IB DP Psychology Core: The Biological Approach to Understanding Behaviour -- Revision Notes

The full syllabus guide confirms all three core approaches – biological, cognitive, sociocultural – are compulsory for every DP Psychology student, tested on Paper 1. These notes go deeper into the Biological approach specifically, alongside the subject overview and assessment revision notes already on the site.

What the biological approach actually claims

The biological approach explains behaviour by looking at physiology (how the body’s systems work), neurochemistry (the chemical processes in the nervous system) and genetics (inherited biological factors). Revise the underlying assumption that unifies these three: that behaviour and mental processes can be at least partly explained by biological structures and processes, without this approach claiming to be a complete explanation on its own – the syllabus expects you to recognise biological explanations as one lens among the three core approaches, not the definitive one.

Physiology

Covers how brain structures and bodily systems contribute to behaviour – for example, the role of specific brain regions in memory, emotion or decision-making, and how techniques such as brain imaging are used to study these structures. Revise being able to name at least one specific brain structure or system relevant to a behaviour you have studied, and describe the evidence (often from a named study) linking that structure to that behaviour, rather than describing brain function in general terms only.

Neurochemistry

Covers how neurotransmitters and hormones influence behaviour – for example, the role of specific neurotransmitters in mood, stress or motivation. A common exam error is naming a neurotransmitter without explaining its actual mechanism of action or the specific behaviour it is being used to explain; revise each neurochemical explanation as a two-part claim (what the chemical does physiologically, and what behaviour that mechanism is proposed to explain), not a single fact to recall in isolation.

Genetics

Covers how inherited factors contribute to behaviour, including twin and adoption studies used to separate genetic from environmental influence. Revise the logic of these study designs specifically: twin studies compare concordance rates between identical (monozygotic) and non-identical (dizygotic) twins to estimate a genetic contribution, while adoption studies compare adopted individuals to both their biological and adoptive relatives to help separate genetic from environmental influence. Being able to explain why these designs are used – not just that they exist – is what distinguishes a strong evaluative answer from a descriptive one.

Revising for evaluation, not just description

Paper 1’s essay question specifically rewards evaluation, not just accurate description of what a study found. For every biological study or theory you learn, build the habit of also recording at least one genuine strength and one genuine limitation – for example, a strength might be that biological measures (like brain scans or hormone levels) offer objective, quantifiable data, while a limitation might be that correlational biological findings cannot establish causation, or that a study’s sample or method limits how far its findings generalise. A answer that states a finding without evaluating it is treated as incomplete relative to the syllabus’s own assessment objectives.

Connecting the biological approach to the other two core approaches

The syllabus deliberately revisits shared topics from more than one approach – memory, for example, can be examined biologically (through brain structures such as the hippocampus), cognitively (through information-processing models), and socioculturally (through the influence of schema and culture on recall). Revising the biological approach in complete isolation from the cognitive and sociocultural approaches misses this deliberate overlap – for any topic you study biologically, it is worth checking whether the same topic also appears under the other two approaches, and if so, being able to compare what each approach adds.

How this links to the internal assessment

Approaches to researching behaviour, taught alongside all three core approaches, is directly relevant to your own experimental study write-up. Many biological-approach studies use experimental or quasi-experimental designs (as opposed to purely qualitative sociocultural research), so understanding how biological psychologists justify their experimental designs and address ethical considerations (such as informed consent for physiological measures) is useful preparation that pays off directly in your own IA write-up, not just in exam answers about published studies.

Self-test

1. Name the three strands the biological approach uses to explain behaviour.
2. Why is it a mistake to name a neurotransmitter’s role without also explaining the specific behaviour it is being used to explain?
3. What is the logic behind using twin studies to estimate a genetic contribution to behaviour?
4. Give one genuine strength and one genuine limitation of biological explanations of behaviour.
5. Name a topic that the syllabus deliberately revisits across all three core approaches, and briefly describe how the biological approach would examine it differently from the cognitive approach.

Answers: 1. Physiology, neurochemistry and genetics. 2. Because a complete biological explanation requires linking the chemical’s proposed mechanism of action to a specific behaviour or mental process, not just naming the neurotransmitter as a fact in isolation – Paper 1 rewards this fuller, mechanistic explanation over a bare factual statement. 3. Comparing concordance rates between identical (monozygotic, sharing all genes) and non-identical (dizygotic, sharing roughly half their genes on average) twins allows researchers to estimate how much of a trait’s variation is explained by genetics versus shared environment. 4. Any valid pair, e.g. strength: biological measures like brain scans or hormone levels provide objective, quantifiable data; limitation: correlational biological findings cannot establish causation, and findings may not generalise beyond the specific sample studied. 5. Memory is a valid example: the biological approach examines it through brain structures (e.g. the hippocampus’s role in forming new memories), while the cognitive approach examines it through information-processing models of how memory is encoded, stored and retrieved.

Official syllabus

International Baccalaureate Organization, Diploma Programme Subject Brief – Individuals and Societies: Psychology, first assessment 2019, (c) 2018 – the same source already cited by the full syllabus guide, which first identified the biological approach as one of the three compulsory core approaches.