Plastic brains – how IQ and brain structure change during the teenage years
Listen to an Interview with Professor Cathy Price
IQ - a measure of a person's general intellectual ability - is not fixed as we first thought, but instead changes as we grow and develop, new research has shown.
Previously, brain scientists and educators had thought that the intelligence of an individual, as determined by an IQ test taken at one point in time, remains stable throughout life and may be used to predict educational achievement and subsequent employment prospects.
But now neuroscientists at University College London, working with scientists at Birkbeck College, also in London, have challenged the view that IQ fluctuations may be due to variability in testing methods and discovered that IQ does change over time with these changes corresponding with alterations in brain structure.
Professor Cathy Price, from the Wellcome Trust Centre for Neuroimaging at University College London, and her colleagues recruited thirty-three healthy adolescents in 2004 when they were between 12 and 16 years old. These volunteers were tested for verbal IQ (which includes measurements of language, arithmetic, general knowledge and memory) and non verbal IQ (such as identifying the missing elements of a picture or solving visual puzzles). The researchers also took structural brains scans of the subjects using magnetic resonance imaging (MRI). This same group of students were then re-tested four years later when they were aged between 15 and 20 years old.
The researchers found that, for each individual, IQ actually changed by up to 20 points between the two testing periods. These changes could also be married up with corresponding changes in certain regions of the individuals' brains.
"What's different about our study is that we studied a sample of teenagers with a wide variability in their verbal and non verbal IQs. We noticed that some of the students had changed in IQ and brain structure from one testing time to another testing time. We were able to demonstrate that these IQ changes were meaningful because they corresponded with changes in the brain," says Professor Cathy Price.
The brain scans clearly showed that the degree to which the non-verbal intelligence changed in an individual was correlated with changes to the structure of the cerebellum, an area responsible for hand eye coordination. And the degree to which the verbal IQ had changed was correlated with changes in a region of the brain's left hemisphere known to control speech.
So what are the implications for this study? Well, the results are encouraging to those who wish that their intellectual ability might improve but also a warning against complacency, because early high-achievers are not guaranteed to remain in pole-position. The findings also raise questions over current educational policies relating to testing and streaming of school pupils.
"It [IQ] is analogous to fitness," points out Price. "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."