New research indicates that the average intelligence quotient (IQ) in the US has declined for the first time in nearly 100 years. But does this mean that the population of the US is actually getting dumber? Not necessarily.
Researchers at Northwestern University and the University of Oregon looked at the results of online IQ tests taken by 394,378 adults in the US from 2006 to 2018.
The team was looking to see whether they could find evidence of the Flynn effect, the idea that the IQ of a population generally appears to increase each generation. As the study authors noted: IQ scores have “substantially increased since 1932 and through the 20th century, with differences ranging from 3.0 to 5.0 IQ points”.
Instead, however, they found the opposite. Overall, the results suggest IQ points had declined over the study period, although the researchers didn't state exactly how many IQ points have dropped.
Declines were seen widely across the board regardless of age and gender, but the steepest slump was found among people with lower levels of education and younger participants aged 18 to 22.
While certain skills, like 3D spatial reasoning tests, had increased from 2011 to 2018, other skills like verbal reasoning, visual problem solving, and numerical series tests had all dropped.
The researchers didn’t explicitly look to explain the trend they sniffed out. However, they did speculate that it might have something to do with changes in education in the US.
“It could be the case that our results indicate a change of quality or content of education and test-taking skills within this large United States sample. As scores were lower for more recent participants across all levels of education, this might suggest that either the caliber of education has decreased across this study's sample and/or that there has been a shift in the perceived value of certain cognitive skills,“ the study authors write in their conclusion.
The US isn’t alone, however. A number of studies in Europe over the last two decades suggest that the Flynn effect had already stagnated or begun to reverse.
For instance, research on people in Finland suggested that IQ scores had dropped by 2 IQ points from 1997 to 2009, while in France scores declined by 3.8 IQ points from 1999 to 2009. Similar findings have also been reported in the UK, Norway, Denmark, Australia, the Netherlands, and Sweden.
No single factor can explain these complex trends, although some researchers have argued it's down to environmental factors, as opposed to genetics. These environmental factors include things such as education, nutrition, reading less, and the rise of technology.
When looking through all these statistics, it’s important to consider that IQ points aren’t perfect measures of intelligence. IQ tests attract a load of criticism because they're only concerned with a narrow set of skills and intelligence is far too complex to be precisely measured.
In 2012, a huge study of over 100,000 people concluded that most intelligence tests are fundamentally flawed as they do not take into account the complex nature of the human intellect. Their findings suggested that no single human trait, such as IQ, could explain all the variations in intelligence revealed by tests.
With all of that in mind, this latest study does still provide some food for thought.
The new study is published in the journal Intelligence.