280 The Animal Mind 



question resolves itself into three : (i) What sensory stimuli 

 does an animal rely upon after it has thoroughly learned 

 the maze path? (2) What sensory stimuli does an animal 

 naturally rely upon in learning the maze path ? (3) What 

 sensory stimuli can an animal do without, if necessary, in 

 learning a maze path? 



(1) All the evidence indicates that when a rat has thor- 

 oughly learned the maze, its movements have become or- 

 ganized into a system such that the sole requisite stimulus 

 for the performance of one movement is the kingesthetic 

 excitation resulting from the preceding movement. The 

 best proof of this is furnished by experiments where the 

 rats which had learned the maze from its beginning were 

 started at points further along; they could not pick up 

 the true path with any speed until, in running back and 

 forth, they chanced to make two or three correct turnings. 

 This set off the remainder of the maze-running process pre- 

 cisely as playing over the preceding passage would enable 

 a pianist to proceed beyond the point of a breakdown. 

 Similarly, when the maze was shortened by removing a 

 section from its middle, the rats ran against the ends of the 

 shortened passages ; when it was lengthened by elongating 

 certain passages, the rats tried to make the turns at the old 

 points (118). 



(2) and (3) It is difficult to make sure just what sen- 

 sory stimuli function in enabling an animal to learn the 

 maze. The only methods that suggest themselves are (a) 

 that of depriving an animal of the use of one sense 

 and seeing whether he can learn the path, thus answering 

 question (3) above; or (b) that of supplying him 

 with cues especially appealing to a certain sense, and 

 noting whether his learning is accelerated. But neither 

 of these methods reproduces the condition of normal maze 



