Walking At Night

Tonight I’m walking home through our lanes. It’s just stopped raining, and I come to a kind of T junction, and as I near it I can hear footsteps.

But when I emerge at the junction nobody is there. I can still hear the footsteps coming closer, as though a ghost approaching.

Now—vaguely scared—I’m scanning from side to side to locate the origin of the phantom footfalls, and for several seconds I’m bewildered.

Then suddenly I can see someone after all. They were in my blind spot and as I tried to locate them my eye movements got it wrong. I skipped too far. But now my radar is locked on, I no longer have any difficulty.

Throughout I have absolutely no inward experience of blindness. Over the two years since I had a stroke I’ve learned to compensate very well, and the remarkable ability of our brains to paper over the cracks means I hardly ever now feel I can’t see things.

But although the cracks don’t bother me, they are still just as wide as ever. And that’s why it would never be safe for me to drive, and I have to be really careful when moving about in busy spaces. I need to watch where I put things down too, in case they mysteriously vanish. And I would be terrible on a glacier.

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Oliver Sacks

More sad news. Oliver Sacks has just died. There is a moving TED blog here.

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A Messenger from Inside

John Hull wrote “Touching the Rock”.

If you want to feel blindness, read this book. We can never understand anything by covering our eyes.

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The Blind Composer of the Concierto de Aranjuez

Joaquin Rodrigo wrote the most famous guitar ever.

Listen to the rendition below. You will recognize it. It has a wistfulness that sounds like a new morning, and an old place.

The composer of this was blind. I had no idea until listening to the radio two days ago. At 3 years he had diphtheria. Blindness is a rare outcome but Rodrigo suffered it.

Reader, it’s possible you have never heard of this disease. It was feared by every parent in the generation before me. A hundred years ago there were 50,000 cases of diphtheria in the UK each year and of them 5000 died, mostly the children.

But vaccination has made diphtheria rare in developed countries. This graph is from a group at Oxford University

Luckily I and my brothers were born after 1942, when the diphtheria vaccination program was introduced where we lived. You see how my parents were released from one deadly fear (althoughthere were many others of course), and why they thought (and I think) everyone should be vaccinated.

But more than 70 years later we still have work to do world wide and if am honest I feel ashamed about it. Why do we not help developing countries more with health care? Who can tell me?

However this post is not about diphtheria, it’s about a blind composer. How did Rodrigo work?

If you look him up, he wrote in Braille, but dictated his music to a sighted helper. I couldn’t follow this at first. I knew there is a Braille musical notation (invented by Louis Braille himself still a teenager at the time) but I was not sure how Braille is written or how Rodrigo and his collaborator worked and was puzzled at first.

After thought and research I see that Rodrigo (who was an accomplished pianist) probably composed at the keyboard, as I imagine most classical composers do. Then he wrote what he’d got down, and revised it as necessary.

But then he had to get the music from Braille into the non-Braille world. That’s where the dictation came in. He read his notes aloud from his Braille version, note by note, and they were transcribed into musical notation for the sighted.

This whole question of how to compose music, if you are blind, never properly occurred to me before. A chance hearing on a radio channel made me realize yet again how little I knew. I’m less ignorant now, but I’ll write more about music and Braille in another post.

Joaquin Rodrigo lived to be 99. Astonishingly, when researching for this post, I found a recorded interview with the composer


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Blind Voters

The UK parliamentary elections are just four days off.

How can blind people mark their ballot slips on the 7 May?

For most of my voting life I never gave this the slightest scrap of thought, but my recent experience of becoming partially sighted prompted me to do some investigation.

Suppose you are not just partially sighted, but blind. You could have a postal vote of course, but suppose you prefer to vote at the polling station. How can you fill in the ballot paper?

One solution is to vote by proxy, with the aid of a companion, or a member of staff at the polling station. But there is an issue of independence and autonomy. So how can blind voters be enable to mark the paper for themselves?

Even for sighted people the business of voting is mildly intimidating – don’t you think? – and if you are totally blind it must be a big challenge.

In 2001 an effective and easy to use system was developed by Goodwin. It’s a nice example of keeping it simple, sensible.

Here’s how it works. At the polling station they have plastic strips that can be stuck over the right-hand side of the ballot slip, the column where you would make your X in one of the boxes.

The strip is like a tiny advent calendar, with windows that peel back. Each reveals a box where you can make a mark to vote for a particular candidate. The windows are numbered 1, 2, 3 etc. and embossed with their number, which is also given in Braille. Tactile voting. You can feel where to put your cross.

You tell the staff at the polling station you are blind. They stick the strip on the right-hand side of your ballot slip. Then someone – I think it can be anyone you choose – reads the names and other details of the candidates out to you in order. You remember what number candidate you want to vote for, go into the booth, find the right window by touch, peel it back, and… make your mark in the right spot.

I think this a model example of good design that focuses on the user experience. Too often design is driven by visual appeal as opposed to good functionality. But visual appeal cuts little ice with the blind!

For more about sight loss and voting see here.

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Crossing the Bridge: Fear of Tumbling

I’m not scared of crossing bridges as such. Just footbridges, and especially this one. It’s at my local railway station and I need to go over it to get to London.

photo (2)

There’s a specific anxiety disorder concerned with crossing bridges. Many people suffer badly from gephyrophobia. They fear the bridge may collapse. This can be severe and is quite common, so it turns out some bridges in the world offer a service to drive your car across for you (although I was puzzled how you then cross yourself).

My fear is different and more trivial altogether. I’m anxious that it may be me that collapses. Loses grip, tumbles down the steps, ends up a limp bag of bones at the bottom. It’s very unlikely to happen, but this vision makes me feel a bit dizzy on the bridge.

My sense of balance has always been below par and I think I’ve relied a lot on vision to stop me falling over. This has probably contributed the fear of heights I have, because in high places your sense of balance becomes more important relative to vision, when it comes to maintaining equilibrium.

I’ve several times had panic attacks in high places. Once I had to be helped down from a mountain because I completely froze. I can recall the feeling. I just wanted God or a helicopter to lift me off.

My bridge is not a mountain but with age and stroke my balance has declined (and so has my vision). So I don’t like it. But I need to conquer the anxiety if I can

As you can see the bridge would be impassable for anyone in a wheelchair. This is an issue the local rail users group have been pursuing.

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Marl Twain and the Catching Reflex

Somewhere in Huckleberry Finn by Mark Twain there is a famous episode where Huck, a boy, masquerades as a girl. Wanting somewhere to stay, he is taken in by a Mrs Loftus, but after a while as they talk she is not taken in by him! To confirm her suspicions  about his gender she throws a ball into his lap and he instantly – too quickly for conscious thought – reacts by closing his legs.

A girl (Mark Twain reasons) would have had a different reaction: she would have spread her legs and caught the ball in her skirt. In the book Huck’s cover was blown by this shrewd test.

When I first read this, many years ago now, I was deeply impressed by Twain’s insight, and it remains a very compelling narrative. It shows how great Twain’s powers of observation, intuition and storytelling were. As a child I just thought : “Wow, that’s right” and I still think it’s very clever.

But is it true? The equation girls=skirts and boys=pants might have been substantially accurate in 19c America but even in that context the whole thing is questionable. Nowadays dress is not so rigid, and culturally and historically gender divisions have been very fluid. Even in times and places where girls were in skirts and boys pants, was Twain’s belief actually correct?

I don’t think there has every been any research, but I guess we could do some together. The next time something unexpectedly falls into your lap, post a comment to contribute to the experiment – did you catch, or try to catch it, and if so how?

Why did I write this? Walking back from my local tonight I had a lollipop in my mouth (bad for the teeth I know) and my hands were free. By accident I let the lollipop fall. Without thinking I caught it on the way down, bringing my hands together to clasp it accurately at roughly the level of my navel.

I was pleased I have still have such good reactions, but what interested me was that I had caught the lollipop in the safety net of my hands. I didn’t try to bring by legs together, or to spread them apart. Either would have caused me to fall over. Instead I cradled that lollipop in my (now sticky) hands!

Now isn’t that surprising , when you think of it? We have an unconscious reflex that can catch things we drop, on their way down. It knows if we are sitting or standing, and whether to use arms or legs, and it is remarkably good at estimating the acceleration due to gravity and predicting how to head a lollipop off at the navel, or a ball off at knee level. We can see into the immediate future remarkably well.

But if we are sitting, does it really act differently depending on whether we were brought up in skirts or trousers? Was Mark Twain just spinning a yarn? I’d love to know.

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Banknotes – Go Compare

Someone blind faces a mountain of problems. One example.

If you’re blind (or have low vision), how can you know the face value of a banknote? You can rustle it in your hands but it won’t whisper its secret.

In the UK and most countries different denominations of banknote are smaller or larger. For example, according to my tape measure, UK notes step up by 1 cm per denomination, in length and width. The 10 GB pound note is 1 cm longer and 1 cm wider than the 5 GB one for instance.

So if you are blind, and lucky enough to be presented with a large fistful of GB notes of different denominations, you can (with a bit of effort!) sort them into piles of 5, 10, 20 and 50 notes, using size comparison.

However it’s much harder in practice. What if (as is most likely) you don’t receive a fistful but only have a few notes (or just a single note) of one or two different values? You can’t do a full comparison. They might be all 10 pound notes, or some 5 and some 10 pound notes, or… You get the idea.

Of course there is plenty of modern technology that can recognize the value of banknotes. But there is also a simple, portable, inexpensive, and homespun approach, needing no special equipment and no batteries. It’s called the ‘Arthur Pearson method’, I assume after the famous blind newspaper proprietor. It uses your fingers as a gauge, i.e. as a measuring device. Here’s how it works and you may like to try it as an experiment.

Get hold of a couple of banknotes of different values. Put them on the table before you. Then shut your eyes tightly.

Place the first note, width-wise, between your index and second finger. Imagine your fingers are scissors and you want to cut the note in half.

Now use your other hand to compare the width of the note with the length of your fingers.

Then do the same with the other note.

It’s a surprisingly good way of distinguishing different values. Of course it would take practice for it to become reliable, but for me

  • A 5 pound note is taller than finger 1 but shorter than finger 2
  • A 10 pound note is taller than finger 1 but about the same size as finger 2
  • A 20 pound note is taller than either finger.

Obviously all this will vary a lot from one person to another, but our fingers do form a rough and ready size (and therefore value) gauge for banknotes.

My fingers are too stubby to tell 20 and 50 pounds apart but I never have 50 pound notes anyway.




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A Tale Of Two Polychromats


A brightly coloured mantis shrimp facing towards the camera.

This gorgeous but rather disturbing creature is a mantis shrimp. It looks like an alien being, and indeed it has superpowers!

But it’s not an alien. Nor a mantis. Nor a shrimp. But it looks a little bit like a mantis. And it’s related to shrimps.

Mantis shrimps are remarkable crustaceans. They are ferocious marine predators, up to about 30 cm in length. There are many species which come in two kinds: ‘clubbers’ and ‘spearers’. Something both kinds share is lightening speed. The clubbers give the prey (such as other crustaceans, or fishes) a knock-out punch, the spearers impale it. To give an idea of how fast these animals can strike, the claws of punchers can achieve speeds of about 17 m per second, or 40 mph.

Anyone who keeps mantis shrimps in an aquarium may find a clubber can break the glass, and a spearer can give a nasty hand injury if handled.

Why do I write about mantis shrimps? It’s because as well as being super-boxers, they have another super power. Extraordinary colour vision.

Humans are typically trichromats, with three types of colour receptors (cones) in our retinas. One type of cone is most sensitive to red, one to green and one to blue. Each type of cone has a peak response at a particular wavelengths of light.

Some people (mostly men) are colour blind, and have more restricted colour vision. It’s also thought some women may have a fourth kind of cone and are tetrachromats. If so they may be able to see more different shades of colour than the rest of us. However the existence of human tetrachromacy is not proved. There are web sites that claim to test for it but I think the results are unlikely to be be reliable.

So three types of colour receptor is the commonest situation for humans. The mantis shrimp can knock coloured spots off this. Some species have as many as 12 dfferent sorts of colour receptor (and that’s leaving out kinds attuned to ultraviolet, and to different polarization of light). Four times the number of an average human being.

Intuitively we’d think from this that mantis shrimps can see far more many different shades of colour than we can. However very recent research has challenged this idea. By rewarding mantis shrimps with snacks researchers were able to train them to respond to 10 particular wavelengths of light. (I was amazed that this degree of training was possible.) The researchers then tested whether the animals could discriminate between the wavelengths they had learned and other wavelengths nearby. And they couldn’t tell the colours apart.

How can this be? If the mantis shrimp has many different types of colour receptors then surely it’s a no-brainer that they must be able recognise a huge palette of colours?

Brainer is the cue. Things are more complicated. Think of a daffodil flower. It’s yellow. But we have no special photoreceptors for yellow, only for red and green. But both types of cones are stimulated to a certain extent by yellow light, and the brain takes this information and combines it. So we perceive the daffodil as yellow (and have a strong sensation of yellowness, a qualia for a colour we can’t see except as a mixture of others).

The research suggests the mantis shrimp cannot (it turns out) see more colours than human beings, in spite of having more different forms of colour receptor. What it seems it  can do is recognize colours from a limited range, but do so blindingly quickly.

Humans have evolved a strategy of being trichromats, but able to enormously expand the variety of colours they can perceive by sending the signals from the different sorts of cone to the brain and combining them there. This requires a lot of brain capacity and effort, but it lets us distinguish between about 10 million colours.

The mantis shrimp has a smaller brain, and seems to follow a simpler strategy. Essentially it has a more complex retina, one that generates enough colour discrimination ‘up front’, without its brain having to process the information in the way ours would. The mantis shrimp can recognize the colours it needs to ‘at a glance’, without investing effort in combining signals from different inputs. It’s reasonable to theorize that this works faster – less to transmit to the brain, less for the brain to process. The mantis shrimp must be swift in club and claw and so speed matters.

I promise a tale of two polychromats, so what is the second sort?

Dragonflies. These are savage predators of air (as flying insects) and water (as larvae). Like mantis shrimps they are brightly coloured, almost jeweled, and they have large and conspicuous eyes.

A dragonfly perched on a leaf.

Other recent research has investigated how many different kinds of colour receptor dragonflies might have. This is more complicated because (as I understand it) there is no direct evidence of what different types of cones the insects actually have, only or what genes they have for opsins – pigments used by visual receptors. The count is 15-33, a bit a ahead of mantis shrimps. It’s been suggested that they can therefore see many more different colours than humans. But there is no direct evidence that dragonflies actually have that many different kinds of cone, and if they do, they probably can’t recognize any more different colours than we can, for the same reason a mantis shrimp can’t – they don’t have the neurological equipment (a dragonfly is too small) to carry out complicated processing of visual signals, but just rely on instant recognition of a small colour range.

It cannot be a coincidence though that predators that hunt by daylight have large eyes and good colour vision. If only we could examine the vision of a velociraptor!

While writing this post I saw a post on one of the blogs I follow (Adventures in Low Wision), which rather magically was also about the number of cones we have, and also mentioned the beloved mantis shrimp. It’s well worth reading. You can find it here.


Mantis shrimp image from http://commons.wikimedia.org/wiki/File:Mantis_shrimp_%28Odontodactylus_scyllarus%29.jpg

Dragonfly from http://commons.wikimedia.org/wiki/File:Dragonfly_9187.JPG


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The Colour of Nothing

Recently Belgian Artist Frederik De Wilde exhibited a square blacker than any human being has ever seen before. Blackboards look black but actually reflect as much as 10% of the light falling on them. De Wilde’s black square reflects 0.01% – one thousand times less.

There is an impressive image here. New Scientist magazine has described it as an attempt to paint nothing.

The work is a reflection of the celebrated Black Square that the Russian Malevich showed in St Petersburg in 1915. The image above is an image of Malevich’s work I found in Wikimedia Commons. The painting had huge influence at the time and I believe at the end of his life the artist had it hanging in his bedroom. Today it’s in a fragile state (with the black foreground crazing to reveal the white below), and in another echo from the past De Wilde’s NanoBlck-Sqr #1, which uses carbon nanotubes on a white frame, is so delicate that you are only permitted to view it under supervision.

But neither Malevich nor De Wilde have captured what nothing looks like. The blind have a better understanding, which you can share by a thought experiment.

Right now, what do you see round the back of your head?

You’ve no eyes there, so you just saw (or didn’t) nothing. And it’s not a bit like black, is it?

This might seem trivial or frivolous, but it’s not at all. I have a large blind spot (a scotoma), that occupies nearly half my visual field. People frequently ask me what I see there. They intuitively expect it to be a black patch.

But it’s not: it’s nothing. That’s very hard to explain. And impossible to paint. Even invisibility has a sort of appearance. Nothingness doesn’t. So how could it have a colour?




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