The Evolution of the Human Intellect 283 
to get food. All these animals manifest fundamentally the 
same sort of intellectual life. Their learning is after the 
same general type. What that type is can be seen best from 
a concrete instance. A monkey was kept in a large cage. 
Into the cage was put a box, the door of which was held 
closed by a wire fastened to a nail which was inserted in a 
hole in the top of the box. If the nail was pulled up out of 
the hole, the door could be pulled open. In this box was a 
piece of banana. The monkey, attracted by the new object, 
came down from the top of the cage and fussed over the box. 
He pulled at the wire, at the door, and at the bars in the 
front of the box. He pushed the box about and tipped it up 
and down. He played with the nail and finally pulled it out. 
When he happened to pull the door again, of course it opened. 
He reached in and got the food inside. It had taken him 
36 minutes to get in. Another piece of food being put in 
and the door closed, the occurrences of the first trial were 
repeated, but there was less of the profitless pulling and tip- 
ping. He got in this time in 2 minutes and 20 seconds. 
With repeated trials the animal finally came to drop en- 
tirely the profitless acts and to take the nail out and open 
the door as soon as the box was put in his cage. He had, 
we should say, learned to get in. 
The process involved in the learning was evidently a 
process of selection. The animal is confronted by a state 
of affairs or, as we may call it, a ‘situation.’ He reacts in 
the way that he is moved by his innate nature or previous 
training to do, by a number of acts. These acts include 
the particular act that is appropriate and he succeeds. In 
later trials the impulse to this one act is more and more 
stamped in, this one act is more and more associated with 
that situation, is selected from amongst the others by reason 
of the pleasure it brings the animal. The profitless acts 
