differences which, placed about 12cm to the left of a constant fixation point, were exposed for one hundredth of a second and judged under three different distributions of attention. The conditions were very similar to Wirth's, although, of course, they were far less complicated. In these observations, my attention was for the moment raised to the very highest pitch of concentration, while the background was so obscure that I could not possibly analyze it. I have found certain observers who agree with me in experiencing, under these conditions, a marked difference between maximal and minimal clearness-levels, while others distinguish simultaneous processes of intermediate clearness-degrees. This difference, which is borne out by the results of a large number of systematic experiments on degrees of clearness,[1] has led me to assume two different types of the attentive consciousness, the 'dual-division' and the 'multi-lever formation. Evidently Wirth, and probably also Wundt, belong to the latter type. Whether Wirth's results would have been different if he had had observers of the first type, it is impossible to say. But it still remains a disadvantage of his experimental work that in all of the final series he was the sole observer (§ 10). The same objection is implied in Grünbaum's review, although he refrains from making it an explicit criticism.[2] It is true that Wirth made preliminary experiments with several less skillful observers; and he regards the results as utilizable, because they show a rough agreement with some of his own observations obtained at an early stage of practice. Nevertheless, these other observers made binocular, and not monocular observations upon a plane, and not upon a funnel-shaped field of vision; so that the experimental conditions in their case were quite different from (much simpler and easier than) those under which Wirth himself later completed the final series. I might add that Grünbaum also considers Wirth's experimental conditions as too complicated and artificial, and the requirements made upon the observer's attention and introspective self-control as too difficult (if not even self-contradictory), to guarantee a successful solution of the problem.
Finally, Wirth objects to my using collectively the results of his Schwellenmethode (§ 11). I combined into a single frequency curve all the numerical clearness values given in his six schemata, each schema representing a different distribution of attention. The reason for his objection is that some of the schemata were obtained at an earlier, some at a later stage of
- ↑ The Measurement of Attention, Am. Jour. of Psych., XX, 1909, 473-529.
- ↑ Op. cit., 98.
