Is it possible to learn echolocation without being blind? as a kid, my doctors were worried my deteriorating vision would leave me blind, so I learned Braille (that never happened). I wonder if I could have learned this skill with vision (if your auditory senses weren't compensating for loss of sight).
The blind man who taught himself to see
71–80 of 87 posts
Re: The blind man who taught himself to see
#72Earlier quoted context omitted.
> "We hear in stereo 3-D." This is not true unless we move our heads. We hear in one dimension, left-to-right. Put on some headphones and listen to this and tell me you cannot visualize it in 3-D: http://www.youtube.com/watch?v=YuxaOO6PsAw This is a binaural recording. More info on these here: http://en.wikipedia.org/wiki/Binaural_recording You can hear in multiple dimensions because, as the original article mentions…
It actually also works because a sound registers differently based on the direction it travels through your own head (i.e. your skull itself is an occlusion source) - your brain recognizes front vs. back based on how your own head dulls the sound
I assume the shape of our ears also affects the sounds, depending on the location of the sound. This converts vertical location into frequency shaping.
And I wonder, why else would we have such oddly shaped ears?
Re: The blind man who taught himself to see
#73Higher frequencies, as bats use, give finer resolution. This seems impossible for humans, but since we have cochlear implants, there's no reason they couldn't respond to a shifted audio spectrum. Or, just have an external hearing aid that frequency-shifts the sounds (and cancels out the original), together with a higher-frequency sound source.
OTOH, eye implants are probably not that far off.
> Just the auditory cortex of a human brain is many times larger than the entire brain of a bat.
This really startled me. It seems plausible that we could do as well, with early training etc. Plus, I imagine that some of the higher-order processing of the occipital cortex would also be seconded.
Re: The blind man who taught himself to see
#74Earlier quoted context omitted.
It actually also works because a sound registers differently based on the direction it travels through your own head (i.e. your skull itself is an occlusion source) - your brain recognizes front vs. back based on how your own head dulls the sound
I assume the shape of our ears also affects the sounds, depending on the location of the sound. This converts vertical location into frequency shaping. And I wonder, why else would we have such oddly shaped ears?
You would be correct. The shaping of the pinna (and resulting sound reflections) help us determine the height of sound sources, even if they're right on our midline.
Re: The blind man who taught himself to see
#75Higher frequencies, as bats use, give finer resolution. This seems impossible for humans, but since we have cochlear implants, there's no reason they couldn't respond to a shifted audio spectrum. Or, just have an external hearing aid that frequency-shifts the sounds (and cancels out the original), together with a higher-frequency sound source. OTOH, eye implants are probably not that far off. > Just the auditory cort…
If you're interested in reading more about pushing the limits of remapping the human brain, check out The Brain That Changes Itself by Doidge. Fascinating.
Re: The blind man who taught himself to see
#76I really enjoyed this article. I do take issue with a couple of sentences: "We hear in stereo 3-D." This is not true unless we move our heads. We hear in one dimension, left-to-right. "We hear better than we see." This is an apples-to-monkeys comparison.
We can hear true 3D. There are actually a couple of ways in which we can sense the direction of sound. One is loudness, which obviously only works for left-right. This is loudness only in the sense of sound-gets-more-silent-farther-from-the-source. Another is the phase difference of the sounds in both ears. Phase difference comes from the fact that sound arriving at one ear had a longer way to travel than sound arriv…
The eye ends up taking in a lot of information from every point you look at though, whereas the ear is always listening in every direction at once. Because of the kind of processing in the eye and brain, our three types of cone cells actually end up capturing most of the information encoded in the different reflectance spectra of the kinds of objects that naturally occur in the world (most of the variation occurring in typical objects in the wavelength range we can detect): today with synthetic materials and various lighting sources metamerism is noticeable in special edge cases, but just wandering around it usually doesn’t matter too much. After all, a decent percentage of males get along just fine as dichromats, and many don’t even realize they’re missing anything until adulthood (because even with two sensor types there is a lot of variation to pick up).
I think it’s pretty silly to argue that hearing can pick up more detailed information about the world than vision can: from vision, we can figure out shape, orientation, distance, texture, gloss, material, lighting, direction and speed of extremely tiny motion, etc., and we can do it for fine details of everything we look at, thereby constructing a tremendously detailed model of our environment without needing to directly touch every part of every thing. Anyway, both hearing and vision are extremely sophisticated. The two gather quite dramatically different kinds of information. Neither should be underestimated.
Re: The blind man who taught himself to see
#77Earlier quoted context omitted.
We can hear true 3D. There are actually a couple of ways in which we can sense the direction of sound. One is loudness, which obviously only works for left-right. This is loudness only in the sense of sound-gets-more-silent-farther-from-the-source. Another is the phase difference of the sounds in both ears. Phase difference comes from the fact that sound arriving at one ear had a longer way to travel than sound arriv…
The eye ends up taking in a lot of information from every point you look at though, whereas the ear is always listening in every direction at once. Because of the kind of processing in the eye and brain, our three types of cone cells actually end up capturing most of the information encoded in the different reflectance spectra of the kinds of objects that naturally occur in the world (most of the variation occurring…
Of course, this is completely true. But note that I did not talk about the amount of information but the precision of information. Also note that every cone cell is equivalent to one hearing cell in the cochlea, of which there are plenty, too. (Only in the eye, they are distributed spatially while in the cochlea, they are distributed by frequency)
But all this is really not as important as the signal processing that makes sense of it. There are interesting connections between hearing and seeing. If you watch TV and someone at your side turns his head to you in order to speak, you will notice and shift your attention to him. You will think that you saw his head movement in the corner of your eye. But truth is, many people wearing hearing aids will not notice the same situation, for the simple reason that you actually did not see his head movement, you heard it.
There are many more examples where things like this happen. What you perceive is different from what your senses detect. All these intricate combinations of sensual information are the really interesting part.
Another fun thing about hearing: The human ear can detect very low sound pressure levels. Actually, it will detect a displacement of the eardrum of about the diameter of an air molecule. In a way, this is saying that the ear can detect the impact of individual air molecules on the ear drum (not really true, but in the ballpark). That is freaking amazing.
Re: The blind man who taught himself to see
#78How do you "explain" to someone who was born blind that he is "blind"?
Beautiful question. You could also ask if blind people are able to perceive vision in dreams. To which the answer, I believe, is that they simply cannot, due to the fact that their brains have no notion of a visual image.
I suspect we commonly underestimate blind people mental capacities.
One can argue that 'seeing' goes beyond the perception of lights and colors. It's also about shape, so I guess a blind person can perfectly 'visualize' a rectangle, a cube, etc. And probably do geometry, or even 3D-object rotations.
Can anyone confirm this?
Re: The blind man who taught himself to see
#79>Others, like a commenter on the National Federation of the Blind’s listserv, consider him “disgraceful” for promoting behavior such as tongue clicking that could be seen as off-putting and abnormal.
Appalling. Forcing people to be cripple because solving it might be "off-putting" or "abnormal" [1]. Blind people being able to do all the things the sighted can do (and more in some cases) is worth hearing a few clicks now and again.
[1] I say "solving" because Kish doesn't seem to be at a strict disadvantage. He has disadvantages and he has advantages in areas we don't (e.g. finding the way out of a car park, "seeing" around corners, etc.).
Re: The blind man who taught himself to see
#80I really enjoyed this article. I do take issue with a couple of sentences: "We hear in stereo 3-D." This is not true unless we move our heads. We hear in one dimension, left-to-right. "We hear better than we see." This is an apples-to-monkeys comparison.
We can hear true 3D. There are actually a couple of ways in which we can sense the direction of sound. One is loudness, which obviously only works for left-right. This is loudness only in the sense of sound-gets-more-silent-farther-from-the-source. Another is the phase difference of the sounds in both ears. Phase difference comes from the fact that sound arriving at one ear had a longer way to travel than sound arriv…
"a dynamic range of about 120 dB"
Sound of a jackhammer at 1m has sound pressure level of approximately 100dB (relative to 20 uPa). Leaves rustling gently in the wind have sound pressure level about 10dB. If our hearing actually had 120dB dynamic range we'd be able to easily hear the rustling of the leaves while jackhammer is pounding right next to us, not to speak of normal conversation which roughly has level of 50-60dB.
As an analogy to radio equipment we might say that human ears have automatic gain control which spans 120dB (or as audio comparison we can adjust the volume on that span) but the range which we can discern two sources (the instantaneous dynamic range) is about 30dB or less.
Also about the frequency resolution of the ear vs the eyes the bandwidth are on a completely different scale. Visible light spans about 380THz which means that the bandwidth of that signal is 19 250 000 000 times the bandwidth spanned by our ears. You cannot do just simple octave based comparison as the amount of information is not dependent on the amount of octaves but only on bandwidth. You are correct in the sense that the eye uses this information in quite limited fashion, however the actual processing is not on normal frequency domain but on spatial domain (eye is not just one sensor but craploads of them).