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in diameter, and, indeed, only about five inches in diameter where it emerged from the trunk, I felt reasonably certain that Congo could not obtain the apple by climbing along the limb. Instead, I supposed that she at first might reach or jump for it from the ground, and, failing to obtain it, look about for something to strike or reach with or perhaps to climb upon. But in this, prophetic insight failed me. The moment she caught sight of the apple, after she had been led from her cage and chained to a stake under the oak tree, she quickly climbed the tree and walked out on the branch until she was able to reach the cord and secure the food. This preliminary observation proved the necessity of chaining her to a stake at such distance from the trunk of the tree that she could not climb it.

The problem was therefore set as follows. A cord fastened to the aforesaid limb of the oak tree suspended food, used as lure, at sixty-six inches from the ground. The point directly under the suspended food will hereafter be referred to as the center. A stake to which Congo could be moored was driven into the ground five feet west of the center. Five feet north of the center a 48-inch broomstick lay on the ground, and five feet south of the center was a rectangular stick approximately 1 by 1 by 60 inches. Congo was given a range of six feet.

On January 11, with the experimental situation as above described, Congo was brought from her cage and chained to the stake. Immediately she looked toward the tree and started for it, evidently with the intention of climbing, but coming to the end of the chain she was halted abruptly. After looking at the apple for a few seconds she attempted to lay hold of her playmate, the Airedale dog Betty, who happened to be near, and to use her as a stepping block. The dog quickly escaped. Then Congo placed herself beneath the apple and reached for it. Failing in this attempt she went to the stake, pulled at it vigorously, and worked with the chain and the snap which fastened it to the stake. From time to time thereafter she played with Betty, ran about, patted her chest or the ground vigorously with both hands, and occasionally reached for the

apple. Quite evidently her failure to obtain the food irritated her. Presently she picked up a bit of stick and began to chew

it.

Mrs. Burbridge now approached and I asked her to stand so that Congo might, if she wished, lead her to a position in which she might be used as means of approach to the apple. But this the gorilla, despite opportunity, did not do. Her previous attempt to use Betty as a stepping block was due, doubtless, to the fact that the dog happened to be nearly under the apple and that therefore a familiar visual configuration was presented.

When, after a few minutes, Mrs. Burbridge retired from the scene of the experiment, the dogs Bobby and Betty were locked in the house, since they tended to distract Congo and possibly to lessen her chances of solving the problem.

It was twenty-three minutes after the beginning of the trial before Congo gave attention to either of the sticks. She then picked up the broomstick, put it down, beat her chest vigorously, again took up the stick and looked toward the apple. It seemed as though she were about to use the stick to aid her, but she promptly abandoned it and began to dig in the sand.

Her behavior made me wonder whether the incentive was sufficiently strong to elicit her best effort. Clearly the nature and quantity of food offered as reward bears an important relation to Congo's interest and effort, and presumably also to the measure of success achieved.

In her attempts to secure the apple by reaching from the ground Congo during this interval of trial stood beneath it and reached directly up. Her maximum reach with one hand certainly did not exceed fifty-eight inches. Each time she stood firmly with both feet on the ground. Not once did she attempt to jump or even to increase her reach by standing on one foot and stretching to the utmost with the arm of the opposite side.

On January 12, and again on January 13, Congo was given opportunity to work for suspended food. A half banana was

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added to the whole apple on the 12th to increase the value of the lure and they were suspended at a distance of sixty instead of sixty-six inches from the ground. Thus by increasing the quantity of food and diminishing the distance I thought to stimulate Congo's interest, effort, and persistence. The sticks previously present were used, and on the chance that a larger, heavier one might prove more readily serviceable, a stout piece of board 1 by 2 by 66 inches was placed within reach. Each stick was at least five feet off center. As Congo watched me place the food in position she gave evidence of eagerness for it, and when brought from her cage and fastened to the stake she worked diligently, but deprived of opportunity to climb, she relied on reaching, which proved futile. My notes describe in detail her efforts to free herself from the stake and to approach the tree. In thirty minutes of almost continuous activity no new method appeared. At one time she played with the broomstick for a few seconds and again with the new, large stick. Later she threw the broomstick out of her way and drawing the large stick to the stake amused herself with it. The trial terminated without yielding evidence of approach to the use of a stick as tool.

On January 13 when the situation was re-presented, despite the fact that a whole banana as well as an apple were offered as reward, Congo was obviously less eager to work for them and decidedly less sanguine of success. As formerly, she reached from beneath the food, tugged at her chain, and circuited about as though endeavoring to achieve freedom or sufficiently increase her range of movement to reach the tree trunk. She merely fingered the sticks. As the time of the trial passed, her attention to the food diminished and before discontinuance of observation she had given up effort and there was complete lack of interest. She seemed to have decided that attempt to secure the food was wholly futile. In view of this behavior I decided to discontinue the suspended food and stick problem temporarily in favor of a suspended food and box problem.

It was not until one week later, January 20, that opportunity to use a stick in a suspended food situation was again offered. On that date, and in a situation essentially like that of experiment no. 8, a 60-inch stick was placed within reach in an experimental setting in which boxes were the primary objects offered as aids. The stick was added with the thought that its presence might possibly lead to the use of stick or box, or perhaps their combination, as aid in obtaining the suspended food. This experiment is no. 10 in the list, suspended food and boxes. As usual the food was suspended from the limb of an oak tree, the boxes and stick placed at least five feet off center, and Congo chained to a stake with sufficient range readily to reach and handle any of the objects which constituted essential parts of the experimental situation.

On January 20, 21 and 22 Congo was given a half-hour for work at this problem. At no time did she attempt to use the stick as tool. Once or twice she touched it or pushed it out of her way as though considering it an obstruction.

Following January 22 the use of the stick was again discontinued, and it was not until February 2 that Congo was given opportunity to display, in the suspended food type of experiment, whatever she may in the meantime have learned from other experiments about the usefulness of sticks. In this case the stick was made auxiliary to the box-stacking experiment, no. 23 in the series. As formerly, the food was suspended from the limb of the tree, this time, however, at a height of seventy-eight inches from the ground, two boxes were placed, one on either side of the center and at a distance of five feet, and near the stake to which Congo was chained a stick five feet long. The trial began at 9:56 a. m., and up to 10:15 Congo had worked with the boxes as tools in a manner later to be described, without giving attention to the stick which was within easy reach. Then suddenly she went to the stick, picked it up, carried it directly and with obvious purpose to box 1, climbed upon the box, and holding the stick with one end on the ground, tried to raise it toward the suspended food.

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For a first attempt she managed fairly well, although she was extremely awkward. The upper figure of plate 7 (p. 110) is a photographic record of this first attempt to use the stick as aid in securing suspended food.

In the midst of her attempt to raise the stick toward the food Congo paused and holding the stick in position remained quiet for a few seconds. It was as though she were reflecting on, or puzzling over, her problem, for there was no evidence of distraction or attention to irrelevant things. Her next move was to abandon the stick and return to the use of the boxes, which for a short time she continued to manipulate. Failing, however, to get them placed successfully she took up the stick and with it in her hand mounted one of the boxes which happened to be directly under the food. It seemed as though she were just about to strike at the food with the stick when suddenly something happened within and she put down the stick and began efforts to place the one box upon the other. In this she presently succeeded, and obtained her reward.

Although in this experiment we have excellent evidence of Congo's desire to use the stick as aid in obtaining suspended food, little credit for invention, or even initiative, can be given her since in all probability interest in the stick and ability to use it transferred directly from the platform and stick experiment. Nevertheless, the behavior has significance as evidence of representational experience and as indication of a mode of adaptation which appears to differ radically from that of "trial and error."

A definite test of transfer was made on February 3 in an experimental setting practically identical with that of problem 8, suspended food and stick. The food, consisting of a banana, sweet potato, and half apple, was suspended sixty inches from the ground. Congo was chained to a stake at one side of the center, and five feet off center, lying on the ground, was a light stick sixty inches long. Observation began at 10:08 a. m.. Within two minutes Congo had noticed the stick, taken it up, carried it directly toward the food, and there tried

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