LOS ANGELES — If your teenager could use a few more IQ points, Norwegian scientists have some good news: It may not be too late for junior to get them.
Many researchers now agree that mental stimulation in one's early years helps IQ to develop, but there is no such consensus that education — or anything else — can boost the IQ of older kids. Studies have seen correlations between a person's total years of schooling and his or her IQ, but there's no good way to tease out the cause and effect. It could be that extra school raises IQ, but it's just as likely that those with higher IQs to start with are inclined to stay in school longer. It's also possible that some other trait, such as family income, influences both IQ and length of education at the same time.
In an ideal world, researchers would divide students into groups, give some of those groups a few extra years in the classroom and then measure everyone's IQ. If additional education was indeed an intelligence booster, then the students who spent more time in school would have higher IQs, on average, than the students who spent less time in school.
It turns out that the government of Norway conducted just such an experiment — albeit unwittingly. From 1955 to 1972, the Norwegian government required schools to increase the number of years of mandatory schooling from seven to nine. This meant that students who used to be done at age 14 now remained in the classroom until age 16. School districts didn't implement the change all at once but rolled it out over many years. This resulted in a data set that allowed researchers to slice and dice the figures in many ways — to check their work, in other words.