MAZE STUDIES WITH WHITE RAT 289 



mastered and while it is being run may and do operate as dis- 

 tractive stimuli in so far as they are sensed through vision; it 

 is also possible that certain alterations may disturb the animal 

 because these stimuli had been utilized as guides in running the 

 maze, but no affirmative statements can be made with confidence. 



Blind animals were also disturbed and this disturbance was 

 mediated through other senses than vision; we must also assume 

 that normal animals were disturbed in part through other modali- 

 ties of sense than vision. This disturbance may also be explained 

 by the assumption that these other senses were susceptible to 

 the altered conditions either as distractions or as motor con- 

 trols. There are no facts which support the directive hypoth- 

 esis in a conclusive fashion. Certain facts can hardly be 

 interpreted in other than distractive terms. The effect of vary- 

 ing the degree of hunger is obvious. The haphazard and occa- 

 sional character of the disturbance was more characteristic of 

 the behavior of the blind than of the normal animals, and this 

 fact is best explained by the distractive hypothesis. The differ- 

 ential sensitivity of the normal and blind rats is thus one of 

 degree and not of kind. Normal animals manifest the greater 

 degree of susceptibility to the changes because they are affected 

 through more sensory avenues. 



The comparative learning records of the various groups of 

 animals furnish certain data relative to the function of vision. 



1. Normal rats master a stationary maze more readily than a 

 rotated maze, and an open maze quicker than a covered one. 

 These facts can be explained in terms of either the distractive 

 or directive hypotheses. If the animal can utilize objective 

 stimuli as guides or controls, the presence and stability of an 

 optical environment should facilitate the learning process. Like- 

 wise these objective stimuli may function merely to attract the 

 animal's attention, encourage unnecessary and disadvantageous 

 excursions, and otherwise distract the animal from the more 

 serious business at hand. On this hypothesis a changing en- 

 vironment would operate as a more effective distractor than a 

 stationary one. Likewise, the distractive effect of a heteroge- 

 neous environment would be greater than that of a uniform one. 



2. Rats with vision learn a stationary maze more easily than 

 do blind animals. This poorer learning capacity of blind rats 

 may be explained in numerous ways: a. We may assume that 



