双生兒を用いた性格に關する研究

抄録

This paper is the report in which the author tried to show his interest in the problem of the influence of heredity and environment upon personality, and in the common factors found in the correlation between the personality traits and some other psyco-physical characteristics in twins.
The subjects are 50 pairs of twins (including 25 pairs of identical twins, 18 pairs of fraternal twins, 7 pairs of unlikesex twins) and 14 pairs of the control group of unrelated individuals. The latter are made up of pairs of children of likesex and of the same birth dates selected from the same classes in which the twins were enrolled. (Age : from 6 to 12)
The experiments were conducted during the period from May, 1952 to Octover, 1952.
The personality traits were appraised by using Uchida's Kraepelin Numeral Addition Test, Nagashima's Adjustment Inventory and the author's Moral Judgement Test. In the first place the author examined the problem of the influence of heredity and environment by the method of Verschuer's mean percentile deviation, then calculating the ratio of the hereditary and environmental influences by F. Lenz's formula, (u₂/u₁)²-1=1. In the second place the author adoped the method of analysis of variance by which one may obtain the intraclass correlation coefficient (r′).
The outline of the result is as follows :
(1) In the ratio of the heredity and environment obtained by Lenz's formula, the results of Kraepelin Numeral Addition Test, the Adjustment Inventory the Moral Judgent Test are 1.38:1, 1.34:1, 1.45:1 respectively. The intraclass correlation coefficient obtained through the analysis of variance are as follow : The r's based on the result of Kraepelin Test are .68** in ident. twins, .43 in frat. twins, the r's based on the Adjustment Inventory being .48* in ident. twins, .23 in frat. twins, and the r's of the Moral Judgement Test are .63** in ident. twins, .36 in frat. twins, (** 1 percent level * 5 percent level), but these r's are relatively low as compared with the r's of other mental and physical characteristics obtained in twins.
(2) The intraclass correlation coefficients which are culculated from concurrence personality traits and intelligence or physical maturity are as follows :
The r′ of C. Q. between personality traits and intelligence are .56*-.82** in ident. twins, .20-.62** in frat. twins. The r′ of C. Q. between personality traits and physical maturity are .86**-.88** in ident. twins, .61**-.70* in frat. twins. These results show that the r's of the C. Q. are higher than the r′ of personality traits, and that the above-mentioned C. Q. of the individuals are influenced by heredity, and more remarkably influenced especially when C. Q. is between the personality traits and physical maturity.
(3) From the above-mentioned study, it is evidently concluded that the correlations between the personality traits and the intelligence or physical maturity degree are influenced by the hereditary factors which are common in mental and physical development, to which the author refers as“general maturity degree”.