I don’t know much about the background of this, but people here might be interested in reading it.
In a host of leading nations, IQ scores have started to decline.
Though there are legitimate questions about the relationship between IQ and intelligence, and broad recognition that success depends as much on other virtues like grit, IQ tests in use throughout the world today really do seem to capture something meaningful and durable. Decades of research have shown that individual IQ scores predict things such as educational achievement and longevity. More broadly, the average IQ score of a country is linked to economic growth and scientific innovation.
One potential explanation was quasi-eugenic. As in the movie “Idiocracy,” it was suggested that average intelligence is being pulled down because lower-IQ families are having more children (“dysgenic fertility” is the technical term). Alternatively, widening immigration might be bringing less-intelligent newcomers to societies with otherwise higher IQs.
However, a 2018 study of Norway has punctured these theories by showing that IQs are dropping not just across societies but within families. In other words, the issue is not that educated Norwegians are increasingly outnumbered by lower-IQ immigrants or the children of less-educated citizens. Even children born to high-IQ parents are slipping down the IQ ladder.