6o2 LIFE : OUTLINES OF GENERAL BIOLOGY 



Unforgettable are the lessons in arithmetic given by Romanes to 

 the chimpanzee Sally in the Zoo. In the course of time, when the 

 teacher asked for three straws, Sally gathered one-two-three. First 

 holding them in her mouth, and then taking them in her hand, she 

 presented them between the bars of the cage. And so with four and 

 five straws, but not successfully with more. An association seemed 

 to be formed between the sound of the number asked for and the 

 number that should be gathered, and to this extent Romanes 

 believed that Sally could "count". He was inclined to go farther, 

 for he told us once that when Sally was in a hurry to get her reward 

 she had been known to bend a straw so that its two ends stuck out 

 between her finger and thumb. She saved time by making one straw 

 count double, and when the reward was refused she would straighten 

 out the bent straw and pick up another to complete in the fit and 

 proper way the number asked for. If this case were well established 

 it is very important; but Prof. Hempelmann, in his Tierpsycho- 

 logic, points out that great care is necessary to exclude the possi- 

 bility that the very alert ape is not taking advantage of conscious 

 or unconscious signs of approval on the part of the instructor or 

 the gallery. If the clever creature, having gathered three straws, 

 sees that the audience is satisfied, then it gathers no more. Prof. 

 Kohler's observations on his happy chimpanzees at Teneriffe 

 yielded no evidence of any ability to estimate numbers; and Lord 

 Avebury's clever dog, Van, after three months of lessons, had made 

 no progress towards a practical appreciation of the number of strokes 

 on white cards. This dog, it may be recalled, was able to go to a box 

 of cards and select the three whose letters spelt T-E-A, or 0-U-T, 

 or the like, but when it was asked for a card with a certain number 

 of strokes, its answers, even after long tuition, were quite at random. 

 That is to say, the dog had either failed to establish any association 

 between the sounds one, two, three, or four, and the images of one, 

 two, three, or four black strokes, or else, less probably, it had 

 failed to detect any difference between the cards bearing different 

 numbers of strokes. 



An old and simple experiment with horses hints at some appre- 

 ciation of quantity, if not of number. The horse was offered on a 

 table a choice between one lump of sugar and two or three lumps. 

 It always preferred the number greater than one, and yet it showed 

 no preference for three over two. This is a better kind of experi- 

 ment than that of the black strokes, for lumps of sugar are of 

 direct practical interest. Perhaps, as we have said, the preference 

 was based on a volumetric rather than on a numerical estimate. Of 

 course, the sides at which the sweet alternatives were placed were 

 continually changed. 



In a striking experiment by Katz and Revesz; grains of wheat 

 were arranged in a row, fixed and free alternately. Very quickly the 



