Biological reductionism
IB Psychology· Biological approach· 14 min read
1. Core concept
Biological reductionism explains a behaviour by breaking it down to its simplest biological parts — a gene, a neurotransmitter, a brain area — rather than the whole person in context. Its strength is that these parts can be isolated, measured and tested in controlled studies, giving clear cause–effect claims and biological treatments. Its limitation is that stripping away cognition, emotion and social context can oversimplify: a single gene or chemical rarely explains a complex behaviour on its own.
2. Key studies
IB Psychology answers must be supported by named studies. Learn these to cite as evidence:
Sullivan, Neale & Kendler (2000)
Twin meta-analysis estimated the heritability of depression at about 37%. — A reductionist-style single-factor estimate — and the ~63% it leaves to non-genetic factors is exactly where reducing to genes alone falls short.
Caspi et al. (2003)
Depressive response to stressful life events depended on 5-HTT genotype; the gene alone did not predict depression. — Shows why strong reductionism fails — the biological factor mattered only in interaction with the environment.
3. Evaluation (AO3)
Strength — testable and useful — Isolating one variable is how controlled science works, and it yields concrete biological treatments (e.g. drugs).
Limitation — necessary but not sufficient — A low-level cause is usually one part of the story; interactionist (gene × environment) models fit the data better.
4. Scope
5. Common Pitfalls
Wrong move:
'Reductionism' is a lazy or automatically bad explanation.
Why:
A frequently penalised misconception in IB Psychology exams.
Correct move:
Reductionism is a necessary step in controlled science (isolate one variable). The valid criticism is OVER-reduction — treating one part as the whole.
Going deeper
- Diathesis–stress modelthe diathesis–stress model is the interactionist answer to over-reduction.
- Genetic inheritancethe heritability estimate used here is genetic inheritance (BIO_6).