Average IQ is falling in Britain and beyond, explains Philip Hunterby Philip Hunter / March 21, 2012 / Leave a comment
Back when Britain was brainy: applicants for the Mensa exam gather at the Russell Hotel in 1961
Intelligence quotients (IQs) have risen in developed nations for almost a century. This phenomenon, named the “Flynn effect” after the New Zealand intelligence researcher James Flynn, was first identified in 1984 in the United States. It has been found to occur in all developed nations, and some others as well. The received wisdom became: IQs always go up. But this trend seems to be stopping and even reversing in some countries, research in Britain, Denmark and Norway has shown. It is discomfiting to find intelligence in decline. There is a strong association between a nation’s IQ, its prosperity and health.
IQ testing is contentious and regarded by some as a crude indicator of ability or potential. When comparing nations, measured average IQ tends to be affected by class, nutrition, and cultural factors including education. There is also disagreement over the influences of nature and nurture.
IQs are collated such that the average test score is 100. The standard deviation—a statistical measure of the variation within a group—is set at 15. This means that if you score 115, you are one standard deviation from the mean; 130, two standard deviations, and so on. The Flynn effect is determined by asking subjects to sit old IQ tests. The finding has been that the average score of groups who take older tests is more than 100, a disparity that suggests rising average intelligence. The rate of increase varies between nations, but on average, IQ scores have risen by three points per decade.
But in Britain, research has found a reversal of this trend. This has also been the case in other nations, including Norway and Denmark (research is not extensive, but the implication is that declines may be occurring more widely). A study in 2009 led by James Flynn himself and published in Economics & Human Biology compared IQ scores obtained by British teenagers in 1980 and 2008, using the same test. The average had declined by two points on average, but by as much as six points among teenagers in the top half of the IQ scale, a fall that wiped out the previous two decades of gains in that group. This added weight to a 2005 study on a sample of 500,000 young Danish men, tested between 1959 and 2004, showing that performance peaked…