1st series  2nd series  5th series  10th series
Skirrl  35 min.     20 min.     14 min.     10 min. 
Sobke   14  "       17  "       10  "        9  " (8th series)
Julius  12  "       11  "       14  "        9  "

It is also noteworthy that Julius in the presence of visitors or under other unusual conditions worked steadily and well, whereas the monkeys, and especially Sobke, tended to be distracted and often refused to work at all.

Almost from the beginning of his work on problem l, Julius began to develop the tendency to enter immediately the open door nearest the starting point.  In case the group of open doors lay to the right of the middle of the apparatus, this method naturally yielded success; whereas if the group included doors to the left of the middle, it resulted in failure.  Obviously it was a most unsatisfactory method, and although it enabled him to make more right than wrong first choices, it prevented him from increasing the number of right choices, and as table 1 indicates, it maintained the ratio of 1 right to .67 wrong first choices for eight successive days.

On April 23 a break occurred in which the number of correct choices was reduced from six to five.  Julius worked very rapidly and with almost no hesitation in choosing.  My notes record “he seems to miss the point wholly.  It is doubtful whether the punishment is sufficiently severe.”  At this time he was being punished by thirty seconds confinement in each wrong box, the interval having been held fairly steadily from the first series of experiments.  On April 26 it was increased to sixty seconds, in an effort to break him of the habit of choosing the “nearest” door.  But he became extremely restless under the longer confinement and tried his best to raise the entrance and exit doors.  Since there was at this time no mechanism for locking them when closed, it was difficult for the experimenter to prevent him from escaping by way of the entrance door or from raising the exit door sufficiently to obtain the food.  Indeed, the longer confinement worked so unsatisfactorily that on the following day I substituted for it the punishment of forcing him to raise the entrance door of the wrong box in order to escape for a new choice.  He was rewarded with food in the alleyway H, beside door 15 (figure 17), only when he chose correctly on first attempt.

This method discouraged him extremely and proved wasteful of time.  Consequently, in a second series on the same date return was made to the former method, and he was rewarded with food whenever he found the right box.  But on April 28, the two methods were again employed, the first in the initial series and the second in a final series of trials.  The animal’s persistent attempts to raise the doors gave the experimenter so much trouble that on April 29 barbed wire was nailed over the windows of the entrance doors with the hope that it might prevent him from working at them.  But he quickly learned to place his fingers between the barbs and raise the doors as effectively as ever.