INTEGRATION OF MOVEMENTS IN LEARNING IN THE RAT 463 



The attainment of posture with the effective production 

 of the neck reflex movement was observed to be facilitated in 

 rats manifesting reflex excitability. In the case of the inclined- 

 plane problem all rats can solve it, and consequently the results 

 obtained are quite different. Posture can not be produced 

 when the reflex thrusts are undeveloped even when reflex excit- 

 ability is hypernormal. Some effect on the organism is evident, 

 however, when excitability is manifest. This effect is shown in 

 the rapidity and constancy with which a response, or even a 

 method to plunge the plane occurs, and the contrary is the 

 case when reflex excitability in rats is hyponormal. It is con- 

 ceivable that rats manifesting hyponormal reflex excitability 

 before the plane was plunged, would not likely show any in- 

 creased excitability thereafter. Little or no disturbance in 

 the movements of rats is observable. When the plane is plunged, 

 progression from the plane is as slow as when ascending or walk- 

 ing over the plane often takes place. On the other hand, an 

 evident increase in excitability is manifest in rats, in which 

 reflex excitability is hypernormal. A parallel to this was seen 

 with the latch-box problem when an evident increase in excit- 

 ability was noticeable in rats after the latch was raised, and 

 taking of food did not occur until reflex excitability had sub- 

 sided. When the plane was plunged, progression from the 

 plane was very rapid and continued frequently for some distance. 

 Sometimes descent from the plane or turning from it w r as at- 

 tended by gazing at it or smelling it. In one or two instances 

 progression was rapid to the front of the problem and then 

 slowly proceeded to the open door and to the food. 



If our conclusions in regard to the importance of the existence 

 of reflex excitability are correct, then the appearance of inter- 

 action of body parts for learning will in some rats appear before 

 the plane is plunged and in others not until the plane is plunged, 

 or when reflex excitability is hyponormal, not until several 

 trials and then only after the plane is plunged. In the last 

 instance either reflex excitability or interaction is developed. 

 In order that the appearance of interaction of body parts be 

 shown to be developed at different periods of learning in accord- 



