Nature and nurture
Move beyond an either-or explanation to ask what heritability can and cannot identify.
The question
How do inherited differences and environments jointly produce variation in a particular trait?
The historical opposition between inborn and acquired characteristics obscures a difference between explaining variation within a population and explaining how a person develops.
What the claims mean
Variance components
Twin models estimate genetic and environmental contributions to differences among people under specified assumptions. These are population estimates, not percentages of an individual.
Developmental processes
A developmental account asks how biological differences and experiences interact over time. It can accept heritable variation while asking which exposures change outcomes.
Evidence to examine
Polderman and colleagues (2015) synthesized twin studies across many human traits. Their reported overall estimate of heritability was 49%, with considerable variation across domains. The result summarizes those studies; it does not assign a genetic percentage to every psychological characteristic.
Shared ground and disagreement
What the accounts can share
A genetic contribution and an environmental contribution are compatible. Heritability is conditional on the people, environments and measures studied.
What remains at issue
How much model assumptions, changing environments and interactions affect an estimate, and which developmental pathways account for it.
Limits and next tests
Twin resemblance is not itself a mechanism. An average across heterogeneous traits cannot tell a teacher or policymaker whether a particular intervention will work.
What would help distinguish the claims?
Compare preregistered longitudinal, genetically informed and intervention studies of the same clearly defined outcome. Check whether proposed environmental changes alter outcomes rather than inferring immutability from heritability.
Textbook connection
DirectOpenStax Psychology 2e: 3.1 Human Genetics
The section directly introduces this question or the named evidence. The profile adds interpretation and limits.
Sources and access
- 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. https://doi.org/10.1038/ng.3285Consulted sourceAbstract inspected
Primary bibliographic record and complete abstract retrieved from Europe PMC on October 21, 2026. Full paper methods and supplements were not inspected.