578 W. T. JAMES 



was employed as the conditioned stimulus. The conditioning 

 signal preceded the shock for 5 seconds and then coincided 

 with it for 5 seconds or longer. The animal was required to 

 make a continued avoiding reaction, that is, the flexed leg 

 must be sustained as long as the signal sounded. Each time 

 the leg was lowered during the signal, the animal received 

 the shock. The behavior may be understood better by refer- 

 ence to plate 101 (fig. 1) showing a dog holding the foot in 

 the avoiding position while the clicker sounds. The kymo- 

 graphic record for this animal is shown in text-figure 101 



(%. 1). 



Most of the dogs used in the development of the motor 

 reflex had already been trained with the salivary reaction 

 and were, therefore, accustomed to the laboratory. Straps 

 under each leg confined the dog to the platform. In these 

 experiments, as in the conditioned food taking reaction, every 

 factor of the performance is important and must be considered 

 in classifying the animals. The periods of inactivity, or in- 

 tervals between the signals, are as significant as the leg 

 movement and postural shift to the stimuli. Behavior differ- 

 ences among the animals were observed in every phase of 

 the adjustment, including the following: 



A. Initial laboratory adjustment. 



B. Strength of shock to elicit the leg movement and nature 



of reaction to first shock. 



C. The nature and course of the reaction. 



(a) time of making the adjustment. 



(b) true avoidance or simple flexion. 



D. Reaction time. 



E. Behavior during interval between signals. 



F. Generalization, or reactions to other signals introduced. 

 (T. Difference in excitatory-inhibitory ratio. 



As in the previous section, the animals showing the greatest 

 behavioral differences will be discussed first, and the groups 

 will be designated again as lethargic group A, active group 

 B, and intermediates, A-minus and B-plus. The results of 

 the experiments are tabulated in table 7, with group A at 



