274 



The Animal Mind 



With the green frog, a maze allowing two choices was 

 used, and was learned in one hundred trials (805). 



With the turtle, a labyrinth distinctly more complex 

 was used. It involved four blind passages, and led to 

 the turtle's comfortable, darkened nest. During the 

 first four trips the time was reduced from thirty-five 



minutes to three 



minutes and thirty 

 seconds; in the 

 fourth trip the an- 

 imal took two wrong 

 turns. The time of 

 the fiftieth trip was 

 thirty-five seconds. 

 In a second laby- 

 rinth (Fig. 1 6), two 

 inclined planes were 

 introduced, up and 

 down which the 

 turtles had to crawl. 

 This labyrinth took 



FIG. 16. Labyrinth used by Yerkes with turtles. 

 A, starting point; F, blind alley; 3, 4, 6, in- 

 clined planes. 



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 connec- 

 tion with the inclined planes. The turtles had to turn 

 about as soon as they had reached the bottom of the de- 

 scending plane. They soon began to make the turn be- 

 fore they got to the bottom, and finally to throw them- 

 selves over the edge as soon as they reached the top (80 1). 

 Some of Thorndike's (704) early experiments on chicks 

 involved a very simple form of the labyrinth method, in 



