---
title: "Race and intelligence"
chunk: 1/9
source: "https://en.wikipedia.org/wiki/Race_and_intelligence"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T04:18:16.114269+00:00"
instance: "kb-cron"
---

Discussions of race and intelligence—specifically regarding claims of differences in intelligence along racial lines—have appeared in both popular science and academic research since the modern concept of race was first introduced. With the inception of IQ testing in the early 20th century, differences in average test performance between racial groups have been observed, though these differences have fluctuated and in many cases steadily decreased over time. Complicating the issue, modern science has concluded that race is a socially constructed phenomenon rather than a biological reality, and there exist various conflicting definitions of intelligence. In particular, the validity of IQ testing as a metric for human intelligence is disputed. Today, the scientific consensus is that genetics does not explain differences in IQ test performance between groups, and that observed differences are environmental in origin. 
Pseudoscientific claims of inherent differences in intelligence between races have played a central role in the history of scientific racism. The first tests showing differences in IQ scores between different population groups in the United States were those of United States Army recruits in World War I. In the 1920s, groups of eugenics lobbyists argued that these results demonstrated that African Americans and certain immigrant groups were of inferior intellect to Anglo-Saxon white people, and that this was due to innate biological differences. In turn, they used such beliefs to justify policies of racial segregation. However, other studies soon appeared, contesting these conclusions and arguing that the Army tests had not adequately controlled for environmental factors, such as socioeconomic and educational inequality between the groups. 
Later observations of phenomena such as the Flynn effect and disparities in access to prenatal care highlighted ways in which environmental factors affect group IQ differences. In recent decades, as understanding of human genetics has advanced, claims of inherent differences in intelligence between races have been broadly rejected by scientists on both theoretical and empirical grounds.

== History of the controversy ==

Claims of differences in intelligence between races have been used to justify colonialism, slavery, racism, social Darwinism, and racial eugenics. Claims of intellectual inferiority were used to justify British wars and colonial campaigns in Asia. Racial thinkers such as Arthur de Gobineau in France relied crucially on the assumption that black people were innately inferior to white people in developing their ideologies of white supremacy. Even Enlightenment thinkers such as Thomas Jefferson, a slave owner, believed black people to be innately inferior to white people in physique and intellect. At the same time in the United States, prominent examples of African-American genius such the autodidact and abolitionist Frederick Douglass, the pioneering sociologist W. E. B. Du Bois, and the poet Paul Laurence Dunbar stood as high-profile counterexamples to widespread stereotypes of black intellectual inferiority. In Britain, Japan's military victory over Russia in the Russo-Japanese War began to reverse negative stereotypes of "oriental" inferiority. 

=== Early IQ testing ===
The first practical intelligence test, the Binet-Simon Intelligence Test, was developed between 1905 and 1908 by Alfred Binet and Théodore Simon in France for school placement of children. Binet warned that results from his test should not be assumed to measure innate intelligence or used to label individuals permanently. Binet's test was translated into English and revised in 1916 by Lewis Terman (who introduced IQ scoring for the test results) and published under the name Stanford–Binet Intelligence Scales. In 1916 Terman wrote that Mexican-Americans, African-Americans, and Native Americans have a mental "dullness [that] seems to be racial, or at least inherent in the family stocks from which they come."
The US Army used a different set of tests developed by Robert Yerkes to evaluate draftees for World War I. Based on the Army's data, prominent psychologists and eugenicists such as Henry H. Goddard, Harry H. Laughlin, and Princeton professor Carl Brigham wrote that people from southern and eastern Europe were less intelligent than native-born Americans or immigrants from the Nordic countries, and that black Americans were less intelligent than white Americans. The results were widely publicized by a lobby of anti-immigration activists, including the conservationist and theorist of scientific racism Madison Grant, who considered the so-called Nordic race to be superior, but under threat because of immigration by "inferior breeds." In his influential work, A Study of American Intelligence, psychologist Carl Brigham used the results of the Army tests to argue for a stricter immigration policy, limiting immigration to countries considered to belong to the "Nordic race".
In the 1920s, some US states enacted eugenic laws, such as Virginia's 1924 Racial Integrity Act, which established the one-drop rule (of 'racial purity') as law. Many scientists reacted negatively to eugenicist claims linking abilities and moral character to racial or genetic ancestry. They pointed to the contribution of environment (such as speaking English as a second language) to test results. By the mid-1930s, many psychologists in the US had adopted the view that environmental and cultural factors played a dominant role in IQ test results. The psychologist Carl Brigham repudiated his own earlier arguments, explaining that he had come to realize that the tests were not a measure of innate intelligence.
Discussions of the issue in the United States, especially in the writings of Madison Grant, influenced German Nazi claims that the "Nordics" were a "master race". As American public sentiment shifted against the Germans, claims of racial differences in intelligence increasingly came to be regarded as problematic. Anthropologists such as Franz Boas, Ruth Benedict, and Gene Weltfish did much to demonstrate that claims about racial hierarchies of intelligence were unscientific. Nonetheless, a powerful eugenics and segregation lobby funded largely by textile-magnate Wickliffe Draper continued to use intelligence studies as an argument for eugenics, segregation, and anti-immigration legislation.