Brave new world: Born stupid - text only -

• The blueprint brain

• Making connections

• The importance of nurture

• Old dogs and new tricks

The newborn baby is complete in the smallest detail from its first fine hairs to its tiny toes. But there's something missing: it has only half a brain. The other half — the half responsible for all but the most basic life-supporting functions — has yet to be formed. And exactly how it is formed is dependent on what happens to the baby in the first few years of its life.

We are not simply pre-programmed with a fixed quota of intelligence, an emotional nature, and certain physical abilities. These defining attributes are largely carved out for us, after birth, by our early experience.

• The blueprint brain
What the newborn baby does have is a skull packed with brain cells, or neurons — 100 billion of them — loosely laid out in a structure that reflects our genes' 'best guess' at what we will need in the life to come. In the womb, spontaneous waves of electrical currents pass along these tentative neural pathways, forming basic networks of connected brain cells. At this stage, the blueprint brain is on standby, and the electrical currents appear to be testing our potential for circuitry.

• Making connections
Shortly after birth, these 100 billion neurons become the focus of a biological explosion. They create trillions of new connections to each other. Each neuron connects to as many as 15,000 others, making more connections than we can possibly use. Now the brain is wired and ready to be configured by all of the experiences life brings to it.

As the baby encounters the world outside the womb, its experiences stimulate electrical impulses which route themselves through the now mind-bogglingly complex connections in the brain. Over time, and through repeated experience, routes travelled by these electrical impulses become defined highways in the brain. Other routes, tried once and forgotten, or never tried at all, will eventually be lost through disuse.

So, the greater the range of experience, it seems, the greater the number of new routes that are formed in the brain, defining an individual's abilities for the rest of his or her life.

• The importance of nurture
The discovery that the brain is only fully formed after birth, through experience, provides a strong argument for the importance of nurturing a young child. Deprived of a stimulating environment, the brain does not develop to its genetic potential. This is true for emotional, visual, linguistic and intellectual ability. Children who are not encouraged to play, or are rarely touched, have brains that are 20-30% less developed than is normal for their age.

Children from deprived backgrounds are at the greatest risk of not receiving the nurture they require. Parents or carers who are struggling to provide food and shelter for their families may not have the time or the energy to provide adequate stimulation.

In the 'Abecedarian Project', run by the University of North Carolina, children from mothers with low levels of income and education were randomly divided into two groups. One group received an intensive five-year programme of child care and activities, starting a few months after birth. The other group received only free baby food and nappies. After three years, the children who had been given extra stimulation had an average IQ of 105, while the other group averaged only 85. And the effects of the programme were enduring for the individuals who received it.

However, the wrong kind of stimulation can also severely inhibit the genetic potential of the brain. If there is repeated abuse or trauma the routes in the brain that experience fear become fixed. As a consequence, traumatised children continue to show the physical symptoms of fear even in the absence of a threat. Such children have high heart rates at rest, high levels of stress hormones in their blood, and difficulty sleeping. In later life these defensive patterns can lead to emotional, behavioural, and learning problems.

• Old dogs and new tricks
The brain's capacity to form new structures does not last forever, though we retain a limited ability to learn. At the age of two, a child's brain contains twice as many connections between neurons — and consumes twice as much energy — as the brain of a normal adult. At around the age of 10, we begin to lose more connections than we create. By the age of 18, our brains have pared down their routes to keep only those that we regularly use.

It is thought that there are windows of opportunity in which the brain can use certain types of input to create lasting structures. Once these windows are closed, it is far more difficult to master the related skills.

For example, children born with a cataract on one eye become permanently blind in that eye if the cataract is not promptly removed. The brain requires sensory stimuli from the eye to form the necessary routes between neurons (see Sight and speech). If those structures aren't formed, the brain won't be able to see with that eye, even if the cataract is removed later in life and there is nothing else wrong with the eye.

Similarly, scientists believe that the ability to develop language may be related to age. The window for acquiring syntax may close at around the age of five or six, while the window for learning new vocabulary may never close. Before the age of six, children tend to learn a second language easily and speak it without an accent. But after this time it becomes increasingly difficult, and in adulthood learning a new language is usually a struggle.

Sight and speech | Primitive brain | First year

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