372 TITCHENER AND PYLE— ON THE AFTER-IMAGES [July 23, 



The control experiments, with 30 sec. exposure, gave the results : 



Observer. Color Seen. A(ter image. 



T Green Purple 



G Yellow Dark blue 



Blue Yellow 



N Pink ? Violet 



Yellow Blue 



The general results of these experiments may be summed up in 

 the following propositions. 



1. With every one of our observers, regular and casual, we have 

 been able to raise a color-component in the stimulus from a sub- 

 liminal to a normally supraliminal value, while the stimulus ap- 

 peared throughout as gray. In no instance of this kind has the 

 observer found the complementary color in the after-image. Our 

 results thus stand in direct opposition to the observation of 

 Tschermak. 



2. There are, however, marked individual dififerences among the 

 observers. In the 7 min. which represented the limit of our obser- 

 vations, it was difficult, with G and N, to increase the color-com- 

 ponent, without detection, to a normally supraliminal amount : with 

 T, P and B there was no such difficulty. The control images, on 

 the other hand, were obtained most readily from T and P. 



The observer N is of the subjective type, and is often misled 

 by an " expected " or " imagined " color. Thus a disc containing 

 17*5° G was seen as B with a rim of Y; the after-image, after 6 

 min., was a Y of irregular form, larger than the stimulus. We 

 recur to these " imagined " colors later. The remaining observers 

 were of a distinctly objective type. 



3. There were also, as might be expected, marked dififerences in 

 the " coloring power " of the Zimmermann papers. Experiments 

 of the form A were easiest with B, less easy with V; then follow 

 in order R, G, Y. The last-mentioned color, indeed, gave results 

 only with entirely naive and unpractised observers. The R and G, 

 when seen as color, usually appeared first as Y. 



4. As a rule, the' after-images, whether colored or gray, devel- 

 oped very slowly. The gray images, in particular, might appear 

 only after a blank interval of 15 to 30 sec. They usually showed 



