556 THE POPULAR SCIENCE MONTHLY 



binations and series of combinations of reflex reactions in the presence 

 of a series of complex stimulations appeared and these in turn were 

 rendered more complex by the development of habits based on indi- 

 vidual experiences repeated anew by every generation. Each useful 

 instinct and every valuable habit made the individual organism more 

 efficient, lessened the effort necessary to live, increased surplus energy. 



As man was approached, however, the factor of habit became more 

 and more important. Some hint of how this occurred may be gained 

 from every-day observation. It is a commonplace that exercise of mus- 

 cles that are fitted to perform certain functions renders the habitual 

 exercise of that function as certain in its operation as is a pure reflex. 

 Young birds awkward in their first flight become expert rapidly. Beasts 

 of prey by trial and error eliminate unsuccessful modes of attack. 

 Before our eyes instinctive actions become modified by experience to a 

 very appreciable extent. Tricks are even taught to seals, lions and ele- 

 phants, and finally habits useful to man are learned by horse and dog. 

 Thus man has appropriated to his own use the surplus energy developed 

 in the higher animals and has profited thereby immensely. 



But the stage of advance now under discussion is that of man's 

 immediate precursors when they, too, had merely learned to profit by 

 past experience through the method of trial and error and elimination 

 of unsuccessful activities. 



At this point doubtless the objection will be made that other functions 

 affecting surplus had by this time appeared in man's precursors. It 

 will be held that imitation, at least, was present far down the scale. 

 Certainly it must be granted that any tendency of an organism A to 

 imitate a useful innovation of a similar organism B would, in most 

 instances, increase the surplus possessed by organism A. A flock of 

 birds may take flight if a single bird flies away in alarm. This may be 

 an advantage to every member of the flock. It is necessary, however, 

 to distinguish sharply at least two kinds of imitation. Instinctive imi- 

 tation, of which the case of the birds which fly when one of the flock 

 takes wing may be taken as an instance, occurs when the sight or sound 

 of one animal's performing a certain act operates as a direct stimulus 

 to the performance of a similar act by another animal whose organiza- 

 tion is such as naturally to lead to that act by reflex response whenever 

 the appropriate stimulus is given. The model-act releases the trigger, 

 the organism does the rest by reflex action in accordance with in- 

 herited functions. The second type of imitation occurs only when the 

 model-act suggests to the observer the feeling of pleasure or the idea of 

 utility that would result if he repeated the act for himself. The process 

 involved in the first type appears to be no different from those which 

 occur when an animal responds to any stimulus whatsoever. The func- 

 tion is reflex in accordance with the inherited structural organization 



