Stereo Sue

Oliver Sacks writes about Sue, who (through vision therapy) recovered
stereoscopic vision (STEREO SUE., Sacks, Oliver, New Yorker, 0028792X,
6/19/2006, Vol. 82, Issue 18). She had lost it when she was very young, and then recovered it through intensive vision therapy. She was (is) completely thrilled by
this. Sacks writes,
“Struggling to find an analogy for her experience, Sue had suggested,
in her original letter to me, that her experience might be akin to
that of someone born totally color-blind, able to see only in shades
of gray, who is suddenly given the ability to see in full color. Such
a person, she wrote, “would probably be overwhelmed by the beauty of
the world. Could they stop looking?” While I liked the poetry of Sue’s
analogy, I disagreed with the thought, for I suspect that someone who
has grown up in a completely colorless world would find it confusing,
or even impossible, to integrate a new “sense” such as color with an
already complete visual world. Color, for such a person, would have no
associations, no meaning.”
One guesses that Sacks has philosophically famous Mary in mind. Ok, so
why does he think that Mary _wouldn’t be able_ to see color, while Sue
is delighted by what she can now see? Is he right?


  1. Ken Aizawa


    I don’t think Saks says that Mary wouldn’t be able to see color. Instead, I think he says that Mary would not be able to integrate color into her visual world.

    It sounds as though he has some version of the Molyneaux problem in mind, as if there were new color vision that had to be integrated pre-existing black and white vision, rather than new vision being integrated with touch.

    I’m not sure if that makes sense–there are disanalogies to be sure–, but it seems to me to be what he is saying.

  2. ck

    I read that New Yorker article, too, and was confused why the world that the color-blind person see is a “complete visual world”, whereas presumably, the person without stereoscopic vision sees an incomplete world (and therefore just is amazed by the gap that was filled in).

    Isn’t the point of Sue’s experience that she only knew what she was missing by the testimony of other people? She was able to function, just as a color-blind person would. And, just as a color-blind person, she could cope with her new skill, seeing stereoscopically, although it took time.

  3. anna-mari


    I agree here. This is mainly about integration, not ability as such. However, it would nice to know, what was the original reason for the loss of stereoscopic vision. At the level of cognitive architecture we can say that ok, this may be an integration-problem, and analyze that, but it is still important to know where the original trauma was in her brains. Does anybody know?

  4. Hi Tony,

    Nice post.

    I speculate that Sacks’ hunch is an offshoot of the “intuition” that so many people express in contemplation of things like Jackson’s knowledge argument.

    The intuition: No one can know what it is like to have an experience of such-and-such type unless they have had an experience of that type.

    Dennett has challenged people to provide an actual argument for that proposition, and to my knowledge no one has yet done so.

    But anyway, relating this to stuff like Molyneux, and the differential intuition Sacks and others have re colors and space, one might say the following:

    While touch and sight are different types of experiences, visual experience of space and tactile experiences of space are, with respect to space, subtypes of spatial experiences. Therefore, even though one has never seen depth, they have had nonvisual depth experiences and can know what it’s like (partially) to see depth.

    (Of course, its overly simple to say that steroblind patients have no visual experience of depth: they still see perspective, occlusion, and other visual markers of depth.)

    In contrast, visual experiences of color aren’t sub types of some broader category of color experience, so one is not going to know what its like to see color unless one has already seen color.

    Of course, all of this depends on the truth of something that, if Dennett is right, no one has any reason to believe.

  5. I agree with the point of Sacks, even if the comparison with color-blindness is conceivable (for Sue…) it’s misleading. For depth perception is a typical multi-cue process (partially retrievable from shading, optical flow, etc.) so Sue – probably – had always a bit of depth perception, it then just become much more accurate.
    I think it might be compared – despiste obvious disanalogies – with the achievement of a great performance with excercises, like playing an instrument.

  6. tony dardis

    ken: right, Sacks says “confusing, or even
    impossible, to integrate a new “sense” such as color” rather than
    “unable to see”.

    anne-marie: Sue Barry was born cross-eyed. She had
    operations (on the muscles of the eyes) to correct the strabismus when
    she was quite young. [She is currently an Associate Professor of
    Neurobiology at Mt. Holyoke .] Her vision was
    deteriorating in the 00’s and she consulted with an optometrist
    (Dr. Theresa Ruggiero) who prescribed vision therapy.

  7. kenneth aizawa


    I think it is plausible that there is “what it is like to see stereoscopically.”  What it is like to see a standard movie differs from what it is like to see a movie presented through a stereoscope with the proper binocular disparity information.  If this is right, then one has at least one part of the argument for the view that one cannot know what it is like to see in stereo unless one has actually seen in stereo.  (Set aside the can’t know unless experienced part.)  The idea here is that, even though there are depth cues other than binocular disparity, e.g. occlusion, binocular disparity and its brain mechanisms give rise to a phenomenology that differs from that had in virtue of other depth cues.  Put in still other words, it is one thing to know what it’s like to see in depth, but another to know what it is like to see in stereo.

    Given the distinction between binocular disparity and other depth cues, one can, I now think, get a good version of a Molyneaux question.  Suppose that a person has been stereoblind all her life, but knows about depth in terms of occlusion, motion parallax, texture gradients, etc.  Now imagine this person granted stereo vision.  Would this person be able, using binocular disparity alone, to determine what is closer and what is farther?  Notice that the test stimulus would have to be free of cues from occlusion, motion parallax, texture gradients, etc. so as to mimic the original Molyneaux stipulation that the subject not be able to see and touch the objects simultaneously.


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