A similar accomplishment of industrial psychology has been in the direction of measuring a man's interests and relating these to the requirements of various kinds of work. Here the psychologist must deal with the individual rather than the group; and since the single measure has a lower reliability, he uses it with full awareness of its limitations. The same may be said of measurements of other vocational aptitudes and proficiencies. The invention of standard tests of skill, trade knowledge, manual dexterity, mechanical ability, mental alertness, and capacity to learn, has reduced to some degree the hazards of predicting an applicant's probable success; but in only a relatively small fraction of the occupations has the validity of such tests as yet been demonstrated, and even here such data must always be appraised in relation to all the relevant facts obtainable about the person's previous experience, social and economic status, success in school, health, temperament, emotional balance, and the like. Employment psychology, let me hasten to add, has provided a scientific procedure for determining what relative weight should be given to each of the several items considered, in hiring for those occupations in which the number employed is sufficiently large.

A man's success in an occupation is obviously conditioned by many factors, both internal and external. His determination to succeed, and his degree of interest in the particular work to be done, may be as crucial as is his ability to perform the tasks required. Can such aspects of human nature actually be pinned down and measured? An uninformed vocational interest is notoriously volatile. Interests shift with knowledge and experience. Deep-lying antipathies can sometimes be overcome. And yet it is almost axiomatic that satisfactory adjustments to one's work are enduring only when that work is of a kind that matches natural tastes as well as abilities. So industrial psychology has eagerly watched the development of scientific means for ascertaining fundamental preferences or bents. The road has been long and the end is not yet. Beginning with Miner's check list of occupational preferences for use in the vocational-counseling interview, the first milepost was a statistical comparison of likes and dislikes among groups of salesmen and engineers in Yoakum's seminar at Carnegie Institute of Technology ten years ago. Moore's research for the Westinghouse Electric Company, on the differentiation of graduate engineers into those who would eventually become successful engineering salesmen rather than designers or supervisors of production, is classic. Freyd developed a still better instrument and used it in his studies of personality; and many others, notably Strong, have further refined and extended these methods of attitude measurement as aids in ascertaining occupational and professional interests. Such techniques have a place and will probably not be entirely superseded even though the psychologist at some future time succeeds in inventing still more direct and objective means of measurement, based on determination of what the individual actually does when confronted by a choice of opportunities.

Industry's Use of Psychological Tests. The successes of the military psychologists in 1917-1918, and during the days of the occupational-rehabilitation movement following the World War, served to spread throughout industry an acquaintance, even though superficial, with the aims and possibilities of employment psychology, giving focus to the general interest which Munsterberg had stimulated some ten years before. Many thousands of intelligence-test blanks were purchased for business use. Firms like the Eastman Kodak Company installed, as part of their selection procedures, peg-board performance tests of manual dexterity and other objective measures of ability, to help in discovering talent for inspection work as well as for assembly operations and jobs requiring mechanical ingenuity. The extent to which some firms have carried the use of tests as an aid in selection is evidenced by the fact that during 1930 the employment department at Macy's gave psychological examinations to more than 14,000 of the applicants for positions in that store.

The value of a rigorously scientific procedure in developing and adapting such tests to the demands of a specific situation is well illustrated by an investigation recently made by Viteles in the Philadelphia Electric Company. Here operating mistakes of electrical substation operators have been reduced 43 per cent through the use of psychological tests in the reassignment of these men. The importance of such a reduction is evidenced when it is recalled that a mistake at the great switchboard of a substation may deprive a hospital of electricity while a surgical operation is in progress, or result in interference with a manufacturing process entailing a loss of many thousands of dollars. Other examples of the same kind could be cited from industrial research both here and abroad.

The federal postal service has been much improved since 1923, through simplification of the work of mail sorters after psychological analysis of their job, and through replacement of the traditional type of civil service examination by a more practical, convenient, objective type of examination, by means of which the U. S. Civil Service Commission has annually tested some 60,000 applicants for employment as distributors, carriers, and railway mail clerks, more easily, accurately, and fairly than before, with much less expense to the government, and with marked improvement in the average ability of the men appointed. Principles and techniques which O'Rourke, Thurstone, and their associates developed in connection with such psychological research on employment procedures have since been applied not only to other civil service examinations, but to similar problems in business and in education also.

In the transportation field, Viteles and Mrs. Shellow, for the Milwaukee Electric Railway Company, developed and validated tests for selecting applicants to be trained as street-car motormen - men who can keep their minds on the job and do the right thing in spite of distractions and sudden emergencies. The work of Snow for the Yellow Cab Company, Segard for the Third Avenue Railway of New York, and Wechsler, Moss, and others for various transportation firms, paralleled in this country elaborate developments in the technopsychological laboratories of the Paris tramways and the German railways. These methods have proved valuable in reducing accidents chiefly in those companies where the major executives have seen that such selection procedures are properly integrated in a well-considered program of training and individual supervision, as has been done among the delivery drivers of R. H. Macy and Company.