33 Heredity and Environment 



plexity and plasticity allow adaptations to the minutest alterations 

 of environment. 



3. Birth and Growth of Freedom. In animals below man and 

 in the stages of human development one may trace the birth and 

 growth of freedom. Even in some of the simplest organisms 

 one can observe inhibitions of responses and modifications of 

 behavior which seem to be due to conflicting stimuli or to changes 

 in the physiological state. In higher organisms such inhibitions 

 or modifications proceed particularly from internal stimuli, which 

 in turn are probably conditioned by hereditary constitution and 

 past experience. The factors which determine behavior are not 

 merely the present stimulus and the hereditary constitution, but 

 also the experiences through which the organism has passed and 

 the habits which it has formed. 



A moth cannot avoid the impulse to fly toward the light, and it 

 does not learn by experience to avoid the flame. Its reactions are 

 relatively fixed and machine-like. Many other animals learn by 

 experience to inhibit responses to certain stimuli; a tame fish or 

 frog will take food from your hand, but if it is repeatedly 

 frightened when it attempts to take food it will not come near 

 you though it is starving, it inhibits the strong impulse of a hun- 

 gry animal to take food by the counter impulse of unpleasant 

 memories or of fear. Here we have the beginnings of what we 

 call freedom, the immediate response to a stimulus is suppressed, 

 internal stimuli are balanced against external ones and final action 

 is determined largely by past experience. Owing to his vastly 

 greater power of memory, reflection and inhibition man is much 

 freer than any other animal. Animals which learn little from 

 experience have little freedom and the more they learn the freer 

 they become. 



In both ontogeny and phylogeny there has been development 

 of freedom. The reactions of germ cells and of the lowest 

 organisms are relatively fixed. In more complex organisms re- 

 actions become modifiable through conflicting stimuli, intelligence, 

 inhibitions. Freedom is the more or less limited capacity of the 



