IB Psychology HLTopic 2 — Models of DevelopmentPaper 1 & 2Biological approach~9 min read
Neuroplasticity in the Developing Brain
Maturation is the timetable the brain follows. Plasticity is how the brain answers back. It reshapes itself around what you practise, and it reroutes around what gets damaged — which is why the same starting brain can end up in two very different places.
📘 What you need to know
Neuroplasticity is the brain’s ability to change in response to experience, learning, illness or injury.
Structural plasticity = the physical structure changes, for example more grey matter in a region that gets heavy use.
Functional plasticity (functional recovery) = another region takes over a job after damage, such as after a stroke.
Grey matter builds up because of increased synaptic connectedness in regions used repeatedly.
The changes are gradual, not instant — they track how much damage there was, or how much practice.
Luby et al. found childhood poverty was linked to reduced brain volume, but nurturing care acted as a protective factor.
Evaluation words: longitudinal, confounding variable, sample bias, population validity.
What plasticity means
The old picture of the brain was a machine that was built, switched on, and then slowly wore out. Plasticity replaced that with something better: a dynamic organ that keeps adjusting to whatever the environment throws at it.
Definition to learn
Neuroplasticity = the brain’s ability to change its structure and function in response to experience, learning, or damage.
A path through a field is my favourite way to picture this. Walk it every day and it becomes a clear track. Stop walking it and the grass grows back. Block it off, and people wear a new path around the obstacle. That is branching, pruning and functional recovery in one image.
The two types you must be able to separate
Almost every mark lost on this topic comes from blurring these two. Keep them apart by asking: has the brain grown, or has it reassigned a job?
Structural change usually follows practice; functional change usually follows damage. Learning a skill grows tissue, a stroke moves a job.
Type
What changes
Typical trigger
Classic example
Structural plasticity
The physical size and density of a brain region
Repeated learning or practice over time
More grey matter in the posterior hippocampus after long practice at navigating
Functional plasticity
Which region does a particular job
Injury, illness or damage
After a stroke, other areas compensate for lost speech or movement
Why grey matter grows. It is not new brain cells appearing out of nowhere. Repeated use increases synaptic connectedness — more and stronger connections between the neurons already there — and that extra wiring is what shows up as extra volume on a scan.
Key study: Luby et al. on poverty and the developing brain
This is the study that links plasticity to the rest of the topic, because it asks a harder question: does the environment a child grows up in change how well the brain develops, and can anything protect against it?
🧩 The study in four steps
Aim — to test whether childhood poverty is linked to delayed brain development, and whether other factors can soften that effect.
Participants and method — 145 children in the USA taking part in a ten-year longitudinal study of preschool depression, categorised as living in poverty. Annual assessments over 3–6 years measured cognitive, emotional and social skills, alongside data on caregiver–child relationships and stressful life events. Each child had two MRI scans: one whole-brain, one focused on the hippocampus and amygdala.
Findings — children living in poverty showed reduced white and grey matter in the hippocampus and amygdala compared with expected levels. Children who received warm, nurturing care showed less of this reduction, especially in the hippocampus.
Conclusion — poverty is associated with poorer brain development, but the quality of caregiving acts as a protective factor.
Draw this shape from memory in an essay plan. The middle bar is the whole point of the study — the effect of poverty was reduced, not fixed and unavoidable.
Different revision sources give different years for this research, so lead with the researcher and the finding: “Luby and colleagues found that nurturing care buffered the effect of poverty on the hippocampus.” Examiners credit accurate content far more than a date.
Evaluating this research
Strengths
Method triangulation. Behavioural, cognitive and social measures were compared with MRI results, which strengthens internal validity — the conclusion does not rest on one type of data.
Longitudinal design. Following the same children for years shows real developmental change instead of a single snapshot.
Applied value. If caregiving protects the brain, then supporting parents is a legitimate way to protect children’s development, not just a nice idea.
Limitations
Confounding variable. Some children already had depression, which may have affected brain development on its own. So we cannot say poverty alone caused the reduced plasticity.
Subjective measures. “Quality of caregiving” and “social skills” are complicated things to score, and judgement creeps in, which lowers validity.
Sample bias. Only US preschool children living in poverty, most with depressive symptoms — so the findings may not apply to other ages, other cultures, or children in poverty without depression. That limits population validity.
Limited explanatory power. MRI can measure volume, but it cannot tell you why the volume changed.
Link to concepts
Causality — the design is correlational at heart. A control group of children without depression would be needed before anyone could claim poverty itself causes the delay.
Bias — a narrow sample produces a narrow conclusion. Always say who the finding applies to.
Exam practice
WORKED EXAMPLE
Explain one example of neuroplasticity in development. [3 marks]
1. Define the term first
Neuroplasticity is the brain changing its structure or function in response to experience or damage.
2. Give a clear exampleStructural plasticity: repeated use of a region increases synaptic connectedness, so grey matter builds up there.
3. Link to development
Luby et al. showed the reverse too — children in poverty had reduced hippocampal volume, but nurturing care limited the loss.
Define → example → linkA definition on its own scores nothing. The example is where the marks live.
WORKED EXAMPLE
Discuss one study of the developing brain. [ERQ paragraph]
Claim
Luby et al. support the idea that environment shapes brain development.
Evidence
MRI showed less grey and white matter in the hippocampus and amygdala in children living in poverty.
Balance itBut pre-existing depression is a confounding variable, so poverty cannot be isolated as the cause.
So what
The study shows a real association and identifies a protective factor, but stops short of proving causation.
Claim, evidence, counter, conclusionEvery ERQ paragraph should end with a judgement, not a fact.
💡 Exam tip
Always name which type of plasticity you mean. “The brain changed” is not an answer.
The word gradual is worth including — plasticity happens over months and years, not overnight.
This study doubles up for poverty in childhood in the Development of Self unit. Learn it once, use it twice.
“Protective factor” is examiner-friendly language. Use it when you describe the caregiving finding.
For evaluation, longitudinal is your strongest strength word and confounding variable your strongest criticism.
If asked about ethics, remember these are vulnerable children — consent, protection from harm and sensitive reporting all apply.
⚠️ Common mix-up
Structural and functional swapped. Growing is structural; rerouting a job is functional. Check yourself before you write.
Plasticity is not only for children. It slows down, but adult brains change too.
“Poverty damages the brain” is too strong. Say poverty is associated with reduced volume.
MRI is not PET. MRI showed structure in Luby; PET showed activity in Chugani.
Do not forget the protective factor. Students describe the sad half of the finding and miss the hopeful half, which is the part examiners want discussed.
Grey matter growth is not new neurons. It is denser connections between existing ones.
Up next: Vygotsky on How Children Learn — we move from what the brain does on its own to what it can only do with somebody else’s help.
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