INTEGRATION OF MOVEMENTS IN LEARNING IN THE RAT 465 



trial, and the degree of reflex excitability manifest. The devel- 

 opment of directive integration is also indicated. The reaction 

 times for each trial were taken with a stop watch with split 

 seconds. 



The first absolute indication of the appearance of interaction 

 of body parts in learning is when directive integration is about 

 to be established. Because of the different times in which an 

 increase in reflex excitability occurs in rats, interaction for direct 

 progression to or from the plane takes place in accordance with 

 this increase. To some extent direct progression in either 

 direction is dependent upon the functional condition of the 

 reflex thrust, but mainly upon the degree of reflex excitability 

 manifest by rats. Table 10 shows that directive integration 

 appears very early in rats with functionally developed reflex 

 thrusts and when, on the first trial, reflex excitability is hyper- 

 normal. When these mechanisms are functionally undeveloped, 

 direct progression to the door and to the plane are not facilitated 

 at the same time. When reflex excitability is hypernormal, 

 that part of directive integration, direct progression to the plane 

 appears first, before direct progression to the door or before 

 both parts are facilitated at the same time. On the other hand 

 when reflex excitability is hyponormal, that part of directive 

 integration, direct progression to the door is facilitated first. 

 Efficient movements result from the increase, or the production 

 of reflex excitability by the plunging of the plane. When 

 reflex excitability is strikingly hyponormal, it is necessary that 

 plunging of the plane take place for several trials before reflex 

 excitability is increased, and direct progression to the door can 

 be facilitated. In some instances, rats 15 and 24, table 10, when 

 excitability is scarcely hyponormal and the reflex extensor thrust 

 undeveloped, direct progression to the door may occur only a 

 trial before the appearance of direct progression to the plane. 



From the results presented in table 10, it is seen that the 

 development of interaction to facilitate the appearance of direc- 

 tive integration is generally a gradual one. The first appearance 

 of either one or both parts of directive integration does not 

 indicate that it is completely facilitated. Often many trials are 



