MENTAL LIFE OF MONKEYS AND APES 53 



the right one. Then followed direct correct choices for settings 

 3, 4, and 5. For setting 6, there is recorded a deliberately made 

 wrong choice, and so on throughout the series, the choices being 

 characterized by deliberateness and definite search for the right 

 box. Uncertainty was plainly indicated, and in this the be- 

 havior of the animal differed markedly from that in the conclud- 

 ing series of the regular experiment. 



It seems safe to conclude from the results of these control 

 series that Sobke has no free idea of the relation of secondness 

 from the right and is chiefly dependent upon memory of the 

 particular settings for cues which lead to correct choice. 



Problem 3. Alternately First at Left and First at Right 



For four successive days after the last control series in con- 

 nection with problem 2, Sobke was merely fed in the apparatus 

 according to previous description (p. 43). He exhibited a won- 

 derfully keen appetite and was well fed during this interval 

 between problems. 



The method of experimentation chosen for problem 3 in the 

 light of previous experience was that of confining the monkey 

 for a short time, ten to fifteen seconds, in the wrong box, in each 

 of the first ten mistakes for a given trial, and of then aiding 

 him to find the right box by the slight and momentary raising 

 of the exit door. Aid proved necessary in a few of the trials 

 during the first four days. Then he worked independently. 

 As work progressed it was found possible and also desirable 

 to increase the period of confinement, and in the end, sixty sec- 

 onds proved satisfactory. It was also thought desirable to in- 

 crease the number of trials per day from a single series during 

 the early days to two or even three series from June 29 on. 

 Often three series could be given in succession without difficulty. 

 During the early trials on this problem Sobke worked remark- 

 ably well, but later his willingness diminished, evidently because 

 of his failure readily to solve the problem, and it became extremely 

 difficult to coax him into the apparatus. On days when he 

 entered only reluctantly and as it seemed against his will, he 

 was likely to be nervous, erratic, and often slow in making his 

 choices, but above all he tended to waste time by not returning 

 to the starting point, preferring rather to loiter in the alleyways 

 or run back and forth. 



