blindness, recovery from The English philosopher John Locke (1632–1704) received a celebrated letter from his friend William Molyneux, posing the question:
Suppose a man born blind, and now adult, and taught by his touch to distinguish between a cube and a sphere of the same metal, and nighly of the same bigness, so as to tell, when he felt one and the other, which is the cube, which is the sphere. Suppose then the cube and the sphere placed on a table, and the blind man made to see: query, Whether by his sight, before he touched them, he could now distinguish and tell which is the globe, which the cube? To which the acute and judicious proposer answers: ‘Not. For though he has obtained the experience of how a globe, and how a cube, affects his touch; yet he has not yet attained the experience, that what affects his touch so or so, must affect his sight so or so…’

Locke comments (in Essay Concerning Human Understanding, 1690) as follows:
I agree with this thinking gentleman, whom I am proud to call my friend, in his answer to this problem; and am of the opinion that the blind man, at first, would not be able with certainty to say which was the globe, which the cube…

It might seem a simple matter to test this by rearing animals in darkness, to deny them vision, for months or years, then discover what they see when given light. A. H. Reisen found severe behavioural losses in such experiments; but they might have been due to degeneration of the retina (found to occur in darkness, though less with diffusing goggles) and also to the remarkably passive state of animals, especially monkeys, reared in the dark. It is not acceptable, of course, deliberately to bring up human babies in the dark; but there are cases of adult recovery from blindness. Can these tell us how human perception develops — and answer Molyneux's question?

Some of the reported cases are much as the empiricist philosophers expected; seeing little at first and being unable to name or distinguish between even simple shapes. Sometimes there was a long period of training before the person came to have useful vision, which indeed in many cases was never attained. It is important to note, however, that the reported cases do not all show extreme difficulty or slowness in coming to see. We should also remember that the early surgical operations to restore sight greatly disturbed the optics of the eye, so there could not have been a useful image on the retina until there had been considerable time for the eyes to heal. This was a particular problem in the early cases, in all of which the lens inside the eye was removed, to treat cataract (clouding of the lens). Treatment of the other kind of operable blindness — opacity of the cornea — by corneal transplantation, gives an adequate retinal image far sooner.

The case of SB

Perhaps the best studied case was a person known by his initials, SB, who, following a life of blindness, was given corneal transplants when he was 52. When the bandages were first removed from his eyes, SB heard the voice of the surgeon. He turned to the voice, and saw nothing but a blur. He realized that this must be a face because of the voice, but he could not see it. He did not suddenly see the world of objects as we do when we open our eyes, but within a few days he could use his eyes to surprisingly good effect. He could walk along the hospital corridors without recourse to touch; he could even tell the time from a large wall clock — having all his life carried a pocket watch, with no glass, so that he could feel the time by touching its hands, as he demonstrated with great skill. This was the first intimation that he could use his earlier touch-knowledge for his new-found vision.

When SB left the hospital, we ( R. I. Gregory and J. Wallace) took him to London and showed him many things he had not known from touch. At the zoo, to our surprise, he was able to name most of the animals correctly. However, he had stroked pet animals when a boy, and had enquired how other animals differed from the cats and dogs he knew by touch. This use of intelligent inference effectively enhanced his vision. We tried to discover what his visual world was like by asking him questions and giving simple perceptual tests. We found that his perception of distance was peculiar, and this is true of other, earlier cases. He thought he would just be able to touch the ground below his window with his feet if he hung from the sill with his hands; but the distance was at least ten times his height. On the other hand, he could judge horizontal distances quite accurately, presumably by knowledge from walking.

Although his perception was demonstrably peculiar, he seldom expressed surprise. He drew a very odd elephant (Fig. 1) just before we showed him one at the zoo; but then he said it looked much as he expected it would. For one object he did show real surprise — an object he could not have known by touch — the quarter moon. From this common description, and his knowledge that the whole moon is round, he thought it would look like a quarter piece of cake!

SB never learned to read by sight (he read Braille, having been taught it at the blind school) but he could immediately recognize capital letters and numbers by sight. This so surprised us we could hardly believe he had been blind. It turned out, from the school records, that he had been taught upper case though not lower case letters, and numbers, by touch at the blind school. The children were given raised letters on wooden blocks to learn by active touch. The children were not given lower case letters to learn, presumably because they were seldom used for touchable brass plates, and so on. He read upper case letters immediately by sight, but it took him a long time to learn lower case letters, and he never managed to read more than simple words. This finding, that he could immediately read letters visually, which he had already learned by touch, clearly showed that he was able to use previous touch experience for his new-found vision. This indicates that the brain is not so departmentalized as sometimes thought. There seems to be a general knowledge-base available to all the senses. But this makes these findings of less obvious relevance to the question of how human infants come to see.

SB's use of early touch experience shows in his drawings. The series of drawings of buses (in Fig. 2) illustrate how he was unable to draw things he did not already know by touch. In the first drawing the wheels have spokes. The wheels of buses and other vehicles did indeed have spokes when he was a boy, presumably known to him by exploratory touch. The windows also seem to be represented as he knew them by touch from the inside. Most striking is the complete absence of the front of the bus, which he would not have been able to explore with his hands, and which he was still unable to draw 6 months or indeed a year later. The gradual introduction of writing in the drawings indicates visual learning.

We saw in a dramatic form the difficulty that SB had in trusting and using his vision — when crossing a busy road. Before the operation he was undaunted by traffic; but afterwards, it took two of us holding him on either side to force him across: he was terrified as never before in his life.

Since he was interested in tools, we showed him a simple lathe (a tool he had wished he could use) in a glass case at the Science Museum in London. With the case closed he was quite unable to say anything about it, except that the nearest part might be a handle (which it was), but when he was allowed to touch it, he closed his eyes and placed his hands on it, and immediately said with assurance that it was a handle. He ran his hands eagerly over the rest of the lathe, with his eyes tight shut for a minute or so; then he stood back a little, and opening his eyes and staring at it he said: ‘Now that I've felt it I can see.’

Paradoxically, people whose sight has been restored commonly complain of depression. They need very special care. Many of the findings with SB have been confirmed. Alberto Valvo in 1971 described extraordinary operations in Italy that sound like a Greek myth. The sight of six patients (including a philosopher) was restored by implanting into the eye an acrylic lens, set like a jewel in a piece of tooth (to avoid rejection of the acrylic). Valvo found that earlier experience of letters by touch gave immediate visual recognition of letters. There are new cases of children in Japan, being intensively studied.

It is extremely difficult if not entirely impossible to extrapolate from these cases to the question of what and how babies see. The cases are interesting and dramatic, but they tell us little about the world of the infant, for adults with restored vision are not living fossils of babies. However, the philosophers did not guess there would be transfer of knowledge from touch to new-found vision. So we have learned something surprising and interesting from these rare dramas.

Richard L. Gregory

Bibliography

Gregory, R. L. and and Wallace, J. (1963). Recovery from early blindness: a case study. Exp. Soc. Monogr, 2. Heffers, Cambridge. (Reprinted in: Gregory, R. L. (1974). Concepts and mechanisms of perception. Duckworth, London.)
Senden von, M. (1960). Space and sight, (trans. P. Heath ). Methuen/Free Press, London.
Valvo, A. (1971). Sight restoration and rehabilitation. American Foundation for the Blind, New York.

See also blindness; vision.