220 



The Animal Mind 



G 



ring it to activity. In fifty experiments the path had not been 

 perfectly learned, although the time was greatly reduced. A 

 still simpler path was then offered the animal by placing a 

 wire screen partition in the middle of the aquarium, with an 

 opening in the centre and food on the other side ; and in ten 

 trials the time occupied by the crab in finding the food was 

 much lessened. Still neither of the two animals tested had 

 learned to go straight to the opening, but each followed a 

 habit of its own, one moving directly toward the food, hunt- 

 ing for an opening 

 near it, and then 

 going to the mid- 

 dle where the 

 opening was; the 

 other always fol- 

 lowing the edge of 

 the screen all the 

 way around until 

 it came upon the 



FIG. 13. Labynnth used by Yerkes and Huggms in ex- . r 



periments on the crayfish. T, compartment from Opening ^453/* 

 which animal was started; P, partition at exit; A labyrinth off 6 r- 



G, glass plate closing one exit. . . 



ing only a single 



choice of passages was used in testing the crayfish ; again one 

 end of the box communicated with the aquarium (Fig. 13). 

 About halfway down the length of the box a partition put in 

 longitudinally divided it into two passages, one of which was 

 closed at the end by a glass plate. In sixty trials the animals, 

 which had originally chosen the correct passage 50 per cent 

 of the time, came to choose it 90 per cent of the time. A 

 second series, with a single animal upon which more tests a 

 day were made, resulted in the formation of a perfect habit in 

 two hundred and fifty experiments. The glass plate was then 

 shifted to the other passage, and the crayfish was naturally 



