Feynman was younger than 15 when he took it, and very near this factoid in Gleick's bio, he recounts Feynman asking about very basic algebra (2^x=4) and wondering why anything found it hard - the IQ is mentioned immediately before the section on 'grammar school', or middle school, implying that the 'school IQ test' was done well before he entered high school, putting him at much younger than 15. (15 is important because Feynman had mastered calculus by age 15, Gleick says, so he wouldn't be asking his father why algebra is useful at age >15.) - Given that Feynman was born in 1918, this implies the IQ test was done around 1930 or earlier. Given that it was done by the New York City school district, this implies also that it was one of the 'ratio' based IQ tests - utterly outdated and incorrect by modern standards. - Finally, it's well known that IQ tests are very unreliable in childhood; kids can easily bounce around compared to their stable adult scores.

So, it was a bad test, which even under ideal circumstances is unreliable & prone to error, and administered in a mass fashion and likely not by a genuine psychometrician.

-- gwern

A related question, concerning Hsu's point: How much can historical data be trusted to reflect current trends? During the 50's and 60's, physics (especially nuclear physics and the closely-related field of particle physics) were "hot topics" and everyone "wanted in"; it's not hard to imagine that the very best and brightest people entered the field during that time. But is that true anymore? It's possible that as the desirability of a physics career has decreased, the average level of intelligence in the physics community has also decreased, and that the reputation that physics has for being "the smartest of the smart" may just be a leftover from a previous era.

Feymann got his Nobel prize for making funny drawings of quantum physics. IQ isn't the limiting factor for that feat. It's willingness to pursue ideas that other people weren't willing to pursue.

IQ is iffy enough as it is, it was even iffier back in the 1930s, and Feynmann doesn't strike me as the sort who'd take IQ tests seriously.