HABIT FORMATION IN THE DOG " 23 



In experiment 4 the following chords were used: (i) Con- 

 taining c' (256 d.v.) c'-e; c'-e'c"; g-c'-e'; c'-eb'; c'-eb'-c"; 

 g-c'-el?'; a-c'; f-c'; f-c'-a' ; a-cT; c'-a'-f; (2) containing g' 

 (384 d.v.); g'-b; g'-b'-g''; g'-bb'; g'-bb'-g'; e'-g'-c"; eb'-g'-c"; 

 g'_b'-d' ; d'-g' ; d-g'-b' ; g'-b'-d". These chords w^ere used in- 

 differently, regard being paid only to which of the two stimulus- 

 tones was contained in the chord. That the chord might be 

 sounded at once, an extra valve was put on the main pipe lead- 

 ing from the tank, which was to be kept closed except when the 

 stimulus was given. Thus the stops opening the valve leading to 

 each variator could be pulled out as desired, and when the main 

 valve was opened the entire chord would be sounded at once. 



The results of this experiment approximate closely those 

 obtained by Kalischer and Rothmann. I have never observed, 

 however, w^hat they both report, namely, that after a few trials 

 have been given the animal becomes "fatigued." If the animal 

 is left alone as many as thirty trials may be given in control 

 tests, evolving a prompt response each time. This makes me 

 suspect that the failure of Kalischer 's dogs to react to the food- 

 tones, if the latter in a four or five minute series were "allowed 

 to sound often one after the other, ' ' was due to a lack of discrim- 

 ination rather than to mere fatigue. 



A control test of retention was given sixty days after the 

 last problem had been "learned." Following a private discus- 

 sion of Kalischer 's contention that the dog has an "exceedingly 

 fine sensitivity to absolute pitch," (of which, however, I have 

 never been convinced) I invited the members of the psychological 

 journal club to witness a test of the animals' ability to react 

 properly to their old stimulus-tones. The animals had not 

 worked on the problem since it had been discontinued — in fact, 

 they were then engaged in learning to open a problem-box for 

 their daily food. The two stimulus-forks used in the first prob- 

 lem w^ere used and struck as before. Each dog was given eight 

 stimuli, in the order indicated -by one of the observers watching 

 the experiment through a glass door. Each dog reacted with- 

 out error. Dog i was sniffing at the place on the floor where 

 her problem-box usually stood, and when the first fork was 

 struck, merely crouched and kept sniffing hastily at the floor 

 where she stood. When after perhaps two seconds the fork was 

 struck again, she again crouched and in some confusion found 



