Brave new world: Sight and speech - text only -

• Learning to see

• Learning to communicate

• Learning to see
Learning to see is one of the few skills that children can develop without any need for deliberate stimulation. But this does not mean that babies are born with 20:20 vision. Before the brain has fully wired its neuron routes for sight, babies cannot see clearly. Although their eyes are functioning, turning light into electrical signals, the fact that the brain is only partially formed means that the cerebral cortex cannot translate the signals into an image. Where one object begins and another ends is not clear.

Babies do have the ability to distinguish between different colours and shades. Their eyes are attracted to high-contrast borders (black and white stripes have 100% contrast), which they can see easily, and focusing on such lines will help their sight to develop. And they can also see far subtler shades, for example, shades of grey with only a 5% contrast between them. By the age of nine weeks, a baby's ability to distinguish between shades has increased tenfold.

Newborn babies can also distinguish colours of equivalent brightness from as early as two weeks old, though it may take them longer to distinguish between subtler colour differences, for example, orange and red.

Babies have to learn to co-ordinate both their eyes. Initially one eye may wander, or the eyes may point in different directions. But by the age of three months, most babies have developed control of both their eyes. This co-ordination is necessary for seeing in three dimensions. Once babies can co-ordinate their eyes, visual experience teaches the brain fine depth perception.

Co-ordination is also necessary to track moving objects. Newborn babies can follow an object that is clearly contrasted to its surroundings if they are not distracted by other things and if the object is large enough and moving slowly enough. However, babies' eyes move jerkily, and it is not until around the age of three months that they begin to track slowly moving objects smoothly.

• Learning to communicate
As their cerebral cortex grows, babies begin to learn from experience, and they start to communicate long before they can actually speak. Crying, for example, is a reflex-driven way of getting their parents to notice them. But as they grow older, they begin to develop more subtle ways of communicating. They learn that smiling is appreciated and is likely to get them plenty of attention. It also encourages adults to talk to them. Although the baby cannot make sense of adult patterns of speech, the more the baby communicates, the closer it gets to speaking and understanding.

Unlike learning to see, learning to speak is a skill that requires stimulation. Fortunately this stimulation is normally plentiful — indeed providing it seems to be instinctive. Parents, other adults, and even older siblings speak to babies in a particular way, often called 'Parentese'. Parentese involves an exaggerated, sing-song pattern of speech. Pitch, speed and melody are altered, and there is frequent repetition of the three vowel sounds that are the most important components of all languages — 'e' as in 'feed', 'o' as in 'pot', and 'oo' as in boot. All other vowel sounds are essentially mixtures of these 'super-vowels'.

Studies of mothers from America, Russia and Sweden found that all mothers spoke to their infants in Parentese, exaggerating the super-vowels. It is thought that the repetition of these vital sounds helps an infant to tune into them and so acquire the essential building-blocks of language.

Sight and speech | Primitive brain | First year

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