title: Childhood socioeconomic status amplifies genetic effects on adult intelligence.
abstract: Studies of intelligence in children reveal significantly higher heritability among groups with high socioeconomic status (SES) than among groups with low SES. These interaction effects, however, have not been examined in adults, when between-families environmental effects are reduced. Using 1,702 adult twins (aged 24-84) for whom intelligence assessment data were available, we tested for interactions between childhood SES and genetic effects, between-families environmental effects, and unique environmental effects. Higher SES was associated with higher mean intelligence scores. Moreover, the magnitude of genetic influences on intelligence was proportional to SES. By contrast, environmental influences were constant. These results suggest that rather than setting lower and upper bounds on intelligence, genes multiply environmental inputs that support intellectual growth. This mechanism implies that increasing SES may raise average intelligence but also magnifies individual differences in intelligence.
authors.affiliation: 1The University of Edinburgh.
authors.forename: Timothy C
authors.initials: TC
authors.lastname: Bates
authors.forename: Gary J
authors.initials: GJ
authors.lastname: Lewis
authors.forename: Alexander
authors.initials: A
authors.lastname: Weiss
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002657:Child Development; D004651:Employment / Q000706:statistics & numerical data; D004777:Environment; D005260:Female; D059647:Gene-Environment Interaction; D006801:Humans; D007182:Income / Q000706:statistics & numerical data*; D007360:Intelligence / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D010290:Parents; D012923:Social Class; D012959:Socioeconomic Factors; D014429:Twins, Dizygotic / Q000235:genetics* / Q000706:statistics & numerical data; D014430:Twins, Monozygotic / Q000235:genetics* / Q000706:statistics & numerical data; D055815:Young Adult
keywords: cognitive ability; cognitive development; genetics; intelligence; socioeconomic status