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the mind's eye

I always enjoy reading Oliver Sacks' books, not least for the wonderful anecdotes but also with the humane, compassionate way in which he described & discusses the various problems that his patients present with. And so I was delighted to get my hands on another one, The Mind's Eye - as the title suggests, this volume examines the ways in which neurological problems manifest themselves in the way we see the world. One reason the book caught my eye was its cover: red with yellow font - & a font that's deliberately fuzzy & blurred in places, by way of mimicking how some people see the world. Another reason was that as a child, I remember being fascinated by the question of how other folks perceived colour. I mean, was their 'red' the same as the 'red' that I saw? And if it was different, how would we actually know, given that we'd both use the same name for the colour of fire-engines & 'red delicious' apples. (I didn't think of traffic lights - there weren't any in Wairoa when I was a kid.)

The Mind's Eye set me thinking about that second reason again, because with at least some of the patients he describes, their self-developed coping mechanisms mean that you wouldn't necessarily know. People without the ability to see in 3-D, for example. This is something that most of us take for granted, & so we assume that everyone else (except, perhaps, those unfortunates who've lost an eye to accident or disease) also sees the world in glorious stereopsis. But they don't; it's just that in many cases they deal with it in ways that mask what we '3-D viewers' would see as a deficiency - & may well have adapted so well that even the possibility of 3-D vision is not attractive to them. And indeed, having monocular vision need not be seen as a handicap: Sacks comments that the first person to fly solo around the world, Wiley Post, did so with only one eye. (The other was removed surgically, following an infection, when Post was in his mid-20s.)

An individual with an uncorrected squint (strabismus) may also lose the capacity for binocular vision, & in the past it was generally thought (based on observations & experiments on other animals) that if a squint wasn't corrected early in a child's life, that person would forever after see the world 'flat', lacking the depth perception necessary for stereoscopy. But Sacks relates how he received a letter from a neurobiologist, Sue, who'd gone for most of her life in just such a 'flat' world after a childhood squint had not been properly corrected. When she was in her late forties, Sue's sight began to deteriorate and, with the support & advice of a developmental optometrist, had practiced & done exercise after exercise until she acquired the ability to see the world in 3 dimensions. Take a moment & think about how this might feel... frightening? terrifying? wonderful? (It was definitely the latter, in her case.)

Another example Sacks discusses is 'alexia', or 'word blindness' - the inability to recognise written language, something that is due to damage to a specific part of the brain (say, by a stroke). As someone who reads & writes - copiously! - on a daily basis, both for pleasure & as part of my job, I simply cannot imagine what it would be like to lose this ability. It was something of a relief to read (heh) that at least one of Sacks' patients was able - slowly and painfully - to recover some of his old skills in this area. A related disorder is 'prosopagnosia' - the inability to recognise faces (something that Sacks described in his 1985 book The Man Who Mistook His Wife For a Hat (Yes, seriously, that's what happened in this particular case study).

Perhaps the most poignant example in the whole book is that of Sacks himself, in an extended essay that combines diary entries with self-reflection following on his diagnosis of a ocular melanoma - a tumour affecting his eye. The details of how the growing tumour encroached on his vision are both fascinating and awful (& if they're bad to read, think how you would feel to have these things actually happening to you). Surgery to insert a radioactive plaque & subsequent lasering, both targeting the tumour, saw him lose his binocular vision - rather ironical given that Sacks at one point belonged to the New York Stereoscopic Society. Four years later, in 2009, bleeding behind the retina of the affected eye saw him lose almost all sight in it - including his peripheral vision. This meant that he experienced something that hitherto he'd only known through working with patients who'd suffered strokes in a particular region lf the brain - anything, any person, any object, on the affected side effectively ceased to exist for him. As Sacks describes it:

This came home even more forcefully when Kate [his PA] and I finished our walk and headed back to my office. I walked ahead and got into the elevator - but Kate had vanished. I presumed she was talking to the doorman or checking the mail, and waited for her to catch up. Then a voice to my right - her voice - said, "What are we waiting for?" I was dumbfounded - not just that I had failed to see her to my right, but that I had even failed to imagine her being there, because "there" did not exist for me.

Such personal anecdotes make The Mind's Eye a compelling and affecting read.

O.Sacks (2010) The Mind's Eye, pub. Picador. ISBN978-0-330-51399-9

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It's hard to walk past Sack's books, eh? I'm still hoping I'll eventually get my hands on a copy of the The MInd’s Eye at the library.

His writing is excellent. So much so that I nicked—erm, make that quoted—some lines from Sacks for my article on prosopagnosia. He has this wonderful description of the guy (Dr. P.) occasionally patting fire hydrants and parking meters in Magoo-like fashion, confusing them for the heads of small children. The thing that really gets to me is just how common (mild) forms of prosopagnosia are, being something ~2.5% of people have.

What on earth is the New York Stereoscopic Society. Or would that be a spoiler?

I can't see in one eye myself—a consequence of congenital rubella—so I can't see in stereo. I've written whinging about the 3-D TV industry, as you know :-) I like my movies and if most are going to be only in 3-D sometime in the future, I'll be peeved.

I can't say I've ever "lost" someone standing next to me, but then I've grown up with only seeing in one eye. Sounds funny to say, but I'm not sure I want to start thinking too hard about it.

It would indeed be a spoiler :-)

the ability to see in 3-D, for example
So you have something like 3% or 4% of the population who are stereo-blind, but not aware of it until they're tested.

On the other hand, there are cases of stereopsis with a single eye.


Ah, OK.

Guess it'll have to wait until I get my grubby mitts on a copy.

(Sorry about rattling on, it's just a topic that interests me.)


True, there's a difference between being able to see in stereo and perceiving depth, etc. It's easy to forget about the various stereopsis effects. By the way, there seems to be no URL in your link. (I've checked the source code.) I briefly mentioned one such effect when I whinged on about 3-D movies :-)

If you'll promise to go & wash your hands :) I could lend you my copy. E-mail me your address & I'll stick it in the snail-mail.

Thanks for the kind offer Alison. I might just take you up on it, but realistically I'd best first spend time lining up another contract (mortgage to feed, etc.) and read the backlog of books I still haven't read yet!

HDB: Looks a very interesting article. Thanks for the link.

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