Body
Story
Brave
new world: Sight and speech
SSight
and sp
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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