Back in 2016, commenter Recuring cited the following quote:

We of the Study of Mathematically Precocious Youth (SMPY) at Johns Hopkins have discovered, chiefly by testing able 12-year-olds, that when the examinee’s SAT-M score vastly exceeds his or her SAT-V score the youth is almost certain to score high on a difficult test of nonverbal reasoning ability such as the Advanced Form of the Raven Progressive Matrices, often higher than a high-M high-V examinee does. To test this out, on 6 May 1985 I administered to Terry the RPM-Advanced, an untimed test. He completed its 36 8-option items in about 45 minutes. Whereas the average British university student scores 21, Terry scored 32. He did not miss any of the last, most difficult, 4 items. Also, when told which 4 items he had not answered correctly, he was quickly able to find the correct response to each. Few of SMPY’s ablest protégés, members of its “700-800 on SAT-M Before Age 13″ group, could do as well.

I found the norms for this test (hat-tip to commenter Rahul for telling me they’re online) so I was finally able to complete part 3 of this series (three years after part 2).

For UK 10-year-olds, the 5th percentile (IQ 75) is a raw score of 1, while the 95th percentile (IQ 125) is a raw score of 15. If we assume raw scores are roughly normally distributed, we can crudely estimate that a 14 point gap in raw score equates to a 50 point IQ gap, and thus Terry’s score of 32, which is 24 points above the median raw score of 8, would thus be 86 points above the median IQ of 100, or IQ 186 (UK norms).

Some might argue that we should deduct a few points for the Flynn effect since the UK norms were six years old, however my sense is that the Flynn effect has been wildly exaggerated. For example, on the WAIS-III Matrix Reasoning subtest, average raw scores are identical for all ages from 18 to 34 and on the Advanced Progressive Matrices U.S. white norms (since it was normed in lily-white Iowa), there’s no change in raw scores from age 20 to 30: