54 L. W. SACKETT 



green colored papers of the Bradley series, and Nos. i, ii, 21, 

 32, 41, 45, and 50 of Nendel's gray papers have been used as 

 stimuli.' This heterogeneous light was made necessary by the 

 fact that the apparatus for obtaining monochromatic light was 

 not available. Had the means for obtaining pure color been at 

 hand such as was recently described by Yerkes and Watson (52) 

 the problem would have been very much more definitized. But 

 just as the apparatus is more highly specialized, the problem 

 and the results are equally limited and specialized. If pure 

 color is used as a stimulus, the conclusion must be that the 

 animal can or cannot, rather does or does not use pure color 

 in determining his reactions. With more definite apparatus 

 results would, no doubt, have been more highly satisfactory, 

 especially in the quantitative brightness reactions. However, 

 it is not entirely safe to draw conclusions concerning an ani- 

 mal's ability to tell color in general when it has been tested only 

 in a laboratory dark room with a form of stimulus which it 

 had never encountered either individually or in its phyletic 

 development. The form of the stimulus used carries out the 

 general policy of this study; viz., to keep all conditions as near 

 to the natural environment as possible. The method employed 

 at least outlines the problem in a broad and general way and at 

 the same time reveals certain unique features of the learning 

 process. 



Similar precautions in regard to odor of food, trailing and 

 special markings were exercised in designing the apparatus and 

 carrying out this series of experiments as were observed in the 

 form tests just reported. The food boxes were made of one- 

 half inch lumber four and one-half inches square inside measure 

 and four inches high. They were made first from four pieces 

 of lumber forming a hollow cylinder from which the boxes 

 were sawed with great care to get them of the same height. 

 These boxes had no bottoms but were set loosely on a base- 

 board raised five inches from the ground. Thus, the food never 

 touched the box, but left most of its residual odor on the base- 

 board which remained constant throughout the experiment. In 

 addition, a secret pocket was made on the base-board inside 

 the box in which a piece of the kind of food being used was 

 concealed so that either box which the animal might approach 

 contained food; but he soon learned that he would not be 



