300 The Animal Mind, 



the right" and "first at the left" problems, but failed in five 

 hundred trials to master the "second at the left" problem. 

 The white rat succeeded with the "first at the right," but 

 failed with the "second from the left" problem. The pig 

 distinguished itself by mastering "first at right," "second 

 from left," "alternately first at left and first at right," 

 failing only to grasp the "middle compartment" problem. 

 The two monkeys tested by Yerkes (824) showed im- 

 provement in dealing with the problems "first at left," 

 "second from right," "alternately first at left and first at 

 right," and "middle," but appeared to owe many of their 

 successes to their acquired preferences and aversions for 

 particular compartments. The "alternating" problem 

 proved to be especially easy. An orang-utan, who showed 

 himself in other tests the most intelligent of Yerkes's sub- 

 jects, failed to improve in solving the problems of the 

 Multiple Choice Method. His wrong choices were so 

 persistent, and so independent of the usual tendency to 

 drop off useless movements, that Yerkes concluded him to 

 be really acting on the basis of wrong ideas as to the cor- 

 rect solution of the problem. It is clear that a human be- 

 ing who had formed an incorrect theory as to the proper way 

 to work out a problem would take longer to solve it than an 

 animal who learned merely by the dropping off of useless 

 movements, provided that the animal could solve it at all. 

 We may now examine the relation of the Multiple Choice 

 Method to the question of the existence of memory ideas 

 in animals. In the first place, if the "right" compartment 

 always occupied the same position in space, clearly an ani- 

 mal might learn to go to it without the use of memory ideas. 

 Kinaesthetic memory, the formation of a habit of turning 

 in a certain direction, would suffice. Next, if the correct 

 compartment is not always in the same absolute position 



