222 



The Animal Mind 



to learn it is not stated. The greater speed and ease of 

 locomotion in the fish as compared with the crustaceans 

 may have been one factor concerned in the former's greater 

 rapidity of learning. 



With the green frog, the labyrinth pictured in Figure 14 

 was used. After one hundred trials, practically no errors were 

 made (454). Another animal whose learning powers have 



been tested by this 



method is the turtle. 



The labyrinth was 

 distinctly more com- 

 plex than that used 

 for the frog. It in- 

 volved four blind 

 passages, and led to 

 the turtle's comfort- 

 able, darkened nest. 



During the first 

 four trips the time 

 was reduced from 



FIG. 15. Labyrinth used by Yerkes with turtles. ,, . J r 



A, starting point; F, blind alley; 3, 4, 6, thirty-five minutes to 



inclined planes. three minutes and 



thirty seconds; in the fourth trip the animal took two 

 wrong turns. The time of the fiftieth trip was thirty-five 

 seconds. In a second labyrinth (Fig. 15), two inclined 

 planes were introduced, up and down which the turtles had 

 to crawl. This labyrinth took them longer to traverse, and 

 the time curve shows greater irregularity, rising, for instance, 

 to seven minutes on the forty-fifth trial, after having been as 

 low as two minutes and forty-five seconds at the thirty-fifth. 

 The process of shortening the path was observed very prettily 

 in connection with the inclined planes. The turtles had to 

 turn about as soon as they had reached the bottom of the 



