Prosocial behaviour and biological influences
Define helping, sharing and caring, separate individual from situational influences, and evaluate a biological account using Rushton’s twin study.
Original teaching mapped to Cambridge IGCSE Psychology 0266 Version 3 for 2027–2029. The course is independent study support, not Cambridge material, an official mark scheme or an awarded grade. Named-study notes summarise the required findings; candidates are not expected to evaluate named studies. Self-check practice is not official grading, a timed Paper 1/2 simulator or teacher review.
Before you begin
- Use the Version 3 syllabus and confirm availability in your administrative zone with Cambridge and your school. Both papers are compulsory. The updated named-study summaries are required context; full original research articles are not required.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Before prosocial behaviour and biological influences, which approach is most useful?
What you will learn
- Define prosocial behaviour and distinguish individual and situational influences
- Explain the roles of serotonin, oxytocin, prefrontal cortex and amygdala
- Explain heritability using MZ and DZ twin similarities
- Use Rushton et al. and a social-environment counterargument
Prosocial behaviour benefits another person
Helping, sharing and caring are examples. Its development can change with age. Individual factors belong to the person, such as age, personality and biology; situational factors are external, such as location, proximity and the immediate environment.
Biology may contribute through several systems
Neurotransmitters transmit chemical signals between nerve cells; serotonin is linked with prosocial behaviour. Oxytocin is a hormone associated with bonding and prosocial responses. The prefrontal cortex supports attention, emotional expression and social behaviour; the amygdala is active in empathic responses. These are contributions, not single causes.
Twin similarity estimates heritability, not destiny
Monozygotic (MZ) twins share more genes than dizygotic (DZ) twins. If MZ pairs are more similar on a behaviour, genetic differences may help account for variation. Heritability estimates the contribution of genetic differences within a population; it does not say what fraction of one person’s behaviour is genetic.
Named study: Rushton
The study compared social-responsibility questionnaire responses from 174 MZ and 148 DZ twin pairs. MZ pairs were more similar, and the estimate attributed 42% of variation to genes. The result supports a biological contribution; social groups and roles remain environmental influences that can shape prosocial behaviour.
Pause and explain
Which response best shows understanding of prosocial behaviour and biological influences?
Worked example
Two MZ twins show more similar helping scores than two DZ twins. What can the biological account infer?
Show the worked solution
- MZ twins share more genes than DZ twins.
- Greater similarity is consistent with genetic influence.
- It does not mean that helping is fixed or entirely inherited.
Answer The pattern supports a genetic contribution to differences in helping, alongside environmental influences.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Classify a crowded, unfamiliar location that makes a passer-by less likely to stop and help.
Give me a hint
Is the factor part of the person or outside them?
Compare my reasoning
- The location is external to the individual.
- It is a situational factor.
- Proximity and environmental features can influence helping.
A situational influence.
Look for these in your work
- Classifies the factor
- Names the category
- Links to helping
Why does greater similarity among MZ than DZ pairs support a biological account without proving that helping is genetic only?
Give me a hint
Use the twin difference and note other influences.
Compare my reasoning
- MZ pairs share more genes on average than DZ pairs.
- Greater MZ similarity is consistent with genetic influence.
- The environment, including social groups and roles, also affects behaviour.
The MZ–DZ contrast supports genetic influence, but environmental factors also contribute.
Look for these in your work
- States the genetic contrast
- Explains the inference
- Includes environment
A scenario links a person's empathetic response with activity in the amygdala. Explain the relevant brain-area contribution and avoid an overclaim.
Give me a hint
Use ‘contributes’ rather than ‘determines.’
Compare my reasoning
- The syllabus links the amygdala with empathic responses.
- Activity may be relevant to the person’s response.
- This supports a contribution, not a claim that the amygdala alone determines helping.
The amygdala may contribute to empathic responses, but it is not the only influence on prosocial behaviour.
Look for these in your work
- Names amygdala
- Links empathy
- Avoids a single-cause claim
Common mistakes
- Treating heritability as a percentage of one person’s behaviour.
- Claiming oxytocin or serotonin alone causes helping.
- Ignoring social groups and roles as environmental influences.
What can you explain now?
What comparison is central to a twin estimate of heritability?
Compare with the explanation
Similarity among MZ and DZ twin pairs
MZ and DZ twins differ in average genetic similarity, enabling a comparison of behavioural similarity.
After trying it yourself, choose your next review. This is your self-assessment.
Your review choice appears on Today. Sign in to sync it across devices.
Make it stick
How do individual, situational, biological and genetic influences each contribute to prosocial behaviour?
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.