(CNN) – IQ scores have been falling steadily over the past few decades, and environmental factors are to blame, according to a new study.
Research suggests that genes are not what is driving the decline in IQ scores. according to the study, published on Monday.
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 and 1975, but then saw a steady decline among those born after 1975.
Similar studies in Denmark, Great Britain, France, the Netherlands, Finland and Estonia have shown a similar trend to low IQ scores, said Ole Rogeberg, principal investigator at the Ragnar Frisch Center for Economic Research in Norway and co-author of the new study.
"The causes in the IQ increase with time and now the decrease is due to environmental factors," said Rogeburg, who believes that the change is not due to genetics. .
"It's not that silly people have more children than intelligent people, to put it crudely, it's something that has 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 the media environment, nutrition, reading less and being online more, Rogeberg said
The earliest increase in IQ scores follows the "Flynn effect" ", a term for the long-term increase in intelligence levels that occurred during the 21st century, possibly as a result of better access to education, according to Stuart Ritchie, a postdoctoral fellow in cognitive aging at the University of Edinburgh whose research It explores the scores and intelligence of the IQ and that it did not participate in the new study.
Researchers have preferred to use genes to explain variations in intelligence about environmental factors. However, the new study turns this idea on its head.
Intelligence is hereditary and, for a long time, researchers assumed that people with high IQ scores would have children who also scored above average. In addition, it was thought that people with lower scores would have more children than people with high IQ scores, which would contribute to a decrease in IQ scores over time and a "blunting" of the general population, according to Rogeberg.
Anyone who has seen the movie "Idiocracy" may already be familiar with these ideas. In the scientific community, according to Ritchie, the idea that non-intelligent parents have more children and disparage the population is known as the theory of dysgenic fertility.
The study analyzed the IQ scores of siblings who were born in different years. The researchers found that, instead of being similar to what is suggested by a genetic explanation, IQ scores often differ significantly among siblings.
"The main interesting finding is not that there was a decrease in the IQ," Ritchie said. "The interesting thing about this work is that they could show a difference in IQ scores within the same families."
The study not only showed the IQ difference between the children of the same parents, but because the authors had IQ scores from several parents, it showed that parents with a higher IQ tended to have more children , discarding the theory of dysgenic fertility as a driver of the decrease in IQ scores and highlighting the role of environmental factors.
What specific environmental factors cause changes in intelligence? relatively unexplored.
Access to education is currently the most conclusive factor explaining disparities in intelligence, according to Ritchie. In a separate study that has not been published, he and his colleagues analyzed existing research in an effort to show that staying in school longer is directly equivalent to higher IQ scores.
But more research is needed to better understand other environmental factors being linked to intelligence. Robin Morris, a professor of psychology at Kings College in London and who was not involved in Ritchie's research, suggests that traditional intelligence measures, such as the IQ test, may be outdated in the dizzying current world of constant technological change.
"In my opinion, we have 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 networks, the way in which it is expressed Intelligence also changes, educational methods must adapt to such changes, "Morris said.
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