INTEGRATION OF MOVEMENTS IN LEARNING IN THE RAT 457 



tance with less pressure than would be required if a single lever 

 was present. The bronze spring supporting the arms of the 

 plane and separating the electrical contact points was suffi- 

 ciently elastic to keep these points 1.5 cm. apart. The exact 

 degree of pressure needed to plunge such a plane was deter- 

 mined by experimentation. 



The experimental procedure when investigating learning in 

 the inclined-plane problem differed little from that adopted with 

 the latch-box problem All rats were 40 days instead of 50 

 days old when fed for 2 days in the problem. One trial a day 

 method was used. During this period of feeding, the plane 

 was thrown back on its hinges, so that in the wanderings of the 

 rats, the plane would not be plunged and the interaction of the 

 body parts that would be partly established in consequence of 

 the act, be less evident in the first trial. The relation of the 

 first to succeeding trials is exceedingly important to observe, 

 and the plunging of the plane for the first time must have the 

 same effect upon rats as that of the raising of the latch of the 

 latch-box problem. 



In order to accomplish the solution of the problem, it is neces- 

 sary that progression be directed from the entrance box to the 

 back of the problem box and to the plane, the plane plunged, 

 and then progression be directed to the front of the problem to 

 the opened door. Direct progresion to the plane and then to 

 the door after the plane is plunged may be regarded as two 

 separate parts of directive integration One additional move- 

 ment must be facilitated in learning the inclined-plane that is 

 not used in the latch-box problem, namely, direct progression 

 for some distance from the mechanism which opens the door of 

 the problem box to the food. One difference in the results from 

 those obtained from the latch-box problem must be considered. 



During the first trial the behavior of the rat was carefully 

 noted to see how far a sequence of events determines the char- 

 acter of this trial. This sequence is more readily observable 

 when the functional condition of the rat's reflex mechanism is 

 known. Of the few movements made, all are directed to the 

 problem, to the door, or to the plane. The response to the 



PSTCHOBIOLOGT, VOL. II, NO. 6 



