IQ, or Intelligence Quotient, has long been considered a fairly stable measurement of a person's intellectual abilities. The results of these standardized, aged-adjusted tests have been used to predict a child's chances of succeeding in school and future job prospects.
But a new study suggests that IQ levels may actually change over time – rising in some and falling in others.
British researchers tested 33 healthy adolescents in 2004 when they were between 12 and 16 years of age. The teens repeated the test about four year later. On both occasions, MRI scans were used to collect precise measurements of their brains.
The results revealed that some subjects performed markedly better on the second test, while others did considerably worst. What's more, the scores seem to match up with observed changes in the brain scans. For instance, an increase in verbal IQ corresponded to an increase in the density of grey matter in a region of the brain associated with speech.
The researchers can't yet explain their surprising findings, which were published this week in the journal Nature. It's possible the change in scores is due to some kids being early or late bloomers, said the lead researcher, Cathy Price of the Wellcome Trust Centre for Neuroimaging at University College London. But it is also possible that education played a role in altering IQ, she speculated.
"We have a tendency to assess children and determine their course of education relatively early in life, but here we have shown that their intelligence is likely still developing," Dr. Price said. "We have to be careful not to write off poorer performers at an early stage when, in fact, their IQ may improve significantly given a few more years."