Spending more time at school may increase intelligence, according to a study of
Norwegian men.
The research, in Proceedings of the National Academy of Sciences, suggested
that an extra year in the classroom could boost IQ by nearly four points.
The authors said that extra schooling had a "sizeable effect" on IQ in early
adulthood.
But they do not know if this applies to all children, or just those in this
study.
A link between a higher IQ and more education has already been established, the
authors say.
However, determining whether spending more time in school actually improves IQ
is more difficult, as it is possible that children with a naturally higher IQ
are those who choose to spend more time in the education system.
'Sizeable effect'
Researchers from Statistics Norway, which publishes official government data,
and the University of Oslo took advantage of a natural experiment in the
Norwegian education system and its effect on 107,223 pupils.
Between 1955 and 1972 regional governments in Norway increased compulsory
schooling from seven to nine years. It meant pupils left school at 16 instead
of 14.
The effect of this forced increase in schooling was measured at the age of 19,
when the military gave all men eligible for drafting an IQ test.
The researchers reported that: "An unusually large increase in both average
education and average IQ is apparent at the same time as the reform was
introduced."
They said one additional year in school raised IQ by 3.7 points.
They added: "By exploiting the increase in schooling induced by a comprehensive
compulsory schooling reform, this study is able to uncover a statistically
significant and sizeable effect of middle school education on IQ scores in
early adulthood for Norwegian men."
The statisticians caution against drawing too many conclusions, as they admit
that the effect may only apply to Norwegian society or its education system at
the time.
However, they argue that it may be possible to improve intelligence in
adolescence.