Page:Mind (New Series) Volume 8.djvu/39

II. SUBJECTIVE COLOURS AND THE AFTER- IMAGE: THEIR SIGNIFICANCE FOR THE THEORY OF ATTENTION. BY MAEGAEET FLOY WASHBURN. SOME time ago, while studying what is called the " flight of colours " in after-images produced by white light, it oc- curred to the writer that it would be interesting to observe the effect on this colour series of an effort to alter the colours subjectively. The following paper is in part a description of the results obtained in a series of experiments bearing on this problem, and performed during the winter and spring of 1898. By " subjective colour sensation," or "subjective alteration of colour," is meant the effect of an attempt to call up in the retinal field of the closed eye, or with open eyes in a dark room, the sensation of a given colour. Prof. Kiilpe notes in his Outlines, 28, 2, and 74, 3, that it is possible in a dark room to call up at will patches of various colours, and that these central excitations sometimes ap- proach the intensity of peripheral excitations. The problem here investigated relates simply to the influence of centrally excited sensations produced by such efforts upon the or- dinary " ringing-off " of after-images. It may be noticed at the outset that these experiments failed to show one hoped for result, which may perhaps yield itself to further investigation. During some of the earlier and less carefully controlled experiments, the effect of an effort to tinge the after-image with a certain colour seemed to be an intensification of the complementary colour ; e.g., a stage which in the preceding experiment had been whitish or indefinite in colour flashed out into vivid green when the subject attempted to turn it red. The obvious suggestion was that this was a contrast-effect, and contrast of a new order, so far as the writer was aware, where the/ inducing colour was of purely central origin. The supposi- tion was rendered more plausible by the recollection of an experience that occurred some years ago. While spending a few days in an unfamiliar house I noticed from time to