HABIT FORMATION IN THE DOG 11 



bring them forth. Even the movements of the head and ears 

 at noises finally disappeared after destruction of the posterior 

 corpora quadrigemina with a needle. The animals' reactions 

 to tones, however, were much less affected. Tests were resumed 

 from three to four days after the operation. Kalischer says 

 that some disturbances of tonal discrimination followed — i.e., 

 the animals did not always react and inhibit correctly. (The 

 percentage of error and the number of trials are not reported.) 

 But he asserts that the animals "undoubtedly discriminated" 

 between their respective food-tones and "Gegentone," and as- 

 cribes the disturbance w^holly to the shock of the operation. 

 This may be correct, but evidence is lacking. If the dogs failed 

 to react properly to the different tones the assumption that 

 their failure was due to some other cause than inability to dis- 

 criminate, is a mere guess. 



Kalischer continues, "from the second week on the animals 

 began to exhibit the old relations ; they snapped in accustomed 

 fashion at the food-tone and shrank back at the 'Gegentone,' 

 and even to the tones adjacent to the food-tone." Indeed, the 

 reactions "appeared almost automatic," the animals "attended 

 exclusively to the food" and less than before to surrounding 

 objects, and their discrimination seemed improved rather than 

 diminished. They reacted correctly when chords and discords 

 were sounded if they contained the food-tone. It was possible 

 to retrain even the "most mutilated" dogs to react to a new 

 food-tone and to inhibit reaction to the former one. Further, 

 animals not trained before removal of both temporal lobes 

 could be taught to make the same discriminations, although they 

 required a longer time than did the others, since they were 

 not easily accustomed to being handled and to making de- 

 finite movements. 



Kalischer does not consider the possibility that the dogs 

 had been rendered deaf by the operation, and were continuing 

 their choice of reaction or inhibition of reaction to certain tones 

 on the basis of rhythmic or habitual order of presentation of 

 stimuli, or of secondary, extra-auditory stimuli, although one 

 would naturally suspect that this were the case. He asserts 

 that no other conclusion is left to us but that the dogs were 

 deaf to noises and not to tone. He concludes accordingly that 

 the perception of noise and that of tone are different functions ; 



