# How does a species who cannot distinguish left from right build their cities?

Fran is on holidays to planet Earth. She is having difficulty coping with the local geometry.

At this second Fran is thirsty. She can see a lemonade stand nearby. She knows a human would have no difficulty getting there. But she's worried of making a fool of herself or getting lost on the way. You see the lemonade stand is neither in front of or behind her. The lemonade stand is in one of the other directions.

According to the guidebook, humans have a bizarre extra-sensory direction-seeking power.Their cities are built with this power in mind, and that makes them very tricky for people like Fran to navigate.

Well, she'll look more a fool just standing around like this. Fran takes the first step. . .

Drat! Where's the lemonade stand gone? Fran can't see it any more.

She looks around. Oh, it's behind me!

Fran turns around and makes her way to the stand.

Phew! That wasn't quite so bad after all.

Fran is no longer thirsty. But she's dreading having to make it back to the hotel before nightfall. . . .

Fran, and every member of her species, evolved with no ability to tell left from right. Suppose she was facing North. She can easily find and move towards things to the North or South. She can tell is something is East-West of her. But she cannot tell which is which. Likewise she cannot tell the difference between North-East and North-West.

Fran's holiday was fascinating but exhausting. She cannot fathom how Humans carry around so much extra information upstairs without going mad! She's glad to be back in her home city.

Question: What does Fran's home city look like? In particular how are streets and corridors laid out to avoid people getting lost? How are roads laid out to prevent collisions?

Some Details: Fran is typical of her species. She has the following attributes:

1. Between 10kg and 1000kg in weight

2. 0 to 10 limbs for locomotion

3. 0 to 10 limbs for dexterity

4. She needs to breath, eat, drink and sleep

5. One distinct 'front' end that processes food, light and sound

6. One distinct 'back' end for excretion

Maybe every member of the species is the same size with the same number of arms and legs. Maybe there is huge variation between individuals. Feel free to modify the species as suits your answer. For example do you think there would be a difference if they has two left-right arms rather than the two arms being arranged one on top of another? Or would a species make sense to have only one big eye rather than pairs?

More Info: Some humans have a similar condition where they are unable to distinguish left and right. One countermeasure they take is to remember 'left' as the side their wedding ring is on, and use that to navigate. Fran cannot by her nature use such a trick. She would certainly be aware that one side of her body has a ring. But since she cannot tell which side is which, it wouldn't help her judge which side to turn towards. If she tried she would just as likely end up facing the wrong way.

• Guys, stop critizing the world. That's not what the OP is after. They have a reasonable question, which has already received one pretty good answer. Not every species in worldbuilding has to evolve, and the OP wasn't asking about the feasibility of his idea in a biological sense. – DonyorM May 23 '17 at 12:46
• Comments are not for extended discussion; this conversation has been moved to chat. – Monica Cellio May 24 '17 at 1:57
• Comments purged. Take it to chat please, further comments will also be purged. – Tim B May 25 '17 at 10:39
• You might find this interesting. – Sigma Ori May 26 '17 at 7:12
• There's just one thing I don't understand about the question. If Fran can tell there's something left or right (but not where it is), what's stopping her from rotating (clockwise or counter-clockwise) until what she's looking for is directly in front of (or behind) her? – Nolonar May 29 '17 at 21:36

Fran is a naturally subterranean boring worm-like creature. Her cilia enable her to move forward and rotate.

On her homeworld, the tunnels are bored with ridges or grooves that serve as affordances for forward locomotion, allowing her species to progress along the intended direction of the tunnel (forward) more easily (and conversely, making it more difficult to walk backwards).

Because the species finds linear forward motion comfortable, their settlements, structures, and rooms are arranged in intersecting rings. Wherever two rings intersect, the being can either choose to continue moving forward along their current ring, or turn off into the adjoining ring. They don't need to decide whether to turn left or right (or up or down, as the case may be) to enter the adjoining ring, since their tunnels all have a natural "forward" direction determined by the ridges in the floors/walls.

Cross-tunnel tracks at the junction of two rings might serve as natural indicators of which way to go if the being wants to switch rings. This keeps the decision to a binary (keep going or change rings) instead of a potentially confusing choice between the left tunnel and right tunnel or forward. (Hat tip to @Yakk for exploring this idea in the comments!)

The ring-tunnels can be quite broad to accommodate multiple beings concurrently moving together, but should not be so large as to be confusing. Long, wide rings might serve as rooms for storage, recreation, and labor, activities which may at times require the beings to rotate or turn around as they undertake their tasks, but the important consideration here is that they always can tell whether they are facing forward or backward based on the design of the tunnel. Forward and backward are the only two cardinal directions. This limited directional sense could be further exacerbated by minimizing the effects of gravity on Fran's homeworld, so even up and down become less relevant.

Extensive three-dimensional intersecting networks of rings compose the underground cities and streets of Fran's people. A human moving along such a network would be utterly confused by the homogeneity of each intersection and the overall structure's inability to conform to a rectangular coordinate system, but Fran's species has both an extremely good kinesthetic sense of forward progress and a knack for remembering the relationships and spacing between rings, allowing them to recall which rings intersect with each other, which entrances belong to which rings, and where they are at a given moment within the ring network.

Note that Fran and her fellows don't need an accurate mental map of the network's layout in physical space to navigate the network; they instead need an accurate mental map of the connections between rings, which would look more like a tree structure or hierarchy diagram than a traditional map.

(I hope you like my MS Paint doodles)

As a final thought on this concept, since a troglodytic lifestyle doesn't necessarily lend itself to the evolution of great eyesight, Fran's species might have a dependency on olfactory markers for subterranean navigation, much like the pheromonal signaling used by ants or the territorial musk/urine marking employed by some mammals. The relative absence or overabundance of scents in an open-air city would add an extra level of navigational confusion for poor Fran.

• I really like this idea because it suggests how the cities could be built in the first place, just relying on natural behaviours. For example the affordances could be created by the process of digging. – Daron May 23 '17 at 17:59
• Sometimes I forget my left and right... I wonder if I could be a subterranean boring worm-like creature...? – Brent Hackers May 24 '17 at 7:24
• I like your MS Paint doodles. Sketches are a great way to visualize your ideas it makes your answer far easier to read with such useful sketches. Fascinating idea. +1 from me – Secespitus May 24 '17 at 11:22
• This answer is so creative and awesome! Great job thinking up this! It is cool to think that they wouldn't even know the overall shape and pattern of their "cities". – forgivenson May 24 '17 at 12:28
• Nice. Such a creature would probably have (more than) a touch of agoraphobia. – JollyJoker May 24 '17 at 13:45

There are a few languages on earth that don't have words for relative direction. Instead of they use absolute the directions North, South, East, and West to describe the positioning of things. For example; speakers of these languages when facing East, would refer to their "North foot" and "South foot", and if they turned 90 degrees would refer to their "East foot" and "West foot".

The speakers of these languages have been successfully foraging in Australia for at least 40,000 years. If the lack of a concept of relative directions impaired their ability to navigate, the languages would have died out.

Other design considerations would dominate the design of their cities, probably building around whatever was built before it became one.

• +1 This is a great answer, since it's a real-life one. The species in question seems to only be able to perceive objects directly in front and directly behind, which is a stricter limitation than lacking words and concepts for the other directions, but I don't think it's an insurmountable limitation. – Jeutnarg May 23 '17 at 14:14
• I imagine people speaking these languages can also rely on landmarks if it is too clunky to check the cardinal directions every time. For example "Turn towards the river" or "Come here to me wudja!" – Daron May 23 '17 at 17:58
• The system of absolute direction used actually matters here as you did not answer the what would their cities be like part of the question. I expect the answer would be: "Pretty similar to ours except you can always tell the direction of the sun / there is nothing that messes with magnetic fields. – Ville Niemi May 23 '17 at 21:37
• @Daron: as I understand, people brought up in cultures with such languages don’t need to consciously or laboriously “check” the cardinal directions to use them — they end up with a very strong intuitive sense of them, by some combination of a well-developed sense of direction, knowing their surroundings well, knowing the environmental cues (sun position + time, etc), and so on. – Peter LeFanu Lumsdaine May 25 '17 at 9:35
• -1: this is about something entirely different from what was asked. Whether somebody uses absolute or relative terms for direction, they still have a clear sense of what directions are, and of an order between them. Somebody speaking such a language might certainly have trouble coping with stuff like traffic rules (though not as much as Sapir-Whorf would like you to believe – it's clear for decades that linguistic relativity is at least not an all-determining effect), but they wouldn't have trouble navigating the space of the city. – leftaroundabout May 25 '17 at 20:54

How about the rationality of object persistence? She doesn't have to know left from right; she knows the lemonade stand exists and will continue to exist if it is out of her sight. Infants know this within a few months. Thus: Turn. Left or right, randomly chosen, does not matter. If the lemonade stand is no longer visible; rationality tells you it is behind you; and that is a direction you know. Turn around. If the lemonade stand is still visible, approach until this procedure must be repeated.

# Fran's City

Off hand, the easiest way to lay out a city is with one-way spiraling streets and one-way radial arms (freeways are side-by-side one-way paths; my city is roughly laid out this way: circles around, about 3 bisecting highways in different directions). Idealized, the species doesn't have to choose left or right, it is chosen for them as the only way to go.

So for example; where the inward spiral turns in, you can only go straight or turn: You happen to be turning LEFT and merging with traffic on the RIGHT, but you don't have to know you are making a left turn, it is the only turn, and you don't have to know you are merging right, there is no other choice. When you exit you choose to turn again: You don't have to realize it is a RIGHT exit, you have no other choice for an exit: follow the turn path, or do not follow it. That is how you make it to an inner ring.

I am presuming, of course, that evolutionarily speaking, no species develops that can literally walk only forward or backward; and this situation is more similar to some form of dyslexia; like not being able to tell lowercase "b" from "d". But dyslexics do not have trouble when there is no choice or the images are symmetrical: "A", "O", "X", etc. So I think the trick may be to eliminate choices that depend on knowing your left from your right.

• This answers how she can navigate Earth. Bot not really how her home city would appear. – CaM May 23 '17 at 16:12
• @CM_Dayton Knowing how this species' cities are laid out tells us what expectations they're working off of. That in turn gives us a starting point for how they might figure out how to navigate in an alien environment. So even if the question didn't mention the cities, it's still worth thinking about. – Ray May 24 '17 at 0:09

I suggest rings.

As I understand, you want a solution that does not depend on the anatomy of the creature. Although I am taking some assumptions that I hope you find reasonable:

• They are land dwelling. No flying, no digging, no swimming, at least not without tools.
• They have eyesight.
• They have some level of intelligence, enough to recognize other individuals.

The intelligence is the hardest part. I can assume that they can recognize symbols, so they can read numbers, so they can have street numbers… but if they can recognize symbols, they may put symbols for left and right and navigate using that. Therefore, I am ruling out systemic abstract symbols. Yet, I am allowing them to recognize their peers and common objects.

Note: There will amounts of items that the creatures will be able to distinguish at a glance (for example you know that “AAA” are three “A”, you do not have to count them – did I just trigger you to ask how to develop a society where people cannot count?). Yet, as I said, I am being conservative on my assumption about the intelligence of these creatures.

First prototype: Have a big tower in the center of town and build rings around. In each ring, it does not matter if you have to go left or right because you can always walk any direction and still pass each house in the ring.

The problem with this solution is that it requires street numbers. The creature would look at the tower from an intersection (a connection between rings), there would be number signs and the creature would decide if it has to go to an inner ring (going forward) or an outer ring (going backward) based on the numbers.

As I said, if you can do that, you can have signs for left and right.

Therefore, we conclude that a single ring is ok, but multiple concentric rings probably not.

Second prototype: Create separate rings, each with a central tower. In the tower, you can place symbols※. This time you do not have to know what symbol comes first or second.

※ Perhaps just use colors. Alternatively, Make rings dedicated to certain things, for example, a ring for restaurants can have a symbol for restaurants. As long as we do not use any symbols that have an inherent ordering that the people need to know which come first. Otherwise you are telling these creature can't tell objects apparts, I'm not going there.

What you need to do is this: First to look at the tower of the ring you are. If you are on the right ring, walk around it, in any direction, until you find the destination. If you aren’t, go to the tower, from the tower you can see the other towers, find the one you need, and walk in that direction.

The above would require the tower to have an elevated (but not necesarily at the top), freely accessible from any direction, open area, from where you can see above the houses in the ring.

After you have seen the tower you need, you walk in that direction. To prevent the creatures to lose their sense of direction, the access points to the center area would need to be abundant. Or even better, design the houses so that you can walk over them.

Perhaps on your way there, you lose sight of the tower; in that case, you will end up in a different ring. Repeat the process until you get there.

Another problem is how to arrange the rings in space so that they do not block the view of other rings…

Pattern of dots in a sunflower behind a spoiler wall to mitigate eye stress.

Observe that in the pattern, from any given spot, the center of the other spot do not align perfectly. It is not a uniform tessellation. Instead they arrange spiral arms. Thus, if you imagine each spot as a ring, with a tower at the center, that tower will not eclipse the view of the other towers (well, unless the tower is too wide, there will be a maximum width given the spacing of the rings).

• Damn my eyes hurt!! O.o – Ditto May 23 '17 at 14:56
• @Ditto hidden the dots on a spoiler. – Theraot May 23 '17 at 15:16
• :) That pattern is harsh .. wow ... :) good answer tho . btw .. – Ditto May 23 '17 at 15:25
• Good answer. It made me wonder how a species that can't tell left from right can develop a writing system, though. Perhaps they write from top to bottom (or the other way around) and have a single line of text per page. It would be difficult to convey long messages on large surfaces (e.g. ads on walls), though, at least until they develop huge screens and can change the message every few seconds. – Rain May 23 '17 at 15:32
• I suspect even their written language would confound humans. It, too, would be spiral or round. No way it would track left/right or up/down. Maybe modeled after Gallifreyan or the language from the movie Arrival. – CaM May 23 '17 at 16:17

Turn towards the thing you want. If you don't see it, keep turning, you'll see it eventually.

Now, it's in front of you. No problem. Walk forward.

A species like this would constantly be orienting itself towards the things it wants. There would be constant spinning. Perhaps even an evolutionary tendency towards pirouetting in place, until they see what they want to get.

So what would the streets look like on her planet? They would look like a circle rather than an axis.

Constant guides, like arrows, would let them know what direction to go in. They can find anything on a street, they just have to keep going around. To get to the next street, you keep going around until you see the entrance to the next street, from one circle to the next. There might be straightways from one to the next, and there might be some things on it, but they would be clearly marked.

I would think that there would be special orienting places where the spinning was allowed in order to chose a forward direction, which would be like turning.

Landmarks will be a big deal. Directions would sound like this: Go to Jasper Circle. Spin towards the clock tower. In front of the clock tower spin until you see the side sign for the grocers. Once you can no longer see the grocers spin until you can see the red street. Follow that until Market Circle. Use the go around there to find the Lemonade Stand. Once you see the sign directly in front of you, spin until you see it.

There will be no choice between left and right, the species is just forced to go a specific direction.

How does this evolve? Well, nature has to be laid out this way. There has to be an evolutionary pressure that makes omnidirectional choices a bad, bad idea, and always facing front a good idea.

EDIT: You said we should be free to redesign your species, so instead of the whole body spinning in place, why not just the head? (ignoring spinal difficulties with this, of course) They spin the head all the way towards what they want, then orient the body and go in that direction.

• The spinal cord is flexible; given a little extra coil of it; just an inch or two, and very plausible (stretchy) muscles and spinal bones; the head could be turned more than a full circle without strain. 360+ degrees with zero injury is not an impossibility. I can swing my arm through a full circle -- If my fist had eyes and that swing traced a horizontal 360 instead of a vertical 360, we're already there... – Amadeus May 23 '17 at 19:41
• The landmark comment is key - that would make navigating much more feasible. – alexanderbird May 25 '17 at 21:36
• constant spinning? what about a spider-like creature that can directly go in any direction without spinning. A creature with 360° sight might have no need for directions, it could be just "its THERE"... – Julian Egner May 30 '17 at 8:08
• @JulianEgner Yes, that would be a good redesign. As written in the question, Fran has forward facing eyes, but I suppose 360 sight and being able to orient towards the thing you want would be good--however, if they can see everything and don't understand left from right, how would they turn toward what they want? If they can see everything how can they know which way to go if nothing is eliminated and they don't understand direction. – Erin Thursby May 30 '17 at 20:13

Fran doesn't have any sense of direction and can't distinguish right from left or north from east etc.. To compensate that she however has developed a perfect sense of height. She always knows at which altitude she is.

The City

Their city is built in a spiral that goes from ground floor on the outside the top in the middle. So that the city looks like the tower of babel.

Whereever she is in the city she always knows at which height she is and to which height she wants to go to. So she turns to go up the spiral or down the spiral. And if she turned the wrong way she always knows that she only has to turn around to go back down/up.

• Welcome to WorldBuilding YanBear! Cool idea. If you have a moment please take the tour and visit the help center to learn more about the site. Looking forward to your contributions. Have fun! – Secespitus May 26 '17 at 7:48

Fran is of a rather pitiful species that has been under a lot of specialized evolutionary pressure by an apex predator. In response, her species has developed the gift of 360° vision and total awareness that we humans can only understand, if proficient in artificial neural networks:

See, there are perceptive neural networks that can tell you everything that's in a picture but not its location. Place a banana on your car, take a picture, feed the picture to such a neural network and it will instantly tell you "banana" and "car" are in the picture. It can't however determine where these items are. The fast processing comes at the cost of information about location, both of which are inherent features of the neural network's design.

This may seem confusing to humans:
Child play books that let you search for stuff in a picture are plain boring for Fran. One look and she knows everything that's in the picture like she had a mental list. However this ability helps in triggering the flight reflex early enough for Fran's species to evade the apex predator of her home planet. It is very much like the eyesight of flies with their faceted eyes. When Fran checked for the lemonade stand, she closed all her eyes (in contrast to a fly she is able to do that) in rapid succession and noticed it's location, when for a short moment it vanished from her mental list of things that are around her. So she can only check for direction, if she is willingly losing sight of what she's searching for. At the same time she feels like something isn't there, which she should know to be there on a whole different level than humans do. This position check is a voluntarily triggered action that employs multiple uncontrolled reflexes: One for each eye.

From all the above the design of a city is obvious:
Narrow and zigzagging passageways that only allow for few things to be seen at any given time. These passageways don't need to be underground, but ceilings help limiting the view to above.

If you're walking along a passageway (which you navigate by touch of your antennae) and something pops up on your mental list, it will simply be further along the passage. That is, if it's not another traveler, who may be going faster than you, catching up from behind. It is therefore common courtesy to recite all that you see upon meeting someone. By the way, that's a lot more helpful, than stating the already obvious time of the day like humans do, when saying "good morning". It tells you not only, if the other one is coming from front (because he tells you something new) or behind (because he tells you thing that just vanished from sight) but also at least one of you will learn what's up ahead.

• Place a banana on your car, take a picture, feed the picture to such a neural network and it will instantly tell you "banana" and "car" are in the picture. It can't however determine where these items are. Actually...yes it can. I'll direct you to this series which is all about recognizing where in an image fingers are. Given tiny amounts of additional data, we can determine where in space objects are, relative to the camera. Tag a GPS coordinate and we know absolute position. See also Google Earth, LeapMotion, and HoloLens. – Draco18s May 25 '17 at 19:01
• We can build a neural network that identifies positions as well as objects, of course. But the thrust of this answer is we can also design one that identifies objects but not position. – Daron May 26 '17 at 8:57

They wouldn't as the species would have long ago gone extinct from extensive starvation. As stated the species cannot feed itself, it can't find food reliably because it cannot navigate nor control its own movement. As described it cannot change direction to seek food even if it can perceive it. It must rely on pure chance to happen to physically encounter food. Changing direction to seek food is one of the most simple behaviors we know of, for good reason it is not difficult to wire and is fundamentally advantageous for any creature capable of motion and absolutely necessary for intelligent life.

Worse yet this means they also can not avoid threats if there is a cliff to the left and it perceives it, this species has a fifty fifty shot of walking off the cliff anyway. If they have any natural predators they are even more impossible for the same reason.

Also you are confusing not knowing the labels for right and left vs not having a concept of right or left. A species with no intrinsic concept of right or left has no voluntary control over its movement and thus would not be intelligent by any sense of the word. A species with only a problem with the labels would have no problem finding the lemonade stand, they might have trouble with giving or taking written or verbal directions, but not with actually finding it. The species described lacks even an intrinsic sense of left vs right.

If you redescribed the creature as having a concept of left vs right but having some directional sense that does not work on earth, similar to how a magnetically sensitive animal taken to a planet without a magnetic field might have trouble navigating, that would be completely believable. But an intelligent locomotive creature with no ability to understand at least a 2D plane makes no evolutionary sense.

• Whether or not this species can feed itself depends on the nature of the world they species evolved in. By saying they cannot feed themselves, you seem to be making assumptions about that world. And in World Building exchange you should show your work! – Daron May 23 '17 at 14:22
• I'm just imagining some advanced alien species making similar statements about us with the same level of righteous confidence somewhere. – Mad Physicist May 23 '17 at 17:27
• which is exactly what I said they have to rely on random chance to find food, they can't turn in its direction. The question states the very concept of veering is alien to them, this could only occur if they have no ability to choose direction. – John May 24 '17 at 19:14
• @tsbertalan Well, recall that Fran might be able to distinguish between up and down as well as forward and backward. She could thus imagine a 2D plane; a flowchart on that plane could flow from backward to forward, branching vertically between options above or below. Of course, that raises the question of why she doesn't just roll onto her side when navigating on Earth, translating left and right to the familiar directions of up and down (and maybe that's the solution she'd eventually stumble upon) unless that directional perception is intrinsically linked to gravity. – Thriggle May 24 '17 at 21:25
• @Jules actually there is decent evidence we co-opted our spacial reasoning skills to handle more esoteric reasoning. And the creature as described is worse off than not being able to perceive right or left, they lack the ability to even conceive of it. so its like US trying to conceive if four dimensional space, except they seem limited to just one dimension as opposed to our 3. – John May 26 '17 at 0:39

Every answer I see here violate, in some manner, the question being asked. Fran is stated as not being able to tell East from West as well as Left from Right. That is, if Fran is pointed East she is unable to distinguish this from being pointed West (other than what is directly in front or behind, due to some concept of "vision").

Ergo I think I know what Fran is.

She is a being that has precisely two light-sensing patches on her: one fore, one aft.

These vision patches are not capable of distinguishing objects. They're closer to being a laser range finder. She can tell the color, distance, and material of an object in front of her and behind her. But she cannot distinguish anything else. A red dixie cup would be indistinguishable from any other piece of red plastic.

Furthermore these two vision patches cannot move independently. They are inextricably linked in a form of hard structural rigidity with both each other and her locomotive system. Additionally her locomotive system has no concept of "no, turn the other way." Turning is turning. There is no, "I see it, I see it, I see it, now I don't, go back" order that she can give to her locomotive system in order to reverse direction.

Which means....she can only turn in one direction. So not only can she not tell which direction she's rotating in she has no control over it in order to turn around. She only has three commands as it were for movement: forward, backward, and turn. 1

At this point I've decided that there's no way this species would survive to sentience. Even a snail can tell that nope, that way is bad, turn the other way.

Fran would have to be completely cylindrical (symmetrical around the up-down axis, the other two are irrelevant), for if she were not, she would get stuck up against a rock or a tree, unable to turn away from it, and then starve to death (or get eaten, or...) and rapidly go extinct.

I have no idea what a city built by her people would even look like. Simple things like hinges would boggle their minds, because hinges would have to bend in a non-uniform way. We also have to do away with gears because those rotate non-uniformly when meshing with each other. At this point you have to basically discount every possible piece of technology above the stone age.

Fran does not live in a city. She's a barely cognizant animal living on a vast rolling plane of grass with no carnivorous animals (or her species reproduces too quickly for it to matter). She's basically blind, deaf, can't move quickly (or at all), and almost certainly either an herbivore or a composter (i.e. feeds off rotting organic matter).2

1 Even this violates the uniformity of movement: turning while moving forward and turning while moving backwards are not mirrors of each other. That is, if an object moves forward 1 unit and rotates local-left 1 unit and repeats this pattern, it will move in a counter-clockwise circle. If it moves backwards 1 unit and rotates left 1 unit, it will move in a counter-clockwise circle. This is important because it does not retrace the path, ergo moving forward and turning and moving backward and turning get you to different places and imply a directionality difference of left and right!

There are only two ways to fix this:

1. make Fran unable to distinguish an object in front of her from one behind at which point all logic and reason have been defenestrated out of the building.
2. make Fran unable to rotate while moving, which seems like a very poor survival strategy

Lets assume #2.

2 Dear god, she's a pre-Uplift Traeki.

Update 5-29-17

As some folks have expressed derision over whether or not mirrored vision is able to sense direction, I built a quick application to test that theory. The compiled executable is not very stable, but if you wish to try it out for yourself, you can find it here (Windows executable, you assume the risks of running arbitrary internet code yourself).

• Controls are randomized, but the keybinds for movement and look rotate are bound to WASD/IJKL in pairs (that is, W and S always perform inverse operations).
• The initial boot will be in Vision Mode 0, which is as I have described above (only distinct along the vertical axis). If you can figure out what any of the keys do in this mode, good job. If not, then point proven: it is impossible to distinguish left from right in this mode.
• Press Q to change modes. Vision Mode 1 is mirrored and Vision Mode 2 is human standard. Controls are shuffled each time the vision mode switches.
• I recommend running in 640x480 as the mirrored effect has to pipe data off the GPU back to the CPU, compute, then return it (i.e. slow as all hell). This is also why the application crashes frequently.
• I would have compiled to WebGL if it hadn't hung during the compile process (Unity bug?).

In mirror vision you can navigate although identifying which direction is objectively left may not be possible, but it can be distinguished from objective right and a creature with this sort of vision would have no trouble tracking down a lemonade stand.

You can watch me navigate the simple maze in this video and aside from some orientation and forgetfulness over which key I need to press next (i.e. moving backwards instead of forwards), you can easily identify when I turn the wrong way briefly before correcting to turn the correct way. There are a few places were I made a decision based on knowing the actual layout of the maze (not having to investigate dead ends) but I think that it is sufficient proof that navigation under this mode of vision is possible and that leftness and rightness can be understood as distinct, even if not readily identifiable (that is, if the world were flipped left to right and the controls were flipped left to right, I would be unable to tell).

That is, given this perfectly centered view, it is impossible to tell if the branch path is to the left or to the right. But by rotating to one side or the other you can see that in one case the branch is farther away from center and in the other, it's closer. And closer to center is "forward" and if that's the direction you want to go, then having it be forward is desirable, ergo the two rotations are distinct and can be labeled as such.

On the other hand this is just meaningless and contains no directional information at all (standard view of the same scene at the same point in space and time).

• Not understanding left and right is different from not seeing left and right. We can infer from the OP text that she can, indeed, see the lemonade stand on her left. So her vision is not just one color and she can distinguish objects. Also, she cannot have eyes in the back of her head: When she turns the wrong way, she cannot see the Lemonade stand behind her. So fixed eyes in front, period. We have humans that can see perfectly but not comprehend, e.g The Man That Mistook His Wife For a Hat. So she sees left and right but mentally cannot tag objects as "left" or "right". – Amadeus May 23 '17 at 19:28
• She can see things to her left and she can see things to her right. She just cannot tell which is which. – Daron May 23 '17 at 20:17
• @Daron I know that you're trying to say that, but what I'm saying is that its a fundamentally unsound premise. Let me phrase it a different way, as a question: if Fran looks at a swinging pendulum (so that its movement is to her left and right), can she tell that it is moving back and forth? I.e. that at one point in time it is on one side and that at another point in time it is on another side? If yes, she can infer leftness from rightness. If not, then she cannot have complex vision. – Draco18s May 23 '17 at 20:21
• Imagine a pendulum that starts high up on the right. It sweeps down to its lowest point then miraculously and instantly changes direction while maintaining speed. It sweeps back up to its starting point and hovers there for a moment before descending again. It repeats forever. A human would find this strange but Fran would experience an identical sensation to that from a normal pendulum. – Daron May 23 '17 at 20:32
• @Amadeus Having no evolutionary pressure to distinguish between left and right would imply a complete lack of any sort of danger in any form. "Don't go that way, you'll fall off the cliff" comes to mind. As well as a lack for a need to hunt (food source is plentiful all the time and generally found in all directions). Both of these things are the sorts of pressures that evolved the complex eye. By removing directionality from the list of concepts this creature understands, you're altering something so fundamental that the end result is incompatible with the question. – Draco18s May 24 '17 at 16:12

Fran's species are a communal burrowing species, but more importantly they're solar navigators which is why she has to be back at the hotel by nightfall or she'd be completely lost. Their two key directions are "towards the light" and "away from the light" *.

Their cities are built along a straight line with a large artificial light at one end. Individual "buildings" are burrows dug straight down from the main route. Passing another person on the street is done by the one going away from the light going over the top of the one going towards the light. Overtaking someone moving more slowly is done much the same way, personal space is not a thing.

Prior to their becoming a technological species they were mostly active in the cool of sunset and sunrise and remained in their burrows during the heat of the day and dark of the night, the cities were orientated East (sunrise) to West (sunset).

Her Earth hotel is specially adapted for her species, having a large light at the top to aid navigation and burrows at ground level for accommodation.

* These directions translate generally to "towards" and "away", for example, "towards the food" and "away from the predator".

• +1 for "which is why she has to be back at the hotel by nightfall or she'd be completely lost." – Daron May 24 '17 at 10:56

I'd propose cities with a simple hierarchical layout, where all cities are build on the following principles:

1. Cities have a point of origin, which also serves as the only access into the city from the exterior. Cities spread south from the point of origin, with a main road going straight from north to south.
3. Tertiary roads spread out from the secondary roads, following the same rule as secondary roads. There may be lesser hierarchy roads, depending on the size of the city.
5. Buildings and sites along a road are also alternating (odd on one side, even on the other).
6. For an addressing system, they use a simple hierarchical reference, starting at the origin point for the city, and then numbering every road that must be taken to arrive to the destination. For example:
• Address 'Lama-3' refers to the third building on the main road of city "Lama".
• To get to address 'Copo-3-6-4-5', starting from the origin point of city "Copo", one would take main road, then go into the third secondary road, then into the sixth tertiary road, and then into the fourth quaternary road, and find the fifth building on that road.

City maps would appear to have a leaf-like structure:

The question seems to boil down to finding a realistic one-dimensional environment for animals still embodied in a fundamentally three-dimensional universe. I think it's impossible for an animal to evolve to have no conception of all three dimensions while living in the same universe as Earth. There's just too much of an evolutionary advantage to fuller navigation. But I think Thriggle's is the best approach to imagining how an animal might be biased to 1D motion. The structure of the underground city wouldn't have to be rings in particular--just a network of 1D pipes. One justification for this might be that tunneling forward or backward is easy, but left and right or up and down (all in the animal's local reference frame) is hard or impossible.

This is analogous to how we surface-dwelling creatures tend to think in terms of 2D maps. Navigating up and down is less common for us, but very far from impossible. I imagine (but have no proof) that animals who don't jump or meaningfully climb (like beetles or turtles) feel this bias more strongly. But they still need to be aware of of predators (or prey?) who are more mobile!

One side effect of this might be an even greater tendency to sort things along a single axis, ignoring multiple dimensions of variation. There is evidence that we tend to employ a 2D conceptual grid for more than just navigation. I bet their politics would be even less nuanced than ours, which sounds frightening.

At the same time, optimization in multiple dimensions (of which the unicellular chemotaxic food-finding alluded to by John is one example) can be sped up considerably by dimension reduction. This is why algorithms like Newton's method or gradient descent work. If the choices at hand truly do come from a one-dimensional submanifold of the ambient 2+ dimensional space, then it makes sense to treat left/right (and up/down) as equivalent. But, in the adversarial setting of evolution, as soon as you make this optimization and sacrifice distinguishing power in the transverse directions (e.g., small krill to eat are at the ocean's surface; protection from surface predators is down), some other creature will take advantage of your disability and outcompete you (just go around the stupid up-down whale).

But you never did say the creature had to evolve this way naturally. This question reminded me of the company QBotix--to save money on solar panel rotation motors, they make a robot that travels along a linear track, rotating each solar panel in an array individually. It only needs to deal with motion along a single axis, simplifying the problems of navigation and control considerably. Maybe Fran is a designed "organism" and the original design spec (say, autonomously navigating a Dyson ring for maintenance) had no requirement for freer movement.

• This is a great answer, and calls to mind the scene from The Wrath of Khan where the Enterprise outmaneuvers Khan because the 20th century warlord is blind to tactics across three dimensions. You've highlighted that the biggest difficulty with this species is imagining a viable ecosystem where the left/right dimension doesn't matter. – Thriggle May 24 '17 at 21:53

# Fran is blind/omni-visional, knows how far away things are, and has a built-in compass

Fran has no sense of vision. Either that or she cannot distinguish directions very well. It all comes into her mind as one big omni-directional sense of vision. Constant and always available 360° vision.

She also has no sense of physical touch. Telling such a person what is left and right is next to impossible.

Fran however has a finely tuned sense of materials, objects and their function. She also knows their distance. She can instantly sense "Mmmm... lemonade... 3.141592 decameters from here".

Fran is also highly sensitive to magnetic fields. She senses the direction of the magnetic field lines. That means Fran has no problem navigating in terms of North, South, East, West, Zenith and Nadir. Some human cultures do that.

So Fran can find the lemonade by simply starting to move and then adjusting her magnetic direction as she is essentially playing a constant game of Hunt The Thimble ("Hot & Cold" game) with herself.

With this Fran will be quite capable of navigating her way around a human city. She will act a bit odd around people though as she quite often will not be facing people that she talks with.

# What does her home city look like?

It will be built on these premises: that the sensory-motor coupling will not be built on absolute knowledge of your position, or the relative direction of things... but on cardinal directions and what functions and materials you have around you.

Exactly how this looks you will have to work out yourself — you are the world-builder of your world, not us — but here you have a concept that might work in trying to figure that one out.

Fran is an omnidirectional creature. For example, the earth equivalent would be a jellyfish or cephalopod.

In Fran's native environment, they would merely point at the target, then "jet" using their native locomotion. On land, they can't do that, but merely flop around until they get to the location of desire.

Natively, Fran's species would use a spherical coordinate system with their own senses point of reference, however, since that species is unstable on land, the coordinates are relatively useless, since even the point of reference moves on every attempt.

First, they can navigate by tall landmarks. (Salt Lake City, Utah is one place on Earth where the mountains make orientation easy and people seem to use cardinal directions often.) If there are none, they can build tall towers that are perceptibly different to navigate by if necessary. Giving them a magnetic sense is probably cheating, but there are the sun and stars.

Second, they can build intersections that are not symmetrical, and do not meet at 90° angles. Even if they can°t tell which turn is left and which is right, they can still tell which one is acute, oblique and straight. Instead of rectangles, their blocks could be parallelograms and directions could be to make the tighter or wider turn. Or they could have rings of beltways, and directions would say to turn inward or outward.

In some situations they might also use uphill/downhill.

As some other commenters noticed, Fran's species is artificial and was definitely created by some other intelligent being*. This is pretty obvious because Fran is a highly intelligent, self-propelled rail car (locomotive?--my rail terminology is a little shaky).

(*Some people speculate that the creator was another species on Fran's planet before Fran's species, unfortunately that species seems to have died of problems caused by over-population shortly after the planet was completely covered with autonomous rail transportation.)

Her city is a collection of rail yards (residential areas), with an extremely complicated switching system. The switches are controlled by some kind of electrical means, and Fran has an ability to operate them through a broadcast organ (wireless modem).

On her home planet, when Fran wants to go from her house to the lemonade stand, she opens her front door (by wifi) and activates (by wifi...) the rail switch in front of her house (which happens to face in the direction she calls "westbound") to connect her house to the Blue 5 Westbound line (the street she lives on*).

(*Side note, she lives on the Blue 5 line, meaning that her house [which is a straight line] is parallel to the Blue 5 line, when she goes out her front door she ends up on Blue 5 Westbound, if she goes out her back door she ends up on Blue 5 Eastbound. She doesn't turn around to do this, because she is equally comfortable traveling backwards and forwards, even though she can tell her front from her back.)

As she travels along Blue 5, she knows the lemonade stand is in the downtown area and she will need to take Red 3 to get there. So when she nears the junction of Blue 5 with Red 3, she activates the rail switch to join Blue 5 Westbound to the Red 3 Downtown line. While on Red 3, she catches up to a couple in front of her who are traveling slowly and holding hands (they have joined front to back). She travels at the same speed as them until they reach a siding and make way for her. She reaches the lemonade stand, transferring onto the siding it is located on, gets her lemonade, and then returns home by traveling in reverse the whole way.

On Earth, Fran really is in trouble! She can still move forward and backward, kind of, but her wheels aren't necessarily pulling evenly due to terrain variations (normally this is corrected by the rails, but on Earth she doesn't have rails). Even if she moves forward and backward until random chance turns her in the direction of the lemonade stand, she will still have considerable trouble getting there since traveling straight toward the lemonade stand will result in slight random curves in her path. Really, it is amazing she got there at all much less back to her hotel. In the future, I would advise Fran to stick with the guided tour, where visitors from Fran's planet are placed on vehicles (possibly using a really gigantic electric claw game type grabber) and a tour guide from Earth drives them around--or she could just stay in the train yards, if the gauge is the same or if she uses some kind of rented adapter to let her run on a different gauge.

All answers so far fail to address one basic problem with Fran. The question describes her process of movement: "Fran evaluates positions of objects. Fran takes a step in a randomly-chosen direction. Fran re-evaluates positions of objects." But for every creature on Earth, movement does not work that way. We continuously evaluate our surroundings (even if that's by touch, vibrations, echo-location or whatever) and continuously evaluate our movement around our surroundings. Unexpected things may happen, but there is not normally a gap in perception.

Fran therefore has a body whose major feature is that any movement prevents vision whilst that movement is taking place. Possibly her species has ultra-low blood pressure and cannot sustain multiple activities at the same time, so she blacks out during the process of moving. Or maybe she detects objects with vibrations through the ground, so she needs to be stationary with her feet in solid contact with the ground to "see" again.

Both of these scenarios though present a basic problem for the question. Creatures with non-continuous vision tend to evolve extremely good mental models of the space around them and their position relative to it. More that that, it's a skill which can be learnt by blind people and animals, so evolution isn't necessarily required.

Have you tried giving directions to an islander? Specifically someone that was born and raised on an island; Tahitians (the one from my personal experience told me that they didn't drive into the city as it was really disorienting) don't always do maps very well. Their directions are: go towards the mountain, then at this object go towards the ocean. Several mountains help as do tall buildings, religious structures.

In addition, everything has an object/feature in their body that connects to something. Heart-side (aka left to us) or from the longest tentacle towards the smallest. Maybe they think in Radians and not all this silly limited connotations that humans use because they lack their internal compass/accelerometers/gyroscopes.

Culturally, there has to be directions or they will never visit anywhere as they could not get off their planet. How could everyone get together to build their spacecraft?

• What spacecraft? – Daron May 24 '17 at 22:01
• Okay, any craft. – dcy665 May 25 '17 at 0:29

Fran civilization don't build cities, because Fran race has extinguished as soon as it began evolving.

What most of the answers here are trying to ignore is that what you are describing is not someone who get confused by left and right like a child could, but it's clearly explained in your example that she has no ability to physically sense directions other the front and back.

So she is not able to turn. She knows where is front and where is back, but not being able to sense what stand in the between, she has no way to turn. Or, to be generous, she can turn randomly.

Let's use a compass: she is facing 0 degrees, so she has 180 degrees behind her. She try to turn right, so now she is facing 1 degree, and behind her it's 181 degrees. 180 degree exist no more, she has no concept of it anymore. Even more, to move from 0 to 1 degree, she needs to rotate in a direction that do not exists for her. But she cannot consciously turn in a direction that do not exists for her, she has no reference for it, she can't sense it at all.

Beware: you clearly say that she cannot even distinguish the sides of her body. She cannot, in any way, turn in a meaningful mode.

So her race can only move in one constant direction, or randomly scatter around. Her race, at best, survives because they are small virus living in a huge pool of nutrients. Cities? No way. Lemonades? Even less.

• Ever playew QWOP? – Daron May 25 '17 at 10:40

The species is nocturnal, they evolved on a planet with an extremely strong aurora borealis, and the continent they evolved on lies fairly near the North Pole. Except in extremely bad weather, you can always tell which direction is north because that's where the sky is lit up. So they use north, east, south, west.

On their home planet, if they go out during the day or in extremely bad weather, they navigate by landmarks (and quite often, they get lost anyway). They have colonized continents that aren't near the North Pole, and there, they erect a lighthouse to the north of every city which is lit at night. Extremely large cities may actually have several lighthouses, which can easily be distinguished. They use whichever lighthouse is most directly to the north of them to navigate.

What if Fran were a water-based creature with either some control of her physical structure or some kind of inherent structure.

All her sensory organs are inside her outer boundary, including her "eyes". The eyes see everything in a 360-degree disc (or possibly 360-degree sphere).

Possibility 1: Her locomotion is fluid-like.. so a flowing mechanism. Traveling "downhill" is quite easy for her. Traveling "uphill" is easier than side to side because she leaves a moist trail in her wake. Traveling over moist surfaces is easier for her than dry surfaces.

Possibility 2: Alternatively, because of the nature of her sight, this liquid-like creature only perceives the world as "forward". So while Fran can move as easily as you or I on a two-dimentional plane, whatever direction she's traveling is always forward to her.

There are many ways to structure a city for this kind of Fran. If you go this direction I'm sure you will have fun exploring the possibilities.