The ups and downs of children's IQs

18th November 2011 at 00:00
Believe it or not, new research shows their intelligence can rise or fall significantly over a four-year period

It will hearten all those who say selection based on a child's academic ability in early adolescence is wrong. A recent study by academics found that children's IQ scores can improve by as much as 20 points over a four-year period.

Childhood IQ scores are often used to predict education outcomes and job prospects, but assessing academic ability by testing and streaming is notoriously difficult. Now researchers at University College London (UCL) seem to have proved precisely that.

An study of 33 children aged 12-16, from high achievers at 11-plus to struggling pupils referred for assessments, showed that their IQs could rise - or fall - by up to 20 points in the four years after they were first tested.

The children were first assessed in 2004, and then again in 2008 when they were between the ages of 15 and 20. "We found a considerable amount of change in how our subjects performed on the IQ tests in 2008 compared with four years earlier," says report co-author Sue Ramsden. "Some subjects performed markedly better, but some performed considerably worse. We found a clear correlation between this change in performance and changes in the structure of their brains, and so can say with some certainty that these changes in IQ are real."

Professor Cathy Price, who led the researchers at the Wellcome Trust Centre for Neuroimaging at UCL and the Centre for Educational Neuroscience, admits it is not certain why IQ should have changed so much and why some children's performance improved while others' declined.

But it is possible, she says, that the differences are due to some of the subjects being early or late developers. She adds that education has a role to play in people's changing IQ scores. "We have a tendency to assess children and determine their course of education relatively early in life, but here we have shown that their intelligence is likely to be still developing."

Professor Price says teachers and assessors would do well not to pigeonhole pupils because they may have failed exams at 11 or performed poorly in subjects in the early stages of education. "We have to be careful not to write off poorer performers at an early stage when, in fact, their IQ may improve significantly given a few more years," she adds. "It's analogous to fitness. A teenager who is athletically fit at 14 could be less fit at 18 if they stopped exercising. Conversely, an unfit teenager can become much fitter with exercise."

The researchers measured each child's verbal IQ, which includes abilities such as language, arithmetic and general knowledge, and their non-verbal IQ, such as identifying the missing elements of a picture or solving visual puzzles.

Professor Price says changes in IQ mirror shifts in a particular area of the brain. An increase in verbal IQ correlates with an increase in the density of grey matter - the nerve cells where processing takes place - in an area of the left motor cortex of the brain, which is activated when articulating speech. And she adds that, similarly, an increase in non-verbal IQ scores correlates with an increase in the density of grey matter in the anterior cerebellum, which is associated with movements of the hand.

What the researchers are keen to point out is that the IQ and capacity of a brain is not set in stone at an early age. Earlier research by the Wellcome Trust Centre for Neuroimaging found that the hippocampus, which plays a key role in memory and navigation, has greater volume in the brains of licensed London taxi drivers, who have gained "the knowledge", memorising in detail the layout and street names of the capital city.

What the results of the study of children's IQ scores demonstrate to those who carried out the research is that an individual's intellect capacity can decrease or increase in the teenage years.

Early high-flyers, says Mrs Ramsden, can fizzle out in the same way that late developers come to the fore. "(These results) would be encouraging to those whose intellectual potential may improve and would be a warning that early achievers may not maintain their potential," she says. "The implication of our findings is that an individual's strengths and weaknesses in skills relevant to education and employment are still emerging or changing in the teenage years."


An earlier study by Edinburgh University said IQ remained stable across a person's life.

All Scottish children born in 1921 were asked to take a psychometric test in June 1932. Sixty-six years later, 199 survivors, as well as 35 others, took the 1932 test again.

The correlation between scores at the age of 11 and those at 77 was 0.63, which was later adjusted to 0.73 for the retested sample. The study concluded: "This shows mental abilities are highly stable from childhood to late life."

So why the difference between the two studies? Professor Price says that the UCL survey was able to pick out marked variables because it was smaller - and it used brain scans. "The brain scans allowed us to validate things which couldn't be measured. For them to brain scan their sample would have been hugely expensive."

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