Intensive pre-school tuition can halve the incidence of mental retardation among the poorest and most deprived children.
The most vulnerable children can show gains in intellectual performance of between 15 and 30 IQ points, according to Dr Craig Ramey, of the University of Alabama.
But help has to be given fast. "Intervening at the kindergarten stage has only a minuscule effect, compared to intervening in the first year of life," he warned.
Dr Ramey said best results came from remedial programmes which began with babies as young as six weeks.There appeared to be a critical stage in the development of children's brains where, if they received the right environmental stimulation, the beneficial effects would last throughout life.
Dr Ramey was speaking at the annual meeting of the American Association for the Advancement of Science in Baltimore yesterday.
The evidence that environmental stimulation could improve IQ and cut the incidence of mental retardation refutes the fashionable view that intelligence is innate, fixed by the genes, and cannot be altered significantly by teaching. "There is now substantial evidence that intellectual development is malleable in the positive sense. Early experience is critical for full development of intellectual capacity," Dr Ramey said.
Professor Christine Hohmann, of Johns Hopkins University in Baltimore, warned the meeting: "We have to be cautious not to ascribe too much of behaviour to genetics. Genes cannot act independently of their environment."
Studies of brain development in animals also show an interaction between genes and the environment. According to Dr Joanne Berger-Sweeney, of Wellesley College, Massachusetts, if a young animal is under stress, that "can impact on its genes and how they are expressed and the way the animal will behave throughout its life".
The evidence for the benefits of early help for children had been borne out in more than 20 studies, Dr Ramey said, involving more than 1,000 children. However, Dr Ramey conceded that the intensive programme he had devised could cost $10,000 a year.
This is twice as much as the controversial "head-start" programmes set up to try and cut juvenile delinquency in some US cities. Dr Ramey said his programme started much earlier - at six weeks rather than four years - lasted longer each day and for more of the year, and used highly professional teachers.
But Professor Joseph Graves, of Arizona State University, recalled an old saying. "If you think education is expensive then you should see the price of ignorance," he said.Reuse content