"Hitherto the literature of mental and physical tests has been scattered in numerous journals; the results obtained by different investigators have too often not been compared; indeed, in many cases where the methods have been divergent, comparison has been impossible. In consequence, there have been no recognized standards of procedure and none of performance. Nevertheless, I believe that the time has now come for the taking of an account of stock, and for the systematization of the available materials. This conviction, which is the outgrowth of my own interest in the experimental study of mental capacities, an interest that has been with me during the past ten years, has been confirmed by many suggestions from colleagues and friends, who have pointed out that a manual of directions for mental tests would meet a real need, and might further the cause of investigation. I began, in March, 1906, to prepare a small handbook of mental tests.