Teen brains’ growing pains

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.”