SAVAGE versus BRUTE.
To the Editor of the 'Times' (Sept. 19, 1888).
Sir,—In connection with the correspondence on the powers of counting displayed by savages, it may be of interest to narrate the following facts with regard to similar powers as displayed by brutes.
One often hears a story told which seems to show that rooks are able to count as far as five. The source of this story, however, is generally found to have been forgotten, and therefore the story itself is discredited. Now, the facts stand on the authority of a very accurate observer, and as he adds that they are 'always to be repeated when the attempt is made,' so that they are regarded by him as 'among the very commonest instances of animal sagacity,' we cannot lightly set them aside. The observer in question is Leroy, and the facts for which he personally vouches in his work on animal intelligence are briefly as follows:
'The rooks will not return to their nests during daylight should they see that anyone is waiting to shoot them. If to lull suspicion a hut is made below the rookery and a man conceal himself therein, he will have to wait in vain, should the birds have ever been shot at from the hut on a previous occasion. Leroy then goes on to say: 'To deceive this suspicious bird, the plan was hit upon of sending two men into the watch-house, one of whom passed out while the other remained; but the rook counted and kept her distance. The next day three went, and again she perceived that only two returned. In fine, it was found necessary to send five or six men to the watch-house in order to throw out her calculation.'
Finding it on this testimony not incredible that a bird could count as far as five, I thought it worth while to try what might be done with a more intelligent animal in this connection. Accordingly, about a year ago, I began, with the assistance of the keeper, to instruct the chimpanzee at the Zoological Gardens in the art of computation. The method adopted was to ask her for one, two, three, four, or five straws, which she was to pick up and hand out from among the litter in her cage. Of course, no constant order was observed in making these requests, but whenever she handed a number not asked for her offer was refused. In this way the animal learnt to associate the numbers with their names. Lastly, if more than one straw were asked for she was taught to hold the others in her mouth until the required number was complete, and then to deliver the whole at once. This method prevented any possible error arising from her interpretation of vocal tones, an error which might well have arisen if each straw had been asked for separately.
After a few weeks' continuous instruction the ape perfectly well understood what was required of her, and up to the time when I left town, several months ago, she rarely made a mistake in handing me the exact number of straws that I named. Doubtless she still continues to do so for her keeper. For instance, if she is asked for four straws she successively picks up three and puts them in her mouth, then she picks up a fourth and hands over all the four together. Thus, there can be no doubt that the animal is clearly able to distinguish between the numbers 1, 2, 3, 4, and 5, and that she understands the name for each. But as this chimpanzee is somewhat capricious in her moods, even private visitors must not be disappointed if they fail to be entertained by an exhibition of her learning, a caution which it seems desirable to add, as this is the first time that the attainments of my pupil have been made known to the public, although they have been witnessed by officers of the Society and other biological friends.
I have sent these facts to you, Sir, because I think that they bear out the psychological distinction which is drawn in your leading article of the 17th inst. Briefly put, this distinction amounts to that between sensuous estimation and intellectual notation. Any child, a year after emerging from infancy, and not yet knowing its numerals, could immediately see the difference between five pigs and six pigs, and therefore, as your writer indicates, it would be an extraordinary fact if a savage were unable to do so. The case, of course, is different where any process of calculation is concerned: e.g. 'each sheep must be paid for separately; thus, suppose two sticks of tobacco to be the rate of exchange for one sheep, it would sorely puzzle a Damara to take two sheep and give him four sticks.' (F. Galton, 'Tropical South Africa,' p. 213.) But if the savage had to deal with a larger number of pigs the insufficiency of his sensuous estimation would increase with the increase of numbers, until a point would be reached at which, if he were to keep count at all, he would be obliged to resort to some system of notation, i.e. to mark off each separate unit with a separate nota, whether by fingers, notches, or words. Similarly with the sense of hearing and the so-called muscular sense. We can tell whether a clock strikes 1, 2, 3, 4, or 5 without naming each stroke, and whether we have walked 1, 2, 3, 4, or 5 paces without naming each pace, but we cannot in this way be sure whether a clock has struck 11 or 12, or we ourselves have, walked as many yards.
Thus there is counting and counting, distinguishing between low numbers by directly appreciating the difference between two quantities of sensuous perceptions, and distinguishing between numbers of any amount by marking each sensuous perception with a separate sign. Of course, in the above instance of animals counting it must be the former method alone that is employed, and, therefore, I have not sought to carry the ape beyond the number 5 lest I should spoil the results already gained. But a careful research has been made to find how far this method can be carried in the case of man. The experiments consisted in ascertaining the number of objects (such as dots on a piece of paper) which admit of being simultaneously estimated with accuracy. It was found that the number admits of being largely increased by practice, until, with an exposure to view of one second's duration, the estimate admits of being correctly made up to between 20 and 30 objects. (Preyer, 'Sitzungsber. d. Gesell, f. Med. u. Naturwiss.,' 1881.) In the case of the ape it is astonishing over how long a time the estimate endures. Supposing, for instance, that she is requested to find five coloured straws. She perfectly well understands what is wanted, but as coloured straws are rare in the litter, she has to seek about for them, and thus it takes her a long time to complete the number; yet she remembers how many she has successively found and put into her mouth, so that when the number is completed she delivers it at once. After having consigned them to her mouth she never looks at the straws, and therefore her estimate of their number must be formed either by the feeling of her mouth, or by retaining a mental impression of the successive movements of her arm in picking up the straws and placing them in her mouth. Without being able to decide positively in which of these ways she estimates the number, I am inclined to think it is in the latter. But, if so, it is surprising, as already remarked, over how long a time this estimate by muscular sense endures. Should we trust Houzeau's statement, however (and he is generally trustworthy), it appears that computation by muscular sense may extend in some animals over a very long period. For he says that mules used in the tramways at New Orleans have to make five journeys from one end of the route to the other before they are released, and that they make four of these journeys without showing any expectation of being released, but begin to bray towards the end of the fifth.[67]
From this letter it will, I hope, be apparent that so far as 'counting' by merely sensuous computation is concerned, the savage cannot be said to show much advance upon the brute. 'Once, while I watched a Damara floundering hopelessly in a calculation on one side of me, I observed Dinah, my spaniel, equally embarrassed on the other. She was overlooking half a dozen of her new-born puppies, which had been removed two or three times from her, and her anxiety was expressive as she tried to find out if they were all present, or if any were still missing. She kept puzzling and running her eyes over them, backwards and forwards, but could not satisfy herself. She evidently had a vague notion of counting, but the figure was too large for her brain. Taking the two as they stood, dog and Damara, the comparison reflected no great honour on the man.' (Galton, loc. cit.) But the case, of course, is quite otherwise when, in virtue of the greatly superior development of the sign-making faculty in man, the savage is enabled to employ the intellectual artifice of separate notation, whereby he attains the conception of number in the abstract, and so lays the foundation of mathematical science. Now, so far as I am aware, there is no trustworthy evidence of any race of savages who are without any idea of separate notation. Whether the system of notation be digital only, or likewise verbal, is, psychologically speaking, of comparatively little moment.