168 BEGINNINGS OF INTELLIGENCE 
agency which preserves or repeats certain activities and re- 
jects others on the basis of their results. 
The importance of random movements lies in the fact that 
they offer opportunities for making favorable adjustments. 
For the development of intelligence they play a réle similar 
to that of variations in the process of evolution. The 
animal that does the most exploration is the one most likely to 
hit upon new advantageous adjustments. In the same way 
intelligent adjustments, as James has contended, are favored 
by a multiplicity of instincts, especially if these instincts are 
of a contrary or conflicting nature, for now one and now 
another instinctive tendency may be reinforced in different 
conditions to which it may be adapted. Instinctive fear 
may be modified through experience so that it is no longer 
attached to objects that arefound to be harmless, while it may 
be intensified in relation to other objects that are found 
to be sources of injury. Where there is hesitation between 
the exercise of two instincts such as the tendency to pursue 
an animal as prey, and the instinctive fear which that animal 
may awaken, experience may quickly point out which 
proclivity is the more advantageous to follow. The pleasure- 
pain reaction enables an animal to select, so to speak out of 
its stock of instinctive endowments those responses which 
are best adapted to the particular situations that confront 
it. It is a means of adapting instincts to new or inconstant 
conditions and thus of effecting a closer adaptation to the 
environment than that which would be possible by following 
purely congenital modes of response. The development of ¥ 
the pleasure-pain reaction marks one of the most important 
steps in the evolution of behavior, for the entire super- 
structure of intelligence in all its stages is based upon it,” 
and it is not surprising that many writers regard it a8 an 
index of the beginning of consciousness, a point where a new 
