There are mixed reports about SES by heritability
interactions for adults. Kremen, Jacobson, and Xian (2005)
identified a significant interaction between parental education
and word recognition scores on the Wide Range
Achievement Test among 690 adult twins in the Vietnam
Era Twin Registry. Descriptive analyses showed that for
the twins with the least educated parents, additive genetics
and shared environment each accounted for 36% of the
variability in reading scores. For the twins with the best
educated parents, additive genetics accounted for 56% of
the variability and shared environment for 12%. The effect
appeared to depend solely on decreases in shared environmental
variation as a function of parental education. The