162 CORA D. REEVES 



by hand, moving through an arc of more than three inches and 

 the light over the other box was left hanging still. The rat 

 was dropped upon the table at the center of the circle (see fig. 2) 

 or 80 cm. from each box. Care was taken to place the animal 

 with head in the direction indicated by the arrow. A record 

 of the time taken by each rat in reaching the box, and as to 

 whether the choice was right or left hand, was made. The 

 boxes were interchanged by chance. They were placed along 

 the arc of circle at all points and all distances apart. The same 

 box always had the light swinging. When the box had been 

 reached and entered the rat was allowed to feed if correct choice 

 had been made, and was then picked up and returned for another 

 test. Two rats, A and B, were fed at the box with the still 

 light; C and D at the one with the swinging light. The first 

 days, ten trials were made each day for each rat; then twenty 

 trials daily for the seven weeks the experiment continued. 



Preliminary work. — The rats were put on the table and the 

 time taken for them to reach a single box without light for 10 

 trials each. During these preliminary tests no food was placed 

 in the boxes. The average time per trial was 32 seconds the 

 first day. The second day A went to the box ten times, but 

 B, C and D went to the box three, five, and five times respec- 

 tively, then quit running about before reaching the empty box. 

 The next two days food was put in the box; the average for 

 the four was 9 seconds the first day, and 4 seconds the second day. 



The following two days the two boxes were placed one with 

 food and one without food. The average time for the rats to 

 reach the box was 5.5 seconds for the first day, and 3.1 seconds 

 the second day. , 



The following day the light was put above the food box and 

 not made to swing. The rats A, B, and D behaved as on days 

 when the light had not been there, at least, any hesitation if 

 present was not sufficient to change materially the average 

 time. The rat C, however, after two trials took a longer time 

 each trial, looking at the light before starting and then refused 

 to move when placed on the table. 



The next day the light was started swinging over the one 

 box while left still over the other. The conditions of the ex- 

 periment had thus gradually been reached. The average time 



