> In addition there are ways to estimate how much can be predicted from genetic information, a term called heritability. Heritability can be estimated from so c

> In addition there are ways to estimate how much can be predicted from genetic information, a term called heritability. Heritability can be estimated from so called twin studies. Where twins who are genetically identical (monozygotic) are compared to twins who are not genetically identical (dizygotic). In this way you can measure the environmental effect (the variation seen in the monozygotic twins) and the genetic effect (the variation that is seen in the dizygotic twins compared to the monozygotic twins). This is, of course, a gross oversimplification, but can provide reasonable measures of an upper bound of what can be explained genetically For most traits this upper bound is around 0.5 R^2, and I believe for educational attainment a bit higher, but I could not find it in the paper or a quick google search. Just wondering, have you ever encountered any of the serious critiques of twin studies. The comparison of dizygotic (DZ) and monozygotic (MZ) twins relies on the Equal Environment Assumption (EEA) - which assumes that the environment experienced by MZ twins is the same as that of DZ twins. This assumption has been shown empirically to be false - parents, siblings, teachers, friends, and the twins themselves treat MZ twins very differently than they treat DZ twins. There are good reasons to think that heritability results derived from twin studies are highly inflated.