Large positive and negative trends in cohort IQ operate within as well as across families, implying at most a minor role for genes, with environment as the main driver.

Evidence

Flynn effect and its reversal are both environmentally caused (PNAS)

Categorization

• corroborated: 2 independent passages support this claim
• XREF: connects to: Intelligence is malleable and shaped by environment, not fixed by heredity — Harriet A. Washington, A Terrible Thing to Waste, 54; Intelligence develops from environment and experience rather than genetic inheritance; Twin and adoption studies estimate genetic contribution to intelligence at 50–70% heritability, though molecular GWAS estimates run lower. — Twin Studies and the Heritability of IQ (+3 more)

Related

• IQ has risen across generations worldwide, and the effect must be environmental since genetic mutation could not act that fast, amounting to about 15 IQ points per generation on fluid tests. (similarity 0.88)
• Twin and adoption studies estimate genetic contribution to intelligence at 50–70% heritability, though molecular GWAS estimates run lower. (similarity 0.87)
• High heritability of individual differences and large environmental effects on population-level IQ are mathematically compatible under a reciprocal gene-environment coupling model (Dickens & Flynn). (similarity 0.86)
• The generational rise in IQ scores is attributed to environmental factors like improved nutrition, education, and reduced toxin exposure. (similarity 0.85)
• With heritability well below 1.00, IQ must be subject to substantial environmental influences, though genetic influence increases with age while shared family environment effects shrink by late… (similarity 0.85)
• Population IQ scores have risen rapidly over decades, refuting fixed-IQ claims (similarity 0.85)
• Intelligence is malleable and shaped by environment, not fixed by heredity (similarity 0.83)
• Intelligence develops from environment and experience rather than genetic inheritance (similarity 0.83)
• Genetic causation of a trait does not imply the trait is unchangeable (similarity 0.82)
• With heritability well below 1.00, IQ must be subject to substantial environmental influences, though genetic influence increases with age while shared family environment effects shrink by late adolescence. (similarity 0.82)
• The secular trend in growth is almost entirely due to environmental factors since genetic changes in a whole population take far longer than the observed time interval. (similarity 0.80)
• Targeted interventions can raise a nation’s average intelligence level (similarity 0.80)
• IQ’s link to income mostly reflects environment’s link to both (similarity 0.80)
• Mixed-race children’s IQ tracks rearing environment, not racial genetics (similarity 0.79)

Library Connections

• Rapid IQ gains from reduced disease burden rule out genetic explanations #corroborates (0.90) — Harriet A. Washington, A Terrible Thing to Waste, 945