June 13. 1889] 



NATURE 



161 



to five, beyond five the accuracy of her computation 

 becomes progressively diminished. 



It is to be noticed that the ape exhibits some idea of 

 multiplication ; for she very frequently (especially when 

 dealing with numbers above five) doubles over a long 

 straw so as to make it present two ends, and thus to 

 appear as two straws. Any of the comparatively rare 

 errors which she now makes in dealing with numbers 

 below six are almost invariably due to her thus endea- 

 vouring to duplicate her straws. In this connection it 

 is to be remembered that, owing to the method above 

 described (whereby the ape is required to place each 

 ' straw separately in her mouth until the sum asked for is 

 completed), when any high number is demanded a con- 

 siderable tax is imposed upon her patience ; and, as her 

 movements are deliberate while her store of patience is but 

 small, it is evident to all observers that the doubling of 

 the straws is intended to save trouble by getting the sum 

 completed with greater rapidity than is possible when 

 every straw is picked up separately. Of course we do 

 not recognize these doubled straws as equivalent to two 

 straws, and therefore the persistency with which she 

 endeavours to palm them off as such is the rnore note- 

 worthy as evidence of her idea of multiplication. 

 Moreover, I am disposed to think that the uncertainty 

 which attends her dealing with the numbers six and seven 

 is more largely due to her losing patience than to her I 

 losing count ; although after seven I believe that her 

 computation of the numbers themselves becomes vague, 

 or merged in a merely general idea of many. It may 

 also be stated that, while picking up the straws and 

 placing them in her mouth, she looks only at the straws 

 themselves and not at the person who asks for them : 

 therefore she is certainly not actuated in her responses by 

 interpreting facial expression, unconscious gesture, &c., 

 as is no doubt the case with many dogs which on this 

 account are sometimes accredited by their owners with 

 powers of "thought-reading." It is needless to add that, 

 after asking for the number of straws required, we remain 

 silent till the ape has handed them out. 



It is not necessary— indeed it would be unreasonable — 

 to suppose that in' this process of "counting" the ape 

 employs any system of notation. We know from our own 

 experience that there is counting and counting, i.e. 

 distinguishing between low numbers by directly ap- 

 preciating the difference between two quantities of 

 sensuous perception, and distinguishing between numbers 

 of any amount by marking each perception with a 

 separate sign. The extent to which the former kind of 

 computation can be carried in the case of man has been 

 made the subject of a careful research by Prof. Preyer, of 

 Jena {Sitz. Ber. d. GeselL f. Med. ti. Naturwiss., 1881). 

 His experiments consisted in ascertaining the number of 

 objects (such as dots on a piece of paper) which admit of 

 being simultaneously estimated with accuracy, and it was 

 found that the number admits of being largely increased 

 by practice, until, in the case of some persons, it may 

 rise to more than twenty. But of course in the case of a 

 brute it is not to be expected that such a high degree of 

 proficiency even in this non-notative kind of " counting" 

 should be attainable. The utmost that could here be 

 expected is that a brute should exhibit some such level 

 of ability as is presented by a young child, or by those 

 savages whose powers of accurate computation do not 

 appear to extend further than numbers which we write as 

 units.^ It was in viev/ of such considerations that 1 did 

 not attempt to carry the education of this ape beyond the 

 number five ; and the result which has attended subsequent 

 endeavours to teach her numbers as high as ten is, as 

 previously remarked, exactly what might have been 

 anticipated. It may here be added that in the only 

 records with which I am acquainted of animals exhibiting 

 any powers of numerical computation, these powers have 



' See, for instance, Gatton, "Tropical South Africa," p. 213 



not extended beyond the number five. Thus, for instance, 

 in his well-known account of these powers as presented 

 by rooks, Leroy says :— "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 

 to shoot the bird on returning to her nest ; but the rook 

 counted and kept her distance. 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 calculations." ^ 

 Again, Houzeau tells us that mules used in 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.'- Lastly, the keeper of the eared 

 seals now in the Menagerie has recently taught one of 

 these animals to " count" as far as five His method is 

 to throw pieces of fish in regular succession, which the 

 animal catches one by one. He throws them in series of 

 fives, and, before the commencement of any series, he 

 tells the seal to miss the first, the second, the third, the 

 fourth, or the fifth, as the on-lookers may dictate : the 

 seal thereupon makes no attempt to catch the member of 

 the series thus verbally indicated. It is only a day or 

 two ago, however, that I witnessed this performance, and 

 as yet I am not satisfied that the seal really " counts," 

 because it appears to me probable that the keeper may 

 unintentionally throw, with some slight difference m his 

 manner of throwing, the piece of fish which he expects 

 the seal to miss, and that it is really this slight difference 

 in the manner of throwing which the seal perceives and 

 acts upon. Therefore, I intend to get an arrangement 

 fitted up whereby the pieces of fish shall be thrown 

 mechanically. But, whatever the result of this experiment 

 may be, I think there can now no longer be any question 

 that it lies within the capacity of animal intelligence to 

 " count" correctly (in the sense already explained) as far 

 as five, and even to show a well-marked appreciation, 

 although progressively a more and more uncertain one, 

 of numbers lying between five and ten. 



The only other direction in which I have thus far 

 subjected the Chimpanzee to psychological experiment 

 has been in that of attempting to teach her the names of 

 colours. It appeared to me that if I could once suc- 

 ceed in getting her thoroughly well to know the names 

 of black, white, red, green, and blue, a possible basis 

 might be laid for many further experiments wherein these 

 five colours could be used as signs of artificially asso- 

 ciated ideas. The result, however, of attempting to 

 teach her the names of colours has been so uniformly 

 negative, that I am disposed to think the animal must be 

 colour-blind. It is perhaps desirable to state the facts 

 which have led me to entertain this as their most probable 

 interpretation. 



The method adopted in these experiments was to 



i obtain from the importers of Oriental matting a number 



: of brightly and uniformly coloured pieces of straw— each 



i piece being either white, black, red, green, or blue. 



i Taking the straws two by two of different colours, on each 



I occasion the ape was invited to choose the straw of the 



! colour named from the one whose colour was not n^"\e<^> 



and, of course, on choosing correctly she was rewarded 



with a piece of fruit. In this way she quickly learnt t(> 



distinguish between the white straws and the straws of 



any other colour ; but she never could be taught to go 



further. Now the distinction between the white straws 



and the straws of any other colour is a distinction which 



could have been drawn by an eye that is colour-blind ; 



and from the fact that the ape is always able to perceive 



this distinction (she will search long and patiently for a 



straw of anv colour when told that it occurs somewhere 



in the general litter of white straws constituting her bed, 



1 " Letters, &c" '"■ " Fac. Ment. des Anim.," torn. ii. p. 207. 



