_Box Stacking Experiment_
For this test, in the case of Sobke, three light boxes made of redwood
about one-third of an inch thick were used. The smallest, box 1, was six
inches in each direction, the next larger, box 2, was twelve inches, and
the third, box 3, eighteen inches. As in the case of the other animals,
bait, either banana or carrot, was suspended from the middle of the roof
of the large cage at such distance from the floor as to be reached by
the animal only by the use of the boxes.
The first observations on Sobke were made on June 14. The three boxes
had been placed in the form of a pyramid directly under the banana,
which hung about eighteen inches above the uppermost box. Sobke's
attention while in his cage had been attracted to the bait by seeing me
fastening it in position, but when admitted to the large cage, he simply
glanced at it and then wandered about the cage, picking up bits of food
and struggling to get at the other monkeys. This he did for about five
minutes. He then went to the boxes, placed his hands on top of the
bottom one, but did not climb up on it. A few minutes later he returned
to the box again, climbed up, and readily reached the food, which he ate
while resting on boxes 1 and 2.
I now replaced the bait and gave the monkey a second chance to obtain
it. Almost immediately he climbed up as far as the second box, but
although he could reach the banana only from the uppermost box, he
deliberately shoved it off to the ground and sat down upon box 2. As he
was unable to obtain the banana from this, he soon began to gnaw and
pull at it, and as he was succeeding all too well in his efforts to tear
the box to pieces, he had to be returned to his cage.
The most important features of his behavior were, first, his stealthy
and indirect manner, and second, his failure to use other means of
obtaining the bait than that supplied by the observer. Instead of
looking straight at the experimenter, or at the object which he wished
to obtain, he apparently looked and attended elsewhere. For this reason
it was often difficult to decide whether or not he had noticed the bait
or the boxes. Finally I was led to conclude that he usually knew exactly
what was going on and had in his furtive way noted all of the essential
features of the situation, and that his manner was extremely indicative
of his mental attitude of limited trust. Both Julius and Skirrl went to
the opposite extreme in the matter of directness, or as we should say in
human relations, frankness. They would look the experimenter directly in
the eye, and they usually gazed intently at anything, such for example
as the bait, that interested them. Sobke, even when very hungry, instead
of going directly toward the bait, and trying to obtain it, usually did
various other things as though pretending that he had no interest in
food.
On the following day, June 15, the three boxes were again placed nearly
under the banana, but this time the two smaller boxes, numbers 1 and 2,
were pushed to the extreme end of the lower box and so far from the bait
that it could not be reached from box 1. It was necessary then for the
animal to push boxes 1 and 2 along on box 3 until they were nearer the
bait.
Sobke, when admitted to the cage, evidently noticed the banana, but as
formerly, he made no immediate effort to obtain it. After wandering in
search of food and quarreling with the other monkeys for several
minutes, he went to the boxes, pushed the topmost one, number 1, off on
to the floor, and then carried it into his cage where he quickly tore
one side off. He next returned to the large cage, climbed up on box 2,
and he was able, by jumping, to reach and obtain the banana.
As Sobke was very good at jumping, his new method rendered the box
stacking experiment of uncertain value, since it was next to impossible
so to arrange the spatial relations of bait and boxes that he should be
neither discouraged by too great a distance nor encouraged to jump by
too small a distance. Evidently it would be more satisfactory to
simplify the conditions by trying to discover, first of all, whether he
would use a single box as a means of reaching the reward.
In pursuance of this idea, I suspended a piece of bread five feet from
the floor of the cage, and a few feet to one side of it, I placed a box
from which it could be reached, or at least easily seized by jumping.
Sobke shortly walked to a point beneath the bait and leaping into the
air, seized it.
I then replaced the bait, raising it to a height of five feet ten inches
from the floor of the cage. When I had retired, Sobke placed himself in
the proper position beneath, looked up at it, but went away without
jumping for it. During the remaining ten minutes of observation, he paid
no further attention to the bait, having satisfied himself evidently
that it was beyond his reach.
My use of this test was concluded on June 16 when once more I suspended
a piece of bread six feet from the floor and placed a few feet to one
side the eighteen inch box, number 3, from which had the monkey pushed
it to a point directly under the bread, he could have obtained the food
easily. Sobke noticed the food promptly, and from time to time as he
wandered about, he glanced at it out of the corner of his eye, but not
once did he sit down and look at it steadily and directly as Julius and
Skirrl might have done.
In the first twenty minutes of observation the monkey made no attempt
either to use the box or to reach the food by jumping. I then placed the
box directly under the bait, and scarcely had I withdrawn from the cage
before Sobke climbed up on it and looked toward the food. He could not
reach it without jumping, and he made no effort to get it. I had left a
second box in the cage,--one which I had been using as a seat. Sobke now
went to this box, placed his hands on it, looked toward the bait, and
then went to a distant part of the cage. No further indications were
obtained during the remainder of the period of observation of interest
in the boxes as possible means of obtaining the desired food.
It is of course obvious that this experiment was not long enough
continued to justify the conclusion that either Sobke or Skirrl could
not use the boxes or even learn to place one box upon another in order
to obtain the bait. The experiment, like several others which are being
described briefly, was used to supplement the multiple-choice
experiment, and the experimenter's chief interest was to discover the
number and variety of methods which would be used by the animal in
the first few presentations of a situation. It is practically certain
that both of these monkeys would have succeeded ultimately in solving
the problem of obtaining the food had they been left in the cage with a
number of boxes, for Skirrl very early indicated interest in moving the
boxes about, and Sobke showed a tendency in that direction which perhaps
was inhibited partially by his distrust of the experimenter.
_Draw-in Experiment_
For Sobke, as for Julius and Skirrl, the draw-in test was made by
putting food on a shelf outside the cage, beyond the reach of the
animal, and placing in the cage with the animal one or two sticks long
enough to be used for drawing in the bait.
Sobke was first given this test on July 24. He tried persistently to
reach the banana with his hand, seized the box which supported the bait,
shook it, picked up one or other of the sticks, and chewed at it
repeatedly, but not once did he make any move to use a stick to draw the
food toward him.
This experiment was repeated on July 27, 29, 30 and 31, a period of
thirty minutes being allowed on each day for observation. At no time did
Sobke show any inclination to use either a stick or any other object as
a means of reaching the bait. Instead, he confined himself strictly to
the use of hands and teeth.
This test makes it fairly certain that Sobke had no natural tendency to
use objects as tools. In so far as he attended to things about the cage
or laboratory, it seemed to be rather to play with them in a general way
than to use them ideationally or otherwise for definite purposes.
The definitely negative result of the draw-in experiment rendered
needless prolonged observation with the box and pole test, whose results
are now to be presented.
_Box and Pole Experiment_
The eighty-four inch box, previously used for a similar test with
Julius, was presented to Sobke on August 24, the wooden cover having
been replaced by a wire one so that the monkey could readily see the
bait in the middle of the box. Sobke, when admitted to the large cage,
went directly to the box and at once discovered the banana which was
midway between the ends. He evidently desired it. Shortly, he went to
one end of the box and looked in. This he repeated later. He also shook
the box and tried to pull it about and tear it with his teeth, but to
the two poles lying nearby on the floor of the cage he gave not the
slightest attention during a thirty minute period of observation.
The experiment was not repeated because of more important work.
_Other Activities_
In more respects than I have taken time to enumerate in the above
descriptions of behavior, the relations of Sobke to objects differed
from those of Skirrl, and still more from those of Julius. Hammer,
nails, saw, stones, sticks, locks, and various other objects received
relatively little attention from Sobke unless they happened to come in
his way; then they were usually pushed aside with but scant notice.
Rarely he would carry something to the shelf of his cage with him, but
as a rule only to lay it down and attend to something else. Skirrl, on
the contrary, attended persistently to anything new in the shape of a
movable object. He was extremely partial to objects which could be
manipulated by him in various ways, and especially to any thing with
which he could make a noise. His interest in hammer and nails, saw,
locks, etc., seemed never to wane. I have seen him play for an hour
almost uninterruptedly with a hammer and a nail, or even with a big
spike which he could use to pry about his cage. In the absence of
anything more interesting, even a staple or a small nail might receive
his undivided attention for minutes at a time. How important is the
species difference in this connection, I have no means to judge, but if
we may not consider these different modes of behavior characteristic of
_P. rhesus_ as contrasted with _P. irus_, we must conclude that
remarkable individual differences exist among monkeys, for whereas
Skirrl is by nature a mechanical genius, Sobke has apparently no such
disposition. I can imagine no more fascinating task than the careful
analytical study of the temperaments of these two animals. Skirrl's
behavior has importantly modified my conception of genius.
V