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IQ, or intelligence quotient, has been thought to be unchanging over the course of a lifetime.
But researchers with the Wellcome Trust Centre for Neuroimaging at University College London have found that IQ can rise and fall in teenagers. Using magnetic resonance imaging (MRI) scans, they showed that ups and downs in verbal and nonverbal IQ correlated with changes in brain structure.
The team's study was released Wednesday by the journal Nature.
Professor Cathy Price and colleagues administered IQ tests and MRI scans to 33 healthy teens -- the first time in 2004, when the kids were 12 to 16 years old, and then a second time in 2007-08, when they were age 15 to 20. They found changes in individual subjects' performance on the tests, with verbal IQ, nonverbal IQ and composite IQ fluctuating up or down, in some cases around 20 points. In all, 39% of the sample had a change in verbal IQ, 21% in nonverbal IQ and 33% in composite IQ.
Studying the MRI scans, the team discovered that changes in verbal IQ tracked changes in gray matter density and volume in a portion of the left motor cortex that is activated by speech. Changes in nonverbal IQ were correlated with gray matter density in the anterior cerebellum, which is associated with hand movement.
Acknowledging this plasticity in the developing brain could have implications for education, the researchers said in a statement.
"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 still be developing," Price said. "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."