This is a bit peculiar because there’s nothing wrong with my depth perception at all. In fact it’s actually very good. But Hello Again has very kindly offered to answer all your questions about this so long as I start the thread.
So, Hello Again - I understand the main issue is that you don’t see in stereo. However, depth perception is not just caused by stereo vision, but also just basic movement - for “norms” who disbelieve, close one eye and stare at something. You will perceive it as 2d (if you don’t then keep on repeating this exercise until you do). Now give your head a mild shake, while keeping your second eye closed. You’ll suddenly see it as 3d (indeed it’s stuff like this that makes 3d movies less than convining - it’s more than just your stereo vision that makes stuff 3d). Thus the starter for ten: Hello Again, when you do this do you see the 3d nature of reality* or does it all still seem 2d?
*As perceived by us humans anyway
You can ask me as well as I’ve always been stereoblind.
Closing one eye just results in seeing less of whatever is in front of me. Shaking my head with one eye closed just makes things move, and it’s pretty much how I navigate, but with both eyes open. Changing the view of how things overlap lets me figure out what’s in front of what, but don’t ask me to determine by how much or how far something is.
When I was in college, I wore contacts…and played on the club volleyball team. I’d occasionally go with only one contact. Trying to judge distance on serves, and adjust to people’s movements…turned out to be very tricky.
What do you all find to be the hardest part? Do you drive?
Mine have been out of alignment since birth, with two surgeries at young ages to straighten them cosmetically. The bummer is that they just aren’t straight enough to have any form of depth perception.
No easy parallel parking, no 3d movies, and definitely no magic posters.
On the up side, it is fairly common for people like me to have one eye nearsighted and one farsighted. Indeed, while driving I use my right eye to see road signs, while I use my left to see the instruments.
Parallel parking is not impossible, since there are several distance cues our brains use besides parallax. Most people with perfect vision have trouble enough mastering the technique itself that I probably park as well as most.
I really don’t understand the exercise, I would never say I see anything in 2d. No matter how long I stare at an object with one eye closed, it always looks the same and has obvious depth. I’m given to understand I actually get most of my depth information from shadows, and shadows are always there except in pitch black and rare lighting conditions. But the worse the light is, the worse I do at judging distance-from-me. For this reason I would feel little discomfort driving on a street with street lights, much discomfort on a dark back road.
Also, or relatedly, or something, I can’t track moving objects – for example, the idea that you can “keep you eye on the ball” in baseball, is just one of those impossible things other people can do. (magic eye pictures are right out of course, and sometimes IMAX type movies make me nauseous).
For fun with monovision, sometimes a floor with those black & white tiles will appear to move and buckle as my brain tries to line up all the white and black squares but cant’) It’s quite entertaining, almost hypnotic.
People’s subjective, introspective reports about matters like this are close to being meaningless. We simply can’t judge how well we experience depth and are able to judge distance compared to other people, because we do not have access to their experiences. The only real way to know how good your depth perception is is to have it tested by doing some well calibrated, standardized depth perception tasks, and seeing how well you do at them under controlled conditions. Furthermore you will need different tasks to measure the different contributions to depth perception of each of the several mechanisms that humans use to judge depth. (The most important mechanisms are binocular disparity, that relies on the distance between the eyes, and head motion parallax, that relies on head motion relative to the object being judged. How good an individual is at judging distance by each of these mechanisms might well vary quite independently.)
How good or bad you are at some complex task such as parallel parking really does not reveal very much about your depth perception. There are just too many potentially variable skills involved in such a task. Depth perception is just one of them.
I have poor, although not non-existent depth perception because one of my eyes had much poorer vision than the other when I was a child. At one point, an opthalmologist did a depth perception test in which I had to use long rods to line up two blocks that were some distance away. He kept asking me if I was sure that the two blocks were equidistant from me. Once I assured him that they were, he had me walk up and check. One block was a good two feet farther from me than the other.
I was never very comfortable driving, and pretty much quit for good in 1988. I also frequently bump into things as I walk, usually walls and trees, but I’ve also had sudden unfortunate encounters with a giant pile of construction dirt, a scaffolding, the box window on a Victorian house, and a horse – I didn’t actually hit the horse, but I got within a few inches of its head before I realized how close I was.
In my school days I attempted many sports, but inability to judge the distance of the ball made it very difficult. I have been hit in the face with a badminton shuttlecock, had a tennis ball served into my stomach, and had a basketball hit me on the top of the head, all when I thought the flying object was in a completely different location.
I agree with the spirit of what you are saying, if not the absoluteness.
Indeed, my point about parallel parking matches your own: maybe it is not so difficult for me to parallel park because I’m pretty good at the mechanics of it, even if one sensory input to the process is missing. I laugh inside when I watch people trying to parallel park who don’t turn the wheel at the correct moments, undoing and redoing the same path.
There are many monocular cues that we depend on beyond the two you mentioned, and a person without true depth person probably gets pretty good at using those monocular cues. In spite of these other cues, people are often surprised that I can drive at all with this condition. When I ask if they could do a task with one eye closed, they tell me that they couldn’t. This leads me to imagine that if a random group of people were forced to go through a series of activities wearing an eye patch, the regular vision people would not fare as well as those without proper binocular vision, simply because they are not used to living life that way.
As a related phenomenon, I have a nontrivial degree of face blindness: not enough to mistake my wife for a hatrack, but enough that I cannot recognize even close friends and family by face alone–I rely on all of the other cues for this, such as locale, dress, gait, voice, hair, and so on. I cannot gauge easily how much worse I am at recognizing faces than one who is just “bad at remembering faces” but the basic problem is still there: when those cues are removed, I always have to ask my wife who the person is, and she laughs at the obviousness of the answer. I remember showing her a test that had a dozen famous people shown with their faces only, hair and everything else cropped out. I watched on in amazement as she said “That’s Bill Clinton… That’s Oprah…” and so on. She got all 12; I recognized none.
Similarly, the complexity of compensatory cues does cloud our absolute understanding of our limitations, but those limits are still there. Most people without depth perception have had their condition professionally diagnosed and have spent their entire life dealing with the limitations.
As a child, the ability to catch or hit a ball is critical to avoid being the last one chosen for teams, and this is one particular area where the lack of binocular depth perception seems to have a disproportionate effect. No matter how many times coaches told me to follow the ball with my eye, it never worked. I watched on in amazement as the other children all were able to do with ease something that was simply a mystery to me. It wasn’t like I was close to doing it but just not as good as others; it really seemed that the worst player among the other kids still was far better than me at this critical kid task.
I felt the same feeling watching those kids as I felt when my wife said “Bill Clinton” while looking at that face-blindness test: an amazement at a physical ability that comes to others naturally, but I could not understand.
Of course, maybe I just stink profoundly at hitting and catching baseballs, but this sure is a convenient excuse and I’m sticking with it.
I too have very bad 3D vision (though not as bad as some of the preceding posters’, it sounds like), presumably because of a strabismus condition/operation when I was 3, and this creates difficulties particularly in driving, and night driving is positively nightmarish–I have great difficulty determining how far up ahead that red traffic light in fact is.
There are certain (not all) patterned stairways that virtually require me to hold onto a handrail.
In sports I was always the Last Kid Picked. But it wasn’t till I was 20 or so that I fully comprehended how my vision differed from most folks’.
Oliver Sacks’s The Mind’s Eye (2010, which coincidentally I proofread) reprints his New Yorker piece “Stereo Sue,” about a woman who regained stereoscopic sight in midage (years before Hugo came out)
This is fascinating. Although my level of faceblindness is trivial compared to yours, I do have some problems identifying faces, and particularly faces of people who change their hairstyle or facial hair. We once had a temp in our office who completely changed her hairstyle and color almost every day; I repeatedly asked her who she was and if I could help her (obviously after a while she started thinking I was a nut). I never associated this problem with depth perception issues, but maybe they are related.
Just to clarify, I didn’t mean to imply that these conditions are correlated, just that they are similar mysteries to me. It would be interesting is there were a link; I had never considered it. My choice of words (“related”) could have been better.
No worries. It does seem to me that they could be related – after all, things like hair length and color are essentially 2D, while many elements of facial recognition, such as nose length, cheekbones, and jawline require depth perception to be properly identified.
Not sure if there’s any correlation to my other issue, which I’ve mentioned many times on the board: almost total lack of any sense of direction, inclluding an inability to tell right from left.