Middle-class teenagers are less intelligent than a generation ago due to the dumbing down

of youth culture and school tests, a new study suggests. IQ tests show that scores for the average 14- year-old have dropped by more than two points between 1980 and 2008. For those in the upper half of the intelligence scale--a group typically dominated by the children of middle-class families-- average IQ scores were six points down on 28 years ago. It is the first time IQ scores have fallen for any age group during the past century.

Leisure time is increasingly taken up with playing computer games and watching TV instead of reading and holding conversations. Education experts said a growing tendency in schools to "teach to the test" was affecting youngsters' ability to think laterally. Other studies have shown how pervasive teenage youth culture is, and what we see is parents' influence on IQ slowly diminishing with age. Previous studies have claimed that using text messages and email can temporarily reduce IQ by causing concentration to drop, while smoking marijuana has also been linked with a decline in IQ.