316 WALTER S. HUNTER 



given in table 3. The significant fact from the standpoint of 

 tone sensitivity is that the animals maintained their relatively- 

 high percentage (60% to 75%) of correct reactions when the 

 chord was not sounded. This is conclusive proof that the slight 

 improvement in accuracy found in the learning records in no 

 way depended upon tone sensitivity. In other words the rats 

 showed themselves as unable to respond to a fairly complex 

 klang as to a simple tone. 



The remaining controls were not. worked out in detail with 

 rats 32 and 38. The diary records indicate clearly that the 

 responses were governed by position habits. Rat 31 was tested 

 more fully. There are two chief points of interest in the data 

 secured through these controls, (1) a high percentage of correct 

 responses can be made on the basis of position (kinaesthetic) 

 habits even though the series of presentations is" very complex 

 and cannot be said to be learned; and, (2) simple alternation 

 seems to be the fundamental position habit. Although data 

 with control 4 are lamentably lacking, it seems probable, from 

 reasons given below, that the position habits were affected 

 by punishment. 



Control 2 did not disturb the reactions of rat 32, but did 

 slightly those of rat 38. Rat 31 was undoubtedly affected by 

 closing up both alleys. This was not a disturbance due to a 

 changed visual (brightness) condition in the alleys, because the 

 relation of the apparatus to the source of light precluded this. 

 It would seem that normally rat 31, and probably rat 38, was 

 greatly dependent upon the atmospheric conditions (freshness 

 and better air circulation) of the two alleys. This is only ad- 

 vanced as a probability. Tests made directly upon the rat's 

 ability to discriminate such stimuli offer the only definite ap- 

 proach to a solution of the question. 



Controls 4 and 5 had no effect upon the animals tested. The 

 poor percentage made by rat 32 with control 4 is to be accounted 

 for entirely in terms of peculiar position habits. Part of the 

 time a simple alternation was present; part of the time there 

 was alternation after a success only. Control 3, by leaving 

 both alleys of the apparatus open, permitted the rats' position 

 habits (or kinaesthetic controls) to assert themselves in an un- 

 modified way. In every case where this control was used, the 

 rats tended to fall back immediately upon the method of simple 



