The Biological Approach

The biological approach argues that behaviour can be explained in terms of physical, biological factors. It assumes that everything psychological is first biological — that the mind resides in the brain, and that behaviour, cognition, and emotion all have biological causes that can be studied scientifically.

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Key Assumptions

1. All behaviour has a biological basis — it can be explained in terms of brain structures, neurochemistry, genetics, and evolution.
2. The mind lives in the brain — all thoughts, feelings, and behaviour are the product of brain activity.
3. Genetics influence behaviour — behavioural characteristics can be inherited, just like physical characteristics.
4. Human behaviour can be explained through evolution — behaviour that promotes survival and reproduction is naturally selected.

Key Definition: Biological approach — the approach that explains behaviour in terms of biological factors including genetics, neurochemistry, brain structures, and evolution. It assumes that all behaviour has a physical, biological cause.

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Genes and Behaviour

The Role of Genetics

Every individual inherits a unique combination of genes from their parents. The biological approach proposes that genes influence behaviour, personality, and susceptibility to mental disorders.

Term	Definition
Genotype	The genetic makeup of an individual — the particular set of genes they carry
Phenotype	The observable characteristics of an individual — the result of the interaction between genotype and environment

Key Definition: Genotype — the set of genes an individual possesses. Phenotype — the observable expression of those genes, which is influenced by both genetics and environment.

Twin Studies

Twin studies are used to investigate the heritability of behaviour by comparing concordance rates between identical (MZ) and fraternal (DZ) twins.

Twin Type	Genetic Similarity	Rationale
Monozygotic (MZ) twins	100% genetically identical	If a behaviour is genetic, MZ twins should show higher concordance than DZ twins
Dizygotic (DZ) twins	50% genetic similarity (like any siblings)	Provide a comparison group to estimate the genetic contribution

Example concordance rates for schizophrenia:

• MZ twins: approximately 48% concordance (Gottesman, 1991)
• DZ twins: approximately 17% concordance

The fact that MZ concordance is higher than DZ concordance suggests a genetic component, but the fact that it is not 100% shows that environmental factors also play a role.

Adoption Studies

Adoption studies compare adopted children with their biological parents (genetic influence) and adoptive parents (environmental influence) to separate the effects of nature and nurture.

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Biological Structures: Brain Localisation

The brain can be divided into areas with specific functions — this is known as brain localisation (or cortical specialisation).

Brain Area	Function
Frontal lobe	Decision-making, planning, personality, motor control
Temporal lobe	Auditory processing, language comprehension (Wernicke's area), memory
Parietal lobe	Sensory processing, spatial awareness
Occipital lobe	Visual processing
Broca's area (frontal lobe)	Speech production
Wernicke's area (temporal lobe)	Language comprehension
Hippocampus	Formation of new long-term memories
Amygdala	Processing emotions, especially fear

Exam Tip: Be able to give examples of evidence for brain localisation. For instance, damage to Broca's area causes Broca's aphasia (difficulty producing speech), while damage to Wernicke's area causes Wernicke's aphasia (difficulty understanding speech). This demonstrates that different brain areas control different functions.

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Neurochemistry: Neurotransmitters

Neurotransmitters are chemical messengers that transmit signals across the synaptic gap between neurons.

Neurotransmitter	Role in Behaviour
Serotonin	Mood regulation, sleep, appetite. Low serotonin is associated with depression
Dopamine	Pleasure, reward, motivation, movement. Excess dopamine is linked to schizophrenia; low dopamine is linked to Parkinson's disease
Noradrenaline	Arousal, alertness, the fight-or-flight response. Linked to anxiety and the stress response
GABA	Inhibitory neurotransmitter — reduces neural activity. Low GABA is associated with anxiety disorders
Acetylcholine	Muscle contraction, memory, attention. Loss of acetylcholine-producing neurons is associated with Alzheimer's disease

graph LR
    A[Pre-synaptic Neuron] -->|Neurotransmitter released| B[Synaptic Gap]
    B -->|Neurotransmitter binds to receptor| C[Post-synaptic Neuron]

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Hormones and Behaviour

Hormones are chemical messengers produced by endocrine glands and carried in the bloodstream. They affect behaviour by influencing target organs and the brain.