AP Syllabus focus:
‘Developmental psychologists investigate how biological factors and environmental influences interact to shape development, highlighting the importance of the nature versus nurture debate.’
The nature–nurture debate asks how much of development is due to inherited biology versus experience. AP Psychology emphasizes interaction: genes shape sensitivity to environments, and environments influence which genetic potentials are expressed.
Core Idea: Not Either/Or
Nature and nurture as joint influences
Nature: Biological influences on development, including genetic inheritance, brain maturation, hormones, and evolutionary predispositions.
Biological influences help explain why some traits (e.g., temperament) show early emergence and cross-cultural consistency.
Nurture: Environmental influences on development, including parenting, peers, culture, education, nutrition, stress, and lived experiences.
Environmental factors help explain variability within families and across contexts, and why the same person may change across settings and time.
The modern view: interaction, not competition
Gene–environment interaction: The idea that genetic predispositions and environmental conditions jointly shape development; the effect of one depends on the other.
In developmental psychology, the key question is often “under what conditions” a predisposition becomes a stable trait, rather than whether the trait is purely inborn or learned.
How Psychologists Study Nature and Nurture
Behavioral genetics (inferring genetic influence)
Researchers estimate genetic contributions by comparing similarity across people with different degrees of genetic relatedness, especially:
Twin studies: Identical (monozygotic) twins share ~100% of genes; fraternal (dizygotic) twins share ~50% on average.
Adoption studies: Compare adoptees to biological relatives (genes) and adoptive relatives (environment).
A stronger resemblance between identical twins than fraternal twins suggests genetic influence, but does not eliminate environmental explanations (e.g., identical twins may be treated more similarly).
Heritability and what it does (and doesn’t) mean
Heritability: A statistic describing how much variation in a trait within a specific population and environment is associated with genetic differences.
Heritability is often misunderstood:
It applies to groups, not individuals.
It can change across environments (e.g., when opportunities become more equal, genetic differences may account for more observed variation).
High heritability does not imply immutability; environmental intervention can still change outcomes.
Mechanisms of Interaction
Gene–environment correlation (how we “select” environments)
People’s genetic tendencies can influence the environments they experience:
This diagram summarizes three ways genes can be correlated with environments: passive (parents provide genes and environments), evocative (others respond to genetically influenced traits), and active (individuals select niches). It helps clarify that genes can shape exposure to “nurture,” even before considering true gene–environment interaction effects. Source
Passive correlation: Parents provide both genes and home environment (e.g., verbal parents provide language-rich homes).
Evocative correlation: Individuals elicit responses based on traits (e.g., a highly irritable infant may receive different caregiving).
Active correlation (niche-picking): Individuals seek environments that fit dispositions (e.g., sensation-seeking adolescents choose riskier activities).
These processes blur simple nature vs nurture claims because genes can shape exposure to “nurture.”
Epigenetics (how experience affects gene expression)
Epigenetics: Changes in gene expression (turning genes “on” or “off”) triggered by environmental factors without altering the DNA sequence.
Experiences such as chronic stress, nutrition, and caregiving quality can influence biological systems (e.g., stress reactivity), illustrating how environmental conditions can become biologically embedded.
Applying the Debate to Developmental Outcomes
Stability and plasticity depend on both influences
Developmental outcomes commonly reflect:
Genetic constraints: Set ranges of potential (e.g., maturational timing, susceptibility).
Environmental inputs: Determine where within that range an individual develops (e.g., learning opportunities, chronic adversity).
Timing and context: Early environments may have stronger effects for some systems, while later experiences can redirect trajectories for others.
Common AP exam framing
When evaluating claims about behavior or development, prioritise:
Evidence for biological influence (genetic relatedness effects, cross-cultural patterns, biological mechanisms).
Evidence for environmental influence (contextual differences, intervention effects, cultural variation).
Evidence for interaction (different outcomes from the same environment depending on predisposition, or different sensitivity to the same stressor).
FAQ
Yes. Heritability describes variation in a population, not fixedness.
Environmental changes can shift average outcomes even when genetic differences still explain some variation.
They can have different non-shared environments (friends, teachers, illnesses).
They may also experience different epigenetic changes across development.
No. It means the impact of each depends on the other.
The same environment can produce different outcomes across people.
Rarely. Genes can influence the environments people experience (gene–environment correlation).
Environments can alter biology through learning and stress physiology.
Often those involving stress, nutrition, toxins, or enrichment.
High-intensity or chronic conditions are more likely to reveal differences in susceptibility.
Practice Questions
Outline one way behavioural geneticists investigate the relative contributions of nature and nurture. (2 marks)
1 mark: Identifies a relevant method (e.g., twin study or adoption study).
1 mark: Explains how comparisons allow inference about genetic versus environmental influence.
Discuss how gene–environment interaction and epigenetics challenge a strict nature versus nurture explanation of development. (6 marks)
1–2 marks: Accurate explanation of gene–environment interaction (effects depend on each other).
1–2 marks: Accurate explanation of epigenetics (environment alters gene expression without changing DNA).
1–2 marks: Clear linkage to why “either/or” accounts are insufficient (integrative argument applied to development).
