Twin studies attribute about seventy percent of intelligence variance to genetics

Evidence

In addition, they have located from around the world over fifty pairs of identical twins reared apart. While the members of these monozygotic twins raised apart (MZ-apart twins) would probably not have been raised in starkly different environments, the researchers determined that most of them had been separated soon after birth. None of them had contact during their formative years, and most of them had no contact for most of their lives. … By comparing these MZ-apart twins with monozygotic twins who had grown up together, Bouchard and his colleagues (1990) calculated that about 70% of the variance in intelligence was inherited. — Bob Altemeyer, The Authoritarian Specter, 886

Categorization

• XREF: connects to: Mixed-race IQ patterns refute claims of inherited racial intelligence differences. — Rebecca A. Martusewicz, Jeff Edmundson, and John Lupinacci, EcoJustice Education: Toward Diverse,…, 1288