The mysterious Flynn effect, which I wrote about here, seems to have gone into reverse for British teens.

Tests carried out in 1980 and again in 2008 show that the IQ score of an average 14-year-old dropped by more than two points over the period.

Yoof culture seems to be the culprit:

[Flynn] found that while children aged between five and 10 saw their IQs increase by up to half a point a year over the three decades, teenagers performed less well.
“It looks like there is something screwy among British teenagers,” said Professor Flynn. “While we have enriched the cognitive environment of children before their teenage years, the cognitive environment of the teenagers has not been enriched.” Other studies have shown how pervasive teenage youth culture is, and what we see is parents’ influence on IQ slowly diminishing with age.

The scientifically interesting question here is whether this is just part of the “buffeting” that IQ and personality traits go through in late childhood and adolescence, before stabilizing at a more-heritable level in adult life, or whether the effect is permanent. We’ll know that a few decades hence when the longitudinal studies come out.

The socially and politically interesting question is how the bottom IQ quartile finds useful work and life purpose in a post-industrial welfare state.