240 THE INTELLIGENCE OF MAMMALS 
ever she made her escape, the cat came to enter the box of 
her own accord. Does she associate the idea of being in 
with the idea of eating fish and enter accordingly? Thorn- 
dike endeavored to answer this question by dropping cats 
into the box through a door in the top, and then feeding 
them as before when they got out. The cats had the same 
opportunity of associating the idea of being in the box with 
the idea of eating fish, but the element lacking was the 
impulse to walk in through the door. All of these cats, 
three in number, failed to enter the box after fifty, sixty 
and seventy-five trials respectively. “Either a cat cannot 
connect ideas, representations, at all,” says Thorndike, 
“or she has not the power of progressing from the thought of 
being in to the act of going in. . . . The impulse is the sine 
qua non of the association. The second cat has everything 
else, but cannot supply that.” 
In several other experiments cats and dogs were placed 
in a box, and the experimenter would take the paw of the 
animal and make the movement necessary to open the box, 
after which the animal would be allowed to go out and get 
food. This was repeated ten or fifteen times and then the 
‘animal was left to its own devices. After numerous ex- 
periments of this sort with various kinds of boxes it was 
found that the animals uniformly failed to profit by this 
mode of instruction. None of the animals which failed to 
get out of a box of their own accord succeeded in escaping 
after having been several times put through the necessary 
movements. They had the opportunity to associate the 
idea of certain movements with escaping and getting food, 
at least provided they paid attention to what was being 
done with them. But the animal’s own impulse to do the 
act was lacking. “The animal cannot form an association 
leading to an act unless the particular impulse to that act 
