Childhood experiences & epigenetics
IB Psychology· Human development· 14 min read
1. Core concept
Early childhood experiences — especially the quality of care and exposure to adversity — can leave lasting marks on how a person develops. One well-studied route is epigenetic: experience can chemically tag genes (for example by adding methyl groups) so that they are expressed more or less, altering systems such as the stress response without changing the DNA sequence itself. This gives a biological pathway by which early nurture or hardship shapes the adult self, while still interacting with later experience.
2. Key studies
IB Psychology answers must be supported by named studies. Learn these to cite as evidence:
Weaver et al. (2004)
Rat pups given little maternal nurturing showed increased methylation of the glucocorticoid-receptor gene and became more stress-reactive adults; well-nurtured pups showed the opposite. — An animal model of the mechanism — early experience biologically programming the later stress response.
McGowan et al. (2009)
People abused in childhood who later died by suicide showed the same increased glucocorticoid-receptor methylation in the hippocampus found in the rats. — Extends the mechanism to humans — early adversity leaving a molecular trace linked to the adult self.
3. Evaluation (AO3)
Strength — a concrete cross-species mechanism — The rat model (Weaver) and the human data (McGowan) converge on the same gene and stress system, giving a rare, specific biological account of how childhood experience becomes embedded.
Limitation — correlational in humans and not deterministic — The human evidence is post-mortem and correlational (abuse co-occurs with much else), and outcomes are not fixed — resilience and later care can shift trajectories, so early experience shapes but does not seal the self.
4. Scope
5. Common Pitfalls
Wrong move:
A bad childhood, or an epigenetic 'scar', permanently and inevitably determines the adult.
Why:
A frequently penalised misconception in IB Psychology exams.
Correct move:
Early experience raises or lowers risk through real biological pathways, but the effects are probabilistic and partly reversible — resilience, later relationships and care matter (McFarlane found family functioning predicted outcomes more than direct trauma exposure).
Going deeper
- Genetic inheritanceepigenetics as gene–environment interaction is genetic inheritance in the biological approach (BIO_6).
- Diathesis–stress modela predisposition meeting an early-life stressor is the diathesis–stress logic (BIO_5).