Page:Mind (New Series) Volume 8.djvu/43

 SUBJECTIVE COLOURS AND THE AFTER-IMAGE. 29' negative stage, and then to try the subjective colour. In the case of the subject D. no such division of the experi- ments seemed necessary ; much less effort was required to visualise the desired colour, simply thinking of some red,, green or blue object being apparently sufficient. The first set of results to be discussed are those obtained from the subjects M., W. and 0. Experiments where the- effect of subjective red on the first half of the image was studied will be referred to as the E. I. experiments ; those with subjective green in the first half as the G. I. experi- ments ; those with subjective blue as the B. I. ; while ex- periments with subjective red, green and blue in the second half will be designated as B. II., G. II. and B. II. respec- tively. The effect of subjective red in the E. I. experiments was./ manifested in three ways : (1) The blue positive image was I observed to be strongly tinged with red. This effect was j never visible on the green positive image, which resisted all efforts to turn it red. However (2), the dark lines on the / green positive image were often made to assume a distinctly reddish tone ; and (3) the blue and green stages were not infrequently much shorter than in the unmodified image, the effort to turn them red having apparently the effect of bringing on the red stage sooner than usual. In the G. I. experiments the subjects were asked to make- the image green at its first appearance, shortening or obliter- ating the blue stage ; to hold the green as long as possible,. and when the red stage appeared to force it back into green. It was found (1) that the blue image was tinged with green ; (2) that its duration was distinctly shortened ; (3) that the green image was noticeably brighter, and lasted longer than usual ; and (4) that in some cases the green colour could be brought back after the image had turned red. The subject 0., to whom the final negative image looked dark green instead of dark blue, found that the effect of trying to bring back the green colour after the image had entered the red stage was to "hurry it on" into the final green negative image. The chief results of the B. I. experiment were (1) that the blue positive stage was brighter and of longer duration than in the unmodified image ; and (2) that blue patches appeared on the green image. W. also noticed during many of these experiments flashes and patches of blue light in the retinal field near the image. In the E. II. experiments the effort was made to hold the red image as long as possible, and when the dark blue or