Teens’ IQ May Rise or Fall Over Time

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The brain undergoes more change in adolescence than at any other time of life, save before birth and during infancy. That may help explain why teenagers’ IQ can fluctuate significantly over time, as a new study finds, registering large enough changes to move a child from “average” to “gifted” or in the other direction, to below average intelligence.

Cathy Price, a neuroscientist at University College London, led the research, imaging the brains of 33 teens, first in 2004 when they were aged 12 to 16, then again in 2007 or 2008 when they were 15 to 20 years old. The researchers also tested the teens’ IQ.

The group’s average IQ stayed the same, but 21% of teens showed large changes, as much as 20 points. “It’s a huge difference,” Price said.

About the same number of teens saw IQ improvement as decline. “It was not the case that the young low performers got better and the young high performers averaged out. Some high performers got even better and some low performers got even worse,” says Price.

“Initially we were concerned that it was measurement error,” Price says, explaining that IQ has largely been thought to remain constant over time. “But we found that the degree to which IQ changed matched the degree to which brain structure changed. Since the two measurements were independent, this cannot be explained by error.”

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In teens whose verbal IQ changed, researchers also found brain changes in regions of the cortex related to the articulation of speech. Changes in non-verbal IQ, such as visual and spatial skills and reasoning, were connected with changes in part of the cerebellum; that region is involved in controlling learned finger movements or, more generally, the process by which a learned skill like playing the piano or driving becomes automatic.

Price notes, however, that there were probably changes in other important regions of the brain that she and her colleagues were not able to measure.

Scientists have typically have believed that IQ is determined early in life and is thereafter resistant to change. So the new research, if replicated in a larger sample, could have important implications for education, suggesting, for instance, that students who show low IQ could make great gains later on and shouldn’t be put on separate educational tracks.

Like early childhood, adolescence appears to be a “sensitive” period, during which large positive or negative brain changes could affect structure permanently.

Simply choosing to view intelligence as malleable — as this study suggests it is — can itself have large benefits. Stanford psychologist Carol Dweck has shown in multiple studies that children who see intelligence as dependent on hard work rather than innate talent tend to outperform those who view it as fixed. In one study of 373 seventh graders, those who believed intelligence could be changed raised their grades during the next two years of junior high, while those who believed intelligence was fixed did not show better performance.

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Commenting on the new research, Oklahoma University professor Robert Sternberg, who was not involved in the study, told the Guardian‘s Ed Yong that 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.”

Sternberg knows this from personal experience. As I wrote when I interviewed him for a story (paywalled article here) on the effects of labeling children for the Washington Post:

Sternberg…did poorly on IQ tests. “The teachers thought I wasn’t very bright — and that led me to meet that expectation, which led them to be happy that I met that expectation, and it became a vicious circle. The next year their expectations were a bit lower,” [he said].

Fortunately, for Sternberg, his fourth-grade teacher didn’t buy it: She saw that there was more to life than test scores, and she encouraged hard work.

As a result, Sternberg became fascinated with psychology and intelligence testing — so much so that he got in trouble in seventh grade for testing classmates himself. He ultimately became a leading expert in the field.

Perhaps the new research on the visible malleability of the teen brain will help inspire a new generation of scientists.

Maia Szalavitz is a health writer at TIME.com. Find her on Twitter at @maiasz. You can also continue the discussion on TIME Healthland’s Facebook page and on Twitter at @TIMEHealthland.