IB DP Psychology Core: The Biological Approach to Understanding Behaviour – Practice Questions

Course note (legacy syllabus): This resource describes IB DP Psychology for first assessment 2019, now in its final teaching cycle (last examination session November 2026). A replacement course (first assessment 2027) reworks the approaches into content areas applied across four contexts, integrated with six named concepts. A companion resource for the 2027 course does not yet exist on this site.

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs – the IB holds copyright in its own papers. Use these alongside the official past papers available through your school or the IB store.

Related: Biological approach revision notes and the IB DP Psychology syllabus guide.

Section A

1. State the three topics of the biological approach that are studied at both SL and HL. [3]

2. Define “concordance rate” as used in twin studies. [2]

3. State one limitation of correlational research in biological psychology. [1]

Section B

4. A study finds that identical (monozygotic) twins have a higher concordance rate for a particular behaviour than non-identical (dizygotic) twins.

(a) Explain what this pattern of results suggests about the role of genetics in that behaviour. [2] (b) Explain one limitation of using twin studies to draw conclusions about genetic influence. [2]

5. A researcher proposes that a specific neurotransmitter is linked to mood regulation.

(a) Explain why simply naming the neurotransmitter is not, by itself, a complete biological explanation. [2] (b) Describe what a complete two-part neurochemical explanation would need to include. [2]

6. Outline one strength and one limitation of using brain imaging techniques to study the physiological basis of behaviour. [4]

Section C

7. “The biological approach provides the most complete explanation of human behaviour.” Discuss this claim with reference to at least one biological study or theory. [9]

Worked answers

1. The relationship between the brain and behaviour [1]; hormones and pheromones and their effects on behaviour [1]; the relationship between genetics and behaviour [1]. (HL students also study a fourth topic, the role of animal research in understanding human behaviour; it earns no marks here.) [3]

2. Concordance rate is the percentage of twin pairs in which both twins share a particular trait or behaviour, used to estimate the degree of similarity between twins for that characteristic. [2]

3. Correlational findings cannot establish causation – a correlation between a biological measure and a behaviour does not show that one causes the other, since a third variable or reverse causality could explain the pattern. [1]

4. (a) Since monozygotic twins share 100% of their genes while dizygotic twins share on average 50%, a higher concordance rate in monozygotic twins suggests that genetic factors contribute to the behaviour – if the behaviour were purely environmental, both twin types (who are typically raised in similarly shared environments) would be expected to show similar concordance rates. [2] (b) Twin studies assume that monozygotic and dizygotic twins experience equally similar environments, but monozygotic twins may in practice be treated more similarly by parents and others (precisely because they look identical), which confounds the comparison and could inflate the apparent genetic contribution. [2]

5. (a) A named neurotransmitter alone does not explain behaviour because it does not specify the mechanism by which the chemical produces its effect, nor which specific behaviour is being explained – a name in isolation is descriptive, not explanatory. [2] (b) It would need to state what the neurotransmitter does physiologically (e.g. which receptors it binds to, or what neural pathway it affects) and link that specific mechanism to the specific behaviour being explained (e.g. how that pathway’s activity is proposed to influence mood). [2]

6. Strength: brain imaging provides objective, quantifiable data about brain structure or activity, reducing reliance on self-report or subjective observation. [2] Limitation: brain imaging typically shows correlation between brain activity and a task or behaviour, not causation, and scanning conditions (e.g. lying still in a scanner) may not reflect how the brain behaves in natural, everyday settings, limiting ecological validity. [2]

7. A strong answer would define the biological approach’s core claim (behaviour explained through the brain, hormones and pheromones, and genetics) and support it with a named study or theory, such as twin study evidence for a genetic contribution to a specific trait, or a neurochemical or hormonal explanation for a behaviour such as stress or motivation. Strengths to raise: objective, often quantifiable evidence (e.g. brain scans, hormone assays); biological explanations can be tested and often replicated using standardised measures; some biological interventions (e.g. drug treatments derived from neurochemical theories) have demonstrable real-world efficacy, which is itself evidence for the underlying explanation’s validity. Limitations to raise: biological studies are frequently correlational, so causal claims often go beyond what the evidence supports; biological explanations alone cannot account for all variation in behaviour, since cognitive and sociocultural factors (such as schema, culture, and social context) clearly also shape behaviour, as the syllabus’s own three-approach structure implies; reductionism – explaining complex behaviour purely at the biological level risks oversimplifying phenomena that involve cognitive and social processes too. A well-rounded discussion should conclude that the biological approach offers valuable and often rigorous evidence, but the claim that it is the “most complete” explanation overstates its scope, since the syllabus itself frames it as one of three complementary approaches rather than a standalone, sufficient account of behaviour. [9] (Marks awarded across accurate description of approach and named study, balanced evaluation with genuine strengths and limitations, and a reasoned conclusion addressing the claim directly.)

Why question 7 carries the most marks

Question 7 uses an essay-style “discuss” prompt because Paper 1’s essay is the paper’s main test of the skill the revision notes identify as decisive: evaluation, not description. It is not set at Paper 1 essay length or mark value. On the real Paper 1 (first assessment 2019), each of the three short-answer questions in Section A is worth 9 marks and the Section B essay is worth 22 marks, so treat question 7 as a shorter rehearsal of the essay’s evaluative skill rather than a full-length essay. Every other question in this set builds towards the two-part habit the notes recommend – naming a mechanism and then explaining what behaviour it accounts for, or naming a finding and then evaluating it – so that by question 7, a student who has worked through Sections A and B has already rehearsed the component skills the full essay demands.

Official syllabus

International Baccalaureate Organization, Diploma Programme Subject Brief – Psychology, first assessment 2019 – the same source cited by the Biological approach revision notes and the IB DP Psychology syllabus guide.