We might also put into this class the meagre experimental investigations concerning the mutual influence of feelings. When sound, light, and touch impressions, each of which, isolated, produces a feeling of a certain degree, are combined with one another, the experiment can show very characteristic changes in the intensity of pleasure and displeasure. From such routine experiments of the laboratory it might not be difficult to come to more complex experiments on the mutual relations of feeling values and especially of the combinations of pleasure with displeasure. This would lead to an insight into the processes which are involved in the fixing of prices, as they are always dependent upon the pleasure in the acquisition and the displeasure in the outlay. The exact psychology of the future may thus very well determine the conditions under which the best effects for the satisfaction of economic demands may be secured, but our present-day science is still far from such an achievement: and it seems hardly justifiable to propose methods to-day, as it would be like drawing a map with detailed paths for a primeval forest which is still inaccessible. XX EXPERIMENTS ON THE EFFECTS OF ADVERTISEMENTS We have said that the time has not yet come for discussing from the standpoint of experimental psychology the means to secure the ultimate effects of economic life, namely, the satisfaction of economic demands. If this were the only effect which had economic significance, this whole last part of our little book would have to remain a blank, as we wanted to deal here with the securing of the best effects after having studied the securing of the best man and of the best work. Yet these ultimate ends are certainly not the only mental effects which become important in the course of economic processes. In order to reach that final end of the economic movement, often an unlimited number of part processes distributed over space and time must coöperate. The satisfaction of our thirst in a tea-room may be a trivial illustration of such a final effect, but it is clear that in order to produce this ultimate mental effect of satisfying the thirst, thousands of economic processes must have preceded. To bring the tea and the sugar and the lemon to the table, the porcelain cup and the silver spoon, wage-earners, manufacturers and laborers, exporters, importers, storekeepers, salesmen, and customers had to coöperate. Among such part processes which serve the economic achievement are always many which succeed only if they produce characteristic effects in human minds. The propaganda which the storekeeper makes, for instance, his display and his posters, serve the economic interplay by psychical effects without themselves satisfying any ultimate economic demand. They must attract the passer-by or impress the reader or stimulate his impulse to buy, and through all this they reach an end which is in itself not final, as no human desire to read advertisements exists.