SOME RESULTS OF EXPERIMENT 147 
meet its deflected course. On the fourth day this method was 
well established. On the fifth, the ball was thrown so as to 
strike the other or right side of the angle, and thus be deflected 
in the opposite direction. The dog followed the old course 
(the short cut to the left) and was completely non-plussed, 
searching that side, then niore widely, and not finding the 
ball for eleven minutes. On repeating the experiment thrice, 
similar results were that day obtained. On the following day 
the ball was thrown just ahead of him, so as to strike to the 
right of the angle, and was followed and caught. ‘This course 
was pursued for three days, and he then learnt to take a short 
cut to the right. On the next day the ball was sent, as at 
first, to the left, and the dog was again non-plussed. I did 
not succeed in getting him to associate a given difference of 
initial direction with a resultant difference of deflection. 
I may here mention that, whenever searching for a ball of 
which he had lost sight in the road, he would run along the 
eutter first on one side and then on the other. A friend who 
was walking with me one day regarded this as a clear case of 
rational inference. ‘The dog knows,” he said, “the effects 
of the convex curvature of the road as well as we do.” I am 
convinced, however (having watched his ways from a puppy), 
that this method of search was gradually established on a 
basis of practical experience. No logical inference on his 
part is necessary for the interpretation of the facts; and we 
should not assume its presence unless the evidence compels us 
to do so. 
Dr. E. L. Thorndike, in a monograph on “ Animal Intelli- 
gence”’ published as a supplement to the Psychological Review 
(June, 1898), has fully described and carefully discussed a 
number of interesting experiments. The subjects (one might, 
alas! almost say victims) of some of these were thirteen 
kittens or cats from three to eighteen months old. His 
method of investigation shall be stated in his own words. 
‘‘ After considerable preliminary observation of animals’ behaviour 
under various conditions, I chose for my general method one which, 
