The roller-coaster teenage years can take IQs along for the ride. A
person’s IQ can nosedive and climb sky-high during adolescence, while
corresponding brain regions wax and wane in bulk, researchers report
online October 19 in
Nature.
The results suggest that the IQ number given to a child is not
immutable, as many researchers believe, says neuroscientist Richard
Haier of the University of California, Irvine. “This is an extremely
interesting paper.”
Back in 2004, Cathy Price of the Wellcome Trust Centre for
Neuroimaging at University College London and colleagues tested the IQs
of 33 healthy participants who were, on average, 14 years old. While the
teens were in the lab, structural MRI brain scans measured particular
brain regions.
About four years later, Price and her team invited the teenagers back
for a redo. Overall, IQ scores held steady: Average IQs were 112 in
2004 and 113 four years later. But when the researchers zoomed in on
individual teens, they found that about a third of the teenagers had
meaningful changes in IQ, and a handful showed dizzying climbs or
plunges.
One such plunge was 18 IQ points — which would be enough to demote a
person from genius status to merely above average. The retest also
turned up an IQ gain of 21 points — which would elevate a below-average
person to above average. Some people who scored high the first time
around scored even higher later, and some low scorers scored even
lower.
To Price and her colleagues, these results were so surprising that
they initially suspected mundane explanations such as differences in the
teens’ levels of concentration at the time of each test. But the brain
scan data argued otherwise.
The IQ changes were accompanied by changes in the brains’ gray
matter, which is made up of nerve cells. Boosts in verbal IQ came along
with denser gray matter in the left motor cortex, a part of the brain
that’s involved in speaking. And boosts in performance IQ, which
measures abilities such as understanding pictures, were accompanied by
denser gray matter in the anterior cerebellum, a part of the brain
important for movement.
These brain changes mean it’s less likely that the IQ variations
represent someone having a bad testing day, Price says. “We therefore
concluded that the fluctuations were meaningful changes in IQ, not
measurement error,” she says.
Evidence for a malleable intellect could change how people’s
abilities are evaluated, she says. For instance, it might help educators
to know that intelligence scores are still in flux during the teen
years.
Some studies, including work by Haier, have found that intense brain
training can boost gray matter, although no one knows exactly how those
brain changes relate to IQ.
Because the current study followed teens in their normal lives,
scientists don’t know what prompted the IQ and brain changes. Rapidly
developing interest in socializing, school and even sports might all
influence the brain, Haier says: “So much is going on in the teenage
years.”