INTEGRATION OF MOVEMENTS IN LEARNING IN THE RAT 487 



ability. When it is hyponormal, progression from the entrance 

 box to the plane may be slightly diverted or wandering pro- 

 gression may take place in any direction. Sometimes climbing 

 and wandering movements return characteristic of the early 

 trials of learning. Similar behavior was observed when investi- 

 gating learning in the latch-box problem, and as was noted in 

 table 8, progression to the latch was ineffectively performed. 

 With the inclined-plane problem, identical ineffective progres- 

 sion appeared, and this is indicated in table 15. With the rat 

 whose record is presented in this table, frequently effective 

 responses and partly ineffective posturing before the plane 

 appeared for the production of the modified extensor thrust. 

 . Such consideration of the physiological conditions as deter- 

 mines the effectiveness of every movement and every method, 

 is significant in the understanding of learning of every problem. 

 Compensation in the use of other methods is very inad- 

 equate when measured with the results obtained the num- 

 ber of perfect consecutive records. The number of these 

 records indicates the effectiveness of the extensor thrust as 

 compared with other methods used in learning the inclined-plane 

 problem. The ineffectiveness of the use of other methods is 

 not alone measured by the number of perfect records, but by the 

 use of other localized parts of the rat's body to plunge the plane 

 when the extensor thrust cannot be produced. Physiological 

 compensation appears as a result of the undeveloped condition 

 of the organism. When the modified extensor thrust is used, 

 the weight of the fore part of the body is added to the force 

 exerted by the extensor thrusts to bring the plane down. When 

 the plane is ascended, compensation is attained by the use of 

 two localized parts, the fore and the hind limbs with the weight 

 of the body. In a similar manner, the weight of the body is 

 used when in running either the fore or the hind limbs strike 

 the plane and the plane is plunged. And this compensation in 

 the use of other parts occurs with the same tendency as was 

 observed to take place in learning the latch-box problem, there 

 takes place a reduction in extensor tone of the rat's limbs to 

 restore symmetry to both sides of the body. 



