Research out of Norway has demonstrated a troubling trend: Human intelligence is dropping with each passing year. And contrary to the popular explanation of genetics, the researchers believe it is environmental factors that are to blame.
Norwegian researchers analyzed the IQ scores of Norwegian men born between 1962 and 1991 and found that scores increased by almost 3 percentage points each decade for those born between 1962 to 1975 — but then saw a steady decline among those born after 1975.
Similar studies in Denmark, Britain, France, the Netherlands, Finland and Estonia have demonstrated a similar downward trend in IQ scores, said Ole Rogeberg, a senior research fellow at the Ragnar Frisch Center for Economic Research in Norway and co-author of the new study.
Rogeberg is convinced the data show genetics are not the cause, pointing instead 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,” he said.
These environmental factors could include changes in the education system and media environment, nutrition, reading less and being online more, Rogeberg said.
The long-held belief that because intelligence is heritable and low IQ individuals are likely to have more children than their high IQ counterparts meant IQ scores would decline overall as the population grows has been turned on its head.
The study not only showed IQ variance between children the same parents, but because the authors had the IQ scores of various parents, it demonstrated that parents with higher IQs tended to have more kids, ruling out the dysgenic fertility theory as a driver of falling IQ scores and highlighting the role of environmental factors instead.
“The main exciting finding isn’t that there was a decline in IQ,” Ritchie said. “The interesting thing about this paper is that they were able to show a difference in IQ scores within the same families.”