Genetic and Environmental Influences on Intelligence

Studies of twins, family members, and adopted children point to significant genetic determinants of intelligence test scores. These and other studies also indicate that environment significantly influences intelligence test scores. Psychologists debate evolutionary and cultural explanations of gender differences in aptitudes and abilities. Environmental differences are perhaps entirely responsible for racial gaps in intelligence. Aptitude tests, which predict performance in a given situation, are necessarily “biased” in the sense that they are sensitive to performance differences caused by cultural experiences. However, the major tests are not biased in that they predict as accurately for one group as for another. Stereotype threat can adversely affect performance and sometimes appears in intelligence testing among African-Americans and women.