Blog commenter Lion of the Judah-sphere has claimed that the SAT does not correlate as well with comprehensive IQ tests as said IQ tests correlate with one another. At first I assumed he was wrong, but my recent analysis suggesting Harvard undergrads have an average Wechsler IQ of 122, really makes me wonder.

While an IQ of 122 (white norms) is 25 points above the U.S. mean of 97, it seems very low for a group of people who averaged 1490 out of 1600 on the SAT. According to my formula, since 1995 a score of 1490 on the SAT equated to an IQ of 141. But my formula was based on modern U.S. norms; because demographic changes have made the U.S. mean IQ 3 points below the white American mean (and made the U.S. standard deviation 3.4 percent larger than the white SD), converting to white norms reduces Harvard’s SAT IQ equivalent to 139.

In addition, the SAT IQ equivalents were based on a scale where institutionalized retardates, the brain damaged, and the mentally ill, were part of the bell curve. Such people are excluded from the norming of the Wechsler IQ scale, and since such people drag the bell curve to the left by 2 IQ points, excluding them from the norms would change the SAT IQ equivalent of Harvard students from 139 to about 137 (40 IQ points above the U.S. mean of 97).

Thus, Harvard students, largely selected based on SAT scores, are 40 IQ points above average as measured by the SAT, but “only” 25 points above average as measured by the Wechsler. This suggests the SAT and the Wechsler only correlate 0.63 (25/40), which is far lower than the 0.88 correlation between the Wechsler and the Stanford-Binet (the two gold standards of IQ testing).

Of course the average Harvard student is not selected exclusively on SAT scores so she might not be cognitively representative of the average 1490 SAT young adult. If she is significantly smarter or dumber, that would have skewed my estimate.

In general, research correlating the SAT with IQ has been inconsistent, with correlations ranging from 0.4 to 0.8. I think much depends on the sample. Among people who took similar courses in similar high schools, the SAT is probably an excellent measure of IQ. But considering the wide range of schools and courses American teenagers have experienced, the SAT is not, in my judgement, a valid measure of IQ. Nor should it be. Universities should not be selecting students based on biological ability, but rather on acquired academic skills.