IQ scores have been steadily falling for decades, but genes aren’t to blame – their environment is at fault.
New research published this week in Proceedings of the National Academy of the Sciences of the United States of America examined the IQ scores of men born between 1962 and 1991. Researchers found that scores increased for men born between 1962 and 1975. However, they decreased steadily among men born after 1975.
The earlier rise in IQ scores follows something known as the Flynn Effect, a name for the long-term increase in intelligence levels that took place in the 20th century, according to the study.
Ole Rogeberg, co-author of the study and senior research fellow at the Ragnar Frisch Center for Economic Research in Norway said studies conducted in Denmark, Britain, France, the Netherlands, Finland and Estonia have all demonstrated this similar downward trend.
“The causes in IQ increases over time and now the decline is due to environmental factors,” Rogeburg told CNN. “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 explained that these environmental factors could range from nutrition, changes in the education system, less reading and more time spent online to changes in the media environment.
Researchers analyzed the IQ scores of brothers who were born in different years and found that rather than being similar, as expected because of genetics, the brothers’ IQ scores were often significantly different. The study also showed that parents with higher IQs tended to have more children. This disproved a long-believed theory known as the dysgenic fertility theory, which states that unintelligent people have more children, leading to the “dumbing down” of society.
These results highlight the role that environmental factors play in the decrease of IQ scores, researchers said.
Robin Morris, a professor of psychology at King’s College in London, who was not involved in the study, told CNN that the IQ test, and other traditional methods of measuring intelligence may be outdated and in need of changes.
“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,” Morris said. “Educational methods need to adapt to such changes.”