D. _Inferior Intelligence._ Includes about fifteen per cent. of soldiers. “D” men are likely to be fair soldiers, but are usually slow in learning and rarely go above the rank of private. They are short on initiative and so require more than the usual amount of supervision. Many of them are illiterate or foreign. D− and E. _Very Inferior Intelligence._ This group is divided into two classes (1) “D−” men, who are very inferior in intelligence but are considered fit for regular service; and (2) “E” men, those whose mental inferiority justifies their recommendation for Development Battalion, Special Service Organization, rejection, or discharge. The majority of “D−” and “E” men are below ten years in “mental age.” The immense contrast between “A” and “D−” intelligence is shown by the fact that men of “A” intelligence have the ability to make a superior record in college or university, while “D−” men are of such inferior mentality that they are rarely able to go beyond the third or fourth grade of the elementary school, however long they attend. In fact, most “D−” and “E” men are below the “mental age” of ten years and at best are on the border-line of mental deficiency. Most of them are of the “moron” grade of feeble-mindedness. “B” intelligence is capable of making an average record in college, “C+” intelligence cannot do so well, while mentality of the “C” grade is rarely equal to high school graduation. _Evidence that the Tests Measure Military Value._—It has been thoroughly demonstrated that the intelligence ratings are very useful in indicating practical military value. The following investigations are typical: 1. Commanding officers of ten different organizations representing various arms in a camp were asked to designate: (_a_) The most efficient men in the organization; (_b_) Men of average value; (_c_) Men so inferior that they were “barely able” to perform their duties. The officers of these organizations had been with their men from six to twelve months and knew them exceptionally well. The total number of men rated was 965, about equally divided among “best,” “average,” and “poorest.” After the officers’ ratings had been made, the men were given the usual psychological test. Comparison of test results with officers’ ratings showed: (_a_) That the average score of the “best” group was approximately twice as high as the average score of the “poorest” group. (_b_) That of men testing below “C−” 70 per cent. were classed as “poorest” and only 4.4 per cent. as “best.” (_c_) That of men testing above “C+,” 15 per cent. were classed as “poorest” and 55.5 per cent. as “best.” (_d_) That the man who tests above “C+” is about fourteen times as likely to be classed “best” as the man who tests below “C−.”