David C. Rowe

Physical attractiveness and the personality resemblance of identical twins

The physical attractiveness of 25 pairs of monozygotic (MZ) twins was rated independently for twins A and B. The MZ twins were rated alike in their physical attractiveness (r=0.54; corrected for attenuation,r=0.94). Physical attractiveness was uncorrelated with verbal intelligence but was associated, controlling statistically for the sex difference in attractiveness favoring females, with three of the eight traits in the Comrey inventory: Conformity, Extraversion, and Emotional Stability. In both sexes, greater emotional stability was associated with attractiveness; in males greater extraversion; and in females, greater conformity. When these twin correlations were adjusted for this association with attractiveness, the mean change in the value ofr was only 0.03, indicating that physical attractiveness does not appear to bias conclusions from twin studies.

IQ similarity in twins, siblings, half-siblings, cousins, and random pairs

Abstract A classic child-development IQ dataset collected by Fels Research Institute contains data on a number of different kinship categories. The present study analyzed IQ scores from five kinship categories of 7–12-year-old children into genetic and environmental components. The common environmental effects were larger for older children than younger children. Overall, the Genetic and Common Environment Sources each accounted for approximately 40% of the IQ variability in these data, leaving 20% of the variability for nonshared environmental effects and for measurement error.