Imagine, if you can, seeing in only two dimensions, as if everything appeared on a screen. Almost all of us, of course, see in three, and don't give depth perception much thought.
You can simulate two-dimensional vision to some degree by merely closing one eye. Nothing seems different at first, used as you probably are to judging distance from visual cues with both eyes. Yet something weird happens if you try something like dropping a paper clip into the top of a bottle a couple of feet away.
Yes, your hand looks smaller as you move it farther from your body, but you may well miss the bottle anyway. That's because your brain is used to relying on binocular vision, which is to say your eyes are on either side of your nose, and your brain processes the left and right eye images by mixing them into one, providing a sense of distance—or three-dimensionality.
Mount Holyoke professor (and neurobiologist) Susan Barry didn't realize she lacked stereo vision until she was in college. When Barry was an infant, her eyes crossed—when she focused on something with either eye, the other turned inward. This led to a series of surgeries to realign her eyes. Both eyes then functioned properly on their own, but the two still did not function together to provide stereo vision; her brain suppressed one of the two images coming from her eyes instead of integrating the two. This problem wasn't really apparent to anyone when Barry was a child in the 1950s—her doctor merely told her parents her depth perception wasn't good.
Barry's book Fixing My Gaze relates her voyage of discovery as she braves unusual waters. When she first discovered her lack of stereo vision, conventional wisdom held that Barry had long passed a critical window (an infant's first year) when her brain possessed the capability to re-adapt to corrected alignment and properly process her vision. Newer research has questioned that notion, and Susan Barry herself has proven that in some cases, that notion is simply wrong. With the help of "vision therapy," Barry learned what she thought was impossible, and now sees with stereo vision.
Fixing My Gaze is no ordinary memoir. It has its passages of recollection, its explorations of the author's life, but it has a whole new dimension, so to speak. As a brain scientist and an acute observer, Barry is uniquely qualified to serve up a book that tickles the brain in fascinating ways.
Rather than simply try to find the right combination of words to describe how vision works, Barry offers exercises to try. Embarking on those odd little adventures is a delight, and an unusual brand of learning experience. She accomplishes a remarkable thing: making readers see anew what they have long learned to take for granted. Most of us long ago learned, for instance, to basically ignore what happens when one gazes past a raised finger into the distance: the finger appears to be two. You can see it if you think about it, but otherwise it's just another part of the brain's sifting of visual information that we are not normally privy to.
Barry's memoir could almost serve as a sort of companion piece to the mind-bending book The Fourth Dimension, in which Rudy Rucker, a mathematician, science fiction writer and all-purpose near-madman, attempts to bring readers on a voyage that mirrors in some ways Barry's work, but with an even more difficult destination: the fleeting envisioning of a world graced with four physical dimensions. That book is peppered with exercises and puzzles, and offers such insights into the workings of the universe that it can, quite literally, expand one's thinking in some revelatory ways.
Fixing My Gaze is perhaps not as madly ambitious as Rucker's book, but its passages of vision-focused memoir make it a highly personal and compelling thought voyage well worth undertaking. By the time one arrives at Barry's sudden discovery of her stereo vision, the concept of seeing is no longer one that's easily taken for granted:
"The grape in my lunchtime salad was rounder and more solid than any grape I had ever seen before. I could see, not just infer, the volume of space between tree limbs, and I loved looking at, and even immersing myself in, those inviting pockets of space."
It is possible, it seems, to get a glimpse of Barry's monocular world through the exercises she offers, and her explanations of vision's delicate dance between eye and brain make the subject entirely accessible. She is, after all, a brain scientist, and her memoir is a captivating experience that painlessly imparts a store of knowledge about how we see. It is, for once, no hyperbole to say you won't see things the same way.