At the Foundation, we have had an enduring interest in genetic contributions to individual differences in aptitudes. In the 1990s, we conducted a twin study of scores on several of our tests. In 2013, David Schroeder initiated an expanded study of the correlations between scores for twins. The accompanying figure shows the correlations for pairs of identical (monozygotic, MZ) and fraternal (dizygotic, DZ) twins for five Foundation tests. As can be seen, the correlations for the monozygotic twins tend to be higher than the correlations for the dizygotic twins, which indicates substantial genetic effects on these aptitudes. In 2014 Schroeder presented findings from this study at the annual meeting of the Behavior Genetics Association.
We are continuing to add scores for twins to our data set for this study.