Why were early intelligence tests used by eugenicists culturally biased?

Early intelligence tests were culturally biased because they were designed to reflect the knowledge, cultural experiences, and educational backgrounds of privileged groups, rather than measuring innate ability.12

In the early 20th century, proponents of eugenics and biological determinism utilized IQ tests to reinforce existing social hierarchies. Because these tests relied on vocabulary, arithmetical skills, and specific cultural knowledge, individuals with access to superior primary education and greater cultural exposure consistently performed better.312

Critics, including psychologist Otto Klineberg, demonstrated that performance on these tests was directly correlated with social class and educational investment rather than heredity. By framing these culturally bound results as evidence of permanent, inherited intelligence, eugenicists sought to justify the systemic marginalization of disadvantaged groups, including African Americans and Native Americans, who had been denied equitable access to the culture and education the tests measured. This misuse of testing to promote racial and social inequality is a profound ethical failure, as it weaponized scientific tools to validate prejudice rather than pursue objective truth.13