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Recently I see a lot of links to Ed Macy's book "Apache" (related from Google glass articles' comments).

It took me two years to learn how to "see" properly -- how to see in an Apache World. I once filmed my face during a sortie with a video camera as an experiment. My eyes whirled independently of each other throughout, like a man possessed.

I doubt that that is the real case, it sound more logical to me that Apache pilots just learn to switch their concentration easily from one eye to another, but they don't actually move their eyes like a chameleon. Can humans even move their eyeballs independently of each other and if so, are pilots more prone to doing this?

Paul
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J-unior
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    Hope you don't mind, but I updated the question to one that should get a lot more attention. – rjzii Jun 02 '13 at 15:05
  • What do you mean by "independently"? –  Jun 02 '13 at 17:06
  • @Sancho - I'm assuming that they mean you can consciously move your eyes so that each is focused in different directions from one another, i.e. moving one does not force the other to move as well. – rjzii Jun 02 '13 at 17:10
  • As a pilot, I never heard such a thing. I can go cross-eyed or wide-eyed if I want to, but it's no use in flying. What's more, binocular vision isn't particularly important either. When you're landing, you're focused several hundred feet down the runway, and relying on peripheral visual cues to gauge height. Maybe it's different in a combat helicopter. – Mike Dunlavey Jun 02 '13 at 17:50
  • @RobZ No, that's not what's meant by "independently" because my answer was downvoted for assuming that definition. –  Jun 02 '13 at 18:00
  • I can move my eyes independently. Not very useful as its like going cross eyed. – Dave Hillier Jun 02 '13 at 18:11
  • There are loads of examples of this on youtube. http://www.youtube.com/watch?v=-7RJd3QSruA – Dave Hillier Jun 02 '13 at 18:16
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    @MikeDunlavey The difference for an Apache pilot is presumably the http://en.wikipedia.org/wiki/Helmet-mounted_display – ChrisW Jun 02 '13 at 22:51
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    IMHO an impressive example http://www.myvideo.de/watch/8362532/Unabhaengige_Augenbewegung – bummi Jun 03 '13 at 16:30
  • @bummi That seems to show that it's feasible, anatomically. The only question left might be whether that's normal for an Apache pilot. – ChrisW Jun 04 '13 at 03:51

2 Answers2

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Chameleons are the only vertebrates that can focus monocularly:

However, unlike other vertebrates, chameleons can focus targets monocularly, using lens effort so that, in theory, they can fixate and focus an approaching threat with one eye, while the other scans in the opposite direction. (From Threat perception in the chameleon (Chamaeleo chameleon): evidence for lateralized eye use).

There is some evidence that the above conclusion isn't so absolute:

This paper will present observations from both normal and abnormal eye movement data that suggest a more complex ocular mo­tor control architecture - independent control of each eye. Because of the inherent bilateral nature of brain stem organization, the latter directly implies independent control of each eye muscle. Taken individually, some of the observations are only mildly suggestive of in­ dependent control; others are strongly sugges­tive. None may, by itself, provide conclusive proof of independent control, although some appear to. However, taken together, they sup­port a strong case for the hypothesis that the neuroanatomy of our ocular motor systems is basically configured for independent control of each eye (muscle) and it is binocularity that imposes the yoking normally seen.

[...]

In 2 of the earlier studies of human saccadic metrics, it was found that the saccadic trajec­tories of each eye might independently over­ shoot or undershoot the target during the pulse portion of the response, and the result­ing "glissade" to the target was specific for the metrics of that eye's saccade.

[...]

The occurrence of uni-ocular dynamic over­ shoots (5) in normals is another instance of disconjugacy that suggests independent neu­ral control signals to each eye.

The above is from (Dell'Osso, L. F. (1994). Evidence suggesting individual ocular motor control of each eye (muscle). J Vestib Res, 4(5), 335-45.)

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Yes, humans can move their eyes independently... just watch these videos (link 1 and link 2).

But, how much use is that? What can you see if you cross your eyes? I know when I do it that crossing eyes serves very little purpose other than to help with pulling faces :) Everything just goes blurry and my eyes start to hurt.

One reason our eyes have evolved to work in harmony is because of binocular vision, it's why they are on the front of our heads, not the sides. Depth perception is difficult with one eye; put on an eye-patch, go play catch, see how you do compared to normal.

A chameleon has evolved independent movement of their eyes. The eyes are mounted on the sides of their heads, this is because some of the time they need 360 vision to spot danger. However, because they are also predators using a highly precise method of capture (requiring good eye-tongue coordination) the ability to point both in the same direction, giving them binocular vision, is also highly advantageous, thus they can move them independently to face the same direction. For more info see the wiki page or this article.

With regards to the quote above, you might want to read the answer to this Quora post, one guy says:

I flew the AH-64s for over 12 years. There's no single Apache pilot I know who can move his eyeballs independently, nor who is required to do so. Similar to what Steve mentioned, the trick is to learn how to ignore input from one eye and refer only to the input coming from the other eye, then switch between them and do this every few seconds.

rg255
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  • Welcome to Skeptics. The YouTube video does not show eyes moving independently. It just shows someone crossing their eyes, looking to the left and right. For example, it doesn't show one eye looking up while the other looks down. – Oddthinking Aug 01 '13 at 16:41
  • @Oddthinking Though the range of movements are limited they are nonetheless independent of one another. I am also editing some support for my speculative points (should have done this in the first place). – rg255 Aug 01 '13 at 16:44
  • @Oddthinking i hope my edits have made the answer better :) – rg255 Aug 01 '13 at 16:48
  • I'm ignoring the German video as evidence. I wish I could find some footage of the first film director to use that special effect. Much more impressive because in those days it was done in camera, blocking half the film off, whereas these days it can be done in post-production. – Oddthinking Aug 01 '13 at 16:54
  • As for independence: If the claim is "Can some people cross their eyes?", as demonstrated in the first video, it is a pretty mundane claim and should be closed. – Oddthinking Aug 01 '13 at 16:56
  • Granted that video could be faked, I haven't taken the time to examine it, but it remains that crossing eyes is moving eyes independently. One eye moves whilst the other remains stationary, some people can do this more so than others. Given that the question is "can humans move their eyeballs independently of one another?" I think I have answered this question. Personally I don't think being mundane warrants closure. – rg255 Aug 01 '13 at 21:52
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    @Oddthinking We don't close questions because they're boring. –  Aug 02 '13 at 17:06
  • I think because the quote says "whirled independently" simply crossing of eyes does not count. Whirling means *to move in a circle or similar curve, to circle, circulate; more vaguely, to move about in various directions.* –  Aug 02 '13 at 17:09
  • (I must be doing something wrong; I am being misinterpreted a lot this week.) @Sancho, this answer proves that people can cross their eyes. You agree the OP meant more than that. If the OP had meant "can people really cross their eyes?" it would be closed pretty quickly - not because it is boring, but because... well, don't ask me which subclause of which rule, but because it would be a ridiculous question that didn't make the Internet a better place. – Oddthinking Aug 02 '13 at 17:19
  • @Oddthinking Yes, I agree that the claim means more than crossing eyes, and thus, this answer doesn't address the question. As for what would happen to a question "can people cross their eyes?", I think it just wouldn't have been asked, or if it was, it would just be downvoted and then after a lot of downvoting, maybe eventually closed/deleted. But, prima facie, I don't think we'd have grounds to close it. –  Aug 02 '13 at 17:28
  • We should also remember he was writing a book, probably over exaggerated a little to make the book less dull, and we have not seen his video. You or I could just as easily look at someone going cross eyed and describe them as whirling independently. But I am going to give up justifying this answer clearly it's utterly pointless because people are separating "independent movement of the eyes" from "making eyes do the river dance." – rg255 Aug 02 '13 at 17:32