There was virtually no correlation at all.36 Mental abilities were decidedly jagged. For a devout believer in ranking, there was worse to come. Cattell also measured the correlations between students’ grades in college courses and their performance on these mental tests and discovered very weak correlations between them. And not only that—even the correlations between students’ grades in different classes were low. In fact, the only meaningful correlation Cattell found at all was between students’ grades in Latin classes and their grades in Greek classes.
