592 W. T. JAMES 



dog's antagonism to the experimenter, and the laboratory 

 situation. In most cases, as soon as they are led to the door 

 of the laboratory they lie down and refuse to enter. 



As in the salivary experiments, there are also intermediate 

 types of behavior observed in the motor situation. The 

 classification of the intermediate group of dogs is based 

 on the excitation-inhibition ratio, and on the general behavior, 

 made up of the reflex system correlated and integrated with 

 the leg action. These animals were not consistent in their 

 response to the signals. In some cases, a complete avoidance 

 of the shock appeared to eliminate the excitatory effect of 

 the following signal, and the animal received a reinforcement 

 on the second signal. The ratio here is 50 positive to 50 

 negative responses. Other dogs responded with 2, 3, 4 or 

 even 5 positive responses for one reinforcement. The phe- 

 nomenon here is probably the same as the "effect" in trial 

 and error learning. The significant thing is the difference in 

 value of those constitutional factors determining the ' ' effect. ' ' 

 One of these is the difference in the ratio or predominance 

 of excitation over inhibition, shown in the excitation-inhibition 

 ratio. It is reasonable to suppose that in those animals in 

 which the conditioned avoiding reaction occurred repeatedly 

 after its formation without continued reinforcement, the ex- 

 citation value of the signal is greater than in those which 

 do not form the reaction. On the basis of our observations 

 in these experiments, it is probable that as a larger number 

 of animals are trained there will be a continuous gradation 

 between the inactive and highly excitable types in terms of 

 this excitation-inhibition ratio. 



The dogs of group A become progressively less active as 

 the experiments continue, until they finally lean against the 

 harness and confine the reaction wholly to the foreleg seg- 

 ment. All movements of the head disappear. Generally the 

 reaction is made to the shock rather than to the signal, and 

 in every case there is an alternation of flexion and extension 

 of the leg as the signal and shock continue. In the dogs of 

 the B group, the postural systems are always active, and 



