[aforrester]

How do twin studies rule out "environmental" that is, non-genetic, causes. Twins look alike, so if there are ideas about how people who look alike ought to act alike we would be expect a correlation between genes and behaviour that has nothing to do with the content of the genes. Rather, that behaviour would be motivated by similar ideas.

[ceejayoz]

> How do twin studies rule out "environmental" that is, non-genetic, causes.

http://en.wikipedia.org/wiki/Twin_study

[aforrester]

I have pointed out that there can be correlations between genes and behaviour that are not caused by genes but by culture. Your link is irrelevant.