IQ Can Change Significantly During Teen Years

New research funded by the Wellcome Trust suggests that IQ scores in teenagers can dramatically change in conjunction with changes that occur in the brain, according to various media reports.

IQ, the standard measure of intelligence, has been thought to remain stable across a person´s life, and childhood scores are often used to predict education outcome and job prospects as an adult. However, based on findings from the study, researchers caution using the 11+ exam for grammar school entrance to predict academic ability.

“A testing industry has developed around the notion that IQ is relatively fixed and pretty well set in the early years of life. This study shows in a compelling way that meaningful changes can occur throughout the teenage years,” Robert Sternberg from the Oklahoma State University, who studies intelligence but was not involved in the research, told the Guardian.

“People who are mentally active and alert will likely benefit, and the couch potatoes who do not exercise themselves intellectually will pay a price,” he added.

The researchers found that mental ability of teenagers can improve or decline on a far greater scale than previously thought. Tests conducted on teenagers at an average age of 14 and then repeated at an average age of 18, showed improvements — and deterioration.

These results have implications for how pupils are assessed, and the age at which decisions about their futures are made.

The study, led by Professor Cathy Price from the Wellcome Trust Center for Neuroimaging at University College London, and published in the journal Nature, involved 19 boys and 14 girls, all undergoing a combination of brain scans and verbal and non-verbal IQ tests in 2004, and then again in 2008.

“We found a considerable amount of change in how our subjects performed on the IQ tests in 2008 compared to four years earlier,” explained UCL´s Sue Ramsden, co-author of the study. “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.”

Price noted that the average of all scores stayed the same across the 4-year period, but individual scores rose or fell by as many as 21 points, enough of a difference to either take a person of “average” intelligence to “gifted” status, or vice versa.

The results showed that a change in verbal IQ was found in 39 percent of the teens, with 21 percent showing a change in “performance IQ” — a test of spatial reasoning.

“On average it all washes out, but there are fluctuations from individual to individual,” Price told Guardian reporter Ed Yong.

The teens split evenly between those whose IQ improved and those whose IQ worsened. “It was not the case that young low performers got better, and the young high performers averaged out. Some highs got even better, and some lows got even worse,” Price noted.

The brain scans found drifting IQ mirrored by changes in density of nerves and other cells in parts of brains, suggesting drifts are real changes in ability, not varying concentration, mood or motivation.

The findings are seen to have greater validity because for the first time the variations in IQ correlated with changes in two particular areas of the brain.

Shifts in verbal IQ — including memory, vocabulary, arithmetic and general knowledge — were reflected in the left motor cortex, the area of the brain used for speech. Shifts in non-verbal IQ — problem solving and the ability to spot patterns — came with changes in the anterior cerebellum, which correlates to hand movements.

“We have a tendency to assess children and determine the course of their education relatively early in life,” said Price in a press release. “But here we have shown that their intelligence is likely to be still developing.”

“We have to be careful not to write off poorer performers at an early age when in fact their IQ may improve significantly given a few more years,” she added.

Price said it is not clear why IQ should have changed so much and why some people´s performance improved whilst others´ declined. It is possible that the differences are due to some of the subjects being early or late developers, but it is equally possible that education played a role in changing IQ, and this has implications for how schoolchildren are assessed.

The researchers did not seek to understand the causes of these changes.

“The question is, if our brain structure can change throughout our adult lives, can our IQ also change?” asks Price. “My guess is yes. There is plenty of evidence to suggest that our brains can adapt and their structure changes, even in adulthood.”

One of Wellcome Trust´s biggest strategic challenges is ℠understanding the brain.´ It funds a portfolio of neuroscience and mental health research. Scientists at the Wellcome Trust Center for Neuroimaging study higher cognitive function to understand how thought and perception arise from brain activity, and how such processes break down in neurological and psychiatric disease.

“This interesting study highlights how ℠plastic´ the human brain is,” said Dr John Williams, Head of Neuroscience and Mental Health at the Wellcome Trust. “It will be interesting to see whether structural changes as we grow and develop extend beyond IQ to other cognitive functions. This study challenges us to think about these observations and how they may be applied to gain insight into what might happen when individuals succumb to mental health disorders.”

Future work may focus on how adaptable the brain may be beyond teenage years, and the implications for tackling mental diseases and other neurological conditions.

The study contradicts a long-standing view of intelligence as fixed. The study contradicts a long-standing view of intelligence as fixed. Alfred Binet, father of modern intelligence tests, believed mental development ended at 16, while child psychologist Jean Piaget thought it ended even earlier. 

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