42 E. L. THORNDIKE. 



the window, swung it open and escaped." (Animal Intelligence, 

 p. 425.) 



A description has already been given on page 9 of the 

 small box (C), whose door fell open when that button was 

 turned, and also of a large box (CC) for the dogs,with a similar 

 door. The thumb-latch experiment was carried on with the 

 same box (G) for both cats and dogs, but the door was arranged 

 so that a greater force (1.3 kilograms) was required in the case 

 of the doss. It will be remembered that the latch was so fixed 

 that if the thumb-piece were pressed down, without contempo- 

 raneous outward pressure of the door, the latch bar would merely 

 drop back into its catch as soon as the paw was taken off the 

 door. If, however, the door were pushed outward the latch 

 bar, being pressed closely against the outer edge of its catch, 

 would, if hfted, be likely to fall outside it and so permit the door 

 to open if then or later sufficient pressure were exerted. Eight 

 cats (Nos. I, 2, 3, 4, 5, 6, 7 and 13) were, one at a time, left 

 in this thumb-latch box. All exhibited the customary instinc- 

 tive clawings and squeezings and bitings. Out of the eight all 

 succeeded in the course of their vigorous struggles in pressing 

 down the thumb-piece, so that if the door had been free to swing 

 open they could have escaped. Six succeeded in pushing both 

 thumb-piece down and door out, so that the bar did not fall back 

 into its place. Of these five succeeded in also later pushing 

 the door open, so that they escaped and got the fish outside. 

 Of these, three, after repeated trials, associated the complicated 

 movements required with the sight of the interior of the box so 

 firmly that they attacked the thumb-latch the moment they were 

 put in. The history of the formation of the association in the 

 case of 3 and of 4 is shown in the curves on page 21. In 

 the case of 13 the exact times were not taken. The combination 

 of accidents required was enough to make it take No. i and No. 

 6 a long time to get out. Consequently, weariness and failure 

 inhibited their impulses to claw, climb, etc., more than the rare 

 pleasure from getting out strengthened them, and they failed to 

 form the association. Like the cats who utterly failed to get 

 out, they finally ceased to try when put in. The history of 

 their efforts is as follows : The figures in the columns represent 



