Kremen et al. study is the only one to date that has documented
the SES by heritability interaction in adults. In
contrast, a study of the cognitive ability test given at the
time of military induction to a Vietnam Era Twin Registry
sample that was part of a larger sample of 3,203 pairs
(which included the pairs included in Kremen et al., 2005)
showed no interaction with parental education (Grant et al.,
2010).