These four procedures in the search for useful vocational tests, in the absence of complete vocational psychographs, are quite generally recognized to be but tentative expedients of an explorative character. Individual workers have not always clearly recognized the principles involved in their work, but have proceeded as best they could under the special circumstances. Each method has its own defects and advantages. The miniature model has the advantage of concreteness and apparent relevance, but, as Muensterberg points out, "a reduced copy of an external apparatus may arouse ideas, feelings and volitions which have little in common with the processes of actual life." This writer is inclined to believe, on the basis of his experiments so far, that "experiments with small models of the actual industrial mechanism are hardly appropriate for investigations in the field of economic psychology. The essential point for the psychological experiment is not the external similarity of the apparatus, but exclusively the inner similarity of the mental attitude. The more the external mechanism with which or on which the action is carried out becomes schematized, the more the action itself will appear in its true character." The second method we have described, viz., that of using as the test a real sample of the work done, has certain very obvious advantages. On the other hand, for the vocational test of this type to be at all significant, either the sort of work involved in the occupation must be fairly uniform and homogeneous in all its different circumstances (as in the case of typewriting at dictation, or in the work of filing clerks, accountants, etc.), or else there must be included a large number of samples representing all the various unrelated sorts of work. Moreover, in neither case is the test in any peculiar sense psychological. Such tests could perhaps be best conducted by the employer himself. In fact, employment on trial, which is a common method of selecting operatives and assistants, is a time-honored form of this test, which is not necessarily improved either by calling it psychological or by putting it in charge of a general expert or by removing it to the laboratory.