558 W. T. JAMES 



nals. If a different signal is used, or even if the negative is 

 applied at the same place in each experimental period, the 

 dog will develop a more stable negative reaction. It is this 

 difference in nervous setting that is especially significant in 

 emphasizing the types, and it is the repeated release of this 

 action without reinforcement which probably contributes to 

 the heightened excitability occurring in many of these dogs. 



Reactions of the active group to other signals. A greater 

 sensitivity and alertness was also exhibited by the dogs of 

 group B when tactile stimuli were employed. The record of 

 the reactions to these stimuli for dog 438 2 is similar to that 

 of the auditory reactions. In the beginning the tactile signals 

 elicited a variety of postural movements directed to the 

 point of stimulation. As the experiments continued the pos- 

 tural movements were directed to the food pans. Although 

 the reaction to tactile signals is weaker, the general course 

 of the behavior is the same when tactile signals or auditory 

 signals are given. The response continued in the case of 

 438 9 until the dog developed an increased restlessness. 



Response of the active group to intense auditor// stimuli. 

 Because of the sensitive nature of these dogs, they were 

 greatly disturbed when the loud buzzer was introduced (text- 

 fig. 93, fig. 2). The signal caused vigorous orientation re- 

 actions and in some cases an escape behavior. Food presented 

 with the signal was refused, indicating that although the 

 animals were acquainted with the laboratory procedure they 

 retained a low threshold of excitation. The postural reactions 

 to the buzzer indicate a wide irradiation of excitation. In- 

 stead of a movement involving only the head, as with the 

 animals of group A, these dogs reacted with total bodily 

 movements, including head, tail, and legs. Further, the re- 

 actions continued for a longer time as an after discharge 

 of excitation. Such behavior emphasizes the fact that these 

 dogs are always subject to stimulation and never become 

 inert and inactive in a habitual situation, as do the dogs of 

 group A. 



