178 Animal Intelligence 



The door was held by a bar about 3 by i by 5 inches which 

 swung on a nail at the left side. 



Box CCC (double bar) was CC with a second similar 

 bar on the right side of the door. 



Box NN (hook) was a box about the size of BB with its 

 door held by an ordinary hook on the left side which hooked 

 through an eyelet screwed into the door. 



Box NNN was NN with the hook on the right instead 

 of the left side. 



Box NNNN was box NN with two hooks, one on each 

 side. 



Apparatus 00 (string box) consisted of a square box tied 

 to a string, which formed a loop running over a pulley by 

 the cage and a pulley outside, so that pulling on the under 

 string would bring the box to the cage. In each experiment 

 the box was first pulled back to a distance of 2 feet 3 inches 

 from the cage, and a piece of banana put in it. The mon- 

 key could, of course, secure the banana by pulling the box 

 near enough. 



Apparatus OOO was the same as OO, with the box tied 

 to the upper string, so that the upper string had to be pulled 

 instead of the lower. 



Box PP was about the size of BB. Its door was held by 

 a large string securely fastened at the right, passing across 

 the front of the door and ending in a loop which was put 

 over a nail on the box at the left of the door. By pulling 

 the string off the nail the door could be opened. 



Box RR (wood plug) was a box about the size of BB. 

 The door was held by a string at its top, which passed up 

 over the front and top to the rear, where it was fastened 

 to a wooden plug which was inserted in a hole in the top of 

 the box. When the plug was pulled out of the hole, the 

 door would fall open. 



