by Dr. Joseph Mercola, Mercola.com
Intelligence quotient (IQ) scores, which had been rising for decades throughout the 20th century, are now on the decline, and researchers with the Ragnar Frisch Center for Economic Research in Norway set out to determine why. The increasing trend, a phenomenon known as the Flynn effect, peaked in the 1970s and has been falling since. In fact, when the Norwegian researchers analyzed IQ scores from 730,000 men born between 1962 and 1975, IQ scores rose by about 3 percentage points a decade.
Then, beginning with those born after 1975, they started to decline. IQ scores have often been tied to genetic factors, and it was long believed that people with higher IQs would have children with higher IQs and also that people with lower IQs would have more children (known as the dysgenic fertility theory), leading to an eventual lowering of IQ scores across the population.
But the Norwegian study challenges both of these assumptions, suggesting instead that declining IQ scores have little to do with genetics and everything to do with the environment.
What made the study particularly interesting wasn’t only the reveal that IQ scores are on the decline. Because the researchers analyzed IQ scores of brothers, they were able to spot differences in IQ scores among families. Surprisingly, brothers born to the same parents often had significantly different IQ scores, suggesting an environmental factor — not a genetic one — was causing the disparity.
Also revealing, parents with higher IQs tended to have more children than people with lower IQs, challenging the dysgenic fertility theory. Study author Ole Rogeberg said in a news release, “The causes in IQ increases over time and now the decline is due to environmental factors … It’s not that dumb people are having more kids than smart people, to put it crudely. It’s something to do with the environment, because we’re seeing the same differences within families.”
As for what environmental factors are drawing down IQ scores, this remains to be seen, but access to education likely plays a role, with more education equating to higher IQ scores. Other environmental factors were also mentioned, including changes in nutrition and time spent on the internet or reading.
However, a number of environmental toxins that children are exposed to regularly have also been linked to cognitive effects, including lowered IQ. It could be that these toxic exposures are harming kids’ intelligence — and have been doing so for decades.
© 2018 Dr. Joseph Mercola