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.
Among those in the upper half of the intelligence scale, a group that is typically dominated by children from middle class families, performance was even worse, with an average IQ score six points below what it was 28 years ago.
The trend marks an abrupt reversal of the so-called “Flynn effect” which has seen IQ scores rise year on year, among all age groups, in most industrialised countries throughout the past century.
Professor James Flynn, of the University of Otago in New Zealand, the discoverer of the Flynn effect and the author of the latest study, believes the abnormal drop in British teenage IQ could be due to youth culture having “stagnated” or even dumbed down.
He used data gathered in IQ tests on UK children to examine how the country’s cognitive skills have changed over time.
He 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.
“Up until the age of nine and ten, the home has a really powerful influence, so we can assume parents have been providing their children with a more cognitive challenging environment in the past 30 years.
“After that age the children become more autonomous and they gravitate to peer groups that set the cognitive environment.
“What we know is that youth culture is more visually orientated around computer games than they are in terms of reading and holding conversations.”
He added that previous studies have shown that IQ increases as teenagers move into adulthood, entering university or starting work.
Professor Flynn also believes that the larger drop in IQ among the upper half of the ability range could be due to effects of social class.
He said: “IQ gains are typically correlated by class, but the results in this case are very mixed. Maybe the rebellious peer culture of the lower half of British society has invaded the peer culture of the upper half.
“It could be the classes in the upper half were insulated from this rebellious peer culture for a time, but now it is universal.”
His research, which is presented in a paper published online by the journal Economics and Human Biology, also refutes the commonly held belief that increases in IQ over time are a result of improving nutrition.
Previous research has suggested that using text messages and email causes concentration to drop, temporarily reducing IQ by 10 points, while smoking marijuana has been associated with a four-point drop in IQ.
IQ, or intelligence quotient, is normally expressed as a single numerical score, with 100 being the average.
Professor Flynn’s study was conducted using a respected IQ test known as Raven’s Progressive Matrices. Questions involve matching a series of patterns and sequences, so that even people with no education can take the test.
Dr John Raven, the Edinburgh-based psychologist who invented the test, said he was surprised by the fall in teenage IQ.
He said: “IQ is influenced by multiple factors that can be dependent upon culture, but the norms tend to be very similar across cultures even in societies that have no access to computers and television.
“What we do see is that IQ changes dramatically over time.”
He cautioned that since the study did not record the social class of participants, “it is very difficult to make inferences about how changes within social classes can impact on these changes in IQ”.
Richard House, a senior lecturer in therapeutic education at Roehampton University and a researcher into the effects of television on children, said: “Taking these findings at face value, it appears that there is something happening to teenagers.
“Computer games and computer culture has led to a decrease in reading books. The tendency for teachers to now ‘teach to the test’ has also led to a decrease in the capacity to think in lateral ways.”
[Editors Note: The full text of “Requiem for nutrition as the cause of IQ gains Raven’s gains in Britain 1938 to 2008,” by James R. Flynn, is available in both PDF and HTLM formats here. There is a charge.]
University of Otago, Box 56, Dunedin, New Zealand
Received 10 January 2009;
accepted 11 January 2009.
Available online 2 February 2009.
The hypothesis that enhanced nutrition is mainly responsible for massive IQ gains over time borrows plausibility from the height gains of the 20th century However, evidence shows that the two trends are largely independent. A detailed analysis of IQ trends on the Raven’s Progressive Matrices tests in Britain dramatizes the poverty of the nutrition hypothesis. A multiple factor hypothesis that operates on three levels is offered as an alternative instrument of causal explanation.
The Raven’s data show that over the 65 years from circa 1942 to the present, taking ages 5 to 15 together, British school children have gained 14 IQ points for a rate of 0.216 points per year. However, since 1979, gains have declined with age and between the ages of 12 to 13 and 14 to 15, small gains turn into small losses. This is confirmed by Piagetian data and poses the possibility that the cognitive demands of teenage subculture have been stagnant over perhaps the last 30 years.
Keywords: nutrition and IQ; recent IQ gains in Britain; intelligence; causes of IQ gains over time; Raven’s Progressive Matrices
JEL classification codes: I10; I312
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