How does the biological approach explain behaviour?
The biological approach: the influence of genes, biological structures and neurochemistry on behaviour. Genotype and phenotype, genetic basis of behaviour, evolution and behaviour.
Covers AQA 4.5 the biological approach: genes, biological structures and neurochemistry, genotype and phenotype, the genetic basis of behaviour, and evolution.
Reviewed by: AI editorial process; not yet individually human-reviewed
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What this dot point is asking
AQA wants you to describe the biological approach: genes, biological structures, neurochemistry, genotype and phenotype, the genetic basis of behaviour and evolution. The examinable skill is to explain each mechanism precisely and to be able to distinguish genotype from phenotype, because the genotype-phenotype distinction is one of the most frequently tested ideas in the whole approaches topic.
Genes, structures and neurochemistry
The approach assumes that everything psychological is at first biological, so to fully understand behaviour we must look at biological structures and processes. At the structural level, specific brain regions are linked to specific functions (localisation), so damage to a region changes behaviour. At the chemical level, behaviour and mood are influenced by neurotransmitters: an imbalance of serotonin is associated with depression and obsessive-compulsive disorder, while excess dopamine activity is implicated in the positive symptoms of schizophrenia. Hormones, secreted by the endocrine system, also shape behaviour, for example the role of cortisol in the stress response or testosterone in aggression. This biochemical focus is what gives the approach its powerful link to drug therapies, since adjusting neurotransmitter levels (with SSRIs, for instance) can change behaviour, providing indirect support for the biochemical explanation.
Genetic basis and evolution
Twin studies work by comparing concordance rates. Because MZ twins share 100% of their genes and DZ twins share about 50%, a higher MZ concordance for a trait points to a genetic contribution. Because concordance is almost never 100%, the environment must also play a part, which is why the biological approach is best described as supporting an interactionist position even though it foregrounds nature. Evolutionary explanations extend the biological account across deep time: Darwin's principle of natural selection holds that any genetically determined behaviour that enhances survival or reproductive success will be naturally selected, becoming more common because the individuals who carry it leave more offspring. This is used to explain phenomena such as attachment (an infant who stays close to a caregiver is more likely to survive) and certain mate preferences. The strength of the evolutionary account is its breadth, but it is hard to falsify, since post-hoc evolutionary stories can be constructed for almost any behaviour.
Exam-style practice questions
Practice questions written in the style of AQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
AQA 20184 marksExplain the difference between a genotype and a phenotype. Use an example in your answer.Show worked answer →
A 4-mark item on Paper 2 (approaches), splitting roughly 2 AO1 and 2 AO2 for the worked example.
The genotype is an individual's actual genetic make-up, the set of alleles they inherit. The phenotype is the observable expression of that genotype, produced by the interaction of genes with the environment. A clear example is identical (monozygotic) twins: they share the same genotype, but if one is raised with a poor diet they may end up shorter, so their phenotypes differ. Another is phenylketonuria, where the genotype is present but a controlled diet prevents the phenotype (brain damage) from developing.
Markers reward an answer that states both terms are not identical, explains why (environmental influence on expression), and grounds it in a worked example showing the same genotype giving different phenotypes.
AQA 20226 marksDiscuss how twin studies have been used to investigate the genetic basis of behaviour.Show worked answer →
A 6-mark "discuss" item invites description (AO1) plus a short evaluation (AO3).
Description: twin studies compare concordance rates (the probability that if one twin shows a trait, the other does too) between identical (MZ, sharing 100% of genes) and non-identical (DZ, sharing about 50%) twins. A consistently higher concordance for MZ than DZ twins suggests the trait has a genetic component. For example, schizophrenia shows higher MZ than DZ concordance.
Evaluation: concordance is rarely 100% even for MZ twins, so genes cannot be the sole cause and the environment must contribute (supporting an interactionist position). A confound is that MZ twins may also be treated more similarly, inflating concordance through shared environment rather than shared genes. Markers reward defining concordance and the MZ versus DZ logic, then at least one developed limitation.
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Sources & how we know this
- AQA A-level Psychology (7182) specification — AQA (2015)