Q.To what extent is our intelligence the result of heredity (nature) and environment (nurture)? Discuss.
Neither nature nor nurture alone explains intelligence; it is the product of a complex interaction of the two — heredity sets a range within which environmental support and opportunities actually shape a person's development.
Evidence for the role of heredity (nature)
Support comes mainly from studies of twins and adopted children:
- Intelligence of identical (monozygotic) twins reared together correlates almost 0.90.
- Identical twins separated early and reared apart still correlate about 0.72.
- Fraternal twins reared together correlate about 0.60.
- Siblings reared together correlate about 0.50, and siblings reared apart only about 0.25.
- Adoption studies show that children's intelligence is more similar to their biological parents than to their adoptive parents.
The falling correlations as genetic closeness decreases point to a real hereditary component.
Evidence for the role of environment (nurture)
- As adopted children grow, their intelligence level tends to move closer to that of their adoptive parents.
- Children from disadvantaged homes adopted into families of higher socio-economic status show a large increase in intelligence scores.
- Environmental deprivation lowers intelligence, whereas rich nutrition, a good family background and quality schooling raise it.
The consensus: interaction, not opposition
There is a general agreement among psychologists that intelligence is a product of the complex interaction of heredity (nature) and environment (nurture). Heredity is best viewed as something that sets a range within which an individual's development is actually shaped by the support and opportunities of the environment. Thus the two do not compete — heredity provides the potential and the environment determines how far and in what direction that potential is realised.
Intelligence is neither purely inherited nor purely environmental — it is the product of a complex interaction of both. Twin and adoption studies confirm a strong hereditary influence, while enrichment, deprivation, nutrition and schooling studies confirm a strong environmental one. Best understanding: heredity sets the range of possible development, and the environment decides how much of that range is achieved.
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