The main line of advance has left far behind it the magical ritual of primitive thought, the medieval search for significant omens and clairvoyant signs, the pseudo-scientific faith in the structural characteristics elaborated in physiognomy and phrenology, and has taken its stand firmly at the point where emphasis is laid on the objective study of the individual's behavior. Educationally this position shows itself in the abandonment of the purely disciplinary ideal of abstract training, and the substitution of training in specific forms of conduct, exercise, and occupation, accompanied by concrete experience with industrial opportunities, rewards, and satisfactions. From the more strictly psychological point of view the position shows itself in the experimental application of mental tests. In the measurement of the more strictly intellectual capacities, the line has shown a very decided advance since the beginning of the present century. The available intelligence scales make possible the diagnosis of intellectual defect, normality or precocity in units of considerable reliability, in the case of pre-adolescents. This step in itself is sufficient to put educational, industrial and social enterprise deeply in debt to the new science of experimental psychology. But this by no means constitutes the only point of marked advance. Thanks to the elaboration of more complex and more diversified tests, and the gradual accumulation of norms, it is now possible to make mental measurements in the case of individuals considerably beyond the age of adolescence. By means of such methods, degrees of sensitivity, dexterity, accuracy, speed, comprehension, docility, discrimination, ingenuity, information, observation, and numerous other general aspects of mental alertness may be recognized. Comparison of such measures, in the case of adult workers with actual success in the field of their activity, tends constantly to show high degrees of positive correlation. The fact that the correlations are not perfect raises numerous problems, the solution of which is now being attempted.