers are needed if you want to see what a colourblind person sees. I have seen a few people asking if it is possible for lenses to turn things grey scale but it seems impossible.

  • $\begingroup$ something like one in ten human males are red-green colour blind. $\endgroup$
    – Jasen
    Commented Mar 30, 2018 at 2:24
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    $\begingroup$ Not directly related to the question at hand, but keep in mind that allowing interbreeding between humans and your demi-cats probably fails the "scientific realism" check without a lot of background work on genetics, how exactly these hybrids would pan out, odds of conception, possibly different reproductive systems, etc etc. You're free to assume that it's possible regardless, but not if you want a "hard" sci-fi story. $\endgroup$
    – Palarran
    Commented Mar 30, 2018 at 2:43
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    $\begingroup$ You can't simulate real colour vision from lenses---EnChroma lenses are an expensive quack product which does not allow colourblind people to, for example, pass an Isahara test. So you couldn't simulate normal colour vision that way. You could simulate colour-blindness with lenses though. $\endgroup$ Commented Mar 30, 2018 at 3:17
  • $\begingroup$ My knowledge of Enchroma is pretty limited, might have to check them out more. But I thought lenses that simulated color blindness was impossible see - photo.stackexchange.com/questions/81966/… and various other answers $\endgroup$
    – Typhado
    Commented Mar 30, 2018 at 4:05
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    $\begingroup$ It should be noted, that having red-green colorblindness doesn't prevent them from seeing red-green, just not being able to distinguish between the two. Meaning, they could see red-green signs, but not read them. But it would not be a stretch for a reasonably intelligent cat person to bribe a human into reading it for them for a small fee. In other words, it is a minor inconvenience, not a way for humans to have a secret means of communication. $\endgroup$
    – Neil
    Commented Mar 30, 2018 at 9:03

3 Answers 3


It is the cats who should be able to see things the full humans cannot.

shirt ad

In gay-themed ads, advertisers employ culturally meaningful symbols or iconographies as part of an effort to not alienate nongay consumers. https://www.tandfonline.com/doi/abs/10.1080/13527266.2013.775179?src=recsys&journalCode=rjmc20

The dominant group has nothing to hide. What do humans care if worthless slave cats see offensive ads? What are they going to do, meow? The slave cats, though, face big trouble if the humans see ads which are frankly disrespectful or offensive to humans, or distasteful because of the cat emphasis.

Groups which must keep a low profile use symbolism that the dominant group does not understand or at least it is "not impossible for them to read the message but... easier for them to ignore." I chose gays here because there are so many great gay advertising images - ones like the above more obvious to our savvy modern eyes. American blacks have an even longer history of coded communications designed to avoid the ire of the dominant group.

Cats have senses humans don't. Cat billboards are not easy to understand and maybe the humans don't really want to understand.

This concept has the making of truly awesome high science fiction: exploring public communications of oppressed groups. If not for a full story this is the sort of side storyline that enlivens scifi.

thinking more about this - persons who want to hate / enslave / eat cats might themselves be a subjugated or underground group. Sort of like white power folks in US (until recently). They may have code talk too as this sort of behavior is now frowned upon by the establishment.

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    $\begingroup$ Kind of related (and I’m not sure how realistic it is) but the humanoid cats from Red Dwarf developed a scent based writing system, so maybe the demi-cats of this world use something similar. $\endgroup$
    – Pleiades
    Commented Mar 30, 2018 at 2:42
  • $\begingroup$ or ultra-violet graffiti that defaces the human billboards/buildings in a way which is invisible to most of them $\endgroup$ Commented Mar 30, 2018 at 3:19

Cats May be Able to See Into the Ultra-Violet Spectrum

Some recent studies seem to indicate that cats may have at least some ability to see into the ultra-violet. Obviously using graffiti or marking areas as unsafe or safe could be achieved (somewhat) clandestinely by using inks that only show in the UV spectrum. These messages say things like "Human cops patrol here!" or "Safe-house here" or maybe "Cat-nip for sale after dark"! or even gang graffiti "Maine-Coon Clan rulez!" Obviously your society needs a dedicated force of slave wranglers and a full time police to ensure the dirty fur-balls don't get too uppity. They might have UV goggles that can let them see in the same UV spectrum as the cat-people so they can read these warnings.

Pic Here is how a cat most likely sees a bird enter image description here

Plus, UV inks can be tattooed so maybe your various cat gangs/clans/whatever ink up and your furry-oppressive police make regular checkpoints where they look over individuals for tattoos with UV lights and UV goggles and stuff too. enter image description here


For the demi-cats, signs should be hidden in plain sight.

A reason for this, is have you wondered why cats stare at walls or even nothing?

enter image description here

"When cats appear to be staring into space, they may actually be detecting subtle motion, as their vision is much more acute than ours," veterinarian Rachel Barrack, article from The Dodo

You can implement a kind of messaging system that's hard for humans to detect, perhaps too subtle to notice. It could be a form of morse code with a rapid and faint flashing light that seemingly just blends with the background, something only a cat might see. And these kind of things are what grabs a cat's attention: they become fixated on it.

I can just imagine your demi-cats gathering in some odd location, and the humans are wondering "what the hell are they looking at!"


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