Because of the fact that there is a percentage of persons who, either through unfamiliarity with the English language or lack of skill in expressing themselves through word and number symbols, do not respond to tests based on the use of words, any comprehensive scheme of mental tests must contain a proportion of tests the response to which may be made without the use of written, printed, or spoken words. Of such a nature were the Army Beta tests, already referred to, and there will be found in the Mentimeter tests presented in this volume a considerable number of forms that fall into this class of tests. To the person accustomed to dealing chiefly with words and ideas, it is not always readily apparent that proof of a high degree of intelligence can be obtained by means of tests which do not employ these familiar symbols. As a matter of practical fact, however, results which check up very closely with every other means of determining the subject’s intelligence were quite uniformly obtained through the use of the Beta tests in the Army, and similar success has been achieved through the application of tests of the same general character in industry and education. There is another general class of tests to which only passing reference need be made here. This is the class of trade tests, in which by a combination of oral examination and specific performance the precise ability or degree of skill of the subject in a given occupation or trade is determined. Although frequently confused with psychological tests, this class of tests does not properly come within the scope of mental tests in the sense of being chiefly measurements of intelligence. It has been found, however, in practice that the individual’s native intelligence or inherent mental capacity has, in most occupations, a very decided bearing upon the degree of skill which he or she can attain, even in the simpler mechanical operations. Because of this fact, as well as because the value of trade tests in industry is of increasing importance, some of the principles underlying the construction of trade tests and their application are discussed briefly in a later chapter. CHAPTER VI MENTAL TESTS IN THE ARMY The United States of America entered the World War under conditions of emergency which demanded the maximum of efficiency in the work of military preparation, with the minimum of effort. France was virtually broken; England was tired; Russia was demoralized and disrupted, and Italy was doing very little more than holding her own. The mere drilling and conditioning of the nearly three millions of men which the Nation had called to arms were not sufficient to meet the requirements of the task assumed. America was expected to develop, almost overnight, a fighting force capable of meeting and defeating a Teutonic military machine which had come to be known as the most powerful and skillful in the world.