242 Animal Intelligence 



depends upon some particular difference in the animal. Each 

 immunity, for example, has its detailed representation in an 

 altered condition of the blood or other bodily tissue. In 

 general the changes in an animal which cause changes in its 

 behavior to the same situation are fully enumerated in a 

 list of the bodily changes concerned. That is, whatever 

 changes may be supposed to have taken place in the animal's 

 vital force, spiritual essence, or other magical bases for life 

 and thought, are useless for scientific explanation and con- 

 trol of behavior. 



No competent thinker probably doubts this in the case of 

 such changes as are referred to by hunger, sleep, fatigue, so- 

 called ' functional ' diseases and immunity, and those who do 

 doubt it in the case of mental growth and learning seem to 

 represent an incomplete evolution from supernatural, or 

 rather infrascientific, thinking. There may be in behavior 

 a surplus beyond what would be predictable if the entire 

 history of every atom in the body was known a surplus 

 necessarily attributable to changes in the animal's incor- 

 poreal structure. But scientific thinkers properly refuse 

 to deliberately count upon such a surplus. 



Every response or change in response of an animal is then 

 the result of the interaction of its original knowable nature and 

 the environment. This may seem too self-evident a corollary 

 for mention. It should be so, but, unfortunately, it is not. 

 Two popular psychological doctrines exist in defiance of it. 

 One is the doctrine that the movements of early infancy are 

 random, the original nature of the animal being entirely 

 indifferent as to what movement shall be made upon a given 

 stimulus. But no animal can have an original nature that 

 does not absolutely prescribe just what the response shall 

 be to every stimulus. If the movements are really random, 

 they occur by virtue of some force that works at random. 



