So, I am writing a world where most mammals, birds, primates, and a few reptiles have been sentient since an 'event' of some sort happened in the late 1700s. This means that something like 'Mr. Ed' is not unusual at all, it would be perfectly normal to have a philosophical argument with a horse.


  • Animals from the above groups can speak the language native to the country they live in, and like a human can learn more.
  • Though still legally considered 'property' in the official sense, it is considered very poor form to disrespect or mistreat animals, as they seem 'human' enough to many people and are treated as such.
  • Like humans, there is a range of intelligence-every animal is different.
  • For the most part, animals still have their biological limitations.

So, I have an issue--in our world, we use red/yellow/green for traffic lights, signals, and many other things. But how can you deal with that, when a horse sees like this: Horse color vision Obviously, red, yellow, and green traffic lights are a no-go (no pun intended)

Dogs and many other animals like Whitetail Deer are also similarly color-blind. So, what colors could be used for warning signals like railroad crossings and traffic lights to give the intended message for all species instead of what we know? Would shaped lights become more popular instead, like is suggested for human color blindness?

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    $\begingroup$ Last I checked, primates are mammals. What about amphibians? Oh, and actually traffic lights are designed so that they can still be "used" by people with red-green color blindness. It's possible they might have developed differently under the circumstances... but also maybe not. $\endgroup$
    – Matthew
    Sep 11, 2020 at 13:23
  • $\begingroup$ Asking "How would this world develop instead?" is a bit too open-ended of a question in my opinion; maybe focus on something specific like the traffic lights you mentioned. $\endgroup$
    – Dragongeek
    Sep 11, 2020 at 13:44
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    $\begingroup$ Roadway traffic signals evolved from railway semaphores, and early traffic signals used shapes as well as color. $\endgroup$
    – user535733
    Sep 11, 2020 at 15:04
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    $\begingroup$ @Alexander Well, you could have horses pulling carriages intependently for example $\endgroup$ Sep 11, 2020 at 18:48
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    $\begingroup$ @John: Not universally; lizards see colors better than we do, snakes worse. Of course, we're all color blind relative to the king of cones, the mantis shrimp. $\endgroup$ Sep 12, 2020 at 1:32

4 Answers 4


They would probably focus more on shape and contrast.

for a real world example look at German public transportation signals. (German)

enter image description here

(Photo from Wikipedia Page)

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    $\begingroup$ Although this answer could be fleshed out a bit more, it's the correct answer. People with color blindness drive without problem because the position of the lights are predictable and shapes are easily discerned. $\endgroup$
    – JBH
    Sep 11, 2020 at 17:57
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    $\begingroup$ I am personally wondering how colorblind people drive at night on unlit roads. I feel it should be difficult. $\endgroup$
    – Alexander
    Sep 11, 2020 at 18:56
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    $\begingroup$ @Alexander Color vision does not immediately relate with scotopic vision (they are mediated by different mechanisms, i.e. cone- vs. rod- cells). Colors become hard to discern in dark conditions for everyone (non-mutant) anyway. This study, for example, concludes that: Our small sample of monochromats had higher absolute thresholds than the corresponding control subjects, but their performance at the scotopic visual field test and perceptual task did not differ significantly from that of color-normal subjects. $\endgroup$ Sep 11, 2020 at 22:47
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    $\begingroup$ @Vector Zita I am talking about a different thing. At night, I, as a non-color blind person with good, but not exceptional vision, can tell if a traffic light ahead is red or green from at least a mile away. However, I'm not able to tell whether the active light is positioned at top or a bottom of the fixture until I am very close. $\endgroup$
    – Alexander
    Sep 11, 2020 at 23:48
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    $\begingroup$ @Alexander I see colors too, but I cannot act on 1 mile ahead light, as it can change (even go full cycle), before I reach it ... I had to be prepared to stop in case yellow/Red came when I am near the lights. Color-blind person/animal would be in the same position. Maybe they would need slow a little near the light, until they see, which position it is, but it would not affect trafic too much - if the road is empty, they may even stop, nobody cares. If the road is frequented, they see car before them driving, or stopping. And the change of light is clearly visible, as it changes position. $\endgroup$
    – gilhad
    Sep 12, 2020 at 0:25

Well, depends on which question you are asking. Is it, "How would the world change to suit color blindness as a commonality," or is it, "How would color blind animals get by in a colorful world."

The answer to the first one is, it wouldn't. No one designed the pre-civil war Southern U.S. to fit slaves. History teaches us that we don't change anything in the world to benefit that kind of "property," only to better suppress them.

The answer to the second one is that they would get by the same as color blind humans. In Britain alone there are 3 million color blind people, very little is designed for them. In fact, before they tested in schools it was common for someone to go 20+ years before they even knew they were color blind. Color is a funny thing in our brains. We all experience being color blind every day temporarily, when we turn off most of the lights at night and wander to bed (color receptors only work in bright light), and we don't even notice. Mostly we dream in grey without noticing as well.

Color blindness is not a devastating handicap. The real problem is, how do the poor things get by in a world built for thumbs? I mean, a dog can't even open a doorknob, let alone a horse hoof...

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    $\begingroup$ On the contrary, the antebellum South was designed and/or evolved to fit slaves, just as was every previous slaveholding society (which was pretty much all of them). FWIW, dogs (at least some of them) can learn to open doorknobs (it would be even simpler if they had European-style levers), and horses can manipulate things like gate latches, if you don't secure them. They use their lips for manipulation, not their hooves. $\endgroup$
    – jamesqf
    Sep 11, 2020 at 17:05
  • $\begingroup$ You shouldn't forget that traffic signs and traffic lights are not that old and were invented after the animals were able to speak. If at that point all traffic is carried independently by horses it might be in the interest of humans to have a system that is most effective for them. $\endgroup$ Sep 11, 2020 at 17:17
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    $\begingroup$ "Mostly we dream in grey without noticing as well." Speak for yourself; pretty sure my dreams are full color. But... dreams are funny, and different people dream differently; maybe I'm in the minority? "I mean, a dog can't even open a doorknob...", this world will have more lever-type handles. "...let alone a horse hoof", true, but a horse's mouth is surprisingly dexterous. They can untie ropes; I think they can handle a doorknob. $\endgroup$
    – Matthew
    Sep 11, 2020 at 17:36
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    $\begingroup$ There's a bit of history to dream research in that statement I must skip, but to summarize the best of our present knowledge, dreams inside of REM sleep are usually in color, and dreams outside of REM sleep are in greyscale. As a bit of trivia, people who are blinded tend to stop dreaming in images after about a couple months. And I would enjoy seeing a horse with a special mouth mouse, I bet it could work. $\endgroup$ Sep 11, 2020 at 18:13

[...] still legally considered 'property' [...]

Then, they would really get by in much the same way they do until now. Consider how some children go to school in a car with no problem at all? Because, obviously, someone else is doing the driving. Given that animals are still "property", there is always an owner to "guide" them around, or delegate the guidance to someone else. If they are "human enough", we could very well simply assist them, out of respect and other similar values.

Beyond that, let me give you some ideas...

Mammals are really mostly dichromats in reality. This means that they are very well sensitive to colors, just not the colors most humans are sensitive to. They can see yellow, green, violet, blue... they see approximately what a red-green colorblind individual does, actually.

The proteins accounting for the most significant part of the difference between dichromacy and trichromacy are called opsins. They are found in cells located in the eyes and exhibit peak reactivity against radiation of different wavelengths. Visible light comes in a range of wavelengths. There are genes encoding those proteins, and we were dichromats too, until, at some interval of history, one of the two genes was probably duplicated and slightly changed with time, to result in a third gene (source). By slightly, I mean that the genes that were duplicated are now ~96% identical, while they are ~43% identical to the third gene (source)

Furthermore, some animals previously thought to be dichromats have been found to be potentially trichromats (some Australian marsupials, actually). From an evolutionary perspective, the evolution of trichromacy in these species seems to have followed a relatively different route, which is not easy to reason about or follow based on what is currently known in terms of genetics and is, thus, an active field of study (source).

I understand that all this probably sounds a bit off-topic but it is necessary to make my point. Most of your animals already possess a tremendously large part of the machinery for three-color vision, but not the totality. All that is needed to actually develop it, though is, I would argue, a balanced effect of the following ingredients:

  • An adequately large and diverse gene pool (i.e. lots and lots of different individuals).
  • Enough time (I couldn't really give even a ballpark figure here, but see below).
  • Selective pressure (trichromacy can't really flourish if it doesn't offer a very significant advantage).

Now, here comes the most important part. Any sequence of events that makes animals sentient in the human sense (as has happened in your story) would require multiple orders of magnitude more of all three of the above "ingredients". Fitting trichromacy into your story is really a lot easier to support in terms of "(im)possibility", so I suggest you could do that. Additionally, I would argue that, among almost 1 billion dogs on earth, given the endless hundreds to thousands of years of evolutionary pressure, I wouldn't really be surprised by the odd trichromat dog, even in real life. Well, we only had 57,780,223 horses in 2018 so the odds of a trichromat horse are a bit less than that of dogs (apparently...).

You could definitely work around the problem by focusing on shapes/patterns, but providing stronger color perception is a much more natural course of enhancement. Shapes are already there, animals can "feel" shapes and patterns and they do use them to derive information and act accordingly in nature. Learning more shapes and how to behave or act in their presence/absence would be like extending their perception space along a single dimension.

If they gain the sensory apparatus for an additional visible light radiation wavelength (as in "color"), they expand their perception space by an entire new dimension. The information was there, they just couldn't feel it. They will become able to transmit and understand a lot more intricately nuanced elements of knowledge using this new information dimension.

Of course, you can expect that something else might give... e.g. their smell may become weaker eventually, but oh well... if they don't need it as much anymore...they probably wouldn't care!


Quite an interesting topic.
I got a few ideas (but they are just that. Ideas, not really scientifically based or proven).

The Basics

  • At what point in time is your world set right now? The incident happened in the late 1700s, but what year is right now? (What level of technology and society...)

  • Depending on what age your world is set in - it might have developed very differently since the incident, compared to our world. Just imagine human scientists talking to birds around 1700 and discovering the most important factors of flight. Even environment pollution and meat consumption could have taken a different development.
    (A negative example in this regard is the Netflix film "Bright", set in the USA of today, not just a world like ours, but inhabited with humans, orcs and elves. However, there are no big changes to our world and history, even though orcs and elves have lived openly among humans for centuries [in contrast to Harry Potter or Underworld with their secret parralel societies].)

  • The first big question is how sentient are we talking?
    Can they just speak or are they all the same level and kind of intelligence as humans? Or can only some of them speak but all of them are intelligent?
    You say that the biological limitations still apply, which could include brain size and instincts. On the other hand some animals are biologically not able to speak like humans (but already able to communicate through symbols etc.). The nature of your initiation event and world (fantasy/magic, science experiment, mutation, extra-terrestrial influences...) could determine/justify the grade of human-like intelligence and speech you are going for.
    It could even be very interesting if you have different species which are able to talk but have different levels of intelligence. (How do people in power treat others they consider weaker, easier to exploit and inferior? On the other hand this different ways of thinking don't necessarily have to be worse, only with different focus (securing the hive vs. individual happiness, living in the moment instead of a stressfull office career.) But you have to be careful with this approach for your story not to appear like promoting racist thinking.
    Here is an article that horses can understand and communicate through shapes (which could be important for traffic signs).
    And there is the approach that (our way of) talking affects (our way of) thinking. (The article is in German but you can use Google Translate).
    (For other species you got an ape reading numbers (and memorizing them better than humans). I am not sure if this cat communicating with a human is real or happened randomly. And crows use primitive tools.)

  • What I don't know is which animals could be (mentally) able to read (e. g. street names).
    The other question would be, which kind of writing would be used/developed by which animals - for horses it seems most effective to develop some kind of Cuneiform with different angles of the hoof (although I don't know how flexible their legs are for turning, maybe they'd have to write horizontal lines as letters instead of vertical ones). Birds could pick some form of Braille with their beaks.
    (However it could be forbidden to use fonts that are unreadable to the human masters, causing them a disadvantage, cf. the human regulations against flight in Carnival Row. Or maybe they simply despise animals for developing their own primitive writings instead of adapting to the real one, compared with the fear of losing influence of the lead culture.)

Traffic / Travel

  • Another question would be if traffic lights are indeed the most effective way for animals in traffic... let's suppose originally all traffic was carried by horse and they are now in charge of getting carriages independently to their destination. Horses definitely can understand commands (cf. dressage) and symbols (see above). But maybe it would be more natural for them to read the body language of other horses to determine the hierarchy and who can go first. (Of course it might be hard for humans to accept having to wait very long at a crossroads because their horse is very low-rank). Or maybe their reflexes are just good enough to estimate, if they can maneuver around each other without clear lanes and traffic lights: Dogs for example are really good in estimating where a thrown ball will be in the air at a certain moment for catching it mid-flight, cats are bad at estimating the speed of cars and horses are said to have the fastest reaction time of all domestic animals and to be quick learners. In this case maybe traffic lights didn't develop in the first place (given that the animals started talking in the 1700s and traffic lights are a more recent invention).
    Equally possible is that traffic lights only developed after the invention of cars (that can be driven by humans and dogs) and mass traffic.
    Alternatively there is indeed some kind of traffic regulation system, but it was only designed with the unique sight and behaviour of horses in mind. (It could conist of a rotating index, symbolizing the tail of a relaxed or anxious horse, or traffic signs in the shape of horse ears, again relaxed and anxious. And for humans and dogs not specialized in horse body language hard to differenciate). Now human (and dog) drivers have to adapt to that system. Maybe this even causes protest among horses who fear they now lose their monopoly and social status. And it might lead to some racist comments - poor humans who have to drive themselves or progressive humans who see the future in indipendent cars are mocked for having to adapt to animals and be "nothing more than a fuckin' beast - do you call that progress?"

  • With the answers of Captain Skyfish, Daniel and myself you have different approaches. You don't have to choose one over the other completely but can implement them in different countries of your world, depending on how considerate or racist they are towards the sentient animals.

  • For long-distance travel you could think of birds as independent navigation service providers. It is suspected that birds (like messenger pigeons) can sense the magnetic field of the earth. But there's a bunch of other animal navigation methods.

More Random Stuff

  • As for the human oppression of animals (owning them) - there are these books about what would happen if nature united against humans (who are in fact except for their brains, language and opposable thumbs quite weak creatures). Giving all animals the ability to communicate (with each other) and some centuries time - I don't know if there might be some matrix-style revolution against humans at some point.
    A key factor in this might be that most human (war) machines aren't fit to be used by animals, which might give humans a big advantage.
    Furthermore they established themselves as some kind of shepherds of the animals for centuries (providing food and shelter), which might have lead to some sociological or even religious justification for their power (like historic aristocracy or racist regimes). And life without humans could result in anarchy - many animals are part of each other's food chain so the shared human oppression still offers some set of rules and security. (For example the leading mare of a herd of horses is not choosen only by her physical fitness).
    Yet there might still be some groups who fight against human rule. Or even some racist animal groups who think the best predator should lead. Or, inverse, predators should be excluded from society (cf. Disney's Zootopia). Maybe even humans are split between parties who include predators and those who live vegetarian and see collaboration with predators as a taboo (if they don't choose to live vegetarian, too, now that they are able to speak and understand their prey and what they do to them).

  • This wouldn't just affect traffic lights. Animals for example also see movies differently So films might be shot especially for one group/species of watchers while excluding others.
    Depending on how modern your world is, maybe Virtual Reality would have developed further (with photo-realistic computer-generated models and real-time rendering, allowing the computer to render the image for the needs of every watcher, even for dogs looking into to two different directions at the same time) and including other senses like smell. On the other hand, if animals are still viewed as property - how much effort would be put into this or are animals only taken into account, if it is useful for humans.

  • The Magicans (available on Amazon) is a TV adaptaion of a series of novels, centering around what the worlds of Harry Potter and Narnia would look like in a more grown up world. There you have the inhabitants of the Narnia-esk Fillory voting for marriages between sentient animals and humans, as they are both sentient and able to communicate their free will. You could have 2 factions, one for that and one against it (for racist, religious or conservative reasons).

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    $\begingroup$ "Even ... meat consumption could have taken a different development." I would hope so. I can't imagine not having a different perspective on meat consumption if the animal is indisputably sapient. I mean, even in times when some humans have been considered, well, not human, I don't think eating them was wide-spread. (Probably not non-existent; cannibalism is a thing, after all.) $\endgroup$
    – Matthew
    Sep 11, 2020 at 17:41
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    $\begingroup$ On a completely different note, don't (this goes for the OP also) make the mistake of assuming that ability to speak means that animals have anything like a human mindset. Recall the old joke about a man about to be eaten by a lion asking God to make the lion Christian. The lion pauses suddenly to thank God for the meal he's about to eat. Just because they can talk to each other doesn't mean lions won't still eat antelope (c.f. The Lion King). $\endgroup$
    – Matthew
    Sep 11, 2020 at 17:45
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    $\begingroup$ ...which is sort of in line with my second comment; animals suddenly becoming sapient and everyone being able to communicate with everyone else (at the level of abstract ideas, that is; animals in the real world can certainly communicate simple things) doesn't necessarily mean we will treat them, or they will treat each other, any differently. My first comment was just about eating meat. I can't imagine it not having some effect if an animal you are going to eat can tell you its life story beforehand. $\endgroup$
    – Matthew
    Sep 11, 2020 at 17:53
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    $\begingroup$ You could even have laws or moral regulations what kind of meat is acceptable to eat (e. g. humans aren't allowed to eat humans but lions are, as long as they didn't kill them or didn't have a contract with them, allowing them to do so). Maybe there is even a death sentence to be included in the food chain. This could lead to some parties being interested in raising the number of death sentences... Here is a documentation about a sowjet work camp for which they actively tried to get as many people convicted as possible youtube.com/watch?v=CaOwcYLGTMo $\endgroup$ Sep 11, 2020 at 17:55
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    $\begingroup$ And then you got nazis making lampshades or binding photo albums in human leather from the concentration camps en.wikipedia.org/wiki/Lampshades_made_from_human_skin $\endgroup$ Sep 11, 2020 at 17:58

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