an irregular distribution makes the number appear larger or a close clustering reduces the apparent number, and so on, the business man would be quite able to profit from such knowledge.  The jeweler who shows his rings and watches in his window wishes to produce with his small stock the impression of an ample supply.  He lacks the psychology which might teach him whether he would act more wisely in having the rings and the watches separated, or whether he should mix the two, whether he ought to choose a background which is similar in color or one which contrasts with the pieces exhibited, whether he ought to present the single object in a special background as in a case, or to show it without one.  He is not aware that by simple psychological illusions, it is not difficult to change the apparent size of an isolated object by special treatment, making his show-piece appear larger by a fitting background or intentionally making a dainty object appear smaller by contrasting surroundings.  These, to be sure, are very trivial illustrations, but the same fundamental psychological laws which are true for the show-window of the next corner store are true for the world-display of the nation.  The point is to present clearly the idea, which can be most simply expressed in such trivial material.  But it may be added that even in the case of the most indifferent example a few hasty experiments with one or two subjects cannot yield any results of value.

All parts of physiological psychological optics can contribute similar material.  The questions of color harmony and color contrast, light intensity and mutual support of uniformly colored objects, of irradiation, depth and perspective, are significant for an effective display in the show-window, and the laboratory results can easily be translated into psychotechnical prescriptions.  But here it is still more necessary to separate carefully the merely optical impression from its aesthetic side.  All that we claimed as to the poster is still more justified for the presentation of the saleable objects themselves.  As soon as the display of the articles forms a real work of art, it must produce inhibitions in the soul of the spectator by which the practical economic desire is turned aside.  Beauty here too has strong power of attraction, and moreover the suggestive power, by which it withdraws our senses from the chance surroundings, forces us to lose ourselves in the offered presentation.  But just through this process the content of the display becomes isolated and separated from the world of our practical interests.  Our desires are brought to silence, we do not seek a personal relation to the things which we face as admiring spectators, and the intended economic effect is therefore eliminated.  Whoever is to examine the psychotechnics of displays and exhibitions must therefore study the psychology of aesthetic stimulation, of suggestion, of the effects of light, color, form and movement, of apperception and attention, and ought not to forget the psychology of humor and curiosity, of instincts and emotions.  For us the essential point is that here too the experimental psychological method alone is able to lead from mere chance arrangements founded on personal taste to the systematic construction which secures with the greatest possible certainty the greatest possible mental effect in the service of the economic purpose.