GENETIC TYPE AND THE ENDOCRINES 547 



Finally the animal responds to the rotation of the disk and 

 food rather than to the conditioning signal, and at this stage 

 the dog sits down or sags against the harness and quietly 

 waits. A typical example of the animal in this stage is shown 

 in plate 100 (fig. 1). It seems that the organism is eliminating 

 useless actions, making short cuts, and retaining only the 

 movements essential for taking food. Spontaneous activity, 

 which is low even in the beginning, is reduced to zero. By 

 the time 150 conditioning signals, including thirty-eight test 

 signals, had been given, the conditioned response disappeared 

 altogether, and, unless the dog was starved, it would lie down 

 and remain passive, as shown in plate 100 (fig. 2). The dog- 

 had now reached what may be termed the logical end of the 

 performance. She fully comprehended the laboratory situa- 

 tion. She had learned that food comes with the rotation of 

 the disk, and waited for this during both the test and short 

 signals. Thus the dog no longer performed in a definite 

 stimulus-response manner, even though the same experimental 

 conditions were maintained. Even after the conditioned re- 

 sponse disappears, however, the animal will go into the lab- 

 oratory ahead of the trainer and remain alert while the 

 apparatus is adjusted; then as soon as the experimenter 

 leaves the room, the dog assumes her passive state. 



At the beginning of the experiments, these dogs are in 

 their most active phase and the variation in the performance 

 is toward inactivity and sluggishness. Only when the bodily 

 processes are functioning at their highest level can these 

 dogs be aroused to conditioned action in a quiet environ- 

 ment. 



Reactions of the lethargic group to negative signals. The 

 records for animal 83 $ show that there was no response to 

 the negative signals (text-fig. 91, fig. 2; text.-fig. 92, fig. 1). 

 These dogs became so passive under laboratory conditions 

 that hardly had the negative been introduced when the in- 

 hibition advanced. Since they failed to respond to the clicker 

 of fifty vibrations per minute, it was thought that they might 

 be a good type to use in differentiation experiments. In the 



