280 HARVEY CARR 



made at those places in the maze where the lighting conditions 

 were altered the most. The blind animals, on the contrary, 

 gave no evidence of reacting specifically to any observable 

 changes. The errors were likely to occur anywhere within the 

 maze. When the experiment was first performed, a group of 

 four blinds was employed mainly as a control as no disturb- 

 ance was expected. Since the number of errors was increased 

 beyond the normal records, the test was repeated upon two 

 other groups of blinds consisting of five each. The same results 

 were obtained; the rats did not seem to be reacting to any specific 

 feature in the environment and yet the normal number of errors 

 was increased; some rats occasionally became almost hopelessly 

 confused. Five animals made over 17 errors in a single trial. 



Rotation of Maze and Environment. The records of five blinds 

 are to be compared with those of ten normals. Eighty per cent 

 of each group was disturbed. The blind animals made errors 

 the more frequently, the percentage of runs with error being 

 42 and 3 1 . The average error records of the blinds and normals 

 were 7.76 and 1.29 respectively. The blinds exhibited the 

 greater range of individual variability; the individual number 

 of errors ranged between 3 and 172 for the blind rats and be- 

 tween 2 and 22 for the normals. The test was not repeated 

 for the blinds so that comparisons as to adaptability are impos- 

 sible. The blind rats, however, exhibited more disturbance after 

 a return to normal conditions. 



Rotation of Cage. Nine blind rats were tested. For the 

 15-min. exposure, all were affected, errors were present in 57% 

 of the trials, and the average error record was 1.90. For the 

 24-hr. exposure, 90% were disturbed, errors were present in 62% 

 of the trials, and the average error record was 4.95. A repeti- 

 tion of the tests disclosed no tendency toward adaptation. 



Blind rats are more susceptible to these alterations than are 

 the normals; blinds were disturbed by the 15-min. exposure 

 while the normals were not. The blinds were also affected more 

 by the 24-hr. shifts than were animals with vision. The blinds 

 exhibited the greater range of individual variability as to num- 

 ber of errors, and the lesser powers of adaptability. 



5. We are also able to compare the records of blind and 

 normal animals in the mastery of the maze problem. 



Vision aids untrained rats in learning a stationary maze, 



