THOUGHT CAPACITY IN ANIMALS 19 



accompanying his assent with a yawn. I am 

 generally obliged to hold out the prospect of some 

 reward as an inducement to do his sums. I should 

 have preferred his rapping against some article one 

 could hold in one's hand, or that he could be induced 

 to " rap out " on a board setting forth the numbers, 

 and which might be placed on the floor before him ; 

 but to neither of these alternatives will he agree, 

 having since his earliest youth learnt to rap in the 

 same way as Rolf does. He will, however, not only 

 rap for me, but for any person he knows well, solving 

 such problems as : 3+4 6, or -v/i2i -f 3> or T" "i" 4 

 or 3 2 , and he seldom makes a mistake, even when the 

 sum he may be asked merely resembles the form of 

 arithmetic he has learnt. But he generally gives up 

 after two or three sums and is generally distracted. 

 He can read the figures too, and generally gives a 

 correct solution to sums which have been written down 

 for him and which I myself have not read. Like Rolf, 

 he only looks at the paper sideways. He reads very 

 reluctantly. His memory is excellent ; especially 

 quick is he at recognizing those persons again who 

 have at any time had to do with him.' 



" When I was in Mannheim on 22 March, 1916, 

 Mr. Justice Leser was kind enough to show me the 

 dog. I put some problems to it verbally and was 

 able to satisfy myself as to its abilities in the matter 

 of arithmetic. Of those then put by me I still call 

 to mind the following : "24-1-3 3 ? ' Answer : 

 ' 5,' and ' -^/IO.OQO 87 ?' Answer : ' 13.'* 



1 The dog had become familiar with square roots in the course 

 of earlier attempts. 



