266 NATURAL SCIENCE [October 



pressing a lever, or stepping on a platform. The animal was put in the enclosure, 

 food was left outside in sight, and his actions observed. Besides recording his 

 general behaviour, special notice was taken of how he succeeded in doing the 

 necessary act (in case he did succeed), and a record was kept of the time that he 

 was in the box before performing the successful pull, or clawing, or bite. 

 This was repeated until the animal had formed a perfect association between the 

 sense-impression of the interior of that box and the impulse leading to the suc- 

 cessful movement. When the association was thus perfect, the time taken to 

 escape was, of course, practically constant and very short. 



" If, on the other hand, after a certain time the animal did not succeed, he 

 was taken out, but not fed. If, after a sufficient number of trials, he failed to get 

 out, the case was recorded as one of complete failure. Enough different sorts of 

 methods of escape were tried to make it fairly sure that association in general, 

 not association of a particular sort of impulse, was being studied. Enough 

 animals were taken with each box or pen to make it sure that the results were 

 not due to individual peculiarities. None of the animals used had any previous 

 acquaintance with any of the mechanical contrivances by which the doors were 

 opened. So far as possible the animals were kept in a uniform state of hunger, 

 which was practically utter hunger." 



To Mr Thorndike's monograph we must refer those who desire 

 detailed information as to apparatus and procedure. It must here 

 suffice to state that the box-cages employed were rudely constructed 

 of wooden laths, and formed cramped prisons about twenty inches 

 long by fifteen broad and twelve high. Nine contained such simple 

 mechanisms as Mr Thorndike describes in the passage above quoted. 

 When a loop or cord was pulled, a button turned, or a lever de- 

 pressed, the door fell open. In another, pressure on the door as well 

 as depression of a thumb-latch was required. In one cage two 

 simple acts on the part of the kitten were necessary, pulling a cord 

 and pushing aside a piece of board ; and in yet others three acts 

 were requisite. In those boxes from which escape was more diffi- 

 cult a few of the cats failed to get out. The times occupied in 

 thoroughly learning the trick of the box by those who were success- 

 ful are plotted in a series of curves, the essential feature of which 

 is the graphic expression of a gradual diminution in the time 

 interval between imprisonment and escape in successive trials. 

 In some cases the cats were set free from a box when they (1) 

 licked themselves or (2) scratched themselves. 



Mr Thorndike comments on the results of his experiments as 

 follows : — 



" When put into the box the cat would show evident signs of discomfort and of 

 an impulse to escape from confinement. It tries to squeeze through any opening ; 

 it claws and bites at the bars or wire ; it thrusts its paws out through any 

 opening and claws at everything it reaches ; it continues its efforts when it 

 strikes anything loose and shaky : it may claw at things within the box. It does 

 not pay very much attention to the food outside, but seems simply to strive 

 instinctively to escape from confinement. The vigour with which it struggles is 

 extraordinary. For eight or ten minutes it will claw and bite and squeeze 

 incessantly. . . . The cat that is clawing all over the box in her impulsive struggle 



