In a second control series given on the following day, June 12, confusion appeared, but less markedly.  For the first setting, a correct choice was made with deliberation.  For the second setting, box 3 was immediately chosen, as should have been the case in the regular series of settings.  Sobke seemed confused when he emerged from this box and had difficulty in locating 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 behavior of the animal differed markedly from that in the concluding 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 connection with problem 2, Sobke was merely fed in the apparatus according to previous description (p. 43).  He exhibited a wonderfully 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 seconds proved satisfactory.  It was also thought desirable to increase 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 remarkably 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.

TABLE 6

Results for Sobke, P. rhesus, in Problem 3