Monkeys have favourite Colours—Can distinguish Numbers and Quantity—Music and Art very limited.

In order to ascertain whether monkeys have any choice of colours or not, I selected some bright candies, balls, marbles, bits of ribbon, &c. I took a piece of pasteboard, and on it placed a few bright-coloured bits of candy, which I offered to a monkey and watched to see whether he would select a certain colour or not. In this experiment I generally used two colours at a time, and changed their places from time to time in order to determine whether he selected the colour by design or accident. After having determined which of two colours he preferred, I substituted a third colour for the one which he cared least for, and continued thus until I exhausted the list of bright colours. By changing the arrangement of the objects a great number of times, it could be ascertained with comparative certainty whether the colour was his preference or not. I find that all monkeys do not select the same colour, nor does the same monkey invariably select the same colour at different times; but I think, as a rule, that bright green is a favourite colour with the Capuchin, and their second choice is white. In a few cases, white seemed to be their preference. I have sometimes used paper wads of various colours, or bits of candy of the same flavour rolled in various coloured papers. They seemed to choose the same colours in selecting their toys. I have sometimes used artificial flowers, and find, as a rule, that they will select a flower having many green leaves about it. It may be that they associate this colour with some green food which they are fond of, and consequently that they are influenced by this in selecting other things. I kept a cup for a monkey to drink milk from, on the sides of which were some brilliant flowers and green leaves, and she would frequently quit drinking the milk to play with the flowers on the cup, and seemed never able to understand why she could not get hold of them. In one test I had a board about two feet long, and laid a few pieces of white and pink candies in four places on it. The monkey took the white from each pile before touching the pink, except in one instance it took the pink piece from one pile. I repeated this test many times. In another test I took a white paper ball in one hand and a pink one in the other, and held out my hands to the monkey, who selected the white one nearly every time, although I changed hands with the balls from time to time. These experiments were mostly confined to the Cebus monkeys, but a few of them were made with Macaques. They seem to be attracted generally by all brilliant colours, but when reduced to a choice between two, such seems to be their tastes.

In my efforts to ascertain their mathematical skill, I would take in one hand a little platter containing one nut, or one small bit of something to eat, such as a piece of apple or carrot cut into a small cube. In the other hand I held a small platter, with two or three such articles of the same size and colour, and holding them just out of reach of the monkey and changing them from hand to hand, I observed that the monkey would try to reach the one containing the greater number. He readily discerned which platter contained one and which contained two or three pieces. I was long in doubt whether he distinguished by number or by quantity, and my belief was that it was by quantity only. I first determined that he could tell singular from plural, by making the one piece larger and sometimes of a different shape, and from his choice of these I quite satisfied my own mind that he could distinguish by number. THE TEST WITH MARBLESI next set out to find how far in numerals his acquirements reached, and after a great number of indecisive trials I fell upon this simple plan: I took a little square wooden box and made a hole in one side just large enough for the monkey to withdraw his hand with a marble in it. I took three marbles of the same size and colour, and gave them to the monkey to play with. After a time I put the marbles in a box and allowed him to take them out, which he could do by taking out only one at a time. I repeated this several times, so as to impress his mind with the number of marbles in the box. I then concealed one of the marbles and returned two to the box. On taking them out, he evidently missed the absent one, felt in the box, arose, and looked around where he had been sitting. Then he would put his hand into the box again and look at me; but failing to find it, he became reconciled, and began to play with the two. When he had become content with the two, I abstracted one of them, and when he failed to find it he began to search for it, and seemed quite unwilling to proceed without it. He would put the one back into the box and take it out again, as if in hope that it might find the other. I helped him to look for the missing marbles, and, of course, soon found them. When he learned that I could find the lost marbles, he would appeal to me as soon as he missed them, and in several instances he would take his little black fingers and open my lips to see if I had concealed them in my mouth, the place where all monkeys conceal what they wish to keep in safety from other monkeys, who never venture to put their fingers into one another's mouth, and when any article is once lodged in a monkey's mouth it is safe from the reach of all the tribe. I repeated this until I felt quite sure of the ability of my subject to count three, and I then increased the number of marbles to four. When I would abstract one of them, sometimes he seemed to miss it, or at least to be in doubt, but would soon proceed with his play and not worry himself about it; yet he rarely failed to show that he was aware that something was wrong. Whether he missed one from four, or only acted on general principles, I do not know; but that he missed one from three was quite evident.

I may here add that there is a great difference in different specimens, and their tastes vary like those of human beings. The same idea is much clearer to some monkeys than it is to others, and a choice of colours much more definite; but I think that all of them assign to different numbers a difference of value. Some are talkative and others taciturn. I think I may state with safety that the Cebus is the most intelligent and talkative of all the monkeys I have known; that the Old World monkeys, as a group, are more taciturn and less intelligent than the New World monkeys, but I do not mean to include the anthropoid apes in this remark.

As a test of their taste for music or musical sounds, I took three little bells, which I suspended by three strings, one end of which was tied to a button. The bells were all alike, except that from two of them I had removed the clappers. I dropped the bells through the meshes of the cage about a foot apart, and allowed the monkey to play with them. I soon discovered that he was attracted by the one which contained the clapper. He played with it, and soon became quite absorbed in it. I attracted his attention to another part of the cage with some food, and while he was thus diverted I changed the position of the bells by withdrawing and dropping them through other meshes. On his return he would go to the place he had left, and, of course, get a bell with no clapper in it. He would drop this and take another, until he found the one with the clapper, which showed clearly that the sound was a part of the attraction. I have repeated to monkeys many musical records on the phonograph, but frequently they show no sign of concern, while at other times they display some interest. It may be, however, that music, as we understand it, is somewhat too high for them. Musical sounds seem to attract and afford them pleasure, but they do not appreciate melody or rhythm. As monkeys readily discern the larger of two pieces of food from the smaller, and by the aid of concrete things can count a limited number, I feel justified in saying that they have the first principles of mathematics as dealing with numbers and quantity in a concrete form. Their ability to distinguish colours and their selection thereof, would indicate that they possess the first rudiment of art as dealing with colour. And the fact that they are attracted in a slight degree by musical sounds shows that they possess the germ from which music itself is born. I must not be understood to claim that they possess anything more than the mere germ from which such faculties might have been evolved. I do not think that they have any names for numbers, colours or quantities, nor do I think that they possess an abstract idea of these things, except in the feeblest degree; but as the concrete must have preceded the abstract idea in the development of human reason, it impresses me that these creatures are now in a condition such as man has once passed through in the course of his evolution; and it is not difficult to understand how such feeble faculties may develop into the very highest degree of strength and usefulness by constant use and culture.

We find in them the rudiments from which all the faculties possessed by man could easily develop, including thought, reason, speech, and the moral and social traits of man. In brief, they appear to have at least the raw material out of which is made the most exalted attributes of man, and I shall not contest with them the right of such possession.