The nature versus nurture debate asks whether our traits come from our genes or from our environment. Because parents usually give us both, answering that question can be tricky.
One method to answer the nature vs. nurture question is through twin studies.
Researchers can compare identical twins to fraternal twins. If identical twins are more alike on a trait than fraternal twins, that suggests genes contribute to that trait.
Researchers can also study identical twins raised apart. They find that identical twins raised apart are often strikingly similar in intelligence and aspects of personality, adding evidence that genetics contributes to those traits.
A second method are adoption studies. Adoption studies separate genes from environment: resembling biological parents points to genes; resembling adoptive parents points to environment.
Family studies study families to see whether traits run in families, but family studies can't establish whether that is a result of shared genes or shared environment.
No single method is perfect, but together the research shows both genes and environment matter, and behavior emerges from their continuing interplay.
Key terms
nature versus nurture
The debate over how much human traits are influenced by our genes versus shaped by our environment.
twin study
Research comparing identical and fraternal twins to see how much genes contribute to a trait.
identical twins
Twins who develop from a single fertilized egg and share virtually 100% of their genetic material.
fraternal twins
Twins who develop from two different eggs and, like ordinary siblings, share about half their genes.
adoption study
Research comparing adopted children to their biological parents (shared genes) and adoptive parents (shared environment).
family study
Research showing whether a trait runs in families; on its own it can't separate genes from shared environment.
environment
All the external influences you encounter, such as school, friends, culture, neighborhood, nutrition, experiences, and major life events.