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The biological approach argues that to understand behaviour fully we must look first to the body — to genes, brain structures, neurochemistry, hormones and our evolutionary past. Its guiding assumption is that everything psychological is at first biological: the mind is the product of the physical brain, and thoughts, feelings and behaviour all have biological causes that can be studied with the objective, measurable methods of the natural sciences. This is the most overtly scientific of the approaches, drawing on genetics, neuroscience and Darwinian evolutionary theory, and it has generated some of psychology's most important real-world applications — above all, drug treatments for mental disorders. Its great power, the precision of biological explanation, is also the source of its main criticism: reductionism and biological determinism.
This lesson addresses the AQA A-Level Psychology (7182) specification topic Approaches in Psychology — The biological approach, requiring you to know and evaluate:
It is examined on Paper 2 (Psychology in Context) and links synoptically to Biopsychology (the nervous and endocrine systems, neural transmission, the fight-or-flight response, Paper 2), the biological explanations and treatments of psychopathology and schizophrenia, and the nature--nurture, reductionism and determinism debates (Paper 3).
Key Definition: Biological approach — the approach that explains behaviour in terms of biological factors including genes, neurochemistry, brain structures and evolution, assuming all behaviour has a physical cause.
Every individual inherits a unique combination of genes from their parents. The biological approach proposes that these genes influence behaviour, personality and vulnerability to mental disorder.
| Term | Definition |
|---|---|
| Genotype | The genetic makeup of an individual — the particular set of genes they carry |
| Phenotype | The observable characteristics of an individual — the product of the interaction between genotype and environment |
Key Definition: Genotype — the set of genes an individual possesses. Phenotype — the observable expression of those genes, shaped by both genetics and environment. The genotype--phenotype distinction is the approach's built-in concession to nurture: identical genotypes (as in MZ twins) can produce different phenotypes.
A clear illustration is phenylketonuria (PKU), an inherited condition caused by a single faulty gene. A child with the PKU genotype who eats a normal diet cannot metabolise phenylalanine, which builds up and causes severe learning difficulties (one phenotype); but if the same genotype is identified at birth and the child is placed on a phenylalanine-restricted diet, development is normal (a very different phenotype). The genotype is identical, yet the phenotype depends on the environment — a textbook demonstration that genes and environment interact, and that biology is rarely destiny.
Because monozygotic (MZ) twins share (effectively) 100% of their genes while dizygotic (DZ) twins share around 50%, comparing concordance rates between them estimates the genetic contribution to a behaviour.
| Twin type | Genetic similarity | Rationale |
|---|---|---|
| Monozygotic (MZ) | ~100% identical | If a trait is genetic, MZ concordance should exceed DZ concordance |
| Dizygotic (DZ) | ~50% (like ordinary siblings) | Provides the comparison needed to estimate heritability |
For schizophrenia, Gottesman's (1991) classic pooled data give MZ concordance of roughly 48% against DZ concordance of about 17%. The much higher MZ figure indicates a substantial genetic component; the fact that it falls well short of 100% shows that environmental factors also matter — if schizophrenia were wholly genetic, MZ concordance would be 100%.
Adoption studies disentangle nature and nurture by comparing adopted children with their biological parents (shared genes, different environment) and their adoptive parents (shared environment, different genes). Greater similarity to biological parents points to genetic influence.
The biological approach holds that specific functions are localised in specific brain regions (cortical specialisation).
| Brain area | Function |
|---|---|
| Frontal lobe | Decision-making, planning, personality, motor control |
| Temporal lobe | Auditory processing, language comprehension, memory |
| Parietal lobe | Sensory processing, spatial awareness |
| Occipital lobe | Visual processing |
| Broca's area (frontal) | Speech production |
| Wernicke's area (temporal) | Language comprehension |
| Hippocampus | Formation of new long-term memories |
| Amygdala | Processing emotions, especially fear and aggression |
Exam Tip: Support localisation with evidence. Damage to Broca's area produces Broca's aphasia (halting, effortful speech production), while damage to Wernicke's area produces Wernicke's aphasia (fluent but meaningless speech and poor comprehension). These dissociations show different regions control different functions.
The brain sits within a wider, hierarchically organised nervous system, which the biological approach treats as the physical basis of all behaviour.
graph TD
A[Nervous System] --> B[Central Nervous System CNS]
A --> C[Peripheral Nervous System PNS]
B --> D[Brain]
B --> E[Spinal Cord]
C --> F[Somatic Nervous System]
C --> G[Autonomic Nervous System ANS]
G --> H[Sympathetic - arousing]
G --> I[Parasympathetic - calming]
This organisation matters for the approach because it shows how behaviour, from a reflex to a stress response, can be traced to identifiable physical structures — and it is a direct synoptic bridge to the Biopsychology topic and to A-Level Biology's treatment of the nervous system.
Neurotransmitters are chemical messengers that carry signals across the synapse between neurons. Imbalances are implicated in many disorders, which is why neurochemistry underpins drug treatment.
| Neurotransmitter | Role in behaviour |
|---|---|
| Serotonin | Mood, sleep, appetite; low serotonin is associated with depression |
| Dopamine | Reward, motivation, movement; excess is linked to schizophrenia, deficiency to Parkinson's disease |
| Noradrenaline | Arousal, alertness, fight-or-flight; linked to anxiety and the stress response |
| GABA | The main inhibitory transmitter; reduces neural activity; low GABA is associated with anxiety |
| Acetylcholine | Muscle action, memory and attention; loss of ACh neurons is associated with Alzheimer's disease |
graph LR
A[Electrical impulse travels down axon] --> B[Vesicles release neurotransmitter into synaptic cleft]
B --> C[Neurotransmitter binds to receptors on post-synaptic neuron]
C --> D{Effect}
D -->|Excitatory| E[Post-synaptic neuron more likely to fire]
D -->|Inhibitory| F[Post-synaptic neuron less likely to fire]
C --> G[Reuptake or enzyme breakdown]
The sequence is: an electrical impulse travels along the axon of the pre-synaptic neuron; at the terminal, vesicles release neurotransmitter into the synaptic cleft; the neurotransmitter diffuses across and binds to receptors on the post-synaptic neuron; this is either excitatory (increasing the chance of firing) or inhibitory (decreasing it); the neurotransmitter is then cleared by reuptake or enzyme breakdown. Understanding this explains how drugs work: SSRIs block the reuptake of serotonin, leaving more in the synapse to stimulate the post-synaptic neuron, which is why they help to treat depression.
Key Definition: Synapse — the junction between two neurons, comprising the pre-synaptic terminal, the synaptic cleft, and the receptors on the post-synaptic neuron. Communication across it is chemical, via neurotransmitters, whereas transmission within a neuron is electrical.
Hormones are chemical messengers produced by endocrine glands and carried in the bloodstream; they act more slowly and diffusely than neurotransmitters but can have powerful, lasting effects on behaviour.
| Hormone | Gland | Effect on behaviour |
|---|---|---|
| Testosterone | Testes (mainly) | Associated with aggression and dominance |
| Cortisol | Adrenal glands | The stress hormone; chronically high levels can damage the hippocampus and impair memory |
| Oxytocin | Released via the pituitary | The bonding hormone; promotes attachment and trust; released in childbirth and breastfeeding |
| Adrenaline | Adrenal medulla | Triggers fight-or-flight — raises heart rate, blood pressure and blood glucose |
The pituitary gland is often called the "master gland" because its hormones control the release of hormones from other endocrine glands, and it works closely with the hypothalamus to coordinate the body's response to stress.
A clear illustration of biology shaping behaviour is the fight-or-flight response to acute threat, which integrates the nervous and endocrine systems.
graph TD
A[Stressor perceived] --> B[Hypothalamus activated]
B --> C[Sympathetic branch of the autonomic nervous system]
C --> D[Adrenal medulla releases adrenaline and noradrenaline]
D --> E[Heart rate, blood pressure and blood glucose rise; pupils dilate]
E --> F[Body primed to fight or flee]
F --> G[Threat passes: parasympathetic branch restores rest-and-digest state]
When a threat is detected, the hypothalamus activates the sympathetic branch of the autonomic nervous system, which stimulates the adrenal medulla to release adrenaline and noradrenaline. These prepare the body for action — increasing heart rate, breathing rate and blood flow to the muscles, while suppressing non-essential functions such as digestion. Once the threat passes, the parasympathetic branch returns the body to its resting "rest-and-digest" state. This response evolved because individuals who could mobilise rapidly in the face of danger were more likely to survive — a direct demonstration of the approach's combination of neurochemistry, the endocrine system and evolution, and a key synoptic link to the Biopsychology topic.
The biological approach draws on Darwin's theory of evolution by natural selection (1859) to explain why certain behaviours exist.
| Concept | Definition |
|---|---|
| Natural selection | Organisms with characteristics best suited to their environment are more likely to survive, reproduce and pass on their genes |
| Adaptive behaviour | Behaviour that increases the chances of survival and reproduction |
| EEA (Environment of Evolutionary Adaptedness) | The environment in which a species evolved and to which it is adapted |
Because genetically influenced behaviours that enhance survival and reproduction are passed on, many psychological characteristics may be adaptations. Examples include attachment (Bowlby, 1969, argued infant--caregiver attachment is innate and adaptive because it promotes proximity and protection), the fight-or-flight response (a rapid physiological reaction to threat that aided survival), and evolved mate preferences reflecting different reproductive strategies.
Key Definition: Evolution — the process by which species change over generations through natural selection; behaviours that enhance survival and reproduction become more common because the genes underlying them are passed on.
| Dimension | Biological | Behaviourist | Cognitive |
|---|---|---|---|
| Cause of behaviour | Genes, brain, neurochemistry, evolution | Environmental conditioning | Internal mental processing |
| Nature vs nurture | Strongly nature | Strongly nurture | Interactionist/either |
| Free will vs determinism | Biological determinism | Environmental determinism | Soft determinism |
| Reductionism | Highly reductionist (biological) | Reductionist (stimulus--response) | Machine reductionist |
| Scientific methods | Very high (imaging, genetics) | High (lab experiments) | High (experiments, imaging) |
This comparison is directly examinable under "comparison of approaches" and is a powerful way to frame AO3: the biological approach sits at the nature and determinist end of every debate, which is simultaneously the source of its scientific strength and of its main criticisms.
A central strength of the biological approach is its use of rigorous scientific methods, which gives it high credibility. It investigates behaviour using objective, precise and replicable techniques — brain scanning (fMRI, PET, EEG), genetic analysis, and hormone and neurochemical assays — that measure biological variables directly. This matters because objectivity and replicability are defining criteria of science, and the biological approach meets them more fully than any other approach. The implication is that its claims rest on a strong empirical footing and place psychology firmly within the natural sciences, although, as noted below, even its best evidence is often correlational.
A second major strength is its extensive real-world application, especially in drug treatment, which demonstrates practical value. Understanding the role of neurochemicals has produced effective psychoactive drugs — SSRIs for depression (increasing synaptic serotonin) and antipsychotics for schizophrenia (reducing dopamine activity). This is important because the success of biologically derived treatments is strong evidence that biology genuinely influences the disorders in question. The implication is that the approach has transformed the management of mental illness, allowing many people to function who could not otherwise — though drug treatments manage symptoms rather than addressing psychological or social causes, and can carry side effects.
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