Circa 2013, Jonathan Wai reported that Harvard undergrads had a mean SAT of 1490 which at the time equated to an IQ of 145. Meanwhile Wai reported that Harvard Law students had a mean LSAT score of 173.5 which also equates to an IQ of 145.
However by definition, elite students over perform on the very test used to recruit them, because one of the things they’re recruited for is “good luck” on the admission test. Thus it’s interesting to ask how Harvard students perform on a random test (not used in the selection process)
As I’ve noted many times the best data on the subject was obtained by Harvard scholar Shelley H Carson and her colleagues who had an abbreviated version of the WAIS-R given to 86 “Harvard undergraduates (33 men, 53 women), with a mean age of 20.7 years (SD 3.3)… All were recruited from sign-up sheets posted on campus. Participants were paid an hourly rate…The mean IQ of the sample was 128.1 points (SD 10.3), with a range of 97 to 148 points.”
Note: The actual scores were 99 to 150 but Carson reduced them by 2 points because it’s known in the literature that the abbreviated version yields IQs 2 points lower than the full-scale IQ. However she can’t just assume measurement error favours the full-scale, so I am going to return these 2 points and say the full-scale IQ was 130.1.
It should be noted however that the WAIS-R was published in 1981, and that the norms were collected from 1976 to 1980. Carson’s study was published in 2003, so presumably the test norms were 25 years old.
James Flynn cites data showing that from WAIS-R norms (circa 1978) to WAIS-IV norms (circa 2006) the vocabulary and spatial construction subtest (used in the abbreviated WAIS-R) increased by 0.53 SD and 0.33 SD respectively. These gains would result in the composite score of the abbreviated WAIS-R becoming obsolete at a rate of 0.26 IQ points per year, meaning the Harvard students’ scores circa 2003 were 6.5 points too high. This reduces the mean IQ of the sample to 122.6 (U.S. norms).
Also recall that this was an abbreviated version of the WAIS-R and thus only correlates about 0.9 with the full version. Dividing the number of IQ points above 100 by 0.9 raises their IQ from 122.6 to 125, a good estimate of how they would have scored on the full test.
It should also noted that this was a psychology study, and thus a disproportionate number of psych students likely took part. Realistically, us psych majors are not as bright (on average) as harcore STEM majors. Add to this the fact that the abbreviated WAIS only had a ceiling of 150, likely preventing some participants from showing their full potential. Given these two facts it seems reasonable to round up the mean score to 130.
Still, 130 is only 66% as extreme as their 145 IQs derived from the SAT. But as Jensen noted, except when content and format is very similar, different IQ tests only correlate 0.66 with one another so this is the expected result. One might ask why I’m regressing to the U.S. mean and not the mean of SAT takers. The answer is that virtually 100% of gifted American teens have taken the SAT, so regressing them to the SAT population would be redundant.
How would Harvard Law students scores on the WAIS?
To my knowledge there have been no studies of Harvard Law students taking any version of the WAIS, but if there were, I’d expect them to also regress to the mean . However unlike the SAT, we can’t assume that virtually all smart young American adults have taken the LSAT and thus we can’t regress them to the U.S. mean. We can however assume that virtually all Harvard Law students become get their degree, and the average IQ of Americans with professional degrees is about 125 so instead of regressing to the U.S. mean of 100, they’d regress to the professional mean of 125.
But given that correlations are lower in a restricted sample like professionals (say 0.56 instead of 0.66) we’d expect their WAIS IQs to be:
145 – 125 = 20(.55) + 125 = 136.
Even though Harvard undergrads and Harvard Law students both score IQ 145 on their respective admission tests, their actual IQs are likely 130 and 136 respectively. This is not to say that the WAIS is necessarily more accurate than the SAT or LSAT; rather it’s to say that the IQ of a group should never be measured by the very test that selected them, because by definition, they likely overperformed on that.