50 Heredity and Environment 



cation of past experience to new conditions, or reason, is added in 

 later years. 



5. Will. Another characteristic, which many persons regard 

 as the supreme psychical faculty, is the will. This faculty also 

 undergoes development and from relatively simple beginnings. 

 The will of the child has developed out of something which is far 

 less perfect in the infant and embryo than in the child. Obser- 

 vations and experiments on lower animals and on human beings, 

 as well as introspective study of our own activities, appear to 

 justify the following conclusions: 



(i.) No Activity Without Stimuli. Every activity of an organ- 

 ism is a response to one or more stimuli, external or internal in 

 origin. These stimuli are in the main, if not entirely, energy 

 changes outside or inside the organism. In lower organisms as 

 well as in the germ cells and embryos of higher animals the pos- 

 sible number of responses are few and prescribed owing to their 

 relative simplicity, and the response follows the stimulus direct- 

 ly. In more complex organisms the number of possible responses 

 to a stimulus is greatly increased, and the visible response may be 

 the end of a long series of internal changes which are started by 

 the original stimulus. 



(2.) Inhibitions. The response to a stimulus may be modified 

 or inhibited in the following ways: 



(a) Conflicting Stimuli. Through conflicting stimuli and 

 changed physiological states, due to fatigue, hunger, etc. Many 

 stimuli may reach the organism at the same time and if they con- 

 flict they may nullify one another or the organism may respond 

 to the strongest stimulus and disregard the weaker ones. When 

 an organism has begun to respond to one stimulus it is not easily 

 diverted to another. Jennings found that the attached infusor- 

 ian, Stentor, which usually responds to strong stimuli by closing 

 up, may, when repeatedly stimulated, loosen its attachment and 

 swim away, thus responding in a wholly new manner when its 

 physiological state has been changed by repeated stimuli and re- 



