Orang utan, Julius, obtaining banana by piling boxes
or by using pole
FIGURE 21.--Julius in act of setting larger box on end.
FIGURE 22.--Placing smaller box on larger.
FIGURE 23.--Balancing on larger box preparatory to reaching for banana.
FIGURE 24.--Balancing and reaching to the utmost.
FIGURE 25.--Standing on three boxes (after stacking them) and
reaching for reward.
FIGURE 26.--Lifting smaller box up toward banana.
FIGURE 27.--The act of stacking the boxes.
FIGURE 28.--Sequel to figure 27.
FIGURE 29.--Box and pole experiment. Pushing the second pole
into the box.
FIGURE 30.--Pushing pole into box.
FIGURE 31.--Enjoying the reward of success.
From my notes I quote the following comment on the results of the
initial experiment: "Despite all that has been written concerning the
intelligent behavior of the orang utan, I was amazed by Julius's
behavior this morning, for it was far more deliberate and apparently
reflective as well as more persistently directed toward the goal than I
had anticipated. I had looked for sporadic attempts to obtain the
banana, with speedy discouragement and such fluctuations of attention as
would be exhibited by a child of two to four years. But in less than ten
minutes Julius made at least ten obvious and well directed attempts to
reach the food. There were also wanderings, efforts to obtain aid from
the experimenter, and varied attempts to escape from the cage."
Before proceeding further with the description of the behavior of Julius
in the box stacking test, I shall describe for contrast the behavior of
a boy three years four months of age when confronted with a situation
practically identical with that which the ape was given an opportunity
to meet. For the child, the banana was suspended, as previously
described, from the roof of the cage. The same two boxes were placed on
the floor at considerable distances from the banana, and in addition, a
light stick, about six feet long, and a piece of board, the latter by
accident, were on the floor. The child was asked to get the banana for
Julius, and he eagerly and confidently volunteered to do so.
His behavior may best be described by enumeration of the several
attempts made. They include (1) placing the larger box nearly under the
banana and reaching from it. (2) Standing of the larger box on end with
resulting failure because the child could not stand on the sloping edges
of the top of the box. (3) The larger box was turned on its side and the
lighter box drawn up opposite it and stood on end. The child then
mounted the larger box and from it stepped to the top of the smaller.
But the boxes had not been placed beneath the banana, and when the child
reached for it, he found himself several feet away from his prize. (4)
The boxes were moved to a position nearly under the banana and another
futile attempt was made to reach it without placing the smaller box on
top of the larger one, the only position from which the child could
readily obtain it. (5) The piece of board was placed on top of the
larger box and from this height the child again reached upward. (6) The
six-foot stick was taken up and an attempt was made to strike the banana
and thus dislodge it, but it was too securely fastened to be obtained
thus. (7) Attention shifted to other things, and the child played for a
time with the board. Reminded of the banana by the experimenter, he
again tried method (3). (8) He again used the stick on the banana. (9)
The effort to knock the prize to the floor having failed, he became
discouraged and said that he must go home. (10) When told that Julius
was very hungry and wanted the banana, he repeated efforts similar to
those described in (3) and (6).
Up to this time the observations had covered a period of twenty minutes.
The child was now taken from the cage and allowed to play about for
fifteen minutes. Asked then whether he would go back and try to get the
banana, he replied, "No, 'cause I don't want to get it," thus indicating
his discouragement with the situation. When taken into the cage, he,
nevertheless, made the additional attempts indicated below: (11) Use of
one of the boxes. (12) He remarked, "Now I know, I'll get it," and after
so saying, repeated (3). (13) Failing, he turned to me and said, "I
could get it if I was on your head," but he did not, as Julius had done,
lead me to the proper place and try to reach the banana by climbing up
or by urging me to lift him. (14) Later, he played in the boxes,
apparently forgetful of his task. Finally he remarked: "I'll get the
banana," but he made no attempt to do so, and instead, watched the
monkeys intently. Thereafter, he showed no further interest in the
solution of the problem, and the experiment, after a total period of
fifty-five minutes, was discontinued.
Comparison of the behavior of the ape with that of the child indicates a
greater variety of ideas for the latter. Julius gauged his distances
much more accurately than the child, attended more steadily, and worked
more persistently to obtain the reward, but he did not so nearly
approach the idea of stacking the boxes as did the child, for the
latter, in placing the board on one of the boxes, exhibited in
ineffective form the idea which should have yielded the solution of the
problem.
The child was given no further opportunity to work at the problem,
whereas Julius, as I shall now describe, continued his efforts on
subsequent days under somewhat different conditions. On Wednesday, March
10, the banana was suspended as formerly, and three boxes, all of them
small and light enough to be readily handled by the ape, were placed in
distant parts of the cage. The six-foot stick which had been present in
the test with the child, but not in the first test with Julius, was also
placed in the cage.
Julius was allowed to work for about an hour. As formerly, he was
sufficiently hungry to be eager to get the food and evidently tried all
of the possible ways which occurred to him. Chief among these were (1)
the use of the various boxes separately or in pairs in very varied
positions but never with one upon another,--the only way in which the
banana could be reached; (2) climbing to various points on the sides of
the cage, with infrequent attempts to reach the banana. Usually his eyes
saved him the vain effort.
Unlike the child, Julius paid little attention to the six-foot stick.
Two or three times he took it up and seemingly reached for the banana,
but in no case did he try persistently to strike it and knock it from
the string. It is but fair, however, to remark that such an act is very
difficult for the young orang utan, as compared with the child, because
of the weakness of the legs and the awkwardness of striking from a
sitting posture. As previously, the steadiness of attention and the
persistence of effort toward the end in view were most surprising. At
one time Julius walked to the end of the cage and there happened to see
one of the monkeys eating. He watched intently a few seconds and then
hastened back to the banana as if his task had been suggested to him by
the sight of the feeding animal. Most interesting and significant in
this behavior was the suddenness with which he would turn to a new
method. It often looked precisely as though a new idea had come to him,
and he was all eagerness to try it out.
On March 11, Julius was given another opportunity to obtain the banana
by the use of the three boxes. Although he used them together he made no
effort to place one upon another. Certain of his methods are shown in
plate V, especially by figures 21, 23 and 24.
This experiment was continued on April 2 under yet different conditions,
for this time only two boxes were placed in the cage, the one of them
the heavy, irregularly-shaped box and the other the smaller, lighter one
originally used. On the end of the heavier box had been nailed a two by
two inch wooden block in order to increase the difficulty in using this
box alone. As previously, Julius made varied attempts to obtain the
banana, but on the whole his interest and attention seemed somewhat
weaker than previously and there were indications of discouragement
because of repeated failures.
He handled the boxes conspicuously well, and it seemed at times that he
would certainly succeed in placing the one upon the other and in
reaching the food.
After one series of attempts from the sides of the cage and from the
large box, he deliberately turned away from the box and neatly executed
a somersault on the floor of the cage, as much as to say, "I am
disgusted with the whole situation." Again, later on the same day, after
falling from the top of the larger box, which tilted over very easily,
he rolled himself into a ball, and childlike, played with his feet. An
additional evidence of his changed affective attitude toward his task,
especially in connection with definite failures, appeared in his rough
handling and biting of the boxes. When most impatient, he worked very
roughly.
Julius was allowed to work for the reward from thirty to ninety minutes,
or, as a rule, until he had become completely discouraged on April 3, 5,
6, 7, 8, 9 and 13. His behavior was interesting and significant, but
nothing new appeared except that his willingness to work gradually
disappeared, and on April 13, although previously hungry, he made only a
single attempt to obtain the banana and then paid no further attention
to it.
The prolonged and varied efforts to obtain the banana were due in a
measure at least to three accidental successes. Thus on April 2, 3 and
again on the 5th, by fortunate combinations of circumstances, he
succeeded in getting the banana, contrary to the intention of the
experimenter.
Although active at first on April 6, he soon wearied of his task and
quit work. The same was true on April 7, and again on the 8th and 9th.
On these days, although hungry, he did not care to enter the large cage
and worked only a few minutes each day, seldom making more than two or
three half-hearted attempts to obtain the banana. His attitude toward
the task had changed completely, in that hopelessness had taken the
place of eager expectancy. By the 13th of April he had so nearly given
up voluntary efforts to solve the problem that it seemed worth while to
test his ability to get the idea by watching the experimenter. For this
purpose the following test of imitation was made.
On the morning of April 14, having placed a banana in the usual
position, I took Julius into the large cage, dragged the two boxes to
the proper position beneath the banana, placed the smaller one upon the
larger one and then climbed up on them to show the ape that I could
reach the banana. I then stepped down and gave him a chance to climb on
the boxes. He did so immediately and obtained the food.
Another piece of banana was supplied, the boxes were placed in distant
corners of the cage, and fifteen minutes were allowed Julius so to place
them that he could obtain his reward. He gave no indications of having
profited by my demonstration, but worked with the boxes singly, usually
with the larger one. On April 16, with the banana in position and the
two boxes also in the cage, Julius was admitted and allowed to work for
five minutes, but again without success. I then placed the boxes
properly for him and he immediately climbed up and got the banana. While
he was eating, the boxes were carried to distant corners of the cage and
another banana placed in position. Now thirty minutes were allowed him
for unaided work on the problem. As formerly, the larger box was used
repeatedly and attempts to reach from the side of the cage appeared, but
there was no tendency to try to use the two boxes together. He worked
fairly persistently, however, and showed clearly the stimulating and
encouraging effect of aid from the experimenter. Once more, on April 17,
Julius was taken into the cage and allowed to watch me place the boxes
in proper position. He then climbed up and obtained the desired food.
After the bait had been renewed and the boxes displaced, he immediately
tried to use the larger one, then he reached for the small one as though
to use both together. But the impulse died out and he turned again to
the larger box as usual, standing it on end, and persistently trying to
balance himself on it. Nothing else of special interest happened during
the interval of unaided effort.
Similarly, I placed the boxes for the ape on April 19, allowed him to
get the banana and then gave him opportunity to try for himself after
the boxes had been displaced. This time he immediately reached for the
smaller box and moved it about a little, thus indicating a new
association. He next turned to the larger box and worked with it
persistently. Later, he once more worked with the smaller box in an
unusual manner. He repeatedly stood on it, but made no attempt to lift
it or to place it on the larger box. Clearly the usually neglected
smaller box had become associated with the satisfaction of obtaining the
banana. The same method was carried out on April 20. As I placed the
boxes in position beneath the banana, Julius watched with unusual
intentness, and when it came his turn to try to obtain the food by the
use of the boxes, he began at once to work with the smaller box, but as
on April 19, he soon abandoned it and turned to the other. While I was
making note of this particular feature of his behavior, he suddenly
seized the smaller box by two corners with his hands and by one edge
with his teeth, and after a few attempts placed it on top of the larger
box, climbed up, and obtained the banana.
Because of bad weather on April 21, the next test was made on April 22,
with everything as usual. Unaided, the ape was given an opportunity to
obtain the coveted reward, while I stood ready to obtain records of his
behavior with my camera. He wasted no time, but piled the smaller box on
top of the larger one immediately, and obtained his reward. As soon as
opportunity was offered, he repeated the performance. The same thing
happened on April 23 and several succeeding dates.
Julius had got the idea, and the only further improvement possible was
in skill in manipulating the boxes.
One of the curious performances which appeared during the imitative
period is pictured in figure 26, plate V, where the ape is seen lifting
the smaller box into the air. This he did three or four times one day,
raising it toward the banana each time as though he expected thus to
obtain the reward. As he did not go up with the box (according to his
expectation?), he abandoned this method, and looking about, discovered
the larger box in a distant corner. Thereupon, he promptly pulled the
boxes to their proper position beneath the banana, stacked them, and
obtained his food.
After considerable skill had been acquired in the placing of the boxes,
the one upon the other, the height of the banana above the floor was
increased so that three boxes were necessary. Figure 25 of plate V shows
him standing on three boxes and reaching upward, and figures 22, 27 and
28 show various modes of handling the boxes and of reaching from them.
He was not at all particular as to the stability of his perch, and often
mounted the boxes when it seemed to the experimenter inevitable that
they should topple over and precipitate him to the floor. Only once,
however, during the several days of experimentation did he thus fall.
Obviously important is the evident change in the animal's attention on
April 20. He watched with a keenness of interest which betokened a
dawning idea. Before he had succeeded in stacking the boxes, I had
written in my note-book, "He seemed much interested today, in my placing
of the boxes." Interesting, and important also, is the ease and
efficiency with which he met the situation time after time, after this
first success. "Trial and error" had no obvious part in the development
of the really essential features of the behavior. The ape had the idea
and upon it depended for guidance.
Except for the fact that Julius was immature, probably under five years
of age, it is likely that he would have stacked the boxes spontaneously
instead of by suggestion from the experimenter or imitatively.
No unprejudiced psychologist would be likely to interpret the activities
of the orang utan in the box-stacking experiment as other than imaginal
or ideational. He went directly, and in the most business-like way from
point to point, from method to method, trying in turn and more or less
persistently or repeatedly, almost all of the possible ways of obtaining
the coveted food. The fact that he did not happen upon the only certain
road to success is surprising indeed in view of the many ineffective
methods which he used. It seemed almost as though he avoided the easy
method.
It is especially important, in connection with these results, to point
out the risk of misinterpretation of observations on the anthropoid
apes. If they can imitate human activities as readily and effectively as
Julius did in this particular experiment, we can never be sure of the
spontaneity of their ideational behavior unless we definitely know that
they have had no opportunity to see human beings perform similar acts.
Of all the methods of eliciting ideational or allied forms of behavior
used in my study of the monkeys and ape, none yielded such illuminating
results as the box stacking test, and although from the technical
standpoint, it has many shortcomings, as a means to qualitative results
it has proved invaluable.
_Other Methods of Obtaining the Reward_
Some weeks later, I tried to discover how Julius would obtain the much
desired banana when the boxes were absent. I placed in the large cage a
stick about six feet long and an old broom. When admitted, he looked
about for the boxes, but not seeing them, picked up the broom and
placing it with the splints down, beneath the banana, he tried to climb
it, but as it fell over with him, he abandoned this after a few trials,
went to his cage, and picking up some old bags which he used at night as
covers, he dragged them out and placed them on the floor beneath the
banana. He next put the broom upon them and tried to climb up. This
general type of behavior persisted for several minutes, everything
within reach being used as were the bags, as a means of raising him in
the desired direction. Finally, he placed his feet on the broom where
the handle joins the splints, seized the handle near the top with his
hands, drew himself up as far as possible, and then launched himself in
the air and tried to seize the banana. On the third attempt he
succeeded.
Later, he was given a plain stick about five feet long. Figure 32 of
plate VI shows him using this to obtain the banana in the manner
described above. He would grasp it with one or both feet, usually one,
ten to fifteen inches from the floor of the cage, meanwhile holding with
his hands near the top of the stick. He would then, with all his
strength, draw himself up suddenly and jump toward the banana. Often he
came down rather hard on the cement floor, much to his disgust.
Yet another method of obtaining the reward developed a day or two later.
A light red-wood stick about five feet long and an inch in its other
dimensions was the only object in the cage which could possibly be of
use in obtaining the banana. The aim of the experimenter was to discover
whether Julius would use this as a club.
Previously, in connection with the use of the boxes, he had taken up the
same stick two or three times and reached for the banana with it, but in
no case had he struck at it or clearly tried to knock it from the
string, as did the child most readily and naturally. When provided with
this same stick, and it alone, as a means of obtaining the food, he hit
upon the following interesting method. Placing one end of the stick
between a wooden brace and the wire side of the cage, he climbed up to a
level with the banana as is shown in figure 33 of plate VI. Then holding
with one hand and one foot to a timber of the cage and to the stick with
his other foot, he swung outward as far as possible and reached the
banana with his free hand. Having once succeeded by the method, he used
it whenever given an opportunity. It was impossible for him to make the
reach without the use of the small stick, while with it he succeeded
fairly easily and regularly.
_Box and Pole Experiment_
Following the box stacking test, Julius was given an opportunity to
exhibit ideation in another type of experiment. This may be designated
the box and pole test. The conditions are describable thus. A strong
wooden box eighty-four inches long, by four inches wide, by four inches
deep, with open ends, was built with one side hinged. Hasps and padlocks
enabled the experimenter to lock this "lid" after food had been placed
in the center of the box. This box could be placed in the center of the
large cage and there fastened by means of cross bars. It is well shown
in position in figure 29, plate V. Two poles each eight feet long and
approximately one and a half inches in their other dimensions were the
only additional materials in the experiment.
On May 1, Julius was allowed to see the experimenter place a half banana
in this box, close the lid, lock it in position, and securely fasten the
box by means of the cross bars. He was then given opportunity to try to
get the banana. The two poles lay on opposite sides of the box and near
the edges of the cage. Doctor Hamilton and the writer were in the cage
watching. Julius looked into the box through one end, and seeing the
banana, reached for it. He could not obtain it in this way, so he began
to bite at the box and to pull at it with all his strength. During the
fifteen minutes allowed him, he worked at the box in a great variety of
ways, fooling with the locks which had been attached to the hasps as
well as with the cross bars and continually reaching in at the one or
the other end. He was somewhat distracted by the presence of the two
observers and attended rather unsatisfactorily to the task in hand. Not
once did he touch the poles, and it is doubtful whether he even noticed
them. He was not very hungry at this time, and after a few minutes
active work he virtually gave up trying to get the food.
Two days later, on May 3, the box was once more placed in position, this
time with a half banana in the middle and a small piece of banana near
each open end. The two poles lay on the floor of the cage, each several
feet distant from the box. Julius was eager for food. When released he
went immediately to the box, reached in and obtained a piece of banana
from the end nearer the laboratory. He then looked in and saw the piece
near the middle of the box. His next move was to pick up the eight foot
pole and push it into the box, but before pushing it all the way
through, he stopped and began to pull at the box in various ways.
Shortly he returned to the pole and twice thrust it in as far as he
could reach. The first time, after thrusting it all the way through, he
pulled it out and examined the end as though expecting the banana to
come out with it. After a third attempt he looked into the box,
presumably seeing the banana, then turned a backward somersault, came to
the end of the cage, and looked at me. Had it been at all possible, he
would have taken me by the hand and led me to the box as a helper. After
a few seconds, he returned to the pole, pried the lid of the box with
it, then gnawed at the pole. For about five minutes he worked fairly
rapidly and steadily, using the poles, pulling, gnawing, and walking
about.
His next move was to go to the opposite end of the box, look in, take
the piece of banana which was near the opening, then pick up the second
pole, which had not previously been noticed, and after a number of
attempts, push it into and through the box, looking after it and then
pulling it out and looking into the box. Having done this he again came
to my end of the cage, and from there returned to try once more with the
pole which he had first used. He pushed this pole all the way through,
then walked to the other end of the box, looked in and reaching in,
obtained the banana which had been pushed far enough along to be within
his grasp. Figures 29, 30 and 31 of plate V show stages of this process.
Julius had worked twenty-four minutes with relatively little lost time
before succeeding. He had shown almost from the start the idea of using
the pole as an instrument, and his sole difficulty was in making the
pole serve the desired purpose.
The experiment was rendered still more crucial on May 5 by the placing
of the two poles upright in opposite corners of the large cage. For a
few minutes after he entered the cage, Julius did not see them, and his
time was spent pulling and gnawing at the box. Then he discovered one of
the poles, seized it, and pushed it into the box. He tried four times,
then went and got the other pole and pushed it into the opposite end of
the box. Twice he did this, then he returned to the original pole,
bringing the second one with him. He pushed it in beside the first, and
as it happened, shoved the banana out of the opposite end of the box.
But he did not see this, and only after several seconds when he happened
to walk to that end of the box did he discover the banana. The total
time until success was fifteen minutes.
Subsequently the ape became very expert in using the pole to obtain the
banana, and often only a minute or two sufficed for success. It was not
possible for him to direct the stick very accurately, for when he was in
such a position that he could look through the box, he could not work
the stick itself. It was, therefore, always a matter of chance whether
he obtained the banana immediately or only after a number of trials.
Although it is possible that the use of the poles in this experiment was
due to observation of human activities, it seems probable in the light
of what we know of the natural behavior of the anthropoid apes that
Julius would have solved this problem independently of human influence.
It was the expectation of the experimenter that the pole would be used
to push the banana through the box, but as a matter of fact the ape used
it, first of all, to pull the food toward him, thus indicating a natural
tendency which is important in connection with the statements just made.
Subsequently he learned that the banana must be pushed through and
obtained at the farther end of the box. I am not prepared to accept the
solution of this problem as satisfactory evidence of ideation, but I do
know that few observers could have watched the behavior of the orang
utan without being convinced that he was acting ideationally.
_Draw-in Experiment_
An interesting contrast with the box and pole test is furnished by what
may be called the draw-in experiment. This was planned as a simple test
of Julius's ability to use a stick to draw things into his cage from
beyond the wire side. A board was placed, as is shown in figure 34 of
plate VI, with sides to hold a banana, carrot, or some other bit of
food, in position. In the actual test either a carrot or a banana was
placed about two feet from the wire netting and a stick two feet long
was then put into the cage with the ape.
When this situation was first presented to Julius, he looked at the
banana, reached for it, and failing, picked up a bag from the floor of
the cage and tried to push it through the wire mesh toward the banana.
He also used a bit of wire in the same way, but was unable thus to get
the food. As soon as a stick was placed in his cage, he grasped it and
used it in a very definite, although unskillful, way to pull the banana
toward him. He was extremely eager and impatient, but nevertheless
persistent in his efforts, and within five minutes from the beginning of
the first trial, he had succeeded in getting two pieces of banana, using
always his left hand to manipulate the stick. This test was repeated a
number of times with similar results. He had from the first the ability
to use a stick in this way, and the only difficulty with the test as a
means of obtaining evidence of ideational behavior is that the
possibility of imitation of man cannot be certainly excluded.
_Lock and Key Test_
By my assistant it was reported on May 5 that the orang utan had been
seen to place a splinter of wood in a padlock which was used on the
cages and to work with it persistently. It looked very much like
imitation of the human act of using the key, and I therefore planned a
test to ascertain whether Julius could readily and skillfully use a key
or could learn quickly to do so by watching me.
The first test was made on May 15 with a heavy box whose hinged lid was
held securely in position by means of a hasp and a padlock. The key,
which was not more than an inch in length, was fastened to a six inch
piece of wire so that Julius could not readily lose it. With the animal
opposite me, I placed a piece of banana in the box, then closed the lid
and snapped the padlock. I next handed Julius the key. He immediately
laid it on the floor opposite him and began biting the box, rolling it
around, and occasionally biting also at the lock and pulling at it.
During these activities he had pulled the box toward his cage. Now he
suddenly looked up to the position where the banana had been suspended
in the box experiment. Evidently the box had suggested to him the
banana. For thirty minutes he struggled with the box almost
continuously, chewing persistently at the hinges, the hasp, or the lock.
Then he took the key in his teeth and tried to push it into one of the
hinges, then into the crack beneath the lid of the box.
Subsequently I allowed him to see me use the key repeatedly, and as a
result, he came to use it himself now and then on the edge of the box,
but he never succeeded in placing it in the lock, and the outcome of the
experiment was total failure on the part of the animal to unfasten the
lock of his own initiative or to learn to use the key by watching me do
so. I did not make any special attempt to teach him to use the key, but
merely gave him opportunity to imitate, and it is by no means impossible
that he would have succeeded had the key been larger and had the
situation required less accurately coordinated movements. However, it is
fair to say that the evidence of the idea of using the key in the lock
was unconvincing. My assistant's observation was, perhaps, misleading in
so far as it suggested that idea. It may and probably was purely by
accident that the animal used the splinter on the padlock.