Scott Alexander recently blogged “Against Individual IQ Worries.” Apparently, he gets many readers writing to him terrified that they scored too low on an IQ test, and therefore they’ll never be able to pursue their chosen career, or be a full-fledged intellectual or member of the rationalist community or whatever. Amusingly, other Scott says, some of these readers have even performed their own detailed Bayesian analysis of what it might mean that their IQ score is only 90, cogently weighing the arguments and counterarguments while deploying the full vocabulary of statistical research. It somehow reminds me of the joke about the talking dog, who frets to his owner that he doesn’t think he’s articulate enough to justify all the media attention he’s getting.

I’ve long had mixed feelings about the entire concept of IQ.

On the one hand, I know all the studies that show that IQ is highly heritable, that it’s predictive of all sorts of life outcomes, etc. etc. I’m also aware of the practical benefits of IQ research, many of which put anti-IQ leftists into an uncomfortable position: for example, the world might never have understood the risks of lead poisoning without studies showing how they depressed IQ. And as for the thousands of writers who dismiss the concept of IQ in favor of grit, multiple intelligences, emotional intelligence, or whatever else is the flavor of the week … well, I can fully agree about the importance of the latter qualities, but can’t go along with many of those writers’ barely-concealed impulse to lower the social status of STEM nerds even further, or to enforce a world where the things nerds are good at don’t matter.

On the other hand … well, have you actually looked at an IQ test? To anyone with a scientific or mathematical bent, the tests are vaguely horrifying. “Which of these pictures is unlike the others?” “What number comes next in the sequence?” Question after question that could have multiple defensible valid answers, but only one that “counts”—and that, therefore, mostly tests the social skill of reverse-engineering what the test-writer had in mind. As a teacher, I’d be embarrassed to put such questions on an exam.

I sometimes get asked what my IQ is. The truth is that, as far as I know, I was given one official IQ test, when I was four years old, and my score was about 106. The tester earnestly explained to my parents that, while I scored off the chart on some subtests, I completely bombed others, and averaging yielded 106. As a representative example of what I got wrong, the tester offered my parents the following:

Tester: “Suppose you came home, and you saw smoke coming out of your neighbor’s roof. What would you do?”

Me: “Probably nothing, because it’s just the chimney, and they have a fire in their fireplace.”

Tester: “OK, but suppose it wasn’t the chimney.”

Me: “Well then, I’d either call for help or not, depending on how much I liked my neighbor…”

Apparently, my parents later consulted other psychologists who were of the opinion that my IQ was higher. But the point remains: if IQ is defined as your score on a professionally administered IQ test, then mine is about 106.

Richard Feynman famously scored only 124 on a childhood IQ test—above average, but below the cutoff for most schools’ “gifted and talented” programs. After he won the Nobel Prize in Physics, he reportedly said that the prize itself was no big deal; what he was really proud of was to have received one despite a merely 124 IQ. If so, then it seems to me that I can feel equally proud, to have completed a computer science PhD at age 22, become a tenured MIT professor, etc. etc. despite a much lower IQ even than Feynman’s.

But seriously: how do we explain Feynman’s score? Well, when you read IQ enthusiasts, you find what they really love is not IQ itself, but rather “g“, a statistical construct derived via factor analysis: something that positively correlates with just about every measurable intellectual ability, but that isn’t itself directly measurable (at least, not by any test yet devised). An IQ test is merely one particular instrument that happens to correlate well with g—not necessarily the best one for all purposes. The SAT also correlates with g—indeed, almost as well as IQ tests themselves do, despite the idea (or pretense?) that the SAT measures “acquired knowledge.” These correlations are important, but they allow for numerous and massive outliers.

So, not for the first time, I find myself in complete agreement with Scott Alexander, when he advises people to stop worrying. We can uphold every statistical study that’s ever been done correlating IQ with other variables, while still affirming that fretting about your own low IQ score is almost as silly as fretting that you must be dumb because your bookshelf is too empty (a measurable variable that also presumably correlates with g).

More to the point: if you want to know, let’s say, whether you can succeed as a physicist, then surely the best way to find out is to start studying physics and see how well you do. That will give you a much more accurate signal than a gross consumer index like IQ will—and conditioned on that signal, I’m guessing that your IQ score will provide almost zero additional information. (Though then again, what would a guy with a 106 IQ know about such things?)