1898] ANIMAL INTELLIGENCE 267 



will probably claw the string or loop or button so as to open the door. And 

 gradually all the other non-successful impulses will be stamped out and the 

 particular impulse leading to the successful act will be stamped in by the result- 

 ing pleasure, until, after many trials, the cat will, when put in the box, 

 immediately claw the button or loop in a definite way. . . . Starting, then, with 

 its store of instinctive impulses, tbe cat hits upon the successful movement, and 

 gradually associates it with the sense-impression of the interior of the box until 

 the connection is perfect, so that it performs the act as soon as confronted with 

 the sense-impression. . . . Previous experience makes a difference in the quickness 

 with which the cat tonus the associations. After getting out of six or eight 

 boxes by different sorts of acts the cat's general tendency to claw at loose objects 

 within the box is strengthened and its tendency to squeeze through holes and 

 bite bars is weakened ; accordingly it will learn associations along the general 

 line of the old more quickly. Associations between licking or scratching and 

 escape are similarly established, and there was a noticeable tendency to diminish the 

 act until it becomes a mere vestige of a lick or scratch. After the cat gets so that 

 it performs the act soon after being put in, it begins to do it less and less 

 vigorously. The licking degenerates into a mere quick turn of the head w r ith one 

 •or two motions up and down with tongue extended. Instead of a hearty scratch, 

 the cat waxes its paw up and down rapidly for an instant." 



These experiments confirm the conclusion to which I have been 

 led by my own observations that the method of animal intelligence 

 is to profit by chance success and to build upon fortunate items of 

 ■experience casually hit upon and not foreseen. I need not here 

 repeat cases already published, such as the opening of a gate on the 

 part of my fox terrier by lifting the latch, a trick he certainly learnt 

 by this method ; but I may very briefly describe one or two further 

 ■observations not yet recorded. I have watched my dog's behaviour 

 when a solid indiarubber ball was thrown towards a wall standing 

 at right angles to its course. At first he followed it right up to the 

 wall and then back as it rebounded. So long as it travelled with 

 such velocity as to be only just ahead of him he pursued the same 

 course. But when it was thrown more violently, so as to meet him 

 on the rebound as he ran towards the wall, he learnt that he was 

 thus able to seize it as it came towards him. And, profiting by the 

 incidental experience thus gained, he acquired the habit — though 

 fur long with some uncertainty of reaction — by slowing off when the 

 object of his pursuit readied the wall so as to wait its rebound. 

 Again, when the ball was thrown so as to rebound at a wide antde 

 from a surface, at first, — when the velocity was such as to keep it 

 just ahead of him, — he followed its course. But when the velocity 

 was increased he learnt to take a short cut along the third side of a 

 triangle, so as to catch the object at some distance from the wall. 

 A third series of experiments were made where an angle was 

 formed by the meeting of two surfaces at right angles. One side of 

 the angle, the left, was dealt with for a day or two. At first the 

 ball was directly followed. Then a short cut was taken to meet its 

 •deflected course. On the fourth day this method was well estab- 



