INHERITANCE OP TEMPERAMENT. 9 1 



of cases is unfortunately small, still the results are clear-cut enough to 

 justify drawing conclusions as to the danger or innocuousness to 

 offspring of given matings. 



Though the hypothesis that we have applied seems to fit the facts 

 satisfactorily, it is desirable to consider other possible hypotheses. 



First, we may consider the hypothesis that there are no inheritable 

 factors in temperament, but that family resemblances are due to 

 imitation or suggestion. The principal fact that seems to nullify this 

 hypothesis is the great dissimilarity of the children of one fraternity 

 under certain conditions; e. g., of class 21 or class 24. Again, if this 

 hypothesis were true, we should expect some of the children of a 

 melancholic parent mated to a non-hypokinetic to show melancholia 

 themselves ; actually, the influence of the suggestion of the melanchoUc 

 parent is not sufficient to overcome the opposing hereditary tendencies. 



Second, there is the hypothesis that temperament, like "criminality" 

 or "insanity" (in its broadest sense), is too complex a thing to be 

 explained by any possible laws of heredity — is an end-result due to 

 numerous dissimilar causes — a mixture of heredity and environmental 

 factors. This may be called the popular view; it is a view that I was 

 prepared to accept if no simple heredity hypothesis would fit the facts. 

 Even yet I find it difficult to get rid of the prejudice that example, 

 teaching, experience, and state of health may do much to modify one's 

 behavior. Behavior is, indeed, reaction to stimuli; conditions modify 

 reactibiUty, irritabiHty; the nature of the stimulus determines (within 

 limits) the reaction. An habitually constipated person is, we are told, 

 apt to be a gloomy person ; also one person may work oflf by hard labor 

 or walking a hyperkinetic tendency that in a more sedentary person 

 shows itself in violent behavior. Also, the social pressure for self- 

 control is much stronger for persons of a certain social status than for 

 others. 



Certarti facts must, however, be regarded in appraising these con- 

 siderations : 



First, immediate "causes" of depression or excitation, such as con- 

 stipation or suprarenal hypersecretion, probably depend in part upon 

 an hereditary factor. 



Second, a life of muscular activity as opposed to one of sedentariness 

 is also determined in part by an hereditary factor. It is not merely the 

 necessity of earning a living that keeps the clerk chained to his desk; 

 he earns in a month as much as a tramp does in a year; but he has no 

 desire to wander the other 1 1 months, if the hereditary nomadic ten- 

 dency is absent. And, again, while the importance of social pressure 

 is not to be neglected, experience indicates that it does not keep from 

 depression, melanchoha, or suicide, nor repress the jovial, garrulous 

 disposition. As Galton (1889, p. 237) says : " Persons highly respected 

 for social and public qualities may be well known to their relatives as 



