Too much emphasis cannot be laid on another function as well, the experimental testing of which has only recently been started.  I refer to the difference in the individual ability of men to profit from training.  If we test an individual at a certain point in his life with regard to a variable ability, our result must be dependent upon three factors, the original disposition for the performance, the original disposition for the advance by training, and the training itself actually passed through up to that moment.  A small amount of antecedent training for the particular task together with a high ability to profit from repetition may be a better reason for the appointment of a man than a long training with small ability to profit from schooling, in spite of the fact that his actual achievement at this time may be in the first case smaller than in the second.  He will do less at first, but he promises to outrank the other man after a period of further training.  Special experiments must be carried on and have been actually started to determine this plasticity of the psychophysical apparatus as an independent inborn trait of the individual.[16]

This invasion of psychology into the field of economic activities is still so little advanced that the thought of a real distribution of the wage-earners among the various commercial and industrial positions on the basis of psychological tests would lead far beyond the present possibilities.  Moreover, many factors would interfere with its being carried out consistently, even if a much higher stage of experimental research were reached.  The thousands of social and local reasons which influence the choice of a vocation to-day would to a certain degree remain in force also in a period of better psychological analysis.  Moreover, the personal inclinations and interests naturally would and ought to remain the mainspring of economic action.  This inclination, which gives so much of the joy in labor, is by no means necessarily coincident with those psychophysical dispositions which insure the most successful work.  Political economists have found this out repeatedly from their statistical inquiries.  Very careful studies of the textile industry in Germany carried out in recent years[17] yielded the result that the intelligent, highly trained textile laborer often dislikes his work the more, the more he shows ability for it, this ability being measured by the wages the individuals earn at piecework.  The wage and the emotional attitude were not seldom inversely related.  Those who were able to produce by far more than others and accordingly earned the most were sometimes the very ones who hated the work, while the less skillful workers earned less but enjoyed the work more.  The consulting economic psychologist will, therefore at first reasonably confine himself to warning the misfits at an early time.  Even within these limits his service can be useful to both parties, the employers and the employees.  He will only slowly reach the stage at which this negative warning may be supplemented by positive suggestions, as to the commercial industrial activities for which the psychophysical dispositions promise particular success.