Is intelligence hereditary?

• A. Purely environmental
• B. Purely genetic
• C. Not influenced by environment
• D. A combination of heredity and environment

Answer: (D)

Intelligence is shaped by both genetic and environmental factors. Genetic influences set a range of potential abilities, as shown by twin studies where identical twins resemble each other in IQ more than fraternal twins, even when raised apart. But the environment plays a crucial role in realizing that potential—stimulating experiences, nutrition, education, socioeconomic conditions, and family support all impact cognitive development. Moreover, genes and environment don’t act in isolation; they interact in ways that can amplify or diminish cognitive outcomes over time. Because the best current understanding recognizes that heredity provides a potential that the environment can enable or constrain, the effect on intelligence is a combination of heredity and environment. The alternatives imply only one factor or deny environmental influence, which does not fit what is observed in research and real-world development.