66 STELLA BURNHAM VINCENT 



very great hindrance in such a situation as this. But while 

 these rats used their noses and vibrissae actively they did not 

 move about so rapidly nor so confidently as the normal animals. 

 Yerkes says, "It is claimed by those who have experimented 

 with blind dancers that the loss of sight decreases the amount 

 and rapidity of movement and the ability of the animals 'to 

 avoid obstacles." -^ 



It is quite possible that vision has a tonic, stimulating effect 

 upon all movements. The loss of it, however, was show^n in 

 other ways than in mere decrease of movement. From the 

 first it was noticeable that the movements of these rats were 

 more indefinite and inaccurate. For instance they could not 

 easily and quickly come to an entrance. Then, too, they often 

 confined their explorations to two pathw^ays or to the same 

 one over and over again. The quick attempt at the third path 

 way, when two had proved closed, was lacking for a long time. 

 They developed a line of conduct, after some signs of discrim- 

 ination had appeared, of going inevitably down the second 

 pathway after one discrimination. They learned, of course, 

 later to complete the act but the immediate possibility of more 

 than two pathways, the quick trial of the whole series seemed 

 to be largely the gift of vision. 2' 



Besides the general stimulating effect and the possibility of 

 the spatial series, vision seemed to lend to objects at a distance, 

 i.e , entrances, ru.ways, etc., an attractive power which led the 

 normal animal in certain definite directions, which constantly 

 tempted it on, kept it going, and enticed it here, there and 

 everywhere. It made possible a wider experience and brought 

 the animal more quickly and more surely into that intimate 

 contact with surfaces which was necessary to this particular bit 

 of learning. 



Thus we may probably say that the blind rat's longer learn- 

 ing period as well as the slowness of its reactions, were the result 

 of the slower and more indefinite movements due to the loss 

 of sight. 



These blind rats were not really needed in the problem but 



2» Yerkes, R. M.: The Dancing Mouse, 1907, p. 179. 



" Note: — Some of the bhnd rats that were being used were in a cage with several 

 normal rats. It was possible to close one's eyes and separate the blind rats from 

 the others by means of the general softness and flabbiness of the body due to loss of 

 tonus. I have tried it many times. 



