Neural Networks and Neural Pruning

Introduction: How the brain builds and refines itself 🧠

students, this lesson explores two important ideas in biological psychology: neural networks and neural pruning. Together, they help explain how the brain changes as we grow, learn, and adapt to the world. The brain is not a fixed machine. It develops through a process of building connections and then keeping the most useful ones. This is a key part of the biological approach to understanding behaviour, because it shows how behaviour is influenced by brain structure and brain development.

By the end of this lesson, you should be able to:

• explain what a neural network is and why it matters,
• describe what neural pruning is and why it happens,
• apply these ideas to real-life examples and IB Psychology HL-style reasoning,
• connect brain development to behaviour, learning, and experience,
• use evidence to support explanations of how the brain becomes more efficient.

A helpful way to think about this is to imagine the brain as a city’s transport system 🚦. At first, the city builds many roads everywhere. Later, unused roads may close while the busiest routes are strengthened. The brain develops in a similar way.

Neural networks: the brain’s communication system

A neural network is a system of connected neurons that work together to process information. Neurons are nerve cells, and they communicate using electrical and chemical signals. When many neurons are connected, they form pathways that can support learning, memory, movement, emotion, and perception.

In simple terms, a neural network is like a team of messengers. One neuron passes a signal to another, which passes it onward, and so on. The more often a pathway is used, the easier it becomes for the brain to send signals along that route. This is why practice can improve performance. For example, when students practices a piano piece, the brain strengthens the pathways used for finger movement, timing, and memory.

Neural networks are important because behaviour depends on communication across the brain. A single neuron does not create a complex behaviour on its own. Instead, groups of neurons collaborate. In IB Psychology HL, this supports the biological idea that behaviour is rooted in brain structure and function.

A useful term here is plasticity. Plasticity means the brain can change in response to experience. Neural networks are a major part of plasticity because they can become stronger, weaker, more efficient, or reorganized over time. This shows that biology and experience work together.

For example, a teenager who learns a new language may initially struggle with vocabulary and grammar. Over time, repeated exposure helps build stronger neural pathways related to listening, speaking, and recall. This is an example of how a neural network supports behaviour in a real-world setting.

Neural pruning: keeping the brain efficient ✂️

Neural pruning is the process by which the brain removes weaker or less-used neural connections. It is also called synaptic pruning. During early development, the brain produces many more connections than it will need. As a child grows, the brain “prunes” away connections that are rarely used, while frequently used pathways are maintained and strengthened.

This process is important because it makes the brain more efficient. Instead of keeping every possible connection, the brain becomes better at using the routes that matter most. Imagine a forest path system 🌳. At first, many paths exist, but over time the most useful ones stay clear while the others become overgrown. The brain works in a similar way.

Pruning happens most rapidly during childhood and adolescence, although brain change continues throughout life. It is guided partly by genetics and partly by experience. If a child repeatedly practices reading, the neural pathways involved in language and comprehension are strengthened. If certain connections are not used often, they are more likely to be pruned.

This means experience influences brain development. However, pruning is not simply “good” or “bad.” It is a normal and necessary part of healthy development. Without pruning, the brain would keep too many extra connections, which would make processing slower and less efficient.

A strong IB Psychology HL point is that pruning helps explain how behaviour becomes more specialized with age. For example, a young child may have broad potential for learning different skills, while an older adolescent may show more efficient performance in skills that have been practiced repeatedly.

How neural networks and pruning work together

Neural networks and pruning are closely connected. First, the brain creates many connections. Then, experience helps determine which pathways are used often. Stronger pathways remain, while weaker ones are removed. This is why neural pruning is sometimes described as the brain’s way of “refining” neural networks.

This process is especially important during sensitive periods of development, when the brain is highly responsive to experience. For example, early exposure to language can shape the neural networks responsible for speech perception and communication. If students grows up hearing and using a language daily, the related pathways become efficient and specialized.

This interaction between connection-building and pruning supports behaviour in everyday life. A child who spends time drawing, playing sports, or learning music may strengthen networks related to those activities. At the same time, unused pathways may be pruned. This does not mean abilities disappear; rather, the brain becomes tuned to the person’s experience and environment.

In IB terms, this helps explain the relationship between nature and nurture. Nature provides the biological capacity for neural growth and pruning, while nurture shapes which connections are used most. Biological psychology often focuses on this interaction because behaviour is not produced by genes alone or environment alone.

Evidence and examples from biological psychology

Research in developmental neuroscience shows that the brain changes dramatically during childhood and adolescence. One well-known finding is that gray matter volume increases in early childhood and then decreases during adolescence in some brain regions. This decrease is linked partly to pruning, which helps the brain become more efficient.

Studies using brain imaging have also shown that experience can shape neural pathways. For example, training in complex skills such as music, navigation, or second-language learning can be associated with structural and functional differences in the brain. These findings support the idea that repeated use strengthens certain networks.

Another important example comes from research on deprivation and enriched environments. Animals raised in enriched settings, with more stimulation and opportunities to explore, often show more complex neural connections than animals raised in less stimulating conditions. This suggests that experience affects brain development through neural networks and pruning.

In human development, a classic real-world application is learning. If students studies a subject every day, the brain gradually becomes better at retrieving facts and organizing information. This happens because the related neural pathways are repeatedly activated. Over time, pruning helps remove less useful connections, making important pathways easier to use.

These findings are useful in IB Psychology HL because they show how empirical evidence supports biological explanations of behaviour. The brain is not static. It is shaped by both inherited processes and experience-based change.

Applying the concept to IB Psychology HL questions

When answering an exam question, students should do more than define the terms. The best answers explain how neural networks and pruning influence behaviour and development.

A strong short answer might look like this: neural networks are interconnected neurons that process information, and neural pruning removes weak or unused synapses to increase efficiency. Together, they help explain how the brain develops and how learning changes brain structure.

For a longer response, students can include an example. For instance, a child learning to read initially uses many neural connections as they decode letters and words. With practice, the most useful pathways become stronger, while less useful ones are pruned. This allows reading to become faster and more automatic.

IB-style reasoning should also include evaluation. For example, one strength of these concepts is that they are supported by neuroscience research and brain imaging. A limitation is that brain scans can show changes, but they do not always prove exactly which experiences caused those changes. Still, the evidence strongly supports the view that behaviour and brain development are linked.

When connecting this topic to the broader biological approach to understanding behaviour, remember the main message: biological structures influence behaviour, and behaviour can also influence biological structures through experience. Neural networks and pruning are clear examples of this interaction.

Conclusion: why this matters

Neural networks and neural pruning show that the brain develops by building many connections and then refining them through use. This process helps explain learning, skill development, and changes across childhood and adolescence. It also supports a core idea in biological psychology: behaviour is connected to the brain, and the brain changes with experience.

For students, the key takeaway is that the brain is efficient because it is selective. Connections that are used often become stronger, while unused ones may be removed. This helps the brain adapt to the demands of life, school, relationships, and skill learning. In IB Psychology HL, these concepts are important because they provide a biological explanation for how behaviour develops over time.

Study Notes

• A neural network is a group of connected neurons that communicate to process information.
• Neural pruning is the removal of weaker or unused synaptic connections.
• Pruning helps the brain become more efficient and specialized.
• Neural networks strengthen through repeated use, practice, and learning.
• Experience shapes which neural connections are kept and which are pruned.
• These ideas show the interaction of nature and nurture in brain development.
• Neural pruning is especially important during childhood and adolescence.
• The topic fits the biological approach to understanding behaviour because it explains behaviour through brain structure and function.
• Real-life examples include learning language, music, sports, and reading.
• Evidence from brain imaging and developmental research supports these concepts.
• In IB answers, define the terms, explain the process, and connect them to behaviour and development.