286 HARVEY CARR 



sensitivity and the adaptive power of the animals. likewise, 

 when normal rats were rotated in an open and a covered cage, 

 the greater sensitivity was manifested in the former case. Many 

 similar illustrations can be given. 



The terms ' ' sensitive ' ' and ' corrective ' have so far been 

 used in a purely descriptive sense, to state certain differences 

 of fact. As explanatory concepts they render but little service. 



In attempting to explain the greater sensitivity of the normal 

 rats to all alterations instituted after the mastery of the maze, 

 two possibilities exist; these functions of vision we may term 

 ' directive ' ' and ' ' distractive. ' ' The first hypothesis assumes 

 that the motor activity of the animal is guided and directed in 

 part by the visual impulses released by the stimuli from the 

 obiective environment. When the relation between the rat and 

 these features of the environment is altered, motor disturbances 

 are the inevitable result. It is possible that this directive 

 function of vision may be present during the mastery of the 

 maze but absent after the act has been thoroughly developed. 

 The distractive hypothesis assumes that the maze habit is in- 

 fluenced in no way by the visual environment so long as it 

 remains stable. Any pronounced alteration, however, is sensed 

 immediately and operates as a distractive stimulus; in common 

 parlance, it attracts the animal's attention, the rat reacts to 

 the new conditions, and as a consequence the maze habit is 

 disrupted. These two functions are not necessarily mutually 

 exclusive; it is possible that both may be efficacious in mediat- 

 ing the disturbance in any run through the maze. 



Between the two explanatory conceptions, we are forced to 

 conclude in favor of the distraction hypothesis as far as the 

 normal animals are concerned. When the position of the ex- 

 perimenter was altered, the rats were never disturbed in that 

 section of the maze near which the experimenter had been 

 standing. In fact the animals were not disturbed at any posi- 

 tion in the maze at which they were oriented towards the old 

 position of the experimenter. This fact would indicate that 

 the rats did not employ visual stimuli from this source in any 

 effective fashion in directing and orienting their conduct in the 

 maze. The disturbance did occur, however, in those sections 

 of the maze near the new position of the experimenter and 

 when the rats were oriented in his direction. When the animals 



