166 BEGINNINGS OF INTELLIGENCE 
We have in this modification of instincts through the 
pleasurable or painful effects they produce the beginning of 
intelligence. The pecking, swallowing, and avoidance of 
certain objects are purely instinctive acts based on the 
chick’s inherited organization. After its first experiences 
with pleasant or nasty caterpillars the chick is a different 
creature; it has learned by experience; and henceforth its 
acts, which at first were in a general way adaptive, become 
more perfectly adapted to its needs as the result of its learn- 
ing. Instinct supplied the impetus to action and ina measure 
determined the direction of action, but intelligence refines 
upon the instinctive behavior and effects a closer adjustment 
to the environment. 
In lower forms associations are formed as a rule with great 
slowness. Behavior is almost entirely instinctive, and the 
organism can be made to deviate from its stereotyped 
methods of action only with difficulty. It is probable that 
in low forms where associations of only the simplest kind can 
be established there is no association of ideas involved; 
and in fact there is no conclusive evidence of the existence 
of ideas even in animals quite high in the scale. Most animal 
learning consists in forming associations between certain 
sense experiences and certain actions which bring pleasure 
or pain. A common way of teaching an animal a trick is to 
try in various ways to induce it to perform the desired 
action and then to reward it by food or some other means 
of giving it pleasure. In this way the connection between 
the situation and the act is reinforced, and the act follows 
more readily when the animal is placed a second time under 
the same conditions. 
Consider the case of a cat placed in a box which can be 
opened by pressing down a lever or pulling a string, as in the 
experiments of Thorndike. If the cat is hungry and food 
