New research shows that the average intelligence quotient (IQ) in the US has dropped for the first time in nearly 100 years.
Researchers at Northwestern University and the University of Oregon studied the results of online IQ tests taken by 394,378 adults in the United States from 2006 to 2018. The team was exploring whether they could find evidence of the Flynn effect, the idea that a population’s IQ usually increases with each generation.
However, they found the opposite. Overall, the results showed that IQ scores dropped over the course of the study, but the researchers did not specify exactly how many IQ scores dropped.
The declines appeared to be independent of age and gender, but the steepest decline was found among people with lower levels of education and younger participants aged 18 to 22 years. Certain skills, such as 3D spatial reasoning tests, rose from 2011 to 2018, while other skills, such as verbal reasoning, visual problem solving, and numerical series tests, all declined.
The researchers did not try to clearly explain this trend they found. However, they speculate that this may have something to do with changes in education in the US.
“Our results may indicate a change in quality or content in education and test-taking skills in this large sample of the United States,” the study authors wrote in the research results. As scores are lower for newer participants at all education levels, this may indicate either a reduced quality of education in the sample of this study and/or a shift in the perceived value of certain cognitive skills.”
Not just the USA…
The United States is not the only country with these results. A number of studies conducted in Europe over the last two decades show that the Flynn effect has already stopped or is beginning to reverse.
For example, studies in Finland suggested that IQ scores dropped by 2 IQ points from 1997 to 2009, while in France they dropped 3.8 IQ points from 1999 to 2009. Similar findings were reported in England, Norway, Denmark, Australia, the Netherlands and Sweden.
Some researchers say this is due to environmental factors as opposed to genetics, but no single factor can explain these complex trends. These environmental factors include many different things, such as education, nutrition, less reading, and the rise of technology.
Also, when reviewing all these statistics, it’s important to remember that IQ scores are not perfect measures of intelligence. IQ tests have received a lot of criticism because they only deal with a limited set of skills and intelligence is too complex to be measured with precision.
A large 2012 study of more than 100,000 people concluded that most intelligence tests are fundamentally flawed because they didn’t take into account the complex nature of human intelligence. The findings suggested that no single human trait, such as IQ, could explain all the variations in intelligence revealed by the tests.
The study was published in the journal Intelligence.
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