The question is, how do you know that getting a PhD relies "heavily on intelligence"? How do you know that intelligence has a strong or weak correlation? Or that there isn't some sort of threshold, where an effective IQ of at least 90 is important, but 140 is no more important?

What other factors have you considered, and why have you concluded they are less significant to getting a PhD than the intelligence that can be measured by the SAT?

jsprogrammer has, I think, a different point. Let's suppose that everyone has an equal chance of getting a PhD should they be admitted into graduate school. Let's also suppose that the selection committees believe that test scores are correlated with intelligence, and that only those with a high test score (and presumably higher intelligence) should get into graduate school.

This would end up with PhDs who all had good test scores, simply because of the selection bias. It would not reveal anything about the underlying population, because it confounds any association between intelligence and getting a PhD.

The people who get a PhD this way become members of a selection committee. They know the process worked for them, and repeat it, making this a stable system.

How do you know that PhD students now aren't selected in part because of a cultural belief which places a higher weight on test scores than is justified? How much of an effect does that bias have on the correlations you keep pointing to?

Then, we would expect that there would be little correlation between testing scores and outcomes. Especially whether they get a degree. For instance, someone who gets a lower test score will have the same outcomes as someone who gets a higher test score.

But that's not what the research suggests:

> The report, which examined 1,753 studies, found that GRE scores could help predict students' graduate grade point averages, first-year GPAs, ratings from faculty, exam scores, degree attainment and number of citations earned. The specific subject tests were even stronger indicators of students' performance.

http://www.apa.org/gradpsych/2012/09/cover-success.aspx

The hypothetical was meant to show that your analysis was insufficiently sensitive, not to posit that the hypothetical was actually the case.

You have an odd habit of pointing to secondary and preprint material, rather than the primary literature. Your APA links to several papers, including http://www.drtomascp.com/uploads/HungryMind_PPS_2011.pdf , titled "The Hungry Mind: Intellectual Curiosity Is the Third Pillar of Academic Performance". It concludes:

> The current study suggests that traditional sets of predictors of academic performance, notably general intelligence and Conscientiousness, should be accompanied by a third factor: intellectual curiosity. Jensen (1998) stated that “[general intelligence] g acts only as a threshold variable that specifies the essential minimum ability required for different kinds of achievement. Other, non-g special abilities and talents, along with certain personality factors ..., are also critical determinants of educational and vocational success” (p. 544–545). A remarkable number of studies on determinants of academic achievement have focused exclusively on ability and effort; the present findings, however, recommend further expanding the “g-nexus” for a better understanding of individual differences in academic performance. The latter requires—beyond intelligence and effort—a hungry mind.

It does say "intelligence is the single most powerful predictor of academic performance", then said:

> intelligence sustained the strongest effect on academic performance with a path weight of .35. TIE and Conscientiousness had slightly lower, identical path parameters of .20.

I believe that means that the other two legs together are more important than intelligence alone.