The psychological ratings are valuable not so much because they make a better classification than would come about in the course of time through natural selection, but chiefly because they greatly abbreviate this process by indicating _immediately_ the groups in which suitable officer material will be found, and at the same time those men whose mental inferiority warrants their elimination from regular units in order to prevent the retardation of training. Speed counts in a war that costs fifty million dollars per day and requires the minimum period of training. _Directions for the Use of Intelligence Ratings._—In using the intelligence ratings the following points should be borne in mind: 1. The mental tests are not intended to replace other methods of judging a man’s value to the service. It would be a mistake to assume that they tell us infallibly what kind of soldier a man will make. They merely _help_ to do this by measuring one important element in a soldier’s equipment, namely, intelligence. They do not measure loyalty, bravery, power to command, or the emotional traits that make a man “carry on.” However, in the long run these qualities are far more likely to be found in men of superior intelligence than in men who are intellectually inferior. Intelligence is perhaps the most important single factor in soldier efficiency apart from physical fitness. 2. Commissioned officer material is found chiefly in the A and B groups, although of course not all high-score men have the other qualifications necessary for officers. Men below C+ should not be accepted as students in Officers’ Training Schools unless the score on the Officers’ Rating Scale indicates exceptional power of leadership and ability to command. 3. Since more than one fourth of enlisted men rate as high as C+, there is rarely justification for going below this grade in choosing non-commissioned officers. This is especially the case in view of the likelihood of promotion from non-commissioned rank. Even apart from considerations of promotion, it is desirable to avoid the appointment of mentally inferior men (below C) as non-commissioned officers. Several careful studies have shown that “C−” and “D” sergeants and corporals are extremely likely to be found unsatisfactory. The fact that a few make good does not justify the risk taken in their appointment. 4. Men below C+ are rarely equal to complicated paper work. 5. In selecting men for tasks of special responsibility the preference should be given to those of highest intelligence rating _who also have the other necessary qualifications_. If they make good they should be kept on the work or promoted; if they fail they should be replaced by men next on the list.