A Not-Entirely-Awful Introduction to IQ and Psychometrics

I reflexively grit my teeth whenever I encounter a presentation on intelligence (IQ) testing, psychometrics, testing methodologies, correlation of IQ with other measures, group differences in mean IQ, and the fraction of IQ attributable to genetics vs. other environmental factors such as nutrition, stimulation during development, education, and coaching/practice in taking tests.

In this video, Veritasium presents a pretty much straight down the middle introduction to this topic, which is one of the best-established phenomena in the human sciences but “controversial” and “contentious” because it contradicts extraordinary popular delusions and the madness of politicians to such an extent they “cancel” anyone who dare speak such “hate facts”.

Here, the data are presented pretty much as they’re known to be, including correlations with academic and job performance, the U.S. military’s experience with lowering the IQ requirement for recruitment during the Vietnam war, twin studies, and a toe dipped into the topic of racial and country IQ differences. There is the obligatory opprobrium directed at “eugenics”, including a bit of argumentum ad Hitlerum, not mentioning the pantheon of “progressive” figures who were enthusiastic supporters of the movement during its heyday. The Flynn effect is discussed, but not the evidence for its having ceased and possibly reversed in recent decades.

There is a good description of the distinction between fluid and crystallised intelligence, which is particularly relevant with the emergence of large language model artificial intelligence, which manifests superhuman crystallised intelligence (knowledge of facts and literature) but marginal fluid intelligence (problem-solving, inference, and creativity).

Those who have studied these topics won’t learn anything new here, but this presentation may play a valuable part in opening the minds of those marinated in the propaganda that “IQ doesn’t exist” and that “intelligence testing is a colonial pseudoscience” and the like to begin to think, “Hey, there may be something to it, after all.”

I discuss these issues in more detail, including answers to commonly asked questions and a reading list for further exploration, in my 2004 article “Global IQ: 1950–2050”.


About the time we get good models that not only are capable of critical thinking but of modeling their human interlocutors’s psychology (ie: educational placement), it will become impractical to keep up the charade that even genes don’t matter, let alone that IQ doesn’t matter. At that point, it will be interesting to see the rhetoric shift from “Let’s outbid the young men for the fertile years of the most intelligent young women until Marching Morons is seen as prophetic,” to “See? We told you all along that intelligence was meaningless and genes don’t matter because now we have all the AI’s running everything and reproducing!”