Different parts of our brain deal with different aspects of vision. They select and combine, and we see a picture which seems to be reality. It is only when one or two of these specialized cortical areas are damaged that the selecting and synthesizing functions of the brain are revealed. After such damage a person might be aware of colour without form or form without motion. Thus a person might be able to see a red mass but not recognize it as a bunch of roses, or be able to recognize a car but not see it as moving from one place to another. When we are seeing, different parts of our brain are used to put the picture together. What the picture means to us depends on our past experience. The retina of your eye might register a small upright rectangle with a triangle on top of it but what you see on the horizon is the huge bulk of the Canary Wharf Tower.
However, not everything we ‘see’ is experienced consciously as a picture. It seems that we have two visual modes, ‘one that allows us to consciously perceive the world and a second, subconscious mode that helps us move around in it by, say, informing a foot where to place itself.’6 Letting the conscious visual mode override the unconscious visual mode can make us stumble or drop things, while letting both modes work in harmony can mean typing fast or making a brilliant return in a game of tennis.
We learn to use both these visual modes when we are tiny babies learning to see. When we are born we do not just open our eyes and see. We open our eyes and set about learning to see the world. In the womb in the developing brain neurons divide and then migrate to their correct locations in the brain. Susan Greenfield explained,
As soon as the neurons have proliferated, migrated to the appropriate brain region, they effectively set down roots, initiate communications with neighbouring neurons by establishing a synaptic circuitry. Much of the increase in brain size after birth is actually due to the development of these connections, rather than simply to the addition of more neurons … As our development continues after birth, the jostling, restless neurons in our brain are very sensitive as they form circuits, to whatever changes, or simply signals, are imposed from the outside world. Inside the brain, right up to sixteen years of age, a bloody battle is being raged between our neurons. It is a battle for establishing connections. If a new neuron does not make contact with a target neuron, then it dies …
Another related and very important factor in determining cell survival, once contact is established between neurons, is activity, the sending and receiving of signals. This point is tragically made by the recent example of a six-year-old Italian boy. This boy was blind in one eye. Yet the cause of his blindness was a medical mystery. As far as the ophthalmologists could tell, his eye was totally normal. Eventually the enigma was solved. It finally emerged that when he was a baby, the boy’s eye had been bandaged for two weeks as part of the treatment for a minor infection. Such treatment would have made no difference to our older brains with their more established connections. But two weeks after birth the connections of the eye were at a critical period for the establishment of eye to brain circuits.
Since neurons serving the bandaged eye were not working, their normal target became taken over by nerves from the normal, working eye. In this case the neurons that were not signalling were treated as though they were not there at all: the target for these inactive, functionally non-existent neurons was readily invaded by the active brain cells. Normally this rule would be beneficial as it would mean that neuronal circuits were being established according to the working cells which reflected in turn the environmental requirements in which the person had to live. Sadly, the bandaging of the eye was misinterpreted by the brain as a dear indication that the boy would not be using that eye for the rest of his life.7
In those weeks following our birth we learn to structure space and distance as we look around us and, if we are not swaddled as many babies still are, we reach out and discover what is near and what is far and how something feels when we put our hand around it or hold it in our mouth. Once we have learned this we can look at something and know how that shape would feel even though it is too far away or too large for us to put it in our mouth or hold it in our hand.
While, through our experiences, we are learning a basic structure for our perception of space we are also having the first of a multitude of experiences which determine how our brain selects and combines to form a picture of the world. No two people ever have the same experiences, so no two people ever have the same picture of the world. If you listen to a group of people discussing an event in which they have all participated you’ll see how individual experience shapes individual perceptions.
I went with a group of friends to the Proms, where the Chinese composer Tan Dun was presenting the European première of his symphony ‘Heaven Earth Mankind’. An important part of this symphony was the Imperial Bell Ensemble of China, who perform on a set of sixty-five ancient Chinese bells made 2,400 years ago and excavated from the tomb of Marquis Yi of Zeng in 1978. The bells are amazingly wonderful and we were all entranced by them. We were also amazed and intrigued by the soloist Yo-Yo Ma, who used his cello in ways we had never seen before, and by the string section of the Scottish Symphony Orchestra, who treated their instruments as things to be slapped and banged as well as played. Moreover, behind the orchestra was the New London Children’s Choir singing as we had never heard a children’s choir sing before.
Afterwards we talked about what we had heard and seen. We all agreed that it had been a special occasion for us, but when we talked about certain details in the performance it was clear that we had each seen a different event. Although we had all watched and listened intently we could still inform one another about what we had seen and the other missed. The parents of children in the choir gave precise accounts of their child’s behaviour. The musicians in our group commented upon the structure of the symphony and the qualities displayed by the performers. I realized that I had missed the significance of the different shapes and textures of the bells and was glad to have this explained to me, but, inveterate people-watcher that I am, I had seen, and others had not, many of the interactions between the participants which were not part of the actual performance.
Every meaning we create is a selection from a vast array of possible meanings. The meanings we choose to create arise from all the meanings we have created in the past. The old saying, ‘If I hadn’t seen it I wouldn’t have believed it,’ might be correct in particular circumstances – for example, when we see an extraordinary sporting achievement or when we see an old friend act out of character, but in general the saying should be, ‘If I hadn’t believed it I wouldn’t have seen it.’ Those people who believe in astrology see in a person’s life the effect of the movement of the planets, which is something that I cannot see.
When I ask myself, ‘Why did that person do that?’ I come up with answers that have to do with the person’s feelings, desires and fears. I do not create theories that have to do with the influence of the planets or evil spirits or God’s mysterious ways, even though I am familiar with the ideas in astrology and in the various religions. However, as I make sense of any situation there are certain meanings which are not in the vast array of possible meanings presented to me because they are meanings which I could not possibly apprehend.
Some of these meanings are beyond my apprehension because I have never had the required experience to form them. I am largely ignorant of mathematics. I speak only one language. I was born at a particular time in the history of the universe and I have lived in particular places and not others. Similar restrictions apply to each of us, but, along with these, there is the restriction which our physiology imposes on us.
Each of our senses responds to some aspect of our environment in a particular way – that is, our senses respond only to change or contrast. The uniform green of a thick bush hides from our eyes a green tennis ball or a green lizard. The tennis ball is visible only when its texture is seen in contrast to the texture of the leaves; the lizard is visible only when it moves.
This necessity for contrast carries over into the meanings we create. Every meaning contains its opposite because, if the opposite did not exist, no meaning could be created.
If,