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.
On April 30 the reward of food was given only when the first choice was
that of the right box and in that event it was placed in the alleyway H
as stated above.
As it seemed absolutely essential to break the unprofitable habit of
choosing the nearest door, on May 3 a new series of settings was
presented, in which only the doors to the left of the middle of the row
of nine boxes were used as right doors. That is, in this new series,
doors 1 to 4 occur as right doors; 5 to 9 do not. As punishment for
wrong choices on this date, Julius was confined in the wrong box from
one to five minutes. It was difficult to keep him in, but by means of
cords which had been attached to the doors, this was successfully
accomplished. Yet another and slightly different series of settings was
employed on May 4, and this, proving satisfactory, was continued in use
until the end of the experiment, with punishment ranging from sixty to
one hundred and twenty seconds for each mistake.
Naturally the modification of settings introduced May 3 greatly
increased the proportion of wrong first choices. Indeed, as appears in
table 8, the ratio of right to wrong immediately changed from 1:0.67 to
1:4.00. Between May 3 and May 10, no steady and consistent improvement
in method or in the number of correct first choices occurred, and on the
last named date, Julius chose correctly only three times in his ten
trials. At this time there was, as my notes record, no satisfactory
indication of progress, and the status of the experiment seemed
extremely unsatisfactory in as much as in spite of the experimenter's
best efforts to break up the habit of choosing the nearest door, the
orang utan still persisted, to a considerable extent, in the use of this
method. The only encouraging feature of the results was an evident
tendency to choose somewhat nearer the left end of a group than
previously.