presuppose any scientific knowledge, any more than an understanding of the principles of electricity is necessary for one who uses the telephone.  But besides the rigid rules which any one may apply, particular prescriptions will be needed fitting the special situation.  This leads to the demand for the large establishments to appoint professionally trained psychologists who will devote their services to the psychological problems of the special industrial plant.  There are many factories that have scores of scientifically trained chemists or physicists at work, but who would consider it an unproductive luxury to appoint a scientifically schooled experimental psychologist to their staff.  And yet his observations and researches might become economically the most important factor.  Similar expectations might be justified for the large department stores and especially for the big transportation companies.  In smaller dimensions the same real needs exist in the ordinary workshop and store.  It is obvious that the professional consulting psychologist would satisfy these needs most directly, and if such a new group of engineers were to enter into industrial life, very soon a further specialization might be expected.  Some of these psychological engineers would devote themselves to the problems of vocational selection and appointment; others would specialize on questions of advertisement and display and propaganda; a third group on problems of fatigue, efficiency, and recreation; a fourth on the psychological demands for the arrangement of the machines; and every day would give rise to new divisions.  Such a well-schooled specialist, if he spent a few hours in a workshop or a few days in a factory, could submit propositions which might refer exclusively to the psychological factors and yet which might be more important for the earning and the profit of the establishment than the mere buying of new machines or the mere increase in the number of laborers.

No one can deny that such a transition must be burdened with difficult complications and even with dangers; and still less will any one doubt that it may be caricatured.  One who demands that a chauffeur or a motorman of an electric railway be examined as to his psychical abilities by systematic psychological methods, so that accidents may be avoided, does not necessarily demand that a congressman or a cabinet minister or a candidate for marriage be tested too by psychological laboratory experiments, as the witty ones have proposed.  And one who believes that the work in the factory ought to be studied with reference to the smallest possible expenditure of psychical impulses is not convinced that the same experimental methods will be necessary for the functions of eating and drinking and love-making, as has been suggested.