28 WALTER S. HUNTER 



olfactory inequalities would persist after the light was turned 

 out and would aid in delayed reactions only if associated with 

 the light. More attention will be given to this possibility later 

 in the discussion. 



After the animal had been trained until it chose the lighted 

 box almost perfectly, delays were be^un. The light was turned 

 off just as the animal reached the box. This was called the 

 first stage of delay. At the second stage, the light was turned 

 out when the animal was half way to the box. At the third 

 stage, the light was turned out just as the experimenter started 

 to raise the release box. Here there was a genuine delay, al- 

 though a small one. The first two stages served primarily to 

 adapt the animal emotionally to the sudden change from light 

 to darkness. The rats and dogs usually ran so fast that their 

 momentum was sufficient to carry them into the box when once 

 they were started toward it. In any case they only needed to 

 continue in the direction in which they were going. This,- how- 

 ever, was not the case with the third stage. The light luas put 

 out before the animal started. Throughout these three stages, 

 the animal was released promptly at the end of five seconds. 

 From this stage on, where the animal was detained one or more 

 seconds after the light was out before being released, it was 

 obviously necessary to let the animal see the light before this 

 was turned off. Occasionally, the interval thus required w^as 

 more than five seconds. In these higher stages of delay, I 

 always waited until I felt sure that the animal had seen the 

 light, and then turned off the current while the animal was 

 still oriented toward the source cf light. Record was kept of 

 any change in the orientation which an animal made after the 

 light was turned oft'. How detailed these records were will be 

 seen in the section on experimental results. 



The delays were gradually increased in length until one was 

 found at which the animal failed. They were then decreased 

 until the animal was again making a high percentage of correct 

 choices, when the intervals were again increased. An animal 

 was thus tested twice for the limit of its ability to delay with 

 the backgrounds surrounding the entrances to the light boxes 

 all similar the one to the other. When this limit was found, 

 the wall of the box about the entrance to c was covered with 

 white cardboard ; that about h, with a black ; and that about 



