Assuming that one can take ones eyeball out of its socket and hold it a couple of inches from ones socket while still connected to the brain by the optic nerve. Now, if you turn this eye around so it is looking straight into your other eye, what would you see?
It’s pretty obvious that you’d see at least one “I”.
Why though?
Using, by my count, 6 mirrors and some cardboad you should be able to simulate such an action. Keep us posted. 
Humans have forward-facing eyes. The brain is geared to combine the field of vision produced by each eye into a single field, or picture. No doubt you’ve seen animals with side-facing eyes (e.g., dolphins). Their brains are geared to handle two totally separate fields of vision. If one of our eyes fell out, I think the brain would automatically stop the input from the damaged eye. I think it would literally not know what to do with the visual input, since it’d be so far out of the norm and totally unmergeable, if you will, with the input from the undamaged eye.
I’ll take a crack at this:
Being that our brain will desperately try to combine the two visuals from each eye to create a beautiful 3-D image, it will try and combine the two different eyes as ONE 3-D eye with limited success, and giving the poor viewer a disorientating experience.
Kind of like what you get when you stick two quarters in front of each eye: Two very blurry quarters (eyes), BUT if you position it just right, and concentrate, you can combine them into ONE quarter, but again: blurry. You just can’t focus that close. sorry.
Seems my follow-up post didn’t take. Well, better late than never.
First, where I came up with 6 mirrors I’ll never know. Two should suffice. Consider the following diagram, where the eyes are represented by a “oO” and a “Oo”, and where the little ball on each set represents the little spot on each eye where the crusties develop. I have no idea what to call it. At any rate, it is, essentially, what makes the eye not symmetrical and so is useful in this diagram.
/----
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Oo oO
There, the dashed lines represent the light path and the mirrors are the slashes. What would we see? Well, one eye to be sure, like this:
oOo
It would have two crust collectors! But, nothing so mysterious.
Incidentally, I was informed in boot camp that in a fight never to hesitate to gouge an eye out if I could. the pain and visual distortion that would occur would cause my opponent to, well, not be in the mood to fight anymore. Just thought I’d mention it, flyboy, but I claim no scientific knowledge.
Should have put that, er, “diagram,” inside of [code**] brackets.
I’m back.
I was just joking with my first post (“eye” vs. “I” - get it?). Flyboy88 is correct here. The brain merges the images from the two eyes and corrects for the difference in images with parallax. Moving one of the eyes corrupts this process. A few experiments will demonstrate this.
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take a pair of binoculars and adjust them for your eyes. Now, squeeze them together and try to look through them. The one focused circle you used to see is now two overlapping circles. Your brain is not able to make that correction.
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take two small pieces of glass and hold them one in front of each eye. Make the two pieces parallel, like eyeglasses. Now, take either piece and spin in around the z axis (vertical) a little bit - as if your eye were pointed outward a little bit. Again, a distorted image due to the brain’s inability to compensate.
People with a “lazy eye” experience exactly what flyboy88 stated. When the eye begins to move, the brain “ignores” its input to vision until it relaxes and returns to its regular position.
I’ll be seeing you,
Spritle
I hold an open hand just down the path of my nose (you know, like guarding Moe’s eye-poke) and both eyes see something almost completely different. I can also clearly make out both sides of my hand, even though where they don’t overlap are somewhat, er, ghostlike. Translucent.
At any rate, your brain superimposes eyeball images. It uses the parallax for the appearence of depth, but two independent images are, indeed, two independant images overlapped. This can be demonstrated any number of ways. Hold a piece of paper close to one eye to obscure its vision while looking at, oh, the straight dope message board. You can clearly both see the paper and read the words.
You would see one eye which is a superposition of both eyes.
Well, it’s not that the signal from one eye or the other is turned off at the optic nerve. It’s still there.
What happens is that the higher visual processing areas of the brain have the ability to ignore the image from one eye, and concentrate on the image from the other.
“Seamless” bifocals take advantage of this same ability. These actually focus two images on the retina and the brain can concentrate on one and block out the other.
And on TV, when a trite soap opera editing job makes an extended 30 second fade between two camera angles, the same visual processing ability permits you to “focus” back and forth between the two images - heck, it also lets you recognize that there’s two images, and not just one confusing one.
erislover, I’m maintaining that the brain merges two separate images into one picture. So is Spritle. I believe bughunter is saying the brain can ignore an input from an eye.
You’re saying:
While I don’t know if I’d use such simple words as “overlapped” and “superimposes” (the term is actually called “stereopsis” and is a bit more complex), I agree with this, since the above seems to be what we’re saying. Although you still seem to be at odds with us.
What does this have to do with anything? Is it comparable to having an eye gouged out? In your example, your brain has no problem seeing two separate things partly because your frame of reference is still solid. Both eyes are firmly in your head and both eyes are moving in unison. You can’t fool your brain so easily. Gouge an eye out, so it’s in an independent frame of reference, free-moving and uncontrollable by your brain, and your brain won’t understand the input.
I can’t do anything with this; I have no idea what it means. The word, btw, is superimposition.
Well, lord knows, we don’t want to get all scientific, now would we? I don’t know if you meant that to sound snotty, but to me it did. And far be it from me to question what they told you in boot camp. In NROTC, we learned it was a good idea to gouge someone’s eyes out because it’d pretty much blind them and hurt like hell. Even assuming your instructors were accurate, visual distortion can come in many different varieties, e.g., bluriness, which would surely be one side effect of getting an eye gouged. Blindness out of the gouged eye could also be considered a visual distortion, when you take into account the brain now having a monocular view (from the good eye) of the world. So thanks for bringing that useful example up.
So, to sum up, I’m still confused as to what you’re saying we’d see with that gouged eye.
No no, no snottiness here. Honest Abe.
I am simply saying that the ability to ignore one eye’s image over the other, or to process signals of different, but simultaneous, patterns (as in the soap opera example) is not that “the brain” chooses to ignore input, it is the seer that ignores the input and chooses how to focus.
Again, with the “eye-poke block” hand over the nose, you can see both sides of the hand at once, or, if you choose, to focus primarily on one or the other.
Were an eyeball to be popped out, I think, something entirely similar would occur. Depth perception would be all wrong, almost instantly, so everything seen would have to be pretty much overlapping images.
If each eye was looking at an eye, you would see an eye. I trust we aren’t debating that?
That there is muscular control over an eye is obviously not debatable, but I have never heard anything about motor control of the direction of the eye being part of processing visual stimulii. In fact, that makes no sense to me. Well, apart from depth perception, of course, which I already mentioned. Is this really the case?
Nope. No feed back. Let’s examine. Visual Feedback happens when you have a image collector (camera/eye) and an image displayer (monitor/brain) displaying the collector’s image, whereby poiting the collector at the very image displayer that is re-creating it’s image. (same thing happens when you point a mirror to another mirror)
Now in the eye looking into an eye, they are BOTH image collectors. Therefore no feedback occurs. it is IMPOSSIBLE to point your eye at the very image processing part of the brain. it just doesn’t make sense.
see what i’m saying?
You’d have to first find a way to output your visual signal to a monitor of some sort, then look at it with the very eye that was making the very image. dcarr was confusing the OTHER eye with a display from the original eye.
hope this helps!