What you'll learn

• How the biological approach explains behaviour through the body, brain and nervous system.
• The three key assumptions for Eduqas: evolutionary influences, localisation of brain function and neurotransmitters.
• How to link the assumptions to named research, especially Raine, Buchsbaum and LaCasse (1997) and Casey et al. (2011).
• How to evaluate the approach using AO3 points such as reductionism, determinism, scientific evidence and ethics.

The big idea: behaviour has biological causes

The biological approach argues that behaviour, thoughts and emotions are strongly influenced by physical processes in the body. These include brain structures, brain chemistry, genes, hormones and evolutionary pressures.

This approach is often linked with scientific methods, such as brain scans, laboratory experiments and drug trials. It tends to look for measurable, physical evidence rather than relying only on what people say about their experiences.

Assumption 1: evolutionary influences

Evolution and natural selection

Evolution means that species change over many generations. In psychology, evolutionary explanations suggest that some behaviours exist because they helped our ancestors survive or reproduce.

A behaviour can be described as adaptive if it increases the chance of survival or reproduction. For example, fear of dangerous animals may have helped ancestors avoid injury, while attachment behaviours may have helped infants stay close to caregivers.

This does not mean every modern behaviour is useful. Some behaviours may be a mismatch: they may have been adaptive in ancestral environments but less helpful today.

Genes are not destiny

A gene is a section of DNA that contributes to inherited characteristics. Biological psychologists may investigate whether behaviours have a genetic component, but this does not mean behaviour is completely fixed.

Most behaviours are influenced by both nature and nurture. Nature refers to inherited biological factors; nurture refers to environmental influences such as upbringing, culture, learning and relationships.

Assumption 2: localisation of brain function

Different brain areas do different jobs

Localisation of brain function means that different areas of the brain are specialised for different tasks.

For example, the visual cortex is involved in vision, the motor cortex is involved in voluntary movement, and the prefrontal cortex is involved in planning, decision-making and impulse control. The amygdala is often linked with emotion and threat detection, while the hippocampus is important for memory.

Localisation is important because damage or unusual activity in a brain area may be linked to changes in behaviour. For example, damage to frontal areas may affect impulse control, while damage to language areas may affect speech or comprehension.

Named study link: Raine, Buchsbaum and LaCasse (1997)

The classic biological study for this approach is Raine, Buchsbaum and LaCasse (1997). They used PET scans, which measure brain activity, to compare 41 murderers pleading not guilty by reason of insanity with 41 matched controls.

They found differences in brain activity, including reduced activity in areas such as the prefrontal cortex, which is linked with impulse control and decision-making. This supports the biological assumption that brain functioning can be linked to behaviour.

However, the study does not prove that brain differences caused the murders. It may be that other factors, such as trauma, substance use, mental illness or social background, also played a role.

Assumption 3: neurotransmitters

How neurons communicate

A neuron is a nerve cell. Neurons communicate using electrical signals within the cell and chemical messages between cells.

A neurotransmitter is a chemical messenger released by one neuron to influence another neuron. The tiny gap between neurons is called a synapse.

When a signal reaches the end of a neuron, neurotransmitters are released into the synapse. They bind to receptors on the next neuron. Afterwards, neurotransmitters may be broken down by enzymes or taken back into the original neuron through reuptake.

Different neurotransmitters are linked with different functions. For example, dopamine is associated with reward and motivation, while serotonin is associated with mood and impulse control. These links are not simple one-to-one explanations, but they are useful in understanding behaviour and treatment.

How the assumptions work together

The three assumptions are often strongest when combined. For example, aggressive behaviour could be explained through:

• Evolutionary influences: aggression may once have helped with competition for resources or protection.
• Brain localisation: reduced prefrontal cortex activity may affect impulse control.
• Neurotransmitters: low serotonin activity has been linked with impulsive aggression.

This kind of answer is more sophisticated than treating each assumption as completely separate.

Contemporary study link: Casey et al. (2011)

A useful contemporary biological study is Casey et al. (2011), which followed up participants from a delay-of-gratification study. The researchers used tasks involving “go” and “no-go” responses, and some participants also had fMRI scans, which measure changes in brain activity.

The study found that people who had been low delayers as children showed more difficulty resisting tempting cues as adults. Brain activity differences were found in areas linked to impulse control and reward, such as the inferior frontal gyrus and ventral striatum.

This supports the biological approach because it links self-control to brain systems. It also shows how biological research can connect brain activity with real-world behaviours such as resisting temptation.

Evaluation: strengths and weaknesses

Strength: scientific and objective

The biological approach often uses objective methods such as PET scans, fMRI scans and controlled drug studies. This can make findings more reliable than relying only on self-report.

Raine et al. (1997), for example, used matched controls and brain scanning, which gives the study a scientific basis.

Strength: useful real-world applications

Biological explanations have led to treatments such as drug therapy. For example, antidepressants and antipsychotics are based on the idea that changing neurotransmitter activity can reduce symptoms.

The approach also helps with understanding brain injury, neurological conditions and mental health difficulties.

Weakness: reductionism

Reductionism means explaining something complex by reducing it to one level of explanation. The biological approach can be criticised for reducing complex behaviours to brain activity or chemicals.

For example, criminal behaviour cannot be fully understood by looking only at the brain. Social learning, poverty, trauma, culture and personal choice may also be relevant.

Weakness: biological determinism

Determinism is the idea that behaviour is controlled by factors outside a person’s free will. Biological explanations can sound deterministic because they emphasise genes, brain structures and chemistry.

This can be problematic if it makes behaviour seem unavoidable. It may also raise ethical concerns, such as labelling people as “dangerous” because of brain differences.

Ethics

Human biological research must follow the BPS Code of Ethics and Conduct, including informed consent, protection from harm, confidentiality, right to withdraw and debriefing. Brain-scan studies also need to consider privacy and the risk of stigma if biological differences are linked to behaviours such as violence.

Animal research may sometimes be used to study brain mechanisms or drug effects. This raises additional ethical issues: researchers must justify harm, minimise suffering and consider whether the benefits outweigh the costs.