The correlation between g loadings and heritability in Japan: A meta-analysis

We focused on the question of the extent to which there is a link between the g factor and heritability coefficients in the Japanese population. Current findings of modest to strong correlations between heritability and the g factor are based only on five studies, all from Western countries. We carried out a meta-analysis of Japanese studies reporting heritabilities of all subtests of IQ batteries to examine whether they would give the same outcomes as Western studies. g loadings of subtests were taken from various sources. Correlations between heritabilities and g loadings were computed for all data points. The meta-analysis was based on four studies yielding six data points and showed a meta-analytical correlation of .38 (total N = 1808). We conclude that there is a clear link between the g factor and heritability coefficients in Japan, but that it contrasts with the quite strong correlations found in Western studies. Moderator analyses suggest that the shorter number of subtests and the smaller samples of twins used in Japanese studies partially explain the lower mean Japanese correlation. We discuss limitations of our study.