Race and intelligence is a controversial area of intelligence research studying the nature, origins, and practical consequences of racial and ethnic group differences in intelligence test scores and other measures of cognitive ability.
This research is grounded in several controversial assumptions:
- The social categories of race and ethnicity are concordant with genetic categories, such as biogeographic ancestry.
- Intelligence is measurable (see psychometrics) and is dominated by a unitary general cognitive ability.
Much of the evidence currently cited is based on IQ testing in the United States. While the distributions of IQ scores among different racial-ethnic groups overlap and often have a comparable range, groups differ in where their members cluster along the IQ scale. Similar clustering occurs with related variables, such as school achievement, reaction time, and brain size. Most variation in IQ in the U.S. occurs within individual families, not between races. However, even small differences in average IQ at the group level might theoretically have large effects on social outcomes. For example, a randomly selected group of Americans with an average IQ of 103 had a poverty rate 25% lower than a group with an average IQ of 100. Similar substantial correlations in high school drop-out rates, crime rates, and other outcomes have been measured.
Many hypotheses have been proposed to explain why average IQ varies among racial-ethnic groups. Certain environmental factors, such as nutrition, are thought to modulate IQ in children, and other influences have been hypothesized, including education level, richness of the early home environment, and other social, cultural, or economic factors. The primary focus of the scientific debate is whether group IQ differences also reflect a genetic component. Hereditarianism hypothesizes that a genetic contribution to intelligence could include genes linked to neuron structure or function, brain size or metabolism, or other physiological differences which could vary with biogeographic ancestry.
The findings of this field have engendered a large controversy. Media portrayal of the role of genetic and environmental factors in explaining individual and group differences in IQ has itself been studied (1988) and found to be misleading regarding mainstream expert opinion. Some critics examine the fairness and validity of cognitive testing and racial categorization, as well as the reliability of the studies and the motives of the authors, on both sides. Some critics fear the misuse of the research, question its utility, or feel that comparing the intelligence of racial groups is itself unethical. The disparity in average IQ among racial groups does not mean that all members of one group are more intelligent than all members of another, nor that ranking group averages from "high" to "low" implies a moral ranking from "good" to "bad" or an overall ranking of "superior" to "inferior". The conclusion that racial groups vary in average IQ scores, and the hypothesis that a genetic component may be involved, have led to heated academic debates that have spilled over into the public sphere.