“Are we to suppose that these animals possess abstract ideas? I reply—That depends upon what is meant by abstract ideas. If it is implied that the abstract ideas are isolates; that is, qualities considered quite apart from the objects of which they are characteristic, I think not. But if it be meant that elephants, in a practical way, ‘recognise such qualities as hardness, sharpness, and weight,’ as predominant elements in the constructs they form, I am quite ready to assent to the proposition.”
I agree fully with this conclusion, adding the one remark that between the pure abstract notion and the “predominant” notion so called, there is only a difference of degree. If the predominant element is not isolated, detached, and fixed by a sign, it is certainly near being so, and deserves on this ground to be called an abstract of the lower order.
The observation of Houzeau has been frequently quoted respecting dogs, which, suffering from thirst in arid countries, rush forty or fifty times into the hollows that occur along their line of march in the hope of finding water in the dry bed. “They could not be attracted by the smell of the water, nor by the sight of vegetation, for these are wanting. They must thus be guided by general ideas, which are doubtless of an extremely simple character, and, in some measure, supported by experience.”
It is on this account that the term “generic image” would in my opinion be preferable for describing cases of this character.
“I have frequently seen not only dogs, but horses, mules, cattle, and goats, go in search of water in places which they had never visited before. They are guided by general principles, because they go to these watering places at times when the latter are perfectly dry.”[13] Undoubtedly it may be objected that association of images here plays a preponderating part. The sight of the hollows recalls the water which, though absent, forms part of a group of sensations which has been perceived many times; but since the generic image is, as we shall see later, no more than an almost passive condensation of resemblances, these facts clearly indicate its nature and its limits.
I shall merely allude without detailed comment to the numerous observations on the aptitude of dogs and cats for finding means to accomplish their aims, the anecdotes of their mechanical skill, and the ruses (so well described by G. Leroy) which the fox and the hare employ to outwit the hunter, “when they are old and schooled by experience; since it is to their knowledge of facts that they owe their exact and prompt inductions.” The most intelligent of all animals, the higher orders of monkeys, have not been much studied in their wild state, but such observations as have been made, some of which have been contributed by celebrated naturalists, fix with sufficient distinctness the intellectual level of the better endowed. The history of Cuvier’s orang-outang has been quoted to satiety. The more recent books on comparative psychology contain ample testimony to their ability to profit by experience[14] and to construct instruments. A monkey, not having the strength to lift up the lid of a chest, employed a stick as a lever. “This use of a lever as a mechanical instrument is an action to which no animal other than a monkey has ever been known to attain.” Another monkey observed by Romanes, also “succeeded by methodical investigation, without assistance, in discovering for himself the mechanical principle of the screw; and the fact that monkeys well understand how to use stones as hammers, is a matter of common observation.” They are also skilful in combining their stratagems, as in the case of one who, being held captive by a chain, and thus unable to reach a brood of ducklings, held out a piece of bread in one hand, and on tempting a duckling within his reach, seized it by the other, and killed it with a bite in the breast.[15]
One mental operation remains which must be examined separately, and in its study we shall pursue the same method, wherever it occurs, throughout this work. The process in question has the advantage of being perfectly definite, of restricted scope, completely evolved, and accessible to research in all the phases of its development, from the lowest to the highest. It is that of numeration.
Are there animals capable of counting? G. Leroy is, I believe, the first who answered this question in the affirmative, in a passage which is worth transcribing, although it has been often quoted. “Among the various ideas which necessity adds to the experience of animals, that of number must not be overlooked. Animals count,—so much is certain; and although up to the present time their arithmetic appears weak, it may perhaps be possible to strengthen it. In countries where game is preserved, war is made upon magpies because they steal the eggs of other birds.... And in order to destroy this greedy family at a blow, game-keepers seek to destroy the mother while sitting. To do this it is necessary to build a well-screened watch-house at the foot of the tree where the nests are, and in this a man is stationed to await the return of the parent bird, but he will wait in vain if the bird has been shot at under the same circumstances before.... To deceive this suspicious bird, the plan was hit upon of sending two men into the watch-house, one of them passed on while the other remained; but the magpie counted and kept her distance. The next day three went, and again she perceived that only two withdrew. It was eventually found necessary to send five or six men to the watch-house in order to put her out of her calculation.... This phenomenon, which is repeated as many times as the attempt is made, is one of the most extraordinary instances of the sagacity of animals.” Since then the question has been repeatedly taken up. Lubbock devotes to it the three last pages of his book The Senses of Animals. According to his observations on the nests of birds, one egg may be taken from a nest in which there are four, but if we take away two, the bird generally deserts its nest. The solitary wasp provisions its cell with a fixed number of victims. Sand wasps are content with one. One species of Eumenes prepares five victims for its young, another species ten, another fifteen, another twenty-four; but the number of the victims is always the same for the same species. How does the insect know its characteristic number?[16]
An experiment, methodically conducted by Romanes, proved that a chimpanzee can count correctly as far as five, distinguishing the words which stand for one, two, three, four, five, and at command deliver the number of straws requested of her.[17]