86 CHARLES A. COBURN AND ROBERT M. YERKES 



iments were resumed at the point of interruption of the regular 

 series of settings. Thus, if five trials were given, beginning with 

 setting 1 and extending through setting 5, the next series would 

 begin with setting 6 and continue through setting 10. 



As a matter of convenience, it was also decided to have the 

 two crows work on different settings. For example, while crow 

 3 was presented with the settings 1 to 5, crow 4 would be presented 

 with settings 6 to 10. This enabled the experimenter to avoid 

 the necessity of refilling the food containers after . each trial, 

 and it also prevented the crows from developing the tendency 

 to follow one another by sensory cues. 



After a very few days of experimentation, both birds reacted 

 with remarkable alacrity and facility. They were, as a rule, 

 prompt to enter the reaction area and almost as prompt to 

 leave the exit area. 



In the initial regular experiments, thirty seconds confinement 

 in the wrong compartment was used as punishment for mistakes. 

 But it shortly appeared that this was too long an interval, for 

 the birds hesitated to enter any of the compartments after a 

 half minute confinement in one of them. It was therefore 

 decided to use the period of fifteen seconds as punishment for 

 incorrect choices. Especially during the early experiments, the 

 crows often exhibited considerable fear and excitement when 

 shut in the small compartments. This diminished toward the 

 end of our work, and it was then possible to confine them for 

 a half minute or even a minute without causing disturbing 

 excitement. 



The experimenter kept, as a matter of routine, a record of the 

 time from admission to the reaction chamber to entrance into 

 the right compartment. There is no special reason to consider 

 these records significant, and we shall omit them from this report. 



Careful record was also kept of the chief features of the behavior 

 of the bird during this interval. The simple system of symbols, 

 which appears below, was adopted for this purpose. 



O, to center of the reaction area 

 r, to left hand far corner of the area 

 -|, to right hand far corner of the area 

 L, to left hand near corner of the area 

 _j, to right hand near corner of the area 

 U, to center of the near side of the area 

 C, to center of the left side of the area 

 3, to center of the right side of the area 



