A BOOK OF THE MOMENT

INTELLIGENCE TESTS FOR CHIMPANZEES

The Mentality of Apes. By Professor Wolfgang Kohler. (Kegan Paul. 16e. net.)

ME chimpanzees which Professor W. Kohler had under observation at Teneriffe for several years were not, nor did they ever become, trained animals. - They were not expected to learn to ride bicycles, or eat with forks. Indeed, Professoi. Kohler considers it impossible without - coercion to make chimpanzees do anything which they do not thoroughly understand.

The animals were allowed to lead as natural and free a life as is possible in captivity, and the best possible relations existed between them and the author, who describes how much they differed individually—as much, indeed, as individuals would do in a similar group of children or men. The most intelligent was Sultan. Nueva, an old female, was particularly ugly and of a gracious disposition. Grande, another female, was temperamental and used to work herself up into harmless, simulated rages, her hair bristling, in a way very alarming to visitors. The young male, Koko, was a pert, short-tempered, egotistic but very lovable little creature. Rana, another female, was the most stupid. It was she who, when not particularly hungry, began " feeding the fowls ?' who wandered outside the cages with bits of bread. The others, more active, foUnd it excellent fun to decoy the hens up to the cages with proffered bits and then jab naughtily at them with sticks. But in all the tests, so simple to us, but, so difficult to the apes, the personality of each chimpanzee is very marked.. This affectionate character-delineation of the animals makes _ the book very pleasing ; and Professor Kohler never loses an opportunity of speaking well of his charges :— " When I had been in Teneriffe a few weeks only, In oticed, whilst feeding the squatting animals pressed up close to me, that a little female, at other times quite well-behaved, was snatching "the food out of the hand of a weaker animal, and as she persisted in this, I gave her a little rap. The little creature, which I had punished for the first time, shrank back, uttered one or two heart- broken wails, as she stared at me, while her lips were pouted more than ever. The next moment she had flung her arms round my neck, quite beside herself, and was only comforted by degrees, when 1 stroked her. This need, here expressed, for forgiveness is a phenomenon frequently to be observed in the emotional life of chimpanzees."

They greeted each other and the human beings affectionately each morning after the night's separation, and by their gestures often expressed gratitude for favours. One night two of them got left out of their sleeping-dens by mistake ; it came on to rain heavily ; Professor Kohler heard them complaining, ran out, and opened the door of their cage :-

"Although the cold water was streaming down their shivering bodies on all sides, and although they had just shown the greatest misery and impatience, and I myself was standing in the middle of the pouring torrent, before slipping into their den they turned to me and put their arms round me, one round my body, the other round my knees, in a fgenzy of joy."

One would show distress because a particular friend had done something forbidden. And again sometimes when an offender was being punished, the friend would first plead with and then threaten the htirnan arm of the law. When Professor KOhler ran a splinter into his finger and showed it to one of the chim- panzees, the animal after a careful examination squeezed out the bit of wood with his finger-nails, nor did he let the injured hand go again until he had satisfied himself that the operation was a success.

The experiments recorded in The Mentality of Apes form part of a series of patient investigations which Professor KOhler and his associate, Professor Koffka—two exponents of the Gestalt psychology—have been making in several directions. The object of the work done in Teneriffe was twofold. First, since it. is already established that the higher apes are physically allied to man, more closely even than they arc to the other ape species, there was a desire to determine what intellectual kinship they might have with man. And, secondly, there was the wish to observe in them some of those simplest primary acts of an intelligent kind which cannot easily be observed in the more complex human being, but which must be observed if we arc ever to learn what at root an act of intelligence is.

In a set of tests, food was put outside a cage so that the chimpanzee inside could not reach it. At the same time a stick was put unobtrusively inside the cage. One animal which had arrived at the station only three days before, finding she could not grasp the food, moaned piteously and flung herself on her back in the typical attitude of despair. Seven minutes after the appearance of the food, she suddenly looked at the stick near her, picked it up, poked it through the bars and drew the food within reach. Later, all the animals learnt by themselves to use sticks ; but at first at any rate the chimpanzee's ability to visualize a stick as a possible tool always depended on the distance the stick lay from the objective.

-In another test, food was hung up on a wall, too high to be snatched down, and a small box with which Koko had pre- viously played was put, not under the food, but three metres away. After fruitlessly jumping up, he suddenly saw the box :-

" He approached it, looked straight towards the objective, and gave the box a slight push, which did not however move it."

Koko had evidently had a vague dawning of the solution of the problem, but it was not until a piece of orange, a favourite titbit, was also added to the suspended food that he seized the box, dragged it right under the objective and, mounting it, tore down the fruit.

The apes had learnt, then, the simple use of tools. Pro- fessor Kohler wished to see if they could make an effective implement. He put food outside Sultan's cage, and gave him two hollow bamboo sticks, one small enough at one end to fit into the open end of the other. The food was too far away to be grasped or to be reached with either of the two sticks. It could only be obtained by making one long stick by fitting the two short ones together. After much per- plexity and some " good errors," while playing with the two sticks, Sultan happened to hold them, one in each hand, so that they lay in a straight line. He immediately pushed the end of the thin stick inside the other one, and in a trice was pulling the food to him with his new-made tool. Later, he became quite expert in the use of double-sticks, and even carefully gnawed down the end of a piece of wood to make it, too, fit into a rod ; yet once he grasped the principle he did not attempt to join two sticks of the same size, or make any error of visual judgment of this kind. Among the illustrations in the book, there is a charming photograph of Sultan, sitting in his cage, with an expression of grave concern on his face, just about to fit his two sticks together.

Sultan, who already understood the use of one box as a footstool, saw at once when he looked at some fruit hanging high up that one box would be useless. Chimpanzees, those expert jumpers, can readily judge distance. Though a second box lay to hand, it did not at once occur to him to use a double implement ; he merely hit the first box in anger. Then, suddenly, he fetched the second box and held it above but did not place it on the first box. The useful idea of " another box " had come to him, and also the idea of " another box up." But that was all. he flew into a rage when the second box would not stay suspended in air above the first box, and failed to solve the difficulty. Still later; the problem of placing one box above another box and on it at the same time puzzled many of them. But, as Professor Kohler says rather grimly, these failures ought not to shock any of his readers who like himself are baffled in the manipulation of a deck-chair !

Footstools soon became the fashion in the station. Stones, tins, ladders, tables, anything portable the apes soon found would serve to stand on and reach food. Indeed, passing keepers and Professor Kohler himself were often dragged and pushed under objectives and used as stepping-stones. Pole- jumping was invented by Sultan as a pure game. Even more refined delights were discovered : the chimpanzees found that by pushing straws through cracks in a covered tank in the playing-ground they could suck up water from it. It was not; of course, thirst that compelled them to do this. Straws came in handy, too, for catching the streams of brown ants that passed over the beams supporting the wire-netting of their yard. They dug " for fun " with sticks in the ground ; they poked with sticks at any stray mice, lizards or creepy creatures which they, like *is, hesitate to touch. , And _ they also invented various kinds of rhythmical stamping and marching in which they all joined—playing, in fact, the good old game of " follow-my-leader." None of these diversions were shown to them, or in any way induced, just as none of the solutions of problems were indicated. Games developed spontaneously, though when they were well developed Professor Kohler sometimes used to join in.

The conclusions which follow from the experiments under- taken are of a profoundly interesting but necessarily technical nature : there is no space in the measure of a review to detail them, or to mention more than two or three of the many experiments carried out. But briefly, Professor Kohler maintains convincingly that " the chimpanzees manifest intelligent behaviour of the general kind familiar in human beings."

He does not mean by this that they are capable of doing multiplication tables. What he does mean is that they solve certain highly difficult problems in the same way as man solves them, or rather as the human infant solves them. Of number they have almost no conception, and they seem not to be furnished mentally with the power of comprehending statics even in the vaguest way. They live almost entirely in the present, though they have memory as have dogs and other animals, and can be said to " live in the future " just in so far as they apprehend the result of a complex action, and no further. But with all their limitations, they do carry out actions which are not instinctive, or imitative, but the result of a degree of insight. The kind of intelligence they show themselves to possess, though infinitely limited in range, is the same as that which distinguishes man.

IRIS BARRY.