IQ scores have been steadily declining for decades, and it’s not caused by genetics, according to a new study.
The study was published on Monday in Proceedings of the National Academy of Sciences of the United States of America by researchers from the University of Michigan.
They used administrative register data with information on family relationships and cognitive ability for three decades of Norwegian families — specifically looking at the IQ of male birth cohorts.
The data enabled them to compare the IQ of brothers born many years apart, ruling out the impact of genetics in changing IQ.
The researchers found that average IQ increased by almost 3 percentage points each decade for those born between 1962 and 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 similar findings, said Ole Rogeberg, co-author of the study and a senior research fellow at the Ragnar Frisch Center for Economic Research in Norway.
“The causes in IQ increases over time and now the decline is due to environmental factors,” said Rogeburg, who believes the change is not due to genetics.
“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.
We’re not getting smarter anymore, according to researchers
The earlier rise in IQ scores in the 20th century was due to the “Flynn effect,” a term used to identify the supposded substantial and long-term increase in both fluid and crystallized intelligence test scores from the earliest years of testing to the present. It’s named after James R. Flynn who did much to document and promote awareness of its implications. See his TED talk below.
Conventional thinking around the “Flynn effect” usually assumes that increases in IQ is the result in genetic variations. Simply put, intelligent people breed with each other and create smarter children.
The study turns this conventional thinking on its head.
It looks at the IQ scores of brothers who were born in different years and found that, instead of being similar as suggested by genetics, IQ scores often different significantly between siblings.
“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.”
This means that environmental factors are the most likely cause of declining intelligence.
What is causing the decline in IQ?
More research is needed to better understand the environmental factors that may be contributing to the decline in intelligence. However, Robin Morris, a professor of psychology at Kings College in London, suggests that the way we measure intelligence needs to change.
“In my view, we need to recognize that as time changes and people are exposed to different intellectual experiences, such as changes in the use of technology, for example social media, the way intelligence is expressed also changes. Educational methods need to adapt to such changes,” Morris said.
This raises the questions: is our environment resulting in decreased intelligence levels? Or do we need to change our definition of intelligence?
And the follow on question: are our media and education systems fit for purpose for modern day citizens? Or do we need to change how knowledge is created, distributed and consumed?