Saturday, May 16, 2009
A question about twin studies
A relatively obvious objection to twin and adoption studies -- I feel like I've seen this mentioned from time to time but don't remember where -- is that adoptive families don't really have much socio-economic variation, esp. in terms of education, settledness, marital status etc.; in samples without a lot of environmental variation, the remaining differences are genetic because that's all they could be; therefore, twin and adoption studies don't prove any general claims about heritability. This argument strikes me as correct if you grant the premise, so either citing adoption studies is disingenuous or the premise is false. So my question is whether anyone (Dice? Grob? James?) knows of studies testing the premise that adoptive families are all alike.