Comparison of different tests performed on the same individual is of value in showing whether tests purporting to be testing the same properties are, in fact, doing so, and also in determining whether certain psychological characteristics tend to occur concurrently in the same subjects. Previous work (Rudolf, 1948) has shown that the accumulation of general knowledge based on the environment and excluding school work, as shown by the I.Q. obtained by the use of Kent's test, correlates highly with the I.Q. obtained by the use of the Stanford Revision of the Binet-Simon, the coefficient being + 0·7499 ± 0·019. With a test of reasoning, Raven's Progressive Matrices (Group), the correlation-coefficient of the Kent Test was less impressive, being + 0·2686 ± 0·038. These results suggest that the accumulation of knowledge of the environment is not markedly dependent on, or connected with, the powers of reasoning.