Modification by Experience 229 



was normal. It would be very strange and quite out of accord 

 with the general behavior of animals in labyrinths if a prac- 

 tised rat should be more disturbed by the removal of an accus- 

 tomed stimulus than an unpractised one. No effect on the 

 learning power of the rats was produced by making their 

 paws anaesthetic (431). Yerkes has shown, although with- 

 out operating on his subjects, that the Japanese dancing 

 mouse does not necessarily depend on sight, smell, or touch 

 for guidance in the labyrinth (469). It should be noted that 

 proof of an animal's ability to learn a maze when deprived 

 of a certain class of sensations does not show that it normally 

 makes no use of those sensations in the learning process. 



As a matter of fact, the stimuli which originally give the 

 "clews" in the case of the white rats must be the rats' own 

 movements. "Muscular sensations dependent on the direc- 

 tion of turning," " kinsesthetic sensations," are the only 

 elements in our own experience that suggest themselves as 

 possibilities where an animal learns the maze equally well 

 when blinded, anosmic, deaf, and partially deprived of touch 

 (431). But this is not the same as saying that when an ani- 

 mal has learned the labyrinth, it is "guided by kinaesthetic 

 sensations." Nor can we show that an animal was not guided 

 by some other stimuli, say visual ones, in learning the laby- 

 rinth, when we prove that having once learned it, the animal 

 is not disturbed by the removal of these stimuli. For when 

 the labyrinth path has been learned, the habit may be in a 

 sense quite independent of the very stimuli that served to form 

 it, precisely as the pianist becomes independent of the notes 

 in playing a familiar piece. The fact that Yerkes's frogs 

 were disturbed, after the habit had been formed, by the inter- 

 change of the cards, indicates that visual stimuli were still 

 important to them; but if they had not been disturbed by 

 such interchange, when they were fully practised, it would 



