Richard J. Viken1, Richard J. Rose1, Jaakko Kaprio2,3, & Markku Koskenvuo4
We investigated genetic contributions to individual differences in the Wiggins (1966, Psychological Monographs, 80, 22 Whole No. 630) content scale for femininity-masculinity (FEM) derived from the MMPI. Subjects were 2,646 adolescent Finnish twin pairs from the FinnTwin16 study. Descriptive data confirmed the very large difference in mean scores for males and females that would be expected for this variable. A structural equation model including additive genetic effects and unshared environmental effects provided the best fit to twin covariances for both males and females, with no evidence of significant shared environmental or sibling-interaction effects. Heritability estimates were .53 for males and .6 for females. The modeling indicated that genetic effects on FEM scores in males and females were almost entirely independent, as reflected in a correlation of .02 for FEM scores among opposite-sex twins. The results suggest that, in the context of large sex differences in mean FEM score genetic factors make the strongest contribution to the individual differences observed within each sex, but that the genetic factors influencing males and females are almost entirely sex-limited.
Address: Department of Psychology, Indiana University, Bloomington, IN, 47405, Phone: (812) 855-1697, Fax: (812) 855-4691, viken@indiana.edu
1Department of Psychology, Indiana University, Bloomington, IN 47405 2Department of Public Health, University of Helsinki, Finland, FIN00014 3Department of Public Health, University of Turku, Finland, FIN20520 4Department of Mental Health and Alcohol Research, National Public Health Institute, Helsinki, Finland, FIN00300 5Supported by NIAAA grants AA-08315, AA-07611, AA-00145