Children who have more schooling may see their IQ improve, Norwegian researchers have found.
Although time spent in school has been linked with IQ, earlier studies did not rule out the possibility that people with higher IQs might simply be more likely to get more education than others, the researchers noted.
Now, however, "there is good evidence to support the notion that schooling does make you 'smarter' in some general relevant way as measured by IQ tests," said study author Taryn Galloway, a researcher at Statistics Norway in Oslo.
Findings from the large-scale study appear in this week's online edition of the Proceedings of the National Academy of Sciences.
In 1955, Norway began extending compulsory middle school education by two years. Galloway and her colleague Christian Brinch, from the department of economics at the University of Oslo, analyzed how this additional schooling might affect IQ.
Using military draft assessment data on men born between 1950 and 1958, the researchers looked at the level of schooling by age 30. They also looked at IQ scores of the men when they were 19.
Comparing IQ scores before and after the education reform, the average increased by 0.6 points, which correlated with an increase in IQ of 3.7 points for an additional year of schooling, Galloway said.
By looking at the reform that increased mandatory schooling and prevented people from dropping out of school after the 7th grade, it is fairly certain that the effects seen are an effect of schooling on IQ, not vice versa, she explained.