That results indicates that if you take children and go from "abused or neglected as infants, then shunted from one foster home or institution to the next" to a

That results indicates that if you take children and go from "abused or neglected as infants, then shunted from one foster home or institution to the next" to a stable adopted family home, you can increase IQ scores. Which is pretty obvious. There is always an amount of abuse that will destroy someone's IQ. Bringing them back to a decent middle-class upbringing will restore them to their baseline. But once that baseline is achieved, evidence is that it can't generally be improved. One can learn skills and knowledge but IQ is stable. Above lower-middle class American abuse-free households, increases in SES don't affect IQ. E.g. People have inherent talent at sprinting. Malnutrition or abuse can destroy this talent. But once people have decent upbringing, and try hard, and have support, what determines the champion is genetics. Which is why pretty much all champion sprinters have west African ancestry (since they have inherited traits that make them good sprinters). EDIT: Here's a source for you on IQ heritability: American Psychological Association’s Task Force on Intelligence report. http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.134.1282&rep=rep1&type=pdf http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.134... “If one simply combines all available correlations in a single analysis, the heritability (h2) works out to about .50 and the between-family variance (c2) to about .25.” And “By late adolescence h2 is around .75 and c2 is quite low (zero in some studies).” (p. 85).