Nature & Nurture: The Relative Importance of Heredity & Environment
Monozygotic (MZ) vs. Dizygotic (DZ) Twins: Researchers compare the similarity of identical twins (MZ) to fraternal twins (DZ). Higher similarity in MZ twins suggests a stronger genetic influence, as both types of twins typically share similar environments but differ in genetic relatedness.
Adoption Studies: By comparing children to their biological parents (nature) and their adoptive parents (nurture), researchers can isolate variables. If a child is more similar to their biological parents in a specific trait, that trait is considered to have high heritability.
Heritability Coefficient (): This is a statistical estimate ranging from 0 to 1.0 that indicates the proportion of variation in a trait within a population that can be attributed to genetic differences.
| Feature | Nature (Nativism) | Nurture (Empiricism) | Interactionism |
|---|---|---|---|
| Source of Behavior | Genetic inheritance / DNA | Environment / Experience | Gene-environment interplay |
| Development | Maturation of innate traits | Learning and conditioning | Epigenetic expression |
| View of Human | Pre-programmed biological entity | Blank slate (tabula rasa) | Dynamic biological system |
| Key Model | Evolutionary Psychology | Behaviorism | Diathesis-Stress Model |
Avoid the Dichotomy Trap: When answering exam questions, never argue that a behavior is only nature or only nurture. Always conclude with an interactionist perspective to demonstrate a higher level of evaluation.
Interpret Concordance Carefully: Remember that concordance rates are rarely 100%. If MZ twins show 48% concordance for a trait, you must explain that while genetics are significant, the remaining 52% must be attributed to environmental factors.
Use Epigenetics as Evidence: Epigenetics is a powerful tool for evaluating the debate because it provides a physical, biological mechanism for how nurture (environment) actually changes nature (gene expression).
Heritability is not Individual: A common mistake is thinking a heritability of 0.6 means 60% of your intelligence comes from genes. In reality, it means 60% of the difference between people in a population is due to genes.
Deterministic Thinking: Students often assume that if a behavior has a genetic basis, it is unchangeable. However, environmental interventions can often moderate or bypass genetic predispositions.
Shared vs. Non-shared Environments: Do not assume siblings have the same 'nurture.' Non-shared environmental factors (different friends, unique life events) often have a larger impact than the shared family environment.