On April 6, 1917, the United States Congress declared the existence of a state of war with Germany. On that same date there was being held in Boston a meeting of a group of psychologists known as the “Experimentalists,” among whom was Dr. Robert M. Yerkes, president of the American Psychological Association. On receipt of news that America was at last at war, all regular business of the meeting was suspended and those present resolved themselves into an informal committee to consider ways and means by which the psychologists of America could best serve their country. On the evening of that day, as the result of many conferences, the president of the association asked the council to authorize him to appoint committees on various phases of applied psychology for the purpose: first, of enlisting the coöperation of every trained psychologist in America, including the entire membership of the American Psychological Association; and, second, of determining precisely what service the psychologists could best perform. The proposal met with an immediate response and Doctor Yerkes and his committee went to work. The Army General Staff was skeptical at first, but Doctor Yerkes and his associates overcame this skepticism and by midsummer of 1917 the Division of Psychology of the Medical Department of the United States Army, with Doctor Yerkes at its head with the rank of major, was actively functioning, and the Committee on Classification of Personnel in the Army had been established and was demonstrating, to the surprise of the General Staff and the War Department, the possibility of determining by scientific means the relative military value and proper military assignment of the officers and men of the Army. By the end of 1917 psychology, as applied to war, had so far justified itself that the Surgeon General reported complete success in achieving the desired results, which he stated, concisely, to be: (a) to aid in segregating the mentally incompetent, (b) to classify men according to their mental ability, and (c) to assist in selecting competent men for responsible positions. The programme of the Division of Psychology of the Medical Department included mental tests for all recruits during a two-weeks detention period. These intelligence ratings, as they were officially termed, aimed to aid: (1) In the discovery of men whose superior intelligence suggested their consideration for advancement; (2) In the prompt selection and assignment to development battalions of men who were so inferior mentally that they were suited only for special assignments; (3) In forming organizations of uniform mental strength where such uniformity was desired; (4) In forming organizations of superior mental strength where such superiority was demanded by the nature of the work to be performed; (5) In selecting suitable men for various army duties or for special training in colleges or technical schools;