There is, however, one other source of increasing error, with the increasing combination of judgments, supposed above. The judgment processes might go on at the same time without any impairment of the accuracy of the single judgment, and yet the results, as expressed, might show a falling-off in accuracy. This imperfection would then be due to a partial failure of the retentive and reproductive processes, and not to the imperfection of the judgment processes. I have found no sure means of separating this factor and excluding it. As the experiments were arranged and conducted, though, I believe any impairment in accuracy resulting from combination is more likely due to interference of the judgment processes. If neither of these factors is efficient, on the other hand, there will result no falling-off in accuracy of results when single judgments are combined. To be sure the conditions of the experiment, as outlined so far, do not preclude the possibility of the combined judgments occurring in succession, and so giving rise to as large a percentage of correct results as when occurring singly. That is, while one of the so-called combined judgments was in process, the latent conditions of the other would remain for the moment as mere physiological or possibly psychical dispositions, and to these one would "hark back" in the next moment. Here the reaction method is suggested as the means of assurance that this is not the case. But this method, we have already seen, will not lend itself to work of such precision as this. The probability of this succession of judgments is reduced to a minimum in the experimental groups following. It can be practically precluded by a prevention of all sensory images. In these experiments every precaution was used to prevent them. In all cases where visual stimuli were used, for instance, a brightly illuminated blue field immediately succeeded the momentary stimulus, while comparative darkness preceded it. I cannot be so sure that there were no memory images functioning. But all observers were carefully questioned on this point at frequent intervals during the experiments, and no evidence of their existence was found in any case. I feel sure sensory images were excluded and think memory images very improbable. SINGLE AND COMBINED JUDGMENTS FROM VISUAL AND TACTUAL STIMULI