学業成績における遺伝の影響

双生児法による

抄録

1) This study is aimed at research into the problem of whether heredity has an effect on school marks or not, and if it has, on which subjects it has the most powerful influence or the least one.
2) Method i) Subjects were as shown in Table 1. ii) The method of measurement on inheritance: 4 indexes; D₁, D₂, D², r in Table 2. iii) The criteria of interpretation of inheritance: a) The smaller the average intra-pair differences (D₁, D₂, D²) for the MZ in a school subject are, the more powerful the inheritance is, but in the case of (r), it is converse. b) The larger the differences between the DZ and the MZ are, the more powerful the inheritance is. This is the same in the case of the ratio H (Heredity)/E (Environment). iv) The zygocity diagnosis of twins: 18 kinds of morphological similarity diagnosis were used.
3) Results and discussion i) The differences between any two groups of 4 twin groups (MZ, DZ, OZ, SB) were generally significant as in Table 3. ii) In Table 2, the rankings of arithmetic were distinctly higher than the other subjects with regard to D₁, D₂, D², r for the MZ, but in Table 4, the rankings of arithmetic were lower conversely on primary school level. The rankings of arithmetic in these two tables were not similar to each other, and the differences between all subjects in Table 2 were not significant. Ida Frischeisen-Köhler and T. Iwashita argued that arithmetic marks were most influenced by the environment, because of the agreement of the results which were gained upon two criteria of the interpretation of inheritance in their studies. These results were not fully applicable to their results, but only in the criteria (a), which were almost similar. iii) In Table 5, the rankings of mathematics were generally higher than the other subjects for the MZ on junior high school level. The tendency of these rankings were identical with these in Table 6. These results were applicable to the results of the two authors above. But, the differences between all subjects were not significant, still the differences (D₁) were nearly significant as in Table 5.
4) Conclusion i) Without doubt, school marks were influenced by heredity on primary and junior high school level, ii) There was a faint indication of the more powerful effect of environment in arithmetic above all the other school subjects on the primary school level, but we could not conclude anything from this finding. iii) On the junior high school level, the mathematics marks seemed to be more influenced by environment than in primary school but it could not be concluded statistically. iv) These results were comparatively similar to the results of Ida Frischeisen-Köhler and T. Iwashita, but quite different to those of Torsten Husén.