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Researchers led by Robert Plomin of the Institute of Psychiatry in London obtained intelligence scores for 7,000 seven-year-olds based on verbal and non-verbal reasoning tests.
They also took DNA samples from the children in the hope of identifying genetic differences between the high and low scorers.
The huge trawl identified 37 variants in six genes that appear to play some role in differences in intelligence.
But the individual effects of these genes was barely detectable.
Together they account for just one percent of the variation in intelligence between individuals.
Upbringing plays a role
Previous research, based on twins and adopted children, suggests
that about half of the variation of intelligence is due to upbringing
and social factors, and the rest is inherited.
Even though the genetic link to intelligence is proving so elusive, that doesn't mean that this 50-50 proportion should be reviewed, New Scientist says.
It simply implies that a complex trait like intelligence clearly results from the cumulative effect of a wide combination of genes, rather than individual ones, it says.
"Intelligence is a function of the way the brain is put together, and at least half of our genome contributes in some way or another to brain function, which means that in order to build a human brain, you need thousands of genes to work together," New York University psychologist Gary Marcus told the publication. – (Sapa/AFP)
Read more:
7 ways for young children to be smart
November 2007
