The only real difficulty of the method lies in the ease with which it can be used.  A device which presupposes complicated instruments deters the layman and will be used only by those who are well trained.  Moreover, the amateur would not think of constructing and adapting such apparatus himself.  But when nothing is necessary but to use words or numbers or syllables or pictures, or, as in those experiments which we just described, newspapers and so on, any one feels justified in applying the scheme or in replacing it by a new apparently better one according to his caprice.  The manifoldness of the proposed tests for special functions, is therefore enormous to-day.  What is needed now is surely much more that order be brought into this chaos of propositions, and that definite norms and standards be secured for certain chief examinations, than that the number of variations simply be increased.

The chief danger, moreover, lies in the fact that those who are not accustomed to psychological laboratory research are easily misled.  They fancy that such an experiment can be carried out in a mere mechanical way without careful study of all the conditions and accompanying circumstances.  Thereby a certain crudeness of procedure may enter which is not at all suggested by the test method itself.  The psychological layman too seldom recognizes how many other psychical functions may play a role in the result of the experiment beside the one which is interesting him at that moment.  The well-schooled laboratory worker almost automatically gives consideration to all such secondary circumstances.  While his experiments may refer to the process of memory, he will yet at the same time carefully consider the particular situation as to the emotional setting of the subject, as to his attention, as to his preceding experience, as to his intelligence, as to his physiological condition, and many other factors which may have indirect influence even on the simplest memory test.  Hence the real performance of the experiments ought to be undertaken only by those who are thoroughly familiar and well trained in psychological research.  And they alone, moreover, can decide what particular form such an experiment ought to take in a given practical situation.  It must be left to them, for instance, to judge in which cases the mental function of economic importance ought to be tested after being resolved into its components and in which it ought to be examined in its characteristic unity.

XI

CONTRIBUTIONS FROM MEN OF AFFAIRS