Key Idea: *Change is shown by measuring behaviour more than once — then ruling out the ordinary reasons it might just look different.*
Topic 1.3 at a glance
- Biological change — Maturation, neuroplasticity, hormones, recovery reshape the brain.
- Behavioural change — Learning: conditioning, habit formation, behaviour modification.
- Measuring change — Before-after/longitudinal designs; watch practice effects and regression to the mean.
Biological · Behavioural · Measuring
IB-style questionExplain[6 marks]
A clinic claims a 6-week course 'changed' patients because their scores improved from start to end. Explain how you would check the change is real.
🔒 Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.
Two engines of change? Biological (brain/body) and behavioural (learning).
How do you show real change? Measure twice, add a control group, check the change is bigger than noise.
What is regression to the mean? Extreme scores drift back toward average on retest, faking a change.
If a study claims a treatment 'worked', check for a control group, a reliable measure, and whether the change beats normal variation.