The big idea: Some of what we are is passed down from our parents. Psychologists ask: how far can behaviour be inherited — carried in our genes — rather than only learned from our surroundings?
A gene is a set of instructions you inherit. Genes help build the brain and body, so they can affect how we think, feel and behave.
But genes rarely fix a behaviour on their own. More often they give a genetic predisposition — a tendency that may or may not appear, depending on a person's life.
To test whether a behaviour is inherited, psychologists often use twin studies. These compare identical and non-identical twins to see how much genes seem to matter.
Memory hook: Genes load the gun; life pulls the trigger. Genes can make a behaviour more likely, but rarely cause it on their own.
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Key idea: Identical twins share almost all their genes; non-identical twins share about half. So we can compare them to estimate how much genes matter for a behaviour.
Researchers measure concordance — how often, if one twin has a trait, the other has it too. If identical twins match far more often than non-identical twins, that points to a genetic influence.
Let us walk through one clear example. Imagine a condition, such as ongoing low mood, seems to run in a family. To test the role of genes, researchers compare concordance in many identical and non-identical twin pairs.
Imagine you are there: Two identical twins were raised in the same home. One develops the condition, and researchers find the other often does too. Across many such pairs, identical twins match more often than non-identical twins. This suggests genes play a part — though the shared home makes it hard to be certain.
From this, researchers estimate heritability. Heritability is almost never 100%, which shows that environment matters too.
This is why psychologists talk about gene-environment interaction: an inherited tendency may only appear if life events trigger it.
Exam tip: Show the logic: identical twins share more genes, so if they share a trait more often, genes probably matter. Then add that it is never the whole story.
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The concept behind it: Genetic inheritance raises the concept of causality. A trait may run in families — but do genes cause it, or the shared environment, or both? Twin studies try to separate these, but cannot do so perfectly.
Studies are just examples: You do not need to memorise a named study. You can explain genetic inheritance with a real twin study or a made-up example — both score full marks — as long as the logic is clear.
Strengths of the explanation
- Twin and family studies give a clear way to estimate a genetic influence
- It explains why some behaviours and conditions run in families
- It fits a diathesis-stress model view of many conditions
- Advances in DNA research make it increasingly testable
Limits of the explanation
- Identical twins often share environments too, so genes and environment are hard to separate
- Heritability is never 100% — environment always matters
- It can be reductionist and even deterministic
- A genetic 'link' is a correlation, not proof of cause
Real examples you could use: You do not have to memorise these, but real ones make strong examples:
• twin studies of mood or intelligence
• family studies of a condition that runs across generations
• adoption studies, which help separate genes from upbringing
Any one — or a made-up example — works, as long as you explain the logic clearly.
How to reach the top marks: The best answers evaluate: weigh a strength (twin studies estimate genetic influence) against a limit (shared environment; correlation not cause), then reach a short judgement — usually that behaviour is shaped by genes and environment together.
How Paper 1 tests this: Genetic inheritance is biological-approach content. On Paper 1 this term is tested in two ways.
Two ways it is tested
- A short-answer question [4 marks]: describe or explain how far a behaviour may be inherited, with one example.
- An applied question [6 marks]: use it to explain a situation in a given context.
The [15] essays: The big [15] essays are concept-framed and come in the four contexts. This term can support one: for example, the concept of causality in the health and well-being context.
A psychologist notices that a certain condition seems to run in one family across three generations. Explain how genetic inheritance could account for this, and one limitation of concluding that it is caused by genes.
Model answer plan
See the answer broken into clear points, with guidance on how each point earns marks.
Common mistakes: 1. Describing, not applying. In the applied [6], explain THIS family, not genetics in general.
2. Ignoring environment. Genes rarely act alone — always mention environment.
3. Claiming proof of cause. A trait running in families is a correlation, not proof genes caused it.
4. Forgetting the concept. Tie back to causality (genes vs environment).