PERSEVERANCE REACTIONS IN PRIMATES AND RODENTS 9 



The Three Possible Alleys are the three exit alleys that would 

 not afford escape during the immediately preceding trial. 

 Although only one of these alleys will actually afford escape 

 during a given trial, all three are inferentially possible ave- 

 nues of escape from the adult human subject's standpoint. 

 The following order is observed by the experimenter in choos- 

 ing right alleys for each of the 100 formal trials: 



1st trial — alley No. 1 will afford escape 



This order is repeated so that, e.g., the right alley of the 

 first trial is also the right one for the seventeenth trial, the 

 right alley for the second trial is also the right one for the eigh- 

 teenth trial, etc. This order is such that each of the four exit 

 alleys is the right alley for 25 of the 100 formal trials. 



