From NBC News:

IQ rates are dropping in many developed countries and that doesn’t bode well for humanity An intelligence crisis could undermine our problem-solving capacities and dim the prospects of the global economy. May 22, 2019, 1:31 AM PDT

By Evan Horowitz Evan Horowitz is the director of research communication at FCLT Global, a financial think tank. The views expressed here are his own. People are getting dumber. That’s not a judgment; it’s a global fact. In a host of leading nations, IQ scores have started to decline. … As yet, the United States hasn’t hit this IQ wall — despite what you may be tempted to surmise from the current state of the political debate. But don’t rush to celebrate American exceptionalism: If IQs are dropping in other advanced countries but not here, maybe that means we’re not really an advanced country (too much poverty, too little social support). Or — just as troubling — if we are keeping up with the Joneses (or Johanssons and Jacques) in terms of national development, that means we are likely to experience similarly plummeting IQs in the near future. … If we want to prevent America from suffering this fate, we’d better figure out why IQs are dropping elsewhere. But it’s uncharted territory. Until recently, IQ scores only moved in one direction: up. … These raw scores have been rising on a variety of standard IQ tests for over half a century. That may sound odd if you think of IQ as largely hereditary. But current IQ tests are designed to measure core cognitive skills such as short-term memory, problem-solving speed and visual processing, and rising scores show that these cognitive capabilities can actually be sharpened by environmental factors such as higher-quality schools and more demanding workplaces. … Scholars called it the “Flynn effect,” in homage to J.R. Flynn, the researcher who recognized its full sweep and import. These days, however, Flynn himself concedes that “the IQ gains of the 20th century have faltered.” A range of studies using a variety of well-established IQ tests and metrics have found declining scores across Scandinavia, Britain, Germany, France and Australia. Details vary from study to study and from place to place given the available data. IQ shortfalls in Norway and Denmark appear in longstanding tests of military conscripts, whereas information about France is based on a smaller sample and a different test. But the broad pattern has become clearer: Beginning around the turn of the 21st century, many of the most economically advanced nations began experiencing some kind of decline in IQ. 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.

OK, but that doesn’t puncture these theories, it just complements them.

In other words, the issue is not

I think the word “just” is missing here.

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. …

But nobody knows why yet.

It always seemed inevitable that the Flynn Effect would eventually run dry.

I would be concerned, however, about methodological issues involving how hard test-takers try. Perhaps in the 20th Century, Norwegian youths tried hard on their conscription IQ test because a high score would get them a better job during their military service, but now that is no longer true, so test-takers have less incentive to work hard on the test. (By the way, I just made that up. I’m clueless about obscure but possibly relevant details of Norwegian life.)

In general, the issue of how hard test-takers try tends to be overlooked. There tends to be a trade-off between high-stakes tests, where self-selection, test prep, and outright cheating are issues, and low-stakes tests, where it’s easier to get a representative sample but it’s not clear to outsiders, or even insiders, just how motivated everybody was.

For example, in 1980 the military renormed its revised AFQT enlistment test on the nationally representative National Longitudinal Survey of Youth 1979 sample. The data was quite high quality — as you can see reading The Bell Curve, which made heavy use of it.

But there was one puzzling anomaly. Black male youths did terrible on the NLSY79 AFQT, a gap of something like 21 points (where 15 is one standard deviation), a notably bigger than normal gap for a cognitive test. It took the military about 15 years to figure out what was the cause. The AFQT was an exhaustive test of 105 pages in length.

Most people who take the AFQT in the real world try hard because they want to do well and be allowed to enlist in military and get a better starting assignment. To them, it’s a high stakes test.

But to standardize the AFQT on a nationally representative sample, they had to give it to kids who didn’t want to join the military. To them, it was a low stakes test.

What was finally puzzled out in the mid 1990s was that it was common for black males in the NLSY79 panel to try hard for awhile on the AFQT, but then get discouraged by how hard the questions were, notice the ridiculous number of pages left to take, give up, and bubble in the rest of the way.

The military upgraded to a computerized adaptive test in which test-takers don’t get as discouraged because if they miss a few in a row they are given softball questions. This was tested on the nationally representative NLSY97 panel.

The black-white gap (both sexes) shrank from 18.6 to 14.7 points.

So, under any testing regime, there will be b-w gap, but the precise size of it can be influenced by subtle methodological questions, especially those related to test-taking effort.

And these can be particularly hard to notice across countries. I mean, what do I know about the subtleties of conscription and testing in Norway? It took American psychometricians 15 years to figure out what was the problem with the NLSY79 test administration, so the odds of Americans noticing some small but significant change in Norway are challenging.

Update: One reason IQ and similar cognitive tests are such relatively remarkable predictors is because they measure some combination of two good things: intelligence and stick-to-it-iveness (a.k.a., conscientousness). But that means when scores go down, it’s not immediately obvious which of the two is falling. And if it’s the latter, is stick-to-it-iveness falling broadly in the real world, or is there just some reason that test-takers aren’t trying as hard on the test anymore?