The Intelligent Quotient (IQ) test has been in existence for almost a hundred years. However, there has always been controversy over what it actually measures. Do IQ scores capture a person's intellectual capacity, which remains stable over time, or is the test really a measurement that is subject to fluctuations?
In a recent issue of the journal Nature, researchers at University College London reported significant fluctuations in the IQs of a group of British teenagers. In a paper entitled, "Verbal and Non-Verbal Intelligence Changes in the Teenage Brain", the researchers tested 33 healthy adolescents between the ages of 12 and 16 years. They repeated the tests four years later and found that some teens improved their scores by as much as 20 points on the standardized IQ scale, while test scores for others went down by a similar amount.
"We were very surprised," says researcher Cathy Price, who led the project. "We had expected changes of a few points, but we had individuals that changed from being in the 50th percentile, with an IQ of 100, to being in the 33rd percentile, with an IQ of 127."
Price and her colleagues used neuro-imaging techniques to confirm that these big fluctuations in performance were not random. They evaluated scans of the teenagers' brains in the early teen years and compared them with scans from their later teen years.
"We were able to see that the degree to which their IQ had changed was proportional to the degree to which different parts of their brain had changed," explains Price. "For example, an increase in verbal IQ score correlated with a structural change in the left motor cortex of the brain that is activated by speech."
There are lots of factors that may explain changes in IQ. Though this study did not attempt to nail them down, lots of prior research has found that educational environment is key. Some researchers have even found that rigorous academic curricula can lead to improved IQ scores.
Teens' personalities, work ethic and the home environments are important, too. "There's a lot of variability in neural development during adolescence and in young adulthood as well," says Stephen Ceci, a professor of developmental psychology at Cornell University. He says this study should caution educators and parents against assuming that a low or high IQ score, measured at one particular time, is a reflection of what an individual is capable of.
However, many researchers still say there's a large body of evidence to suggest that IQ scores do reveal something essential about a child's intellectual capability. But Ceci is convinced that one test is not enough to accurately assess a person's talents or future potential, as demonstrated by this study.