Intelligence quotients (IQs) testing is controversial 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 have risen in developed nations for almost a century. But in Britain, research has found a reversal of this trend. 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.
No cause for this fall in IQs has been established: the internet, the dumbing down of education, and an obsession with exam results have been suggested. Flynn has argued that youth culture has made a contribution.