PERSEVERANCE REACTIONS IN PRIMATES AND RODENTS 7 



It is undesirable that a subject, while within the semicircular 

 enclosure, shall be able to see whether the slides in the boxes 

 at the outer mouths of the exit alleys are in an open or a closed 

 position. On this account the apertures that allow passage from 

 the semicircular enclosure into the exit alleys extend only half 

 way from the top of the apparatus. The subject must, there- 

 fore, climb over a 7.5 cm. partition in order to get into any 

 exit alley, and he cannot see the lower half of the slides at the 

 exit alleys mouths from any part of the semicircular enclosure. 

 His tendency to cling to the top of the partition in an effort 

 to keep his feet off the apparatus floor is discouraged by means 

 of a copper wire which runs parallel to and just in front of the 

 upper edge of the metal partition. This wire is connected with 

 one pole of the induction coil and the partition is connected 

 with the other pole. 



The walls of the apparatus and the surfaces of the slides that 

 are visible from within the apparatus are battleship gray. The 

 interior of the transfer boxes and the inner surfaces of the slides 

 are black. The top of the apparatus is glass. 



Apparatus for Primates. — This type of apparatus is described 

 in a previous communication (1), hence it is necessary to give 

 here merely its essential points of difference from the rodent 

 apparatus just described. The primate subject's willingness to 

 enter the apparatus for the sake of reward for escape there- 

 from renders transfer boxes and an equipment for electrical 

 stimulation unnecessary. The mouths of the alleys are blocked 

 by means of doors, which are hinged to the apparatus. The 

 main enclosure is fan-shaped rather than semicircular. The only 

 important difference between its reactive value and that of the 

 rodent apparatus is contained in its lack of all means for rein- 

 forcing the confinement-stimulus with the more definitely dis- 

 agreeable electrical one. 



Method of Conducting Experiments 

 First Preliminary Trial. — The rodent subject is forced into 

 the entrance alley and is given an electrical shock. The strength 

 of this stimulus is determined for each individual by increasing 

 it until a definite escape-response is obtained. After the initial 

 shock the rodent is allowed to explore the apparatus, and the 

 stimulus is not repeated until visible escape-responses cease. 



