2 68 THE POPULAR SCIENCE MONTHLY 



their instinctive reactions to the same stimuli may often vary consider- 

 ably. It is in this degree that sex enters as a modifying factor into all 

 forms of association. Just as biological variation constantly alters the 

 physical aspects of heredity, so it also constantly alters the inborn 

 psycho-physical dispositions of individuals. The concept of instinct, 

 therefore, leaves as large a place as any sociologist could desire for the 

 influence of selection, of race, of sex and of inborn individual differences 

 in the social life. 



While there can be no question but that instinctive reactions, from 

 the psychological point of view, are the basis of the relationships of 

 individuals in society, nevertheless, it is very difficult to say just what 

 proportion of human activities may be regarded as primarily in- 

 stinctive. It is especially difficult to trace the instinctive element in 

 human institutions as they exist in modern civilized society. It is cer- 

 tainly incorrect to explain anything important in the social life of civil- 

 ized peoples simply through instinct, on account of the fact that in- 

 stinctive reactions under such conditions are overlaid with a mass of 

 habits which we term custom and tradition, and are constantly modified 

 or inhibited by many other social factors. On the other hand, it is an 

 equally serious error to ignore the instinctive element, even in the com- 

 plex conditions of modern life. Even though we can not determine 

 quantitatively the relations between the instinctive and acquired ele- 

 ments in any given social situation, it is important to note that they 

 both exist and that the instinctive is the basis of the acquired. Some 

 tests of the instinctive element in human society can, however, be 

 devised by psychologists and sociologists. In general we may safely 

 regard those activities as instinctive which characterize the species, 

 that is, which are relatively common to all men in all stages of culture. 

 Again, those activities which man shares with the animals below him 

 may, for the most part, be regarded as instinctive. Finally, from the 

 study of the child and the adolescent, the sociologist may also perceive 

 with more or less clearness some of the instinctive elements in human 

 conduct and character. 



Another difficulty which confronts the sociologist in tracing con- 

 cretely the instinctive element in any given social situation is the great 

 complexity of human instincts themselves. It is, of course, a grave 

 psychological error to suppose that there are a number of separate and 

 distinct human instincts "vyhich exist side by side without running into 

 each other and which have each a separate function to perform. Eather 

 human instincts, corresponding to the conception of them just given as 

 inborn pathways in the nervous system, continually run into each other 

 and reenforce each other like a network of streams or electric currents. 

 The consequence is that human institutions are generally expressions 

 of a number of instincts combined in various ways, besides being, of 

 course, often built up largely on the basis of acquired traits. It is 



