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The world without visual depth perception

  1. Jul 13, 2010 #1
    Though this sounds silly in itself to ask, I would still ask it. Is there any animal or bird which lacks the ability of depth perception? How would the world look to humans if they didn't have the ability to perceive visual depth?

    I'm not a biology or science student. Therefore, please be descriptive and straightforward.

    Best wishes
  2. jcsd
  3. Jul 13, 2010 #2
    There are many cues that enable us to perceive depth and one of the strongest is due to binocular vision where the brain processes the signals from the two separate retinal images and merges them into one.Try walking around with an eye patch and this will give you some sort of practical answer to your question.People who have lost an eye learn to compensate by relying more heavily on other depth cues.
  4. Jul 14, 2010 #3


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    Any animal that has its eyes on the side of the head, instead of in front.
  5. Jul 15, 2010 #4
    Fore example? Hen?
  6. Jul 15, 2010 #5
    Chickens are one, but generally, any prey animal. Cows, deer, rabbits, etc. sacrifice binocular vision for improved field of view. It is harder to sneak up on them when they can see in all directions at once.

    Predators tend to have good overlap between the two eyes in order to better perceive prey position. Binocular vision also improves the ability to grasp important things, like a tree branch a dozen meters off the ground, which is probably why vegetarian primates have it.
  7. Jul 16, 2010 #6
    I now realize my approach was wrong. I know how a depth perceptive vision works because I have one. I should have first confirmed, how does it look like without the depth perceptive vision? By depth perceptive vision I mean the one which enables one to discern the spatial relation between the things under observation like distances between them, their relevant heights.

    Suppose there is a kid three feet tall in front of me. Behind him is a five feet guy, and further behind him is a six feet tall. They are exactly in front of me. I have a depth unperceptive vision. How would that picture of three persons in front of me look to me? Would the five and six feet appear exactly above the three feet tall? If that would be the case, it would surely be a terrible sight of a three headed monster, with on head at three feet, the second at five, and the topmost at six.

    I hope it would be easy for you to see what I'm after. If chicken lacks depth perception, then they won't be able to tell the difference between the distance of a goat and a dog (predator) standing right behind the goat some meters away. Please help me. And please keep your replies simple.
  8. Jul 19, 2010 #7
    Is it so tough or silly that no one is pitching in to help? Please help!
  9. Jul 19, 2010 #8


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    I guess you don't mean, "What is it like without binocular vision" because you could shut an eye or look at photos. In such a case I think you would have the same depth perception as you would with two eyes at distances further than about around 6 metres (20 feet), I think.

    Other things help with depth perception, monocular cues, like motion parallax and perspective, where it is understood that parallel lines converge, peripheral lines curve, objects in the foreground occlude those behind and objects get smaller, less distinct and usually lighter and cooler in colour as they occur further into the distance.

    Your description could be discussing lack of binocular cues, such as having an eye shut, or viewing a photo, in that the lack of two eyes allows tricks like holding up the leaning tower of Pisa with your finger. But to not know how to interpret it, reminds me of something I heard years ago about an adult who had recently been given or regained sight. She was looking at her window unable understand what these two, long, seemingly vertical stripes were doing up against it. It turned out they were the horizontal, concrete strips of her drive-way, outside. I think this describes someone who hasn't learnt to interpret depth, amongst other things, and I recently linked to a youtube that also happened to discuss the difficulty of interpreting vision in someone who regained the mechanisms of vision in adulthood, after losing sight the age of 3.

    It strikes me as clever that we see things with depth and perspective in space, and that it seems it would be very difficult to make sense of things if we didn’t have these cues, such as if things didn’t appear smaller in the distance.

    Mgb-phys seems to be discussing related things with 3D films in GD.
  10. Jul 21, 2010 #9
    Hi Fuzzy

    Thank you for the reply. Didn't she know that she was looking down at the ground, I mean you have to bend your head down to see something on the ground from a window?

    Because I believe you had a problem understanding what I was actually asking. My question was more like asking how the world would look to a blind person. Now I think it's somewhat difficult to answer the real question which was to know how it feels like without that sense of depth.

    Could you please provide that Youtube link?

    Best wishes
  11. Jul 22, 2010 #10


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    Hi Jack,

    I wasn't sure if I understood your question, but found it interesting all the same.

    I'm not sure about the vantage point in the anecdote, but imagine that even if she was looking downwards she may not realise that the driveway was further away than the window.

    This is the link I mentioned-

    I really linked it regarding other things in another thread, so there is probably much better work on topic available. At around 20.00 (more precisely about 23.00) to 30.00 the difficulties of those who’ve had their contrast sight restored is described, including the man I’d mentioned. He is described as becoming smarter and quicker at reasoning in order to understand what is seen.
    Last edited by a moderator: Sep 25, 2014
  12. Jul 25, 2010 #11


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    Having said there is probably more to find on the interenet, I thought I'd look-

    "May still has no intuitive grasp of depth perception. As people walk away from him, he perceives them as literally shrinking in size"

    Although he hasn’t use of two eyes, he also doesn’t recognize perspective lines, and these illusions aren’t effective-

    ‘Sitting in the lab one day, MacLeod, smirking like a schoolboy who's hatching a prank, slides a drawing across the table to May. On the paper are four cubes. The top right cube and the bottom left cube are dark; the other two are light. The drawing is shaded as if light were coming from above, so the tops of the squares are lighter than their fronts. This makes the top of the dark square the same shade as the front of the light square. Experience tells us that the top of the dark cube has been brightened by a hidden light, but it still seems darker than the front of a light cube. It's an illusion based on knowledge. Naturally, May doesn't fall for it.

    ‘"He's actually closer to reality," Fine says. "We once showed him two circles—a small one close to him and a larger one farther away. To you or me they would have appeared to be the same size. But when we asked, 'What's the apparent size?' he couldn't understand. He kept saying, `I know it's bigger because it's far away.'" Similarly, May's tactile experience with hallways and highways tells him that their sides are parallel, so he simply can't perceive converging lines of perspective. "A hallway doesn't look like it closes in at all," he says. "I see the lines on either side of the path, but I don't really think of them as coming closer in the distance." He pauses to mull this over. "Or maybe my mind doesn't believe what it is perceiving. When I see an object, it doesn't look different to me as I circle around it. I know orange cones around vehicles are cones because of context, not because I'm seeing the shape. If I picture looking down on a cone, it still looks like a cone."

    ‘Learning to see, for May, is really about learning to fall for the same illusions we all do, to call a certain mass of colors and lines his son, to call another group of them a ball.’
    http://nfb.org/legacy/bm/bm02/bm0211/bm021105.htm [Broken]

    I understand from this that in this case motion is more easily understood, and he enjoys throwing and catching balls with his son, and similarly, so is peripheral vision. However, some foveal activation is missing- related to depth, facial recognition, reading and colour.

    Removed from the topic, but notable also is that looking at the eyes of people outside his immediate family can cause anxiety. As well, integrating sound with vision can also be problematic, e.g. preferring to close eyes to listen to speech.
    Last edited by a moderator: May 4, 2017
  13. Jul 25, 2010 #12
    Jackson, I suppose you didn't get a lot of replies because people felt they did not have much to contribute, or simply missed your thread (as I did, for one.)

    Fuzzyfelt has given you some very thoughtful and thought-provoking material. Give it the deepest attention you can manage; it has lots of implications.

    I am no perception psychologist, but from the information theoretic point of view, our sensory view of the world necessarily lacks many dimensions, with the result that much of what we see we are reduced to interpreting on a commonsense basis, filtering out perceptions of unlikely effects, and adjusting perceptions to accommodate sensory distortions that are normally misleading. In doing so we save ourselves a great deal of confusion and effort, but expose ourselves to misleading, deliberate distortion (as occurs in visual illusions for example.)

    Have a look at the art of M. C. Escher. Read at least the first half of "The Island of the Colour-Blind" by Oliver Sacks, and "The Blank Slate" and "How the Mind Works" by Stephen Pinker. Surf the web for visual illusions.

    Perception is too wide and subtle a field to take lightly, or I would go more deeply than my competence would justify into such subjects as camouflage for one. However, one field that you might find worth trying to find material on, is the perceptions of technologically and graphically naive subjects such as tribalised peoples (not that they don't have their own technology and graphics, but that is not what I mean!)

    In the South African mining industry thousands of such people have been employed in the mines for over a century, and their personnel departments have accumulated whole fields of experience in training their recruits. Using first-world graphic techniques and conventions for communication simply didn't work. For example, a safety poster showed a normal perspective drawing of a worker turning round while carrying a ladder on his shoulder and accidentally hitting a colleague with the hind end. They asked some workers to interpret the picture and got such responses as "The big man (the one carrying the ladder, nearer in perspective, and correspondingly objectively larger) is angry with the little man, so he hits him with the ladder." What worked better was the use of two-dimensional silhouette representation. It cut out a lot of information, but dispensed with the need to have mastered our first-world conventions.

    Remember, conventions enable us to imply extra information by making logically unwarranted assumptions about missing information. Our self-centred physiological view of the world similarly forces us to make analogous assumptions about what we see and hear.

    One of the stock figures of South African superstition is the tokoloshe, a small, but powerful and if not actually malicious, at least easily-angered spirit. For safety from him at night, the traditional precaution is to put your bed onto bricks. (At least it should help for fleas!) Like the King of Id, tokoloshe is touchy about his stature. If you happen to meet him he asks you: "Where am I?" The prudent answer is something like "You are far, faaarrr away, great Tokoloshe!" The implication is that the only reason he looks small is that he is in the distance.

    Asked to draw a picture of four-legged animals, such people might draw them as if spread-eagled on the ground. Whether this is because that is how they commonly see them, or whether they are trying to get everything possible into the picture, Picassolike, don't ask me!

    Note that people extracted from exactly the same communities, but that have grown up in cities and been to school show no generic abnormalities of such types that I ever have heard of or experienced.

    But as you can tell, though I respect the field of study, I know practically nothing about it. I can tell however that it is full of pitfalls for the unwary.

    Go well,

    Last edited: Jul 25, 2010
  14. Jul 25, 2010 #13
    Hello Jackson,another source that you may find informative is the book:
    Eye and Brain - author Professor R L Gregory
  15. Jul 28, 2010 #14


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    Very interesting, and thanks, Jon, for your comments. I probably still made some assumptions. It is hard to use enough caveats!
  16. Jul 28, 2010 #15
    Thank you, Fuzzy, Jon, and DFace. Fuzzy, Jon, I understand that it has taken you a considerabe amount of energy and time to write those replies. I'm very much grateful for your help. I'm reading them and trying to make sense out of them.
  17. Jul 28, 2010 #16
    Good grief FF, one cannot cover everything! You gave some very insightful and helpful remarks and references; what could be better?? I certainly am in no position to smirk!:approve:


  18. Jul 28, 2010 #17
    Feel welcome. Don't hesitate to ask for clarification.
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