As the link states, they've controlled for education (degree earned) and then measured IQ with a vocabulary test; as a result they hypothesize that students who

As the link states, they've controlled for education (degree earned) and then measured IQ with a vocabulary test; as a result they hypothesize that students who are verbally-inclined might be earning degrees in less profitable fields. If you look at the data included with the GRE CD, you can see the same trend: those who perform spectacularly on the verbal portion are philosophy majors and the like. How much would you expect their average salary to be? No doubt it's significantly less than for most engineers, who don't verbally perform as well, but hit close to the (low) ceiling of the math portion. Income vs. verbal IQ within the same education class is probably all over the map because of this, and no doubt significantly confounded wrt cause-and-effect. On the other hand, I would expect there to be a strong benefit to verbal intelligence within each profession. TLDR: The link hardly proves that a higher IQ does not cause higher income.