What the biological approach claims

• Behaviour has a physiological origin — the brain, biochemistry and genes shape what we think and do.
• Psychologists use brain-imaging (e.g. fMRI, which detects changes in blood oxygenation to show which regions are active), lesion and case studies, and twin/family/adoption studies.
• The approach is often reductionist (explaining behaviour by biology) and much of its evidence is correlational rather than strictly causal.

Key idea: the same behaviour can be studied at the level of brain structure, chemical messengers and inherited genes — these levels complement, not replace, one another.

Localisation of function

Localisation means specific functions are handled by specific brain regions. Classic evidence comes from case studies of brain damage.

• Patient HM (studied by Milner) had his hippocampi removed to treat epilepsy and could no longer form new long-term declarative memories — evidence the hippocampus is central to memory formation.
• fMRI lets researchers see localisation in living brains without surgery.

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Neuroplasticity — the brain changes with experience

Neuroplasticity is the brain's ability to reorganise itself, forming and pruning connections in response to experience.

• Maguire et al. (2000) used MRI to compare London taxi drivers with controls. Taxi drivers had significantly more grey matter in the posterior hippocampi, and the volume correlated with the number of years spent driving a taxi — experience (learning "The Knowledge") reshaped the brain.
• Draganski et al. (2004) found that learning to juggle increased grey matter in visual-motion areas, which shrank again when practice stopped.

Evaluation: Maguire's design is correlational — we cannot be certain the taxi work caused the difference rather than larger hippocampi predisposing people to the job.

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Neurotransmitters and behaviour

Neurons communicate across the synapse using chemical messengers called neurotransmitters. Changing their levels changes behaviour.

• Antonova et al. (2011) gave healthy volunteers scopolamine, which blocks the neurotransmitter acetylcholine. In a virtual-reality spatial task ("the Arena"), scopolamine reduced activation in the hippocampus and impaired encoding of spatial memory — evidence acetylcholine is important for creating spatial memories.

Real design: Antonova used a double-blind, placebo-controlled, repeated-measures design with fMRI — a strong causal method.

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Hormones and pheromones

Hormones are chemical messengers released into the bloodstream by glands; they act more slowly and widely than neurotransmitters.

• Cortisol (a stress hormone): Newcomer et al. (1999) found participants given high doses of cortisol showed impaired verbal declarative memory.
• Oxytocin: Baumgartner et al. (2008) found intranasal oxytocin maintained trust in an investment game even after betrayal.
• Pheromones (putative chemical signals): Zhou et al. (2014) reported that smelling androstadienone biased women, and estratetraenol biased men, toward perceiving a gender-neutral walker as more masculine/feminine.

Critical point: evidence for human pheromones is contested — several attempted replications have failed, so claims should be treated with caution.

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Genetics and behaviour

Twin, family and adoption studies estimate how far behaviour is inherited (its heritability).

• Bouchard et al. (Minnesota Study of Twins Reared Apart) found monozygotic (identical) twins raised apart still had highly similar IQ scores, suggesting a substantial genetic contribution to intelligence.
• Caspi et al. (2003) showed a gene-environment interaction: people carrying the short allele of the 5-HTT serotonin-transporter gene were more likely to develop depression after stressful life events than those with two long alleles.

Nuance: genes rarely act alone. Caspi shows that a genetic vulnerability often needs an environmental trigger to affect behaviour — nature and nurture.

Sort each finding to its level of analysis

Tap a finding, then tap the level of the biological approach it belongs to.

Research methods and ethics

The biological approach relies on brain imaging, case studies, correlational twin/kinship designs and, historically, animal models.

• Rosenzweig and Bennett found rats raised in enriched environments developed thicker cortices — early evidence of plasticity, using animals.
• Human studies must respect informed consent, protection from harm and confidentiality; drug studies (like Antonova) need especially careful ethical review.

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Match each researcher to their contribution

Tap a researcher on the left, then their key contribution on the right.

HL extension — the value of animal models in research

At HL you evaluate the use of animal research in understanding human behaviour.

• Why animals are used: tighter experimental control, the ability to study brain mechanisms invasively, shorter lifespans, and physiological similarities (e.g. Rosenzweig and Bennett on enriched environments).
• Strengths: establishes cause-effect for mechanisms that would be unethical to test in humans.
• Limitations: problems generalising from animals to humans, and serious ethical concerns — addressed by guidelines such as the 3Rs (replacement, reduction, refinement) and cost-benefit review.

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The big ideas to know

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