Self-Attributed Innateness Beliefs Moderate the Heritability of Psychological Traits

People vary in how strongly they believe their psychological traits are innate. Using a twin/sibling design (N = 5,844; 1,043 MZ and 2,607 DZ families), I tested whether such beliefs moderate the heritability of 11 traits spanning sexuality, personality, attitudes, and health behavior. Innateness beliefs significantly moderated heritability for all traits: individuals who considered a trait more innate showed higher heritability for that trait. The effect was more trait-specific than indicative of a general essentialist tendency and largely driven by the individual's own belief rather than shared familial or genetic factors (religiosity and risk-taking were partial exceptions). A stringent sensitivity analysis reduced the number of significant traits from 11 to 6, indicating that for some traits the moderation may at least partly reflect a confound between extreme trait scores and innateness beliefs. The low heritability of innateness beliefs is consistent with largely non-genetic beliefs gatekeeping the expression of genetic variation.