248 The Animal Mind 



it away from a certain object, while the crabs had no outlet 

 at all for their photic and nutritive instincts. Very likely 

 a longer course of training than that employed by Bethe 

 might have succeeded in suppressing the instincts. The 

 chick's case really belongs to a form of learning which we 

 shall consider later on; that where the inhibition depends 

 on the discrimination of different stimuli. The purest 

 instance of the kind of modification of behavior by ex- 

 perience at present concerning us is furnished by Mobius's 

 experiments with the pike (276), afterward repeated by 

 Triplett with perch (407). The pike was kept in one half of 

 an aquarium, separated by a glass screen from the other 

 half, in which minnows were swimming about. The pike 

 naturally dashed at them, and received a bump on its nose 

 whenever it did so. After a considerable period of this 

 sort of experience, the glass screen was removed, and the 

 minnows were allowed to swim freely around the pike, 

 when it was found that the latter's instinct to seize them 

 had been Wholly inhibited by the disagreeable consequences of 

 such action. Triplett's description of the occasional struggles 

 of the instinct to assert itself is extremely interesting. An 

 analogous case is offered by Goldsmith's account of the 

 shell-inhabiting fish, Gobius, which, when a glass partition 

 was placed between it and its shell domicile, dashed against 

 the glass for a time, but after three and a half hours went 

 around it, and the next day did so after only a quarter of an 

 hour's unsuccessful attempting to get through the parti- 

 tion (146). 



The second kind of training in the inhibition of an in- 

 stinct, where the performance of an action opposed to instinct 

 is made to produce pleasure, is illustrated by Spaulding's 

 work on "Association in Hermit Crabs." He found that these 

 animals, which are positively phototropic, could be trained 



