The author goes on to point out that there are real, measurable, predictive personality traits like conscientiousness and they still don't come close to IQ. It

The author goes on to point out that there are real, measurable, predictive personality traits like conscientiousness and they still don't come close to IQ. It should also be noted that IQ is five or more times as powerful a predictor as even good personality trait predictors such as conscientiousness. The true relationship between grades, for example, and IQ might be as high as r = .50 or even .60 (accounting for 25-36% of the variance in grades). Conscientiousness, however, probably tops out at around r = .30, and is more typically reported as r = .25 (say, 5 to 9% of the variance in grades).