Inheritance of temperament

Abstract

Temperament, which determines mood, is generally recognized as having an hereditary basis. It is obvious, however, that the method of inheritance is not a simple one, but what factors are involved have not hitherto been plain. An examination of 150 matings of two persons the mood of both of whom is known as well as that of their children and that of the children's four grandparents has afforded the means to test various hypotheses of which the following seems to satisfy the conditions very closely. There are two hereditary factors involved in temperament, one of which makes for excitation, the absence of this for self-control. The other factor is one that makes for cheerfulness as opposed to depression; the depression being the more easily possible because of the absence of this factor for cheerfulness or normality. The exciting and the normalizing factors and their absence may be combined in the matings in over 50 ways, but for a given mating the disposition of the offspring follows a definite law and the dispositions occur in certain proportions in a fraternity of brothers and sisters. Dominance in the simplex condition is frequently or usually imperfect so that a clear difference between the disposition of children who receive two doses and only one dose of a factor can be recognized. The exciting factor may occur in the child simultaneously with the factor for normality, in which case the person is constantly or periodically elated and when depressed he is not depressed below the normal. The absence of normality, or depression, may occur without elation, in which case the person is constantly or periodically depressed and when not depressed does not rise above the normal.