During this change in theoretical description and continuing into our present era of compromise and revision, methods were developed of measuring the amount and quality, or, more simply conceived, the speed, strength and regularity of mental and motor ability. Beginning in the form of experiments on sensory discrimination, reaction time and imagery type, and combined with physiological measurements of motor strength, rapidity and fatigue, these experiments developed, in certain hands, into what are now known as "mental tests." Since the principle and method of mental and physical tests is the chief characteristic of the present status of vocational psychology, and since the work of the immediate future seems destined to develop mainly in this same direction, we may profitably consider at this point the history and development of the mental test. We may later take up the general principle and theory of the test as an instrument of psychological analysis and diagnosis, with special reference to the requirements and implications of such tests as may be of service in vocational psychology. We shall then be in position to review the special vocational tests that have as yet been proposed, to evaluate their outstanding results, and to point to some of the more immediate prospects and problems under consideration by those interested in the application of psychological tests in vocational analysis and guidance. We may begin with an account of the first definite attempt to explore systematically the personality of individuals by the method of tests. The "Columbia Freshman Tests" are of especial interest in the history of vocational psychology, since in their formulation and plan explicit thought was given to the practical use to which the results of tests might be put by the individuals examined, and by the statistical study of the results by students of the subject. In 1894, under the guidance of Professor Cattell, there was instituted the plan of testing the students of Columbia College during their first and fourth academic years. A description of the tests employed was published by Cattell and Farrand in 1896, and a statistical study of results was published by Wissler in 1901. The motive back of these tests is well expressed in the following paragraph which was also used as material for a test of logical memory: "Tests such as we are now making are of value both for the advancement of science and for the information of the student who is tested. It is of importance for science to learn how people differ and on what factors these differences depend. If we can disentangle the complex influences of heredity and environment we may be able to apply our knowledge to guide human development. Then it is well for each of us to know in what way he differs from others. We may thus in some cases correct defects and develop aptitudes which we might otherwise neglect."