Biological Approach to Behaviour
What this domain asks
The biological approach explains behaviour through physiology: brain structure and localisation, neurotransmission, hormones, genes and evolutionary adaptation. In SL exam questions you are expected to describe biological variables, use specific research as evidence, and evaluate methods and causality-not just name a brain region.
Core rules and concepts
- Localisation vs distributed processing: functions can be linked to areas (e.g., hippocampus and memory), but complex behaviour usually involves networks. HM's surgery (Milner) showed the hippocampus is critical for consolidating new explicit memories while procedural memory can remain.
- Neuroplasticity: experience changes synaptic connections. Maguire et al. found larger posterior hippocampal volume in London taxi drivers, correlated with navigation experience; Draganski et al. showed grey-matter changes after juggling practice. These are correlations or short-term training effects-do not claim the brain region "caused" the skill.
- Neurotransmitters and hormones: neurotransmitters cross synapses; hormones travel via blood. Baumgartner et al. found oxytocin increased trust in an investment game, but effects varied with betrayal feedback. Correlation with brain activity is not proof of causation.
- Genetics: twin and adoption designs estimate heritability. Bouchard's Minnesota twins suggest substantial genetic contribution to traits, but reared-together twins share environments, so heritability estimates depend on assumptions.
- Evolution: behaviours may be adaptive; pheromone research (e.g., Wedekind's sweaty T-shirt study) links MHC similarity to attractiveness, but findings are debated and not deterministic.
Worked example
Question: "Evaluate the claim that one brain area controls memory." Reasoning: define localisation; cite HM-hippocampus damage impaired new explicit memory but left procedural learning; note KF had impaired short-term memory with intact long-term learning, suggesting multiple systems. Conclude: evidence supports specialisation but not one-area control; use "contributed to" and "associated with."
Traps
- Describing a study without linking it to the question's biological variable.
- Treating correlation as causation.
- Using animal studies as if they automatically generalise to humans.
- Confusing neurotransmitters (synaptic) with hormones (bloodstream).