Nature versus Nurture Debate

🧠 Psychology By CampusDown Wiki Editorial Team Last updated October 15, 2026

Quick answer: the nature–nurture debate is the long-running argument over whether human traits such as intelligence, personality and behavior are set by heredity (nature) or shaped by experience (nurture). Today the consensus is that the two continually interact.

Contents

1. Background
2. The two positions
3. Twin and adoption studies and heritability
4. How genes and environment work together
5. Current view
6. References

Background

The phrase "nature and nurture" was popularized by Francis Galton in English Men of Science: Their Nature and Nurture (1874). Galton argued for hereditarianism on the basis of family studies showing that eminence runs in families. On the other side stood Locke's empiricist view of the mind as a blank slate and John B. Watson's behaviorism, with his boast that, given a dozen healthy infants, he could train any one of them to become any kind of specialist. Because it touched on group differences in IQ, education policy and the causes of crime, the debate was long politically charged.

The two positions

Nature (maturationism): development unfolds according to a genetic plan. Gesell's maturational theory, Chomsky's language acquisition device and temperament research lean this way.
Nurture (learning): development results from experience and learning. Behaviorism, social learning theory and research on culture and parenting are typical.

Twin and adoption studies and heritability

Behavioral genetics estimates the contributions of genes and environment by comparing identical twins (sharing 100% of their genes), fraternal twins (about 50%), and adopted children with their biological and adoptive parents.

Minnesota Study of Twins Reared Apart: Bouchard et al. (1990) reported that identical twins separated in infancy were strikingly similar in intelligence, personality and interests, estimating that about 70% of IQ variance was associated with genetic variation.
Meta-analysis: Polderman et al. (2015) pooled 50 years of twin studies covering some 18,000 traits and found an average heritability of about 49%, roughly half genes and half environment.
What heritability means: heritability is the proportion of variance in a trait within a particular population that is due to genetic differences. It does not say what percentage of one person's trait is genetic, and it changes when environments change.

Plomin et al. (2016) list among behavioral genetics' most replicated findings that all psychological traits show substantial genetic influence, that no trait is 100% heritable, and that the nonshared environment, experiences siblings do not share, matters a great deal.

How genes and environment work together

Gene–environment interaction: the same environment has different effects depending on genotype. Caspi et al. (2002) found that among maltreated boys, risk of antisocial behavior rose sharply only in those with a low-activity MAOA genotype.
Gene–environment correlation: genes also select environments, whether parents provide settings that fit their own dispositions (passive), a child's temperament evokes responses (evocative) or children seek out environments that suit them (active).
Epigenetics: experiences such as nutrition and stress can switch gene expression on or off without changing the DNA sequence.
Range of reaction: heredity sets a range of possible outcomes, and environment determines where within it a person ends up.

Current view

Modern developmental psychology asks not "nature or nurture?" but "how do they work together?" Even highly heritable traits such as intelligence and personality can change with education and environmental intervention, and the effects of environments in turn depend on individual genetic makeup. Stage theories are covered in child development theories.

References

Galton, F. (1874). English Men of Science: Their Nature and Nurture. London: Macmillan.
Bouchard, T. J., Jr., Lykken, D. T., McGue, M., Segal, N. L., & Tellegen, A. (1990). Sources of human psychological differences: The Minnesota Study of Twins Reared Apart. Science, 250(4978), 223–228.
Caspi, A., McClay, J., Moffitt, T. E., Mill, J., Martin, J., Craig, I. W., Taylor, A., & Poulton, R. (2002). Role of genotype in the cycle of violence in maltreated children. Science, 297(5582), 851–854.
Polderman, T. J. C., Benyamin, B., de Leeuw, C. A., Sullivan, P. F., van Bochoven, A., Visscher, P. M., & Posthuma, D. (2015). Meta-analysis of the heritability of human traits based on fifty years of twin studies. Nature Genetics, 47(7), 702–709.
Plomin, R., DeFries, J. C., Knopik, V. S., & Neiderhiser, J. M. (2016). Top 10 replicated findings from behavioral genetics. Perspectives on Psychological Science, 11(1), 3–23.

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