Twins reared apart show authoritarianism is almost entirely heritable

Evidence

However, this conclusion was completely contradicted by a subsequent study, conducted by Thomas Bouchard with his samples of twins reared apart (Lykken, personal communication, March 14, 1994). These data (sensibly not broken down by gender since the samples were so small) produced a correlation of . between the RWA scores of 44 pairs of identical twins reared apart, and a nonsignificant —. among 22 pairs of fraternal twins reared apart. Comparing these two coefficients, I would say that genes rule. (And then some: h? = 160%, which is an upper limit with a vengeance!.) — Bob Altemeyer, The Authoritarian Specter, 955

My conclusion at this point is that the twin data confuse me. The problem is not the monozygotic twins. They rack up correlations in the .60s quite regularly, whether they grew up together or not. But the dizygotic twins blur the picture enormously, for their correlations wander all over the place. — Bob Altemeyer, The Authoritarian Specter, 965

Categorization

• XREF: Correlates with earlier personality-heritability twin literature; the absurdly high heritability estimate (~160%) is a statistical impossibility worth flagging. — connects to: Rigid distant fathers and self-sacrificing mothers raise children prone to authoritarian personality — Leonard S. Newman and Ralph Erber (eds.), Understanding Genocide: The Social…, 443
• QUESTION: The impossibility of >100% heritability suggests serious methodological artifact or small-sample inflation in the twins-reared-apart study.
• DEEPTHINKING: The stable MZ correlations paired with wildly unstable DZ correlations is a genuinely puzzling pattern that resists simple genetic or environmental explanation — a substantive scientific anomaly.
• corroborated: 2 independent passages support this claim — Bob Altemeyer, The Authoritarian Specter, 955; Bob Altemeyer, The Authoritarian Specter, 965