I have read that IQ is highly heritable.
How could this be tested?
For honest testing, it seems to me that only children who were abandoned should have been tested, to exclude education effect. Was it really done?
Intelligence is one of the traits, that can be inherited both by genes and by education. You can't educate your children to have blue eyes, but you can educate them to count or to read.
So, to study heritability of intelligence, educational inheritance should be excluded.
I know that usual way to study heritability is to compare variability for monozygotic and dizigotic twins. Being sufficient for other traits, this method is highly insufficient for intelligence (which is obvious). Having identical perception system, monozygotic twins will respond identically to an education, so they will be more closely educated, even if IQ is completely independent of genes.
So, to study IQ heritability, subjects should be studied under different education conditions. I.e. they should be abandoned by parents and/or adopted separately.
My question is: was this done or not?
If not, then the question is, how education effects were eliminated?
Also I would like to know, if my reasoning about why just studying twins is insufficient is wrong.